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Page 1 of 38 June 2009 Update WATERSHED BASED PLAN FOR THE FORT COBB WATERSHED Prepared By: Oklahoma Conservation Commission Water Quality Division 4545 N. Lincoln Blvd., Suite 11A Oklahoma City, OK 73105 Page 2 of 38 June 2009 Update FORT COBB WATERSHED BASED PLAN Table of Contents PAGE PREFACE 3 INTRODUCTION 6 CAUSES AND SOURCES 7 LOAD REDUCTIONS 14 CRITERIA 15 NPS MANAGEMENT MEASURES 15 TECHNICAL AND FINANCIAL ASSISTANCE NEEDED 18 IMPLEMENTATION SCHEDULE 21 INTERIM MILESTONES 26 PUBLIC OUTREACH 27 MONITORING PLAN 31 REFERENCES 36 APPENDICES 37 Page 3 of 38 June 2009 Update PREFACE The Fort Cobb Watershed covers 314 square miles in southwestern Oklahoma in Caddo, Washita, and Custer Counties. Ft. Cobb Reservoir’s designated beneficial uses include public and private water supply, warm water aquatic community, agricul-ture, municipal and industrial uses, primary body contact recreation, and aesthetics. The reservoir is the primary drinking water source for the Cities of Anadarko and Chickasha. The watershed is located in the Central Great Plains Ecoregion in southwestern Oklahoma. Landuse in the watershed includes agricultural fields, cattle operations, rural communities, and one hog operation. Most soils in the watershed are highly erodible, sandy clays and loams. The water quality of the reservoir and its tributaries has been of concern for more than a decade with water quality problems identified beginning in 1981. Oklahoma Water Quality Standards list Fort Cobb Reservoir as a Nutrient Limited Watershed (due to high primary productivity) and a sensitive public and private water supply. 1998 Oklahoma Water Resources Board (OWRB) data showed the lake was hypereutrophic and in 1999, eutrophic (OWRB 2002). Studies indicated biological, chemical, and habitat degradation within the Ft Cobb Reservoir Watershed. DDT was detected in fish flesh tissue in 1981. Ft. Cobb Reservoir and six waterbody segments in its watershed were listed on the 1998 303(d) list as being impaired by nutrients, pesticides, siltation, suspended solids, and unknown toxicity (Table 1). The Reservoir and three streams, Cobb, Willow, and Fivemile Creek, are currently listed on the 2008 303(d) list as being impaired (see Table 1; ODEQ 2008). In addition, concerns have been expressed by the Master Conservancy District reservoir managers regarding the nutrient and sediment loads. Page 4 of 38 June 2009 Update Table 1. 303(d) Listed Causes of Impairment in Fort Cobb Watershed. 303(d) list year OK Waterbody ID Name Cause of Impairment 1998 OK 310830050020 Fort Cobb Reservoir pesticides, suspended solids, turbidity 1998 OK 310830060030 Willow Creek nutrients, siltation, suspended solids 1998 OK 310830060040 Lake Creek unknown toxicity, pesticides, nutrients, siltation, other habitat alterations, suspended solids 1998 OK 310830060050 Cobb Creek pesticides, nutrients, siltation, suspended solids 1998 OK 31080060080 Fivemile Creek nutrients, siltation, suspended solids 1998 OK 31080060130 Crowder Lake nutrients, organic enrichment/D.O., suspended solids 2002 OK310830050020 Fort Cobb Reservoir phosphorus 2002 OK 310830060030 Willow Creek pathogens 2002 OK 310830060040 Lake Creek low dissolved oxygen1, turbidity 2004 OK310830050020 Fort Cobb Reservoir phosphorus 2004 OK 310830060030 Willow Creek Fecal coliform, Enterococcus, E. coli 2004 OK 310830060040 Lake Creek selenium 2006 OK310830050020 Fort Cobb Reservoir phosphorus, turbidity 2006 OK 310830060030 Willow Creek Fecal coliform, Enterococcus, E. coli 2006 OK 310830060040 Lake Creek selenium 2006 OK 31080060130 Crowder Lake turbidity, dissolved oxygen 2008 OK310830050020 Fort Cobb Reservoir turbidity 2008 OK 310830060030 Willow Creek Fecal coliform, Enterococcus, E. coli 2008 OK 310830060050 Cobb Creek ammonia, Enterococcus, E. coli 2008 OK 31080060080 Fivemile Creek Enterococcus, E. coli 2008 OK 31080060130 Crowder Lake turbidity, chlorophyll-a, dissolved oxygen Considerable efforts have been made to identify the causes, sources, and extent of water quality threats and impairments in the basin, and extensive remedial efforts have occurred in the past several years. Previous studies of the reservoir and watershed were conducted by the U.S. Fish and Wildlife Service (USFWS), the Bureau of Reclamation (BOR), and the U.S. Geological Survey (USGS). These studies identified the causes, extent, and some of the sources of water quality impairment in the watershed. 1 Listing for D.O. later determined to be in error during TMDL development. In 2006, the Oklahoma Department of Environmental Quality (ODEQ) released the final draft of a TMDL for phosphorus loading to Fort Cobb Reservoir (Appendix A). This TMDL recommended a 78% phosphorus load reduction to restore beneficial use support to the reservoir. Because there are no point source dischargers in the watershed, this reduction must come entirely from nonpoint sources in the watershed. Page 5 of 38 June 2009 Update The TMDL was based on watershed data collected between 1990 and 2001; therefore, loading reduction recommendations are based upon loading during that period. Since that period, many changes have taken place in the watershed which suggests that Oklahoma is making significant progress towards the TMDL goal. These efforts include, but are not limited to, a decrease in peanut production in the watershed following the loss of government subsidies of peanut production, a 2001 §319 Project focused on education and demonstration of practices to reduce sediment and nutrient pollution in the watershed, a 2005 §319 Project focused on no-till, and continued effects of previous NPS education programs in the watershed which have resulted in the voluntary implementation of best management practices such as riparian zones, nutrient management, and conservation tillage. Additional work in the watershed includes education programs developed by the Oklahoma Cooperative Extension Service (OCES), the Deer Creek, West Caddo, North Caddo, and Mountain View Conservation Districts, the Natural Resources Conservation Service (NRCS), and the Oklahoma Conservation Commission (OCC), and various programs to reduce nonpoint source loading in the watershed. As a result of these efforts, Lake Creek was delisted for pesticides and unknown toxicity in 2002. A Conservation Reserve Enhancement Program (CREP) is planned for the Fort Cobb watershed, which will further address sediment and nutrient loading. This watershed based plan (WBP) discusses the efforts which have already occurred as well as those necessary to expand the programs ongoing in the watershed to reach the load reduction goals established by the TMDL and to restore beneficial use support to Fort Cobb Reservoir and the waterbodies in its watershed. Page 6 of 38 June 2009 Update INTRODUCTION In 1997, on the 25th anniversary of the 1972 Federal Clean Water Act, Vice President Al Gore initiated development of a nationwide strategy to protect water quality. This initiative resulted in the development of the Clean Water Action Plan (CWAP), which established goals and implementation schedules for numerous strategies dealing with point and nonpoint sources. Oklahoma’s Office of Secretary of Environment (OSE) was designated as the state lead agency to implement the provisions of the CWAP in Oklahoma. Under OSE’s leadership, Oklahoma has successfully met the CWAP requirement to establish a Unified Watershed Assessment (UWA) strategy. Oklahoma’s UWA is a written document whose development and implementation relied upon input from the state’s UWA Work Group. Through the UWA process, the Work Group identified “Category I” watersheds in Oklahoma that were recognized as significantly impaired and in need of immediate federal and state funding to target restoration activities. Fort Cobb Watershed was one of these high priority watersheds (Figure 1). EPA’s Nonpoint Source Program and Grants Guidelines for States and Territories for FY 2004 and Beyond requires a Watershed-Based Plan (WBP) to be completed prior to implementation using incremental funds. The guidance defines the 9 key components to be addressed in a watershed-based plan, much of which builds from the strategies outlined in a Watershed Restoration Action Strategy (WRAS). These components are: 1) identification of causes and sources that will need to be controlled to achieve load reductions, 2) estimate of load reductions expected from the management measures described, 3) a description of the management measures that will need to be implemented to achieve load reductions, 4) an estimate of the amounts of technical and financial assistance needed, associated costs, and/or the sources or authorities who will bear responsibility, 5) an information/education component that will be used to enhance public understanding of the project and encourage early participation in the overall program, 6) a schedule for implementing the Non-Point Source (NPS) management measures identified in this plan that is reasonably expeditious, 7) a description of interim, measurable milestones for determining whether control actions are being implemented, 8) a set of criteria that can be used to determine whether loading reductions are being achieved over time and substantial progress is being made or whether the Watershed Plan or Total Maximum Daily Load (TMDL) needs to be revised, and 9) a monitoring component to evaluate the effectiveness of the implementation efforts over time. The WBP for the Fort Cobb Watershed has been developed as a dynamic document that will be revised, when necessary, to incorporate the latest information, address new strategies, and define new partnerships between watershed shareholders following this initial documentation. Also, it is understood that the water quality goals set forth in this WBP, as well as the technical approach to address the goals, may not be comprehensive and it may be necessary to revise or expand them in the future. Page 7 of 38 June 2009 Update Figure 1. Fort Cobb Watershed. West Caddo CD Mountain View CD Deer Creek CD North Caddo CD Fivemile Creek Lake Creek Cobb Creek Willow Creek Federal and state funding allocations for future water quality projects designed to address the Fort Cobb Watershed problems should not be based solely upon their inclusion in this WBP, rather the WBP should be considered a focal point for initial planning and strategy development. In order for this WBP to become an integral part of the entire watershed restoration program, it must be amenable to revision and update. It is anticipated that at least biannual revisions may be necessary, and that the responsibility for such revisions will rest primarily with the OCC with support from the Office of the Secretary of the Environment (OSE) and the NPS Working Group. CAUSES AND SOURCES Causes Currently, Fort Cobb Reservoir, Willow Creek, Cobb Creek, and Fivemile Creek are impaired by turbidity (reservoir), bacteria (all creeks), and ammonia (Cobb Creek) (Table 1). The Fort Cobb TMDL (ODEQ 2006) focuses on phosphorus as the primary cause of impairment in Fort Cobb Reservoir and suggests that the dissolved oxygen listing for Lake Creek was in error. In addition, it confirms that pesticide impairments cited by the 1998 303(d) list are no longer present, as indicated by current water quality and biological data (Appendix A). Page 8 of 38 June 2009 Update Sources Point Sources The TMDL verified that there were no permitted point source dischargers in the Fort Cobb Watershed. However, there are two Concentrated Animal Feeding Operation (CAFO) farms in the watershed, both with total retention NPDES permits. Permits on these farms, one a cattle farm with 2700 animal units, and the other a swine farm with 800 animal units allow overflows only under 25 year, 24 hour storm events. According to the TMDL, these provisions are determined sufficient to protect the waters in the Cobb Creek watershed. The TMDL recommends no additional measures for these CAFO farms. In order to rule out effects of these facilities on nearby stream health, the relative load contribution attributable to these facilities should be considered by the State to verify that these facilities are not significant contributors to local or watershed-wide water quality problems. Based on these findings, the TMDL may need to be revised. Nonpoint Sources In rural settings, the primary sources of nutrients may include runoff of applied fertilizer and manure to agricultural land, runoff of animal wastes associated with the erosion of sediments in grazing fields, runoff from concentrated animal operations, failing septic tanks, and contributions from wildlife. The TMDL used the Soil and Water Assessment Tool (SWAT) model to estimate NPS loadings from landuse in the watershed (Appendix B). This is the same model and model runs that were used to target NPS implementation with an FY 2001 §319 project in the Fort Cobb Watershed. The model subdivided the basin into 90 subbasins, based on 10-meter USGS Digital Elevation Model data for the basin (Figure 3). Loading estimates for these 90 subbasins as predicted by SWAT are seen in Table 2. Loading estimates from Fort Cobb landuses as predicted by SWAT are seen in Table 3. Figure 4 displays the SWAT predictions related to phosphorus loading from subbasins in the Fort Cobb watershed. The darkest red basins produce the highest phosphorus in runoff. The SWAT model estimated a total sediment load to the lake (excluding roads) of 276,000 metric tons per year and a total phosphorus load of approximately 70,000 kg P/year. Typical landuse in the Fort Cobb Watershed (photo courtesy of Storm et al. 2003). Page 9 of 38 June 2009 Update Figure 1. Sub-basin layout used in the Cobb Creek SWAT model (Storm et al. 2003). Figure 3. Total phosphorus loading by sub-basin as predicted by SWAT (Storm et al. 2003). Page 10 of 38 June 2009 Update Table 2. SWAT Estimated Sub-basin Loading. Sub-basin AREA (km2) Surface Runoff (mm) Baseflow (mm) Total Water Yield (mm) Sediment (mg/ha) Organic Nitrogen (kg/ha) Organic P (kg/ha) Nitrate in surface runoff (kg/ha) Soluble Mineral P (kg/ha) Sediment bound mineral P (kg/ha) Total P (kg/ha) 1 1.92E+01 27.198 21.307 51.494 3.02 4.895 0.603 0.106 0.009 0.452 1.064 2 2.12E+01 44.085 35.825 84.136 6.228 6.636 0.803 0.308 0.005 0.828 1.636 3 1.86E+01 45.708 41.17 91.644 4.087 7.324 0.917 0.139 0.015 0.589 1.521 4 8.41E+00 59.531 54.213 121.906 3.919 6.681 0.814 0.173 0.01 0.589 1.413 5 1.51E+01 59.522 35.941 105.415 1.371 9.323 1.123 0.21 0.119 0.951 2.193 6 1.15E+01 54.575 44.673 104.907 1.299 10.146 1.179 0.153 0.092 0.869 2.14 7 7.76E-01 64.588 93.128 175.716 4.213 3.414 0.427 0.221 0.006 0.538 0.971 8 1.18E+01 83.927 68.263 158.491 5.242 7.35 0.92 0.285 0.03 0.837 1.787 9 1.48E+01 50.333 41.2 94.889 2.573 4.644 0.576 0.149 0.012 0.465 1.053 10 2.92E+01 31.725 28.935 64.179 3.398 6.12 0.763 0.081 0.007 0.482 1.252 11 8.49E+00 49.722 43.356 100.008 4.762 7.552 0.933 0.143 0.014 0.688 1.635 12 3.92E-01 81.615 63.218 150.528 4.692 4.613 0.591 0.288 0.008 0.637 1.236 13 4.08E+00 57.373 45.845 109.125 4.154 5.687 0.689 0.172 0.012 0.647 1.348 14 1.49E+01 51.162 45.908 101.745 3.902 6.746 0.844 0.145 0.016 0.619 1.479 15 6.40E-01 67.495 56.309 133.605 4.144 3.42 0.445 0.244 0.006 0.555 1.006 16 1.04E+01 66.203 48.74 118.653 5.349 7.315 0.898 0.219 0.007 0.786 1.691 17 3.25E+00 65.768 53.966 125.363 3.876 5.338 0.673 0.233 0.007 0.628 1.308 18 8.27E+00 61.75 65.052 135.163 4.894 6.626 0.815 0.238 0.009 0.844 1.668 19 2.34E+00 63.825 41.101 109.131 3.083 4.99 0.623 0.227 0.007 0.557 1.187 20 1.56E+01 52.451 43.091 98.176 4.097 6.665 0.816 0.174 0.006 0.643 1.465 21 1.17E+01 62.091 37.157 119.144 2.322 3.437 0.384 0.103 0.026 0.413 0.823 22 1.58E+01 54.363 47.485 112.845 5.096 7.144 0.845 0.14 0.03 0.761 1.636 23 1.54E-01 57.438 54.933 119.686 5.707 6.978 0.85 0.235 0.006 0.7 1.556 24 2.58E+01 63.747 38.638 116.515 1.651 3.385 0.38 0.135 0.035 0.413 0.828 26 8.30E+00 55.895 41.336 102.702 3.631 6.642 0.812 0.148 0.013 0.595 1.42 27 3.16E-01 70.184 82.381 159.887 3.497 3.602 0.441 0.251 0.006 0.47 0.917 28 1.11E+01 58.754 90.282 162.144 3.27 4.629 0.573 0.157 0.01 0.497 1.08 29 1.33E+00 60.497 53.606 127.77 3.833 4.113 0.503 0.207 0.005 0.525 1.033 30 1.63E+01 56.704 79.111 143.377 4.087 5.737 0.709 0.168 0.006 0.602 1.317 31 1.56E+01 59.96 35.11 96.799 3.669 5.706 0.705 0.214 0.008 0.694 1.407 32 1.60E+01 44.063 49.617 102.287 4.17 3.912 0.497 0.155 0.004 0.559 1.06 33 9.64E+00 45.049 45.392 95.578 4.119 5.626 0.685 0.162 0.004 0.61 1.299 Page 11 of 38 June 2009 Update Sub-basin AREA (km2) Surface Runoff (mm) Baseflow (mm) Total Water Yield (mm) Sediment (mg/ha) Organic Nitrogen (kg/ha) Organic P (kg/ha) Nitrate in surface runoff (kg/ha) Soluble Mineral P (kg/ha) Sediment bound mineral P (kg/ha) Total P (kg/ha) 34 1.38E+01 42.272 36.619 82.554 4.841 7.858 0.943 0.14 0.018 0.752 1.713 35 8.03E+00 45.779 47.536 103.311 4.865 5.756 0.713 0.147 0.015 0.648 1.376 36 1.63E+01 41.155 36.611 81.13 5.508 8.637 1.034 0.123 0.016 0.808 1.858 37 7.86E+00 71.821 93.901 178.555 3.963 4.737 0.582 0.301 0.009 0.714 1.305 38 6.23E-01 60.379 52.918 117.398 10.491 8.53 1.027 0.221 0.005 1.078 2.11 39 2.97E+01 51.589 100.085 167.169 3.579 4.675 0.575 0.184 0.018 0.599 1.192 40 1.10E+01 32.863 32.221 66.38 3.782 6.5 0.791 0.094 0.003 0.554 1.348 41 2.39E-01 37.573 89.244 141.895 1.859 2.549 0.322 0.117 0.003 0.256 0.581 42 9.76E+00 35.479 57.285 99.696 2.994 5.537 0.682 0.104 0.014 0.562 1.258 43 5.64E+00 50.394 37.238 90.2 2.031 3.753 0.47 0.159 0.007 0.432 0.909 44 2.39E-01 68.272 51.862 126.06 1.636 2.306 0.328 0.197 0.005 0.257 0.59 45 3.41E-01 54.859 69.637 137.479 0.968 1.207 0.175 0.151 0.003 0.149 0.327 46 1.08E+01 44.676 82.178 133.882 2.73 3.618 0.436 0.141 0.005 0.472 0.913 47 3.17E+01 67.633 71.945 148.966 5.84 6.645 0.821 0.233 0.007 0.844 1.672 48 9.09E+00 72.984 51.113 128.756 4.478 6.09 0.747 0.267 0.008 0.694 1.449 49 1.56E+01 48.316 64.608 122.413 2.924 4.499 0.556 0.148 0.018 0.534 1.108 50 7.69E+00 59.272 119.231 185.652 2.76 3.342 0.397 0.198 0.007 0.509 0.913 51 4.69E-01 52.32 99.866 172.358 0.875 0.793 0.11 0.14 0.003 0.14 0.253 52 4.18E-01 72.596 53.314 139.115 4.258 4.933 0.624 0.248 0.006 0.58 1.21 53 4.18E-01 51.149 59.582 117.475 5.527 3.89 0.455 0.164 0.005 0.634 1.094 54 1.02E+01 51.24 42.769 97.537 4.672 5.997 0.734 0.157 0.005 0.678 1.417 55 3.56E+00 55.822 69.517 133.307 3.071 3.307 0.396 0.186 0.006 0.494 0.896 56 1.80E+00 56.706 56.26 120.711 2.619 3.573 0.456 0.177 0.005 0.413 0.874 57 8.04E+00 50.824 75.133 131.671 2.129 3.164 0.4 0.172 0.006 0.418 0.824 58 2.83E+01 37.324 73.863 116.036 1.448 3.002 0.372 0.105 0.01 0.297 0.679 59 2.56E-04 29.149 122.047 151.789 5.553 8.264 0.982 0.258 0.009 0.686 1.677 60 1.20E+01 43.583 55.189 103.275 2.564 4.431 0.551 0.138 0.006 0.494 1.051 61 5.99E-02 92.043 48.162 145.011 1.77 2.39 0.302 0.375 0.009 0.366 0.677 62 1.11E+01 34.114 31.551 67.489 5.613 7.922 0.949 0.099 0.003 0.739 1.691 63 3.92E+00 61.29 95.521 171.36 3.253 3.11 0.386 0.206 0.007 0.551 0.944 64 9.31E+00 45.097 120.841 184.917 3.077 2.532 0.3 0.148 0.005 0.492 0.797 65 1.03E+01 45.126 41.258 88.964 2.588 5.11 0.63 0.123 0.016 0.505 1.151 66 1.57E+01 53.374 106.726 177.098 2.706 3.754 0.457 0.168 0.014 0.48 0.951 Page 12 of 38 June 2009 Update Sub-basin AREA (km2) Surface Runoff (mm) Baseflow (mm) Total Water Yield (mm) Sediment (mg/ha) Organic Nitrogen (kg/ha) Organic P (kg/ha) Nitrate in surface runoff (kg/ha) Soluble Mineral P (kg/ha) Sediment bound mineral P (kg/ha) Total P (kg/ha) 67 3.85E+00 59.375 71.051 137.048 2.903 4.243 0.522 0.191 0.005 0.466 0.993 68 8.70E-03 43.584 63.164 112.436 0.007 0.009 0.001 0.094 0.001 0.001 0.003 69 1.80E+00 44.714 46.247 95.734 2.079 3.344 0.417 0.135 0.004 0.344 0.765 70 1.30E+01 26.598 126.714 163.971 1.14 1.639 0.199 0.077 0.003 0.215 0.417 71 7.55E+00 37.126 32.073 71.802 2.793 4.819 0.579 0.094 0.007 0.482 1.068 72 1.40E+00 53.081 82.98 143.678 3.572 5.059 0.614 0.176 0.005 0.548 1.167 73 3.34E+00 45.478 55.954 107.349 1.931 3.024 0.382 0.129 0.004 0.336 0.722 74 8.29E+00 59.304 81.656 151.916 3.641 4.695 0.59 0.187 0.005 0.512 1.107 75 1.24E+01 55.807 87.467 155.92 4.042 5.144 0.618 0.183 0.014 0.651 1.283 76 2.75E+00 96.8 81.318 192.216 12.309 9.954 1.204 0.411 0.012 1.557 2.773 77 1.13E+00 70.043 55.222 132.27 6.565 7.172 0.872 0.246 0.006 0.836 1.714 78 2.70E+00 68.549 64.252 144.007 4.496 5.311 0.699 0.259 0.008 0.717 1.424 79 1.25E+00 68.765 58.196 139.176 4.478 4.673 0.581 0.235 0.006 0.63 1.217 80 1.36E+01 40.901 125.391 186.441 2.599 3.061 0.369 0.132 0.004 0.408 0.781 81 3.33E-01 47.632 90.536 159.356 4.14 4.9 0.674 0.138 0.003 0.388 1.065 82 1.71E-02 35.8 84.674 120.944 1.205 2.99 0.397 0.09 0.004 0.207 0.608 83 9.91E+00 40.605 55.685 99.948 2.405 4.03 0.499 0.123 0.005 0.432 0.936 84 5.80E-01 49.712 86.352 148.054 1.111 1.33 0.175 0.132 0.003 0.17 0.348 85 9.08E+00 53.278 124.399 194.81 2.157 2.228 0.262 0.185 0.021 0.465 0.748 86 1.68E+00 33.15 34.701 69.55 1.149 2.413 0.299 0.092 0.004 0.242 0.545 87 1.96E-01 53.203 84.646 154.727 0.935 1.425 0.2 0.137 0.002 0.121 0.323 88 7.79E+00 39.372 118.206 168.503 1.84 2.465 0.3 0.125 0.005 0.342 0.647 89 8.69E+01 26.772 81.711 113.273 1.679 2.725 0.336 0.076 0.003 0.292 0.631 90 1.62E+01 53.325 61.977 120.823 2.375 4 0.494 0.197 0.006 0.423 0.923 Page 13 of 38 June 2009 Update The SWAT model predictions are subject to the following limitations: • Loads are subject to all the same limitations as those presented in the report: Fort Cobb Basin – Modeling and Land Cover Classification 2003; • The loads are from upland sources only and do not consider bank or stream bed erosion, instream nutrient processes, or deposition of sediment in reservoirs or flood control structures on main channels; • These data contain significantly more uncertainty than absolute load predicted to the lake or basin outlet. With limited calibration data, these data would be best utilized to relatively rank subbasins in terms of their nutrient contributions. Although these predictions are subject to limitations, the estimates provide valuable information about areas contributing most significantly to watershed loading and suggest areas where incentives and other implementation programs should be targeted to have the greatest impact on water resources. These high priority subwatersheds (highest contributing watersheds as depicted in Figure 3) account for approximately 66.17 or 20% of the 329.35 square miles in the watershed and about 30% of the load. Including the next highest contributing set of subwatersheds increases the area to 210.83 square miles or 47% of the watershed and approximately 61% of the load. The TMDL estimated phosphorus loading from septic tanks to be 3,608 kg/year, assuming all watershed residents used septic systems and using a worst case scenario where: • All septic tanks were failing, • Every household was assumed to have one septic tank, equaling 1,124 septic tanks in the watershed, • Effluent from the tanks (11.6 mg P/L) drained directly to streams and lakes, • Persons in the watershed produced 75 gallons of wastewater per day. This loading would be approximately five percent of the total phosphorus loading to the watershed. Given that this is an over estimate of the loading from the current systems, the TMDL determined that loading from septic tanks was insignificant. The primary crops grown in the watershed are wheat (80% of cropland), peanuts, sorghum, and cotton (Storm et. al 2003). Wheat, peanuts, and sorghum are the landuses that provided the highest nutrient and sediment loading in the watershed (Table 3); croplands, which are about 50.4% of the total land in the watershed, account for 90.4% of total P load. With the loss of peanut subsidies, peanut pro-duction has declined in the watershed, and many formerly peanut fields have been con-verted to cotton fields. The SWAT model esti-mated that the conver-sion of peanuts to cotton without BMPs to address cotton could result in increased phosphorus and sediment loading to the lake (Table 4). Cotton is one of the row crops produced in the Fort Cobb Watershed (photo courtesy of Storm et al. 2003). Page 14 of 38 June 2009 Update Table 3. SWAT simulated loads by land cover for the Fort Cobb Basin for the period 1/1990 - 10/2001 (from Storm et al. 2003). Land Cover Fraction of Basin (%) Surface Runoff (mm) Total Stream Flow (mm) Sediment (Mg/ha) Total N (kg/ha) Total P (kg/ha) Forest 6.0% 23.98 178.98 0.01 2.20 0.01 Pasture-Range 41.4% 40.34 105.36 1.61 3.60 0.62 Peanut 7.1% 61.76 147.15 4.06 7.74 1.87 Sorghum 2.8% 96.02 161.33 3.16 6.95 1.20 Urban 0.1% 87.60 100.95 0.05 1.20 0.09 Water 2.1% 0.00 0.00 0.00 0.00 0.00 Wheat for Grain 30.8% 57.58 121.60 5.88 9.90 1.91 Grazeout Wheat 9.7% 56.10 118.77 5.16 8.69 1.81 Basin Average --- 48.47 118.46 3.36 6.26 1.19 Table 4. Load summary for Fort Cobb Basin as predicted by the SWAT model (from Storm et. al 2003). Crop Scenario Runoff (CMS) Total Water Yield (CMS) Sediment (Mg/yr) Total P (kg/yr) Total N (kg/yr) Current 1.37 3.05 301,277 108,031 543,615 Peanuts converted to cotton 1.28 2.95 307,131 110,103 543,461 Further details about the estimation of causes and sources in the Fort Cobb Watershed can be found in the TMDL (ODEQ 2006) and SWAT model reports (Storm et. al. 2003). LOAD REDUCTIONS The draft TMDL estimated that a 78% phosphorus load reduction2 would be necessary to restore beneficial use support to Fort Cobb reservoir. This sets a goal of reducing phosphorus loading from 70,000 kg/yr to 15,400 kg/yr. The TMDL addresses both phosphorus and turbidity impairment to the reservoir because most phosphorus is found attached to sediment, one of the primary causes of turbidity. The TMDL reasons that if phosphorus is reduced to meet water quality standards, then turbidity levels in contributing streams will also be reduced to a level that will meet the turbidity standard. Fortunately, BMPs recommended by the TMDL will also work to address the other sources of impairment in watershed streams including pathogens. The TMDL also estimates that every 1.0% reduction in phosphorus will correspond to a 1.33% reduction in total nitrogen and a 1.5% reduction in sediment delivery to the lake. Further explanation of the methodology for arriving at the 78% load reduction can be found in the TMDL and SWAT model reports (ODEQ 2006; Storm et. al 2003). 2 This includes the load reduction to allow for a margin of safety and potential growth in the watershed. Page 15 of 38 June 2009 Update CRITERIA Fort Cobb Reservoir’s designated beneficial uses include public and private water supply, warm water aquatic community, agriculture, municipal and industrial uses, primary body contact recreation, and aesthetics. The reservoir is the primary drinking water source for the Cities of Anadarko and Chickasha. The goal of the TMDL is to reduce the 1998 – 2001 loading to the lake of approximately 70,000 kg P/year to 15,400 kg P/year. That load reduction is based on the following endpoints, based on Oklahoma’s Water Quality Standards (OWRB 2004a, b): • Trophic State Index (chlorophyll-a based) for Fort Cobb Reservoir less than 62 • Dissolved Oxygen (surface water) o Summer (June 16 – October 15): 4.0 mg/L o Seasonal (October 16 – June 15): 5.0 mg/L • Anoxic volume in Fort Cobb Reservoir less than 50% of water column. Additional criteria that apply to causes of impairment in the watershed are (OWRB 2004): • Turbidity (only applicable during baseflow) 25 NTU for lakes 50 NTU for streams • Coliform bacteria Monthly geometric mean <5000 colonies/100 ml at point of intake • <5% of total samples in any 30 day period will total coliform exceed 20,000 colonies/100 ml • Enterococci bacteria Geometric mean of 33 colonies/100 ml • Escherichia coli (E. coli) Geometric mean of 126 colonies/100 ml • Warm Water Aquatic Community IBI = 22 These criteria stem from Oklahoma’s Water Quality Standards (OWRB 2004a). The procedures by which the data must be collected and analyzed to verify whether or not these criteria have been met are identified in Oklahoma’s Use Support Assessment Protocols (OWRB 2004b). Both of these documents fall under the jurisdiction of the Oklahoma Water Resources Board. NPS MANAGEMENT MEASURES According to the TMDL, croplands account for about 90% of the phosphorus loading in the watershed; therefore, load reduction efforts should focus on cropland (Table 3). The TMDL SWAT modeling applied various scenarios relative to landuse and BMPs used in the watershed to estimate the possible solutions to achieve the recommended 78% phosphorus load reduction. As shown in Table 5, below, the TMDL evaluated the Page 16 of 38 June 2009 Update effectiveness of various BMPs to achieve a phosphorus load reduction. No single BMP type will fully address the required load reduction; a combination of BMPs will be necessary. Table 5. Load reductions for different BMPs (from ODEQ 2006). Practice % Reduction In Total Basin Load Sediment Total N Total P No-till wheat and row crops -51.10% -42.80% -34.40% No winter cover on row crops 9.20% 11.10% 6.80% Worst 1% of cultivated land to pasture -6.00% -3.20% -4.40% Worst 2.5% of cultivated land to pasture -11.50% -8.10% -8.00% Worst 5% of cultivated land to pasture -18.00% -13.90% -12.30% Worst 7.5% of cultivated land to pasture -23.00% -18.30% -15.50% Worst 10% of cultivated land to pasture -26.50% -21.40% -17.90% Worst 15% of cultivated land to pasture -33.00% -27.10% -22.10% Worst 20% of cultivated land to pasture -37.50% -31.10% -25.10% Worst 25% of cultivated land to pasture -41.50% -34.70% -27.70% Worst 35% of cultivated land to pasture -48.00% -40.40% -32.00% Riparian Buffer -75% to -90% -35% to -55% -40% to -60% Nutrient Management -15% -35% In addition to the BMPs mentioned above, grade stabilization structures are necessary in this watershed due to the highly erodible soils; damage is already evident in the watershed with extensive gullying and rill erosion being relatively common. The SWAT model could not predict areas where grade stabilization structures would be necessary, nor could it predict the loading reduction that would result from installation of these structures. Such a prediction would require extensive reconnaissance in the watershed and ultimately, a conservation plan for every producer. However, an estimate of the need can be roughly extrapolated from the need demonstrated with the FY 2001 §319 project, where approximately 25% of the cooperators required grade stabilization structures to reduce erosion. The FY 2001 §319 project funded a targeting exercise based on the SWAT model that was later expanded into the TMDL. Results of that exercise were used to focus implementation into areas of origin for the bulk of the sediment and phosphorus loading. Subsequently, the OCC used these results in conjunction with the recommendations of the TMDL as part of a FY 2005 §319 project. Figure 6 displays results of the 2003 targeting effort. Implementation of BMPs in the red areas was expected to reduce nutrient loading to the watershed by approximately 50%. Implementation of BMPs in the yellow areas could reduce nutrient loading by an additional 30%. Page 17 of 38 June 2009 Update Figure 6. Location of areas in Fort Cobb Watershed most likely contributing the greatest portions of total sediment, and therefore phosphorus loading. Page 18 of 38 June 2009 Update TECHNICAL AND FINANCIAL ASSISTANCE NEEDED The amounts of technical and financial assistance needed are closely tied to one another. All programs to implement NPS BMPs outlined in the above section require technical assistance in the form of a plan writer, certified by the NRCS. Such a position typically costs a total of $42,000 - $61,000 per year, including benefits. NRCS funds this technical support for their own programs (mainly EQIP in this watershed), but programs like a Conservation Reserve Enhancement Program or §319 must fund technical support through some other means. In addition, part-time help may be required to address the needs of the tri-county area. Any staff that provides technical support would be best served to work through the local conservation district and NRCS offices, as these are the places local landowners are most comfortable in going to for technical support. Therefore, it is beneficial to provide assistance to these districts to help support the program. Funding necessary to implement the BMPs recommended by the TMDL is estimated using a combination of best professional judgment, based on experience in the watershed, and use of the PRedICT model. These values are seen in Table 6. An initial value of approximately $16 million has been estimated as necessary to implement the TMDL recommended practices. However, this value will likely change as the programs evolve and the Watershed Based Plan is updated. The actual amount of funding for BMP implementation in each of the OCC’s projects is given below: 2001 Fort Cobb project (2001-2005): 128 cooperators $1,386,611 of practices installed, total: $365,650 from State funds $498,054 from Federal 319 funds $522,907 from landowners (38%) 2005 Fort Cobb project (2005-2008): 60 cooperators $865,403 of practices implemented, total: $502,556 from State funds $290,250 from Federal 319 funds $72,597 from landowners (8%) Table 7 provides some estimates of funding planned or already implemented for technical support in the watershed. Some of these are multi-year efforts, and some are single-year efforts. At a minimum, around $160,000 is required for technical support each year to provide support to the conservation districts and personnel to meet with landowners and draft conservation plans. Table 8 estimates funding necessary to support monitoring needs in the watershed. Not all information is available at this time regarding monitoring costs for USGS or Bureau of Reclamation; however, available information suggests that at least $230,000 is needed every five years. Page 19 of 38 June 2009 Update Table 6. Funding Needs for Technical Support for Implementation of BMPs. Project/Funding Source Task Federal State Cost Share Funds Total FY 2001 §319 Fort Cobb Project- five year period On-Site Coordinator $225,000 $225,000 Plan Writer $80,000 $80,000 District Support $75,000 FY 2005 §319 Fort Cobb TMDL Implementation Project- salaries and support for 2 years beyond 2001 project On-Site Coordinator $121,000 $121,000 District Support $15,000 $15,000 Conservation Reserve Enhancement Program (CREP)- funding for 2-3 years of technical support Plan Writer $94,000 - $312,000 $94,000 - $312,000 NRCS District Conservationists (3) $52,000 - $85,0003 $52,000 - $85,000 Total $609,800 - $642,800 $94,000 - $312,000 $703,000 - $954,800 3 Estimated from GS 9/11 salary range + benefits. Page 20 of 38 June 2009 Update Table 7. Funding Necessary to Implement TMDL Recommended Practices to Restore Beneficial Use Support to Fort Cobb Reservoir. Load Reduction TMDL Recommended BMP Project/Funding Source TMDL Federal State/Local Total target Anticipated from this project 17% 7% No-till in 50% of wheat and other row crop FY 2005 §319 Fort Cobb TMDL Implementation $672,380 $586,754 $1,259,1344 10% CSP, EQIP $930,000 25% Convert 20% of worst cultivated land to pasture FY 2001 §319 Fort Cobb Project EQIP, CSP $2,050,0005 30% 1% Riparian Areas in 60% of watershed FY 2001 §319 Fort Cobb Project $38,802 $25,867 $64,669 15% 2010 CREP $4,726,790 $945,358 $5,672,148 14% EQIP, CRP, CSP $4,235,204 $1,058,801 $5,294,005 31.5% 31.5% Nutrient Management Plans for 90% of producers FY 2001 and 2005 §319 Programs, EQIP, CRP, CSP $375,0006 ??? ??? Grade Stabilization Structures FY 2001 §319 Fort Cobb Project $92,804 $61,870 $154,674 ??? EQIP,??? Total $15,799,630 4 Represents an estimated start-up costs for no-till on 39% of cropland based on purchase of no-till drills for the 4 conservation districts, 30% cost-share on purchase of 10 drills for landowners, and $10/acre incentive payment (rate recommended by Fort Cobb WAG) for a three year period. Does not include technical support costs seen in Table 3. 5 Assumes a cost of $51 per acre (based on pasture costs in 20% of cultivated land (40,192 acres) 6 $5.00/acre/year for 90% of all crop and pastureland in the watershed, based on annual incentives offered through other State 319 programs, plus annual cost of soil testing. Most likely would only need to apply to all cropland, as few producers fertilize pasture, which would reduce costs to $250,000 annually. Page 21 of 38 June 2009 Update Table 8. Monitoring Funding Needs Associated with Fort Cobb Watershed. Monitoring Program Parameters assessed State Federal Total OCC Rotating Basin Stream water quality, biological community, habitat, hydraulic budget, riparian condition, landuse / landcover, $10,000 - $30,000 every 5 years $10,000 - $30,000 every 5 years OWRB BUMP Program Lake Water Quality $10,000 annually $10,000 annually Watershed modeling (OSU, ODEQ, ARS) Landuse / Land Cover, BMP implementation, Load reduction $150,000 every 5 years USGS Groundwater/Surface Water Quality, Load reduction ??? ??? Bureau of Reclamation ??? ??? ??? IMPLEMENTATION SCHEDULE The TMDL recommends a 78% load reduction from loading seen between 1998 and 2001. Implementation towards this load reduction has progressed with formal programs such as the FY 2001 and 2005 §319 Projects and passive changes resulting from the loss of peanut subsidies. Measures of water quality changes as a result of those efforts are not fully available at this time; however, information is available on the implementation completed through the FY 2001 and 2005 programs such that an estimate of potential load reductions attributed to the project activities thus far has been estimated. These reductions are seen in Table 7 under the “Load Reduction” column under “Anticipated from this project”. These efforts are initial steps towards full implementation of the TMDL recommendations. Table 9 presents a schedule towards implementation of the remaining TMDL recommendations. Included in table 9 is a column that schedules the evaluation of each program. Failure of the programs to meet planned implementation level or load reduction goals will result in adaptations, as possible during the program period or, as necessary, with follow-up, supplemental programs until the load reduction goals have been met. The ARS CEAP program provides an excellent opportunity to evaluate the progress of these programs towards the TMDL-established goals. The Watershed Based Plan will be updated following the completion of the ARS effort in 2010 to summarize its findings and to make necessary adaptations to reach the TMDL load reduction goals. Page 22 of 38 June 2009 Update Table 5. Schedule for Implementation of TMDL-Recommended Practices. TMDL-recommended practice Program proposed to implement Begin Date Completion Date Date to evaluate Agency(ies) / Group(s) involved No-till 50% of row crops and wheat pasture FY 2005 §319 Project October 2005 January 2009 Annually during project, and following completion of the CEAP program. OCC, conservation EQIP, CSP, ??? Immediate Ongoing districts, USDA Convert 20% worst cultivated land to pasture FY 2001 §319 Project7 October 2001 September 2006 Annually during the project, and following completion of the CEAP program. OCC, conservation districts, USDA USDA Programs such as EQIP, CRP, etc. ongoing ongoing following completion of the CEAP program NRCS, FSA, ARS, Conservation Districts Riparian Buffers in 60% of Watershed FY 2001 §319 Fort Cobb Project October 2001 September 2006 Annually during the project, and following completion of the CEAP program. OCC, conservation districts, USDA 2010 CREP 2010 2025 Annually during the project period FSA, NRCS, OCC, Conservation Districts EQIP, CRP, CSP, and ??? ongoing ongoing following completion of the CEAP program NRCS, FSA, ARS, Conservation Districts Nutrient Management Plans for 90% of Producers FY 2001 and 2005 §319 Programs, EQIP, CRP, CSP, and ??? ongoing ongoing Annually during the projects, & following completion of the CEAP program NRCS, FSA, ARS, Conservation Districts, OCC Grade Stabilization Structures FY 2001 §319, EQIP, CSP, and ??? ongoing ongoing Annually during the project & following completion of the CEAP program NRCS, FSA, ARS, Conservation Districts, OCC 7 The project did not implement much of this conversion; however, based on recommendations of the TMDL, the Project Coordinator attempted to contact landowners of the worst-cultivated lands to encourage them towards pasture conversion using either the 319 program or USDA programs. Page 23 of 38 June 2009 Update The following is a summary of the implementation achieved through the OCC’s 2001 and 2005 §319 projects (2001-2008): 21,086 acres of no-till farming 32 grade stabilization structures 8 diversions, 7 grassed waterways, and 2 terraces 230 acres of riparian area exclusion fencing 1 stream crossing 10,767 acres of cropland converted to pasture 957 acres of grass planting for pasture improvement 35,030 linear ft of cross-fencing 4 wells 4 septic systems Visible improvements from no-till implemented through the §319 program are obvious throughout the watershed. Often, large piles of sandy soil accumulate along fence lines and in fields when dry and windy conditions occur in this area. No-till helped to hold moisture in the soil and reduce the amount of soil lost by wind and rain erosion, as seen in the photos below (Figure 7). The first two photos are of a no-till field, while the next two photos are of an adjacent, conventional till field. Much of the wheat in the conventional till field has been covered by soil which blew or washed over the plants. No-till wheat field Fence along no-till wheat field Figure 7. Two adjacent wheat fields, the top in no-till and the bottom in conventional till. Conventional till wheat field Fence along conventional till wheat field Eroded soil mounded along fence line Eroded soil covering wheat in field Fence along conventional till Conventional till wheat field wheat field Page 24 of 38 June 2009 Update The OCC’s no-till program has resulted in implementation of almost 30% of the TMDL goal for no-till. An additional 30% of row crops have been converted to conservation tillage, so at least 60% of the row crop acreage in the watershed is now in some form of conservation tillage (Table 10). In addition, approximately 63% of the TMDL goal for converting row crops to pasture has been achieved through the §319 program. NRCS EQIP has provided funding for both no-till and conservation tillage as well, so additional progress toward the overall TMDL goal has been made. Table 10. OCC §319 progress toward TMDL goals, 2001-2008. Total conventional row crop in basin at start of project: 98,289 acres BMP Total Amount Implemented (acres) Goal for TMDL (acres) % Towards TMDL Goal Row Crop Converted to No-Till 16,401 58,973 27.8 Row Crop Converted to Conservation Tillage 17,286 58,973 29.3 Convert Worst Row Crop to Pasture 12,462 19,658 63.4 Establish Riparian Buffers 169 8,547 2.0 A phosphorus load reduction of approximately 20% has already been accomplished since 2001 due to a dramatic change in crop production in the watershed (ODEQ 2006). Specifically, many acres that were used for peanut production have now been converted to wheat production or pasture. According to the SWAT watershed model (Storm et al. 2006), if there was 100% conversion of row crops and wheat to no-till, total phosphorus loading would be expected to decrease by 34%. Based on the conversion of 16,000 acres to no-till, total phosphorus loading should be reduced by approximately 6%. The maturation of other BMPs, installed as part of the 2001 and 2005 projects, will further reduce the phosphorus loading in the watershed. Approximately one-third of the implementation from 2001-2008 occurred in areas that were expected to be contributing high levels of phosphorus, according to the SWAT model: • Of the 9,188.6 acres that were in the top 10% of phosphorus load supplying areas, 32% now have BMPs on them; • Of the 10,033.2 acres in the next 10% of high phosphorus areas, 27% have BMP implementation. Figure 8, below, shows the overlay of implementation and targeting. Further details about the OCC implementation projects can be found in the final reports associated with the 2001 and 2005 projects. Page 25 of 38 June 2009 Update Figure 8. Overlay of regions of high phosphorus loading (targeted regions) onto areas of BMP implementation through the §319 program, 2001-2008. A Conservation Reserve Enhancement Program (CREP) is planned for the Fort Cobb watershed beginning in 2010. This project aims to restore stable riparian vegetation and riparian buffers and to reduce livestock access to floodplains. This will result in reduced overland flow of pathogens and phosphorus to the streams and will lessen streambank erosion by stabilizing stream banks. Overall, this will lead to better water quality, lower maintenance requirements to the road and highway system, and will help to preserve existing floodplain cropland, pasture, and rangeland. The WBP will be updated at the conclusion of the CREP signup to estimate the load reductions expected from this implementation. Page 26 of 38 June 2009 Update INTERIM MILESTONES Interim milestones towards addressing the recommendations of the TMDL will continue to be developed as activities are implemented under the Watershed Based Plan. Some of these have already been completed through various project workplans, others are ongoing or planned. Project Description Responsible Party Target Date Complete TMDL Compile watershed loading model and link to lake model ODEQ, OSU 2003 X Calibrate model to water quality monitoring data ODEQ 2003 X Develop draft TMDL ODEQ 2004 X Solicit public input to draft TMDL ODEQ 2005 X Submit to EPA ODEQ 2005 X 2001 §319 Project Hire Local staff- project and education coordinators and plan writer OCC, Conservation Districts (CDs) 2002 X Establish agreements with CDs OCC, CDs 2001 X Establish a WAG and EdWAG CDs 2001 X Complete GIS-Based Targeting OCC, WAG 2001 X WAG selection of BMPs and cost-share rates WAG, OCC 2001 X Watershed Implementation Plan OCC 2002 X BMP Demonstration OCC, CDs 2002 – 2006 X Develop education program to educate producers and other watershed citizens about problems and solutions EdWAG 2002 X Identify oil and gas related sources in the watershed Corp. Comm 2001 - 2002 X Hire companies to plug abandoned wells Corp. Comm. As needed Ongoing Educate current operators and when necessary take enforcement actions Corp. Comm. As needed Ongoing Sample creeks, streams, and agricultural lands in watershed for pesticides and fertilizer-related parameters ODAFF8 2002 X Conduct pesticide education programs ODAFF 2001 - 2003 Ongoing Summary of Project Activities including estimation of load reduction due to practices implemented and comparison of implementation to TMDL recommendations OCC, ODAFF, Corp. Comm. 2006 X 8 Oklahoma Department of Agriculture, Food, and Forestry Page 27 of 38 June 2009 Update Project Description Responsible Party Target Date Complete 2005 §319 Project Further delineate targeted areas based on TMDL recommendations OCC 2006 X Implement no-till practices OCC, CDs 2006 - 2008 X Update WBP OCC 2008 X Follow-up GIS evaluation of implementation OCC 2008 - 2009 X Instream Habitat Monitoring to Support ARS CEAP Project and evaluate success of BMPs OCC 2006 - 2008 X CEAP Water Quality monitoring, watershed modeling, and compilation of BMPs implemented in watershed to evaluate impacts of BMPs ARS, NRCS, OCC 2005 - 2010 Ongoing CREP Develop program plan with FSA and NRCS OCC, FSA, NRCS 2003 – 2005 X Secure State match and Governor’s approval OCC, OSE 2007 X Submit plan to USDA OCC, FSA, NRCS 2009 Planned Begin implementation OCC, FSA, NRCS 2010 - 2013 Planned EQIP Explore possibility of declaring watershed a special emphasis area to secure higher funding level FSA, NRCS, CDs Annually Ongoing Continue to implement EQIP practices annually in watershed CSP Designate watershed as a CSP priority watershed FSA, NRCS, CDs ??? ??? WBP Update Watershed Based Plan and evaluation of progress towards TMDL goals with watershed modeling at least every five years or more frequently upon completion of major tasks/projects OCC, WAG 2012 Ongoing Continue water quality monitoring to identify sources, causes, and progress towards TMDL goals OWRB, Bureau of Recl., USGS, OCC, ARS Annually Ongoing PUBLIC OUTREACH Many local efforts, as well as efforts by state and federal agencies and other organizations, are collectively contributing to the Public Outreach efforts in the Fort Cobb Watershed. Public outreach will need to be continued in order to reach the water quality goals of restoring beneficial use support and attaining water quality standards in the watershed. This section identifies those agencies, organizations, and services that are active in the Page 28 of 38 June 2009 Update watershed (in no particular order). To varying degrees, these groups have been, and will continue to be, active in development and expansion of the Watershed Based Plan and other planning efforts in the watershed. The roles of these groups and programs are summarized below: 1. Deer Creek, West Caddo, North Caddo, and Mountain View Conservation Districts These agencies are critical to ensuring participation of local landowners in water quality improvement programs. Local Conservation Districts are generally the most effective means to bring a large federal or state program to private citizens because the local agencies know the local people. Local agencies often have the most accurate knowledge concerning current land management practices and local needs. In addition, these agencies have existing programs and mechanisms directed towards the goals of the WBP. The Conservation Districts, partnered with the OCC, NRCS, and Cooperative Extension, have been among the primary agencies responsible for public outreach in the watershed. The districts and NRCS work one-on-one with citizens of the watershed to reduce pollution and educate about the importance of protecting water resources. These groups also organize or participate in seminars, training sessions, and meetings to interact with local people and provide technical assistance and information. The Deer Creek Conservation District has a very active education program through its outdoor classroom. This program targets mainly elementary school children and teaches them about environmental issues. In addition, Deer Creek has housed the Education Coordinator for the FY 2001 and 2005 §319 Fort Cobb Projects and served as the hub for education activities of that project. 2. Watershed Advisory Group (WAG) and Education Watershed Advisory Group (EdWAG) The success of water quality protection programs in the Fort Cobb Watershed depends on the approval and cooperation of the local landowners and various government agencies. The WAGs were made up of local shareholders in the watershed (including private citizens, representatives of local industries, and local government) who provided guidance in delivering the §319 programs based on information supplied to them by technical agencies in conjunction with their knowledge of the needs of the watershed residents. The WAGs were developed to help insure that the programs most effectively worked towards reducing water quality impacts, but, at the same time, met the needs of and were acceptable to the local producers and other landowners. The WAG recommended the practices and cost-share rates to reduce the NPS pollution problems in the watershed. The EdWAG considered the issues in the watershed and recommended an education program to help inform watershed citizens about those issues using a “show and tell” approach. 3. The Oklahoma Conservation Commission (OCC) With the 2001 project, the OCC devoted almost $2.3 million towards a program to educate citizens and implement best management practices to reduce nonpoint source pollution in the watershed. A portion of these funds support the WAG, a portion is devoted to Page 29 of 38 June 2009 Update identifying the major sources in the watershed and monitoring the success of the program, another portion is devoted towards education, but the majority of the funds provides cost-share assistance to farmers to implement WAG-recommended and OCC-approved BMPs to protect the water resources of the watershed. This effort was extended through the FY 2005 program, which focused on recommendations of the TMDL, primarily no-till. The OCC’s main function is to provide oversight for successful completion of the program. To do this, they provide technical guidance and final approval to the WAG and local conservation districts for implementation of the BMPs. The OCC implemented an education program targeted towards citizens of the watershed whose change in behavior could have the most substantial impacts on water quality. The OCC is also responsible for monitoring the success and providing administrative support for the §319 projects, and working with NRCS and FSA to implement a CREP Program in the watershed. In addition, Blue Thumb, OCC’s education program, is active in the Fort Cobb watershed. Streams are monitored by volunteers and school groups are taught about water quality through this program. 4. Oklahoma Cooperative Extension Service (OCES) The Oklahoma Cooperative Extension Service (OCES) is another leader in promoting water quality education efforts in the State, working closely with the conservation districts and the NRCS to promote water quality awareness. The OCES provides one-on-one meetings and education with landowners along with group presentations and other forms of technical assistance to improve awareness in the watershed. The OCES also develops and utilizes test plots and demonstration sites to educate producers about the effectiveness of certain best management practices. One such set of test plots, developed by the Oklahoma State University Cooperative Extension Service, was utilized to demonstrate methods of integrated pest management and effectiveness of more managed fertilizer application in wheat production. The OCES also holds public meetings and workshops to educate landowners on topics such as pesticide and fertilizer management, animal waste issues, and general BMPs. 5. NRCS Local Offices and FSA (USDA) The United States Department of Agriculture Natural Resource Conservation Service (USDA/NRCS) and Farm Services Agency (FSA) in Oklahoma have several programs active in or that could be expanded in the Fort Cobb Watershed. These programs include the Environmental Quality Incentives Program (EQIP), Conservation Reserve Program (CRP) and Conservation Reserve Enhancement Program (CREP), Wildlife Habitat Incentives Program (WHIP), and the Wetlands Reserve Program (WRP). These programs are employed by the USDA to help landowners protect natural resources. 6. Oklahoma Corporation Commission (Corp. Comm.) Corp. Comm., as the state agency with jurisdiction over oil and gas mining activities, has Page 30 of 38 June 2009 Update ongoing efforts in the watershed to identify and reduce impacts from oil and gas activities. These include efforts to identify location and severity of erosion related to well sites and pipelines, followed by cleanup by the operators and pipeline companies. Corp. Comm. will begin additional work in the watershed to further identify problem areas in the watershed and initiate educational and other actions for site operators. These efforts range in extent from informing landowners about who to contact in the case of pollution occurring at well sites or exploration sites to what best management practices can be utilized during exploration and operation of oil and gas sites. Another focus of additional planned Corp. Comm. activities includes efforts to reduce impacts from abandoned oil and gas activities. 7. Oklahoma Department of Agriculture, Food, and Forestry (ODAFF) The ODAFF has an ongoing project aimed at reducing impacts of fertilizers and pesticides to surface and groundwater in the watershed. The program has attempted to locate sources or likely sources of contamination from these fertilizers or pesticides and conduct educational programs to reduce the impact of those sources. 8. Bureau of Reclamation Fort Cobb Reservoir is owned by the Bureau of Reclamation, which has played an active role in the watershed with cooperative efforts towards water quality monitoring, land management, and education. 9. Agricultural Research Service (ARS) The ARS is currently pursuing a project to evaluate the success of BMPs implemented in the watershed through the Conservation Effects Assessment Project (CEAP). This program will involve water quality monitoring, watershed modeling, and cooperation with local conservation districts, NRCS, OCC and similar agencies to obtain current information on management practices in the watershed. Information will be shared regarding the success of programs and can be used to improve efficiency with cost-share and other implementation programs, as well as to evaluate progress towards meeting the goals of the TMDL. Youth education is a significant effort pursued by OCES, NRCS, and the conservation districts. Most youth education activities focus on general water quality maintenance and improvement and include activities such as 4-H group water quality monitoring and education, “Earth-Day-Every-Day” activities fair where hundreds elementary school children and some of their parents are exposed to environmental education, and various other training sessions. Newspaper articles and other media are a method that can be used to inform citizens of the watershed about programs focused on water quality. The OCES, Conservation Districts, and NRCS often contribute articles that were released to local papers, covering a wide range of topics related to water quality, and more specifically, advertising education Page 31 of 38 June 2009 Update events and programs. Many articles serve as promotions for various upcoming trainings or other events. Other media related activities such as radio spots and logo contests can be used to further the efforts of the program. However, in using media and advertising in education programs, efforts must focus on measurable results. An information article about water quality is not enough; the article must be associated with some additional effort that is likely to change behaviors. Information alone doesn’t often change people’s behaviors; people must be persuaded to change their behavior. Persuasion is more likely to occur as part of a program of repeated contact and interaction than as the result of a well-written article in a newspaper. Current outreach programs in the watershed will need to expand and perhaps partially redirect their public outreach efforts to work towards more measurable results. Although current education efforts are valuable programs, efforts may need to be expanded to insure that the target audience is being reached. The target audience is the people whose change of behaviors could have the most substantial benefits to water quality. In other words, the target audience in the Fort Cobb Watershed should include people such as county commissioners and road maintenance crews, agricultural producers, and people in the oil and gas industry, among others. Existing and planned outreach programs will need to coordinate among themselves and with other ongoing efforts in the watershed in order to educate more watershed citizens and more importantly, change behaviors of land users in the watershed. Public Outreach to assure support of this and future evolutions the Watershed Based Plan will come from: • Conservation District Newsletter and/or website • Continued support the WAG or a similar group • Public meetings and listening sessions held throughout the local communities (and eventually, throughout the watershed) • Regular media coverage of activities/issues (both at local and State levels) • Education programs such as the ones developed in the 2001 and 2005 §319 projects that involve segments of the community ranging from school children to agricultural producers to homeowners and lakeside residents • Programs that encourage local citizens to experience “ownership and understanding” of environmental issues such as volunteer monitoring, clean-up events, and other educational grassroots efforts to address the problem MONITORING PLAN Every Watershed Based Plan requires a monitoring plan to gage overall success of restoration and remediation efforts. The goal of the monitoring plan for this WBP will be to expand current monitoring efforts into a long-range monitoring program with clearly defined milestones that will oversee the progress towards the TMDL recommended load reductions, restoration of the beneficial use support in the watershed, and preservation of natural resources for future generations. Page 32 of 38 June 2009 Update The monitoring plan for this WBP provides for development of individual monitoring plans and associated quality assurance plans and Standard Operating Procedures for each underlying project or effort working toward the ultimate goal of restoration of beneficial use support. These monitoring efforts must be based on Oklahoma’s Water Quality Standards and Use Support Assessment Protocols, which define the process by which beneficial use support can be determined. Technical assistance in developing these plans can come from various sources including the Oklahoma State Agency peer review process, and the Oklahoma Water Quality Monitoring Council. In addition, local stakeholders need to be involved in developing these plans to ensure that the plans address monitoring needs identified by stakeholders and that stakeholders remain informed about watershed monitoring activities. Monitoring methodologies specified in this WBP have been selected to provide: 1) a quantifiable measure of changes in parameters of concern, 2) success measures that can be easily understood by cooperators and stakeholders with a variety of technical backgrounds, and 3) consistent, compatible information throughout the watershed. As the WBP evolves, it is anticipated that this list will expand and contract. Monitoring will focus on the primary causes of impairment, as listed in the 303(d) list, but will also consider related causes that may exacerbate the impacts of the primary causes or may ultimately reach impairment levels without improved management. The primary types of monitoring to be conducted in the Fort Cobb Watershed include: • Surface water quality: nutrients, sediments, suspended solids, fecal bacteria, dissolved oxygen, temperature, pH, conductivity, alkalinity, hardness, turbidity, chlorophyll-a, pesticides, BOD • Hydraulic budget: in-stream flows, infiltration rates, aquifer recovery, groundwater levels • Groundwater quality: nutrients, metals, pesticides, pH • Landuse/Land cover: acreage in different landuses, quality and type of land cover, timing and other variables of associated management practices • Riparian Condition: extent and quality of riparian zones in the watershed, to include quality and type of vegetation, degree of impact or stability, condition of streambanks, and primary source of threat or impact • Aquatic Biological Communities: assessment of the condition of fish and benthic macroinvertebrate communities related to reference streams and biocriteria • BMP and other implementation effort coverages: type, extent, and when possible, specific location of practices to include an estimate of the potential load reduction effected by implementation • Behavioral change: participation in Watershed Based Plan-related activities and behavioral changes of affected communities • Sediment quality: nutrients, pesticides, other organics of concern With each WBP-related program, as well as for the WBP as a whole, baseline conditions will be established and monitored prior to implementation. A monitoring schedule and Quality Assurance Project Plan (QAPP) will be developed based on the type of project and Page 33 of 38 June 2009 Update timing of its implementation. Monitoring results will be reported to appropriate local, state, and federal entities as defined in the QAPPs. Baseline Data The baseline data to evaluate progress in the Fort Cobb Watershed has been established by the draft TMDL. This includes watershed data from primarily the period between 1998 – 2001. Specifically, this data is listed below: • 2000 census data to estimate watershed population and septic tank loading in the watershed • SWAT model used: o Land use was determined using data retrieved from June 10, 2001 30 m resolution Landsat TM imagery, a crop type breakdown based on 1999-2001 Oklahoma Agricultural Statistics Service data, and center pivot irrigation locations tagged from aerial photos. o 1 meter resolution Digital Orthophoto Quarter Quads (DOQQ) from 1995 for the entire Fort Cobb Basin were used in ground-truthing the Landsat data. o Soil test phosphorus for common agricultural land covers was derived from OSU county level averages for the period 1995-1999. o The model was calibrated for flow for the period January 1990 through October 2001 and validated for flow in Cobb Creek for the period 1975 – 1989. o 10 m USGS DEM o 200 m NRCS MIADS Soils Data o EPA Reach3 Streams o National Inventory of Dams o County level National Agricultural Statistics Service (NASS) cattle estimates for the period 1996-2000 were combined with land cover data to estimate the number of cattle within the basin. o Approximate CAFO locations and animal numbers were taken from an Oklahoma Department of Agriculture coverage available at the ODEQ website. The metadata are listed at the following address: http://www.deq.state.ok.us/deqmap/help/CAFO.htm. o Few stream gage data were available to calibrate the SWAT Model for the period Jan 1990 - Oct 2001. The only suitable gage was Cobb Creek near Eakley (USGS 07325800). The hydrologic calibration was performed almost entirely with data from this gage. Another gage downstream of the Fort Cobb Reservoir was also utilized as a check of the calibration. • OWRB and USFWS lake data collected in 1998-1999 was used to calibrate the model, and USGS and USFWS data collected in 2000–2001 was used to validate the model. • Atmospheric deposition of nutrients was based on annual data for Oklahoma downloaded from National Atmospheric Deposition Program’s web site. The average of the data from 1998 to 2001 was used in the model. • Hourly weather data, daily flow data, and daily loadings (from the SWAT model) to the lake were also used in the model. Weather data was obtained from Oklahoma Mesonet for the Fort Cobb station. The data includes hourly atmosphere pressure, Page 34 of 38 June 2009 Update air temperature, wind speed and direction, relative humidity, rainfall, and solar radiation. The hydraulic data was downloaded from Army Corps Of Engineer's web site (http://www.swtwc.usace.army.mil/FCOBcharts.html). The data includes daily inflow, release, pool elevation, and evaporation. Once again, 1998 – 1999 data was used in calibration, and 2000 – 2001 data was used in validation. Data Collection Responsibilities for Current and Future Monitoring Responsibility for the collection of additional data of the types described above will reside with project managers of the individual projects as spelled out their individual work plans. These project managers will be responsible for ensuring that the data is submitted to the ODEQ for inclusion in the Oklahoma State Water Quality Database, which will ultimately be uploaded to the National STORET database. Data reporting under individual workplans will also be the responsibility of the project managers. Monitoring results will be made public through the ODEQ’s website, at a minimum. In addition, project and monitoring results should be presented locally with a public meeting or to the WAG or similar group. In addition to those monitors to be identified in the workplans of the individual projects under this WBP, the following groups, at a minimum, will be involved in monitoring activities: • Oklahoma Water Resources Board: Beneficial Use Monitoring Program and Oklahoma Water Watch Monitoring Program • Oklahoma Conservation Commission: Rotating Basin Monitoring Program, Priority Watershed Project Monitoring, and Blue Thumb Project Monitoring • U.S. Geological Survey: Surface and Groundwater quality and quantity monitoring and special studies • Oklahoma Department of Agriculture, Food, and Forestry: soil sampling associated with CAFO regulations • ARS: CEAP associated monitoring • US Bureau of Reclamation Currently, the OCC has two sites in the Fort Cobb watershed which are part of the Rotating Basin monitoring program. These sites were sampled every five weeks from 2004-2006 and will be sampled again from 2009-2011. The parameters measured include water temperature, dissolved oxygen, pH, specific conductance, alkalinity, turbidity, instantaneous discharge, nitrate, nitrite, orthophosphate, total phosphorous, total Kjeldahl nitrogen (TKN), ammonia, chloride, sulfate, total suspended solids, total dissolved solids, 5-day biochemical oxygen demand (BOD5), and total hardness, as well as biological (fish and macroinvertebrates) and habitat data. The OWRB has 6 sites in the reservoir from which physico-chemical data are collected quarterly. The parameters measured include turbidity, true color, dissolved oxygen, metals, chloride, sulfates, total dissolved solids, pH, nutrients, temperature, and chlorophyll-a. The USGS has 5 “real time” gauging stations in streams in the Fort Cobb watershed, as Page 35 of 38 June 2009 Update well as one reservoir station and a meteorological station from which data may be accessed. The parameters collected include temperature, instantaneous discharge, conductivity, dissolved oxygen, pH, nutrients, suspended sediments, and alkalinity. The ARS has been monitoring 15 sites in the Fort Cobb watershed since 2004 as part of a national CEAP Watershed Assessment Study. Fortunately, Fort Cobb is included within one of the 12 benchmark watersheds in the US, and as a result, ARS, working collaboratively with the Great Plains RC&D, will complete an extensive bi-weekly water quality monitoring program. This program includes monitoring of the following paramters: pH, dissolved oxygen, conductivity, salinity, total dissolved solids, temperature, turbidity, oxygen reduction potential, nitrate concentration, ammonia concentration, suspended sediment, and phosphorus. The Great Plains RC&D will work collaboratively with ARS to contact farmers to obtain conservation and production management information relevant to the assessments. Benefits of the Monitoring Plan Implementation of this monitoring plan will enable Fort Cobb partners to meet the goals of the WBP, which is ultimately to restore beneficial use support to waters of the Fort Cobb Watershed. Implementation of the monitoring plan will help further define areas of the watershed where restoration activities should be focused to realize the optimum benefit for the investment as well as evaluating the impacts (realized and potential) of implementation efforts. Collection of the data described under this monitoring plan will help define the relative contributions from various sources in the watershed and the processes contributing to water quality degradation in the watershed. And finally, continued collection of this data and evolution of the monitoring plan for the watershed will allow the program to adapt to meet the changing needs of watershed protection in the Fort Cobb Watershed. Page 36 of 38 June 2009 Update REFERENCES ODEQ. 2008. The State of Oklahoma 2008 Water Quality Assessment Integrated Report. Oklahoma Department of Environmental Quality, Oklahoma City, OK. ODEQ. 2006. TMDL Development for Fort Cobb Creek Watershed and Fort Cobb Lake: FY 99 Section 319(h) Grant #C9996100-07 Final Report. Oklahoma Department of Environmental Quality, Oklahoma City, OK. OWRB. 2002. 2002 Report of Oklahoma Beneficial Use Monitoring Program. Oklahoma Water Resources Board, Oklahoma City, OK. OWRB. 2004a. Oklahoma Water Quality Standards, Oklahoma Administrative Code, Chapter 45. Oklahoma Water Resources Board, Oklahoma City, OK. OWRB. 2004b. Implementation of Oklahoma’s Water Quality Standards, Oklahoma Administrative Code, Chapter 46. Oklahoma Water Resources Board, Oklahoma City, OK. Storm, D. E., M.J. White, and S. Stoodley. 2003. Fort Cobb Modeling and Land Cover Classification Final Report. Oklahoma State University Biosystems and Agricultural Engineering. Stillwater, OK. Page 37 of 38 June 2009 Update APPENDIX A: TMDL Development For Cobb Creek Watershed And Fort Cobb Lake FY99 Section §319(h) Grant #C9996100-07 FINAL REPORT 2006 TMDL Development For Cobb Creek Watershed And Fort Cobb Lake FY99 Section 319(h) Grant #C9996100-07 FINAL REPORT Prepared by Paul Yue Oklahoma Department of Environmental Quality June 26, 2006 June 26, 2006 Table of Contents EXECUTIVE SUMMARY …………………………………………………………………….vi 1. INTRODUCTION................................................................................................................... 1 1.1 LATEST REVISION.................................................................................................................. 1 1.2 INTRODUCTION..................................................................................................................... 1 2. PROBLEM DEFINITION...................................................................................................... 6 3. APPLICABLE WATER QUALITY STANDARDS............................................................. 8 3.1 STANDARDS FOR STREAMS.................................................................................................... 8 3.1.a. Standards for nutrients ................................................................................................ 8 3.1.b. Standards for Dissolved Oxygen................................................................................ 10 3.2 STANDARDS FOR FORT COBB LAKE ..................................................................................... 10 3.3 PESTICIDE STANDARDS ....................................................................................................... 11 3.4 ANTIDEGRADATION POLICY ................................................................................................ 13 4. IMPAIRMENT ASSESSMENT & TMDL TARGETS...................................................... 14 4.1. STATUS OF NUTRIENT IMPAIRMENT IN STREAMS ................................................................ 14 4.1.a. Data from OCC.......................................................................................................... 14 4.1.b. Data from USGS ........................................................................................................ 16 4.2. STATUS OF NUTRIENT IMPAIRMENT IN FORT COBB LAKE................................................... 21 4.3. STATUS OF PESTICIDE IMPAIRMENT .................................................................................... 24 4.3.a. Lake Creek ................................................................................................................. 25 4.3.b. Cobb Creek ................................................................................................................ 25 4.3.c. Fort Cobb Lake .......................................................................................................... 27 4.4. STATUS OF DISSOLVED OXYGEN IMPAIRMENT FOR LAKE CREEK ....................................... 27 4.5. ENDPOINT AND TARGETS FOR FORT COBB TMDL.............................................................. 28 5. SOURCE ASSESSMENT ..................................................................................................... 29 5.1. ASSESSMENT OF POINT SOURCES ....................................................................................... 29 5.2. ASSESSMENT OF NONPOINT SOURCES ................................................................................ 31 5.2.a. Septic Systems ............................................................................................................ 31 5.2.b. Migratory Birds ......................................................................................................... 33 5.2.c. SWAT model for Nonpoint Source Loadings ............................................................. 36 6. MODEL DEVELOPMENT.................................................................................................. 41 6.1. MODEL SELECTION ............................................................................................................ 41 6.2. MODEL SETUP.................................................................................................................... 42 6.2.a. Watershed Representation ......................................................................................... 42 6.2.b. Lake Representation................................................................................................... 42 6.2.c. Selection of Model Simulation Period........................................................................ 43 6.2.d. Model Inputs .............................................................................................................. 45 6.3. MODEL CALIBRATION ........................................................................................................ 46 i June 26, 2006 6.3.a. Hydrodynamics .......................................................................................................... 46 6.3.b. Water Quality............................................................................................................. 47 6.4. MODEL VERIFICATION ....................................................................................................... 57 6.4.a. Hydrodynamics .......................................................................................................... 57 6.4.b. Water Quality............................................................................................................. 57 7. NUTRIENT REDUCTION................................................................................................... 64 7.1. LOAD REDUCTION .............................................................................................................. 64 7.2. MARGIN OF SAFETY AND LOAD ALLOCATION.................................................................... 71 7.3. BEST MANAGEMENT PRACTICES........................................................................................ 73 7.3.a. Effectiveness of Best Management Practices............................................................. 73 7.3.b. Options for Implementing BMPs ............................................................................... 80 8. PUBLIC PARTICIPATION................................................................................................. 82 9. REFERENCES...................................................................................................................... 84 10. APPENDIX A....................................................................................................................... 88 ii June 26, 2006 List of Figures FIGURE 1-1. COBB CREEK WATERSHED STUDY AREA................................................................. 5 FIGURE 3-1. STREAM ORDER (COBB CREEK WATERSHED).......................................................... 9 FIGURE 4-1. TOTAL-P, NO3/NO2 CONCENTRATION IN LAKE CREEK ......................................... 15 FIGURE 4-2. TOTAL-P, NO3/NO2 CONCENTRATION IN TRIBUTARY OF LAKE CREEK ................ 16 FIGURE 4-3. USGS MONITORING STATIONS (PROVIDED BY USGS) .......................................... 17 FIGURE 4-4. TOTAL-P, NO3/NO2 CONCENTRATION IN WILLOW CREEK .................................... 18 FIGURE 4-5. TOTAL-P, NO3/NO2 CONCENTRATION IN LAKE CREEK ......................................... 19 FIGURE 4-6. TOTAL-P, NO3/NO2 CONCENTRATION IN COBB CREEK......................................... 20 FIGURE 4-7. OWRB MONITORING STATIONS IN FORT COBB LAKE........................................... 22 FIGURE 4-8. USFWS MONITORING STATIONS........................................................................... 23 FIGURE 5-1 STORM WATER DISCHARGES ................................................................................. 30 FIGURE 5-2. 2000 U.S. CENSUS BLOCKS IN COBB CREEK WATERSHED .................................... 32 FIGURE 5-3. SUBBASIN LAYOUT USED IN THE COBB CREEK SWAT MODEL ............................. 39 FIGURE 5-4. LAND USE COVERAGE ........................................................................................... 40 FIGURE 6-0. ANNUAL PARTICIPATION FOR FORT COBB WATERSHED........................................ 44 FIGURE 6-1. BATHYMETRIC AND COMPUTATIONAL GRID OVERLAY - FORT COBB LAKE.......... 44 FIGURE 6-2. COMPARISON OF MODELED AND OBSERVED LAKE ELEVATION............................. 48 FIGURE 6-3. TEMPERATURE PROFILE NEAR THE DAM................................................................ 49 FIGURE 6-3A. TEMPERATURE PROFILE NEAR THE DAM................................................................ 50 FIGURE 6-4. CHLOROPHYLL-A CONCENTRATION NEAR THE DAM............................................. 51 FIGURE 6-5. CHLOROPHYLL-A IN THE MIDDLE PART OF THE LAKE ........................................... 51 FIGURE 6-6. CHLOROPHYLL-A IN THE UPPER PART OF THE LAKE.............................................. 51 FIGURE 6-7. TROPHIC STATE INDEX NEAR THE DAM ................................................................. 52 FIGURE 6-8. TROPHIC STATE INDEX IN THE MIDDLE PART OF THE LAKE................................... 52 FIGURE 6-9. TROPHIC STATE INDEX NEAR IN THE UPPER PART OF THE LAKE............................ 53 FIGURE 6-10. DISSOLVED OXYGEN NEAR THE DAM .................................................................... 53 FIGURE 6-11. DISSOLVED OXYGEN IN THE MIDDLE PART OF THE LAKE...................................... 54 FIGURE 6-12. DISSOLVED OXYGEN IN THE UPPER PART OF THE LAKE ........................................ 54 FIGURE 6-13. TOTAL-P NEAR THE DAM....................................................................................... 54 FIGURE 6-14. TOTAL-P IN THE MIDDLE PART OF THE LAKE ........................................................ 55 FIGURE 6-15. TOTAL-P IN THE UPPER PART OF THE LAKE........................................................... 55 FIGURE 6-16. LAKE ELEVATION (2000)....................................................................................... 59 FIGURE 6-17. WATER TEMPERATURE NEAR THE DAM (2000)..................................................... 59 FIGURE 6-18. TROPHIC STATE INDEX NEAR THE DAM (2000)...................................................... 60 FIGURE 6-19. TROPHIC STATE INDEX IN THE MIDDLE PART OF THE LAKE (2000) ....................... 60 FIGURE 6-20. TROPHIC STATE INDEX IN THE UPPER PART OF THE LAKE (2000).......................... 60 FIGURE 6-21. CHLOROPHYLL-A NEAR THE DAM (2000)............................................................... 61 FIGURE 6-22. CHLOROPHYLL-A IN THE MIDDLE PART OF THE LAKE (2000) ................................ 61 FIGURE 6-23. CHLOROPHYLL-A IN THE UPPER PART OF THE LAKE (2000)................................... 61 FIGURE 6-24. DISSOLVED OXYGEN NEAR THE DAM (2000) ......................................................... 62 FIGURE 6-25. DISSOLVED OXYGEN IN THE MIDDLE PART OF THE LAKE (2000) .......................... 62 iii June 26, 2006 FIGURE 6-26. DISSOLVED OXYGEN IN THE UPPER PART OF THE LAKE (2000)............................. 62 FIGURE 6-27. TOTAL-P NEAR THE DAM (2000) ........................................................................... 63 FIGURE 6-28. TOTAL-P IN THE MIDDLE PART OF THE LAKE (2000)............................................. 63 FIGURE 6-29. TOTAL-P IN THE MIDDLE PART OF THE LAKE (2000)............................................. 63 FIGURE 7-1. CARLSON’S TSI NEAR THE DAM (REDUCTION)...................................................... 67 FIGURE 7-2. CARLSON’S TSI IN THE MIDDLE PART OF THE LAKE (REDUCTION) ....................... 67 FIGURE 7-3. CARLSON’S TSI IN THE UPPER PART OF THE LAKE (REDUCTION).......................... 67 FIGURE 7-4. CHLOROPHYLL-A NEAR THE DAM (REDUCTION).................................................... 68 FIGURE 7-5. CHLOROPHYLL-A IN THE MIDDLE PART OF THE LAKE (REDUCTION) ..................... 68 FIGURE 7-6. CHLOROPHYLL-A IN THE UPPER PART OF THE LAKE (REDUCTION)........................ 68 FIGURE 7-7. DISSOLVED OXYGEN NEAR THE DAM (REDUCTION) .............................................. 69 FIGURE 7-8. DISSOLVED OXYGEN IN THE MIDDLE PART OF THE LAKE (REDUCTION) ............... 69 FIGURE 7-9. DISSOLVED OXYGEN IN THE UPPER PART OF THE LAKE (REDUCTION) .................. 69 FIGURE 7-10. TOTAL-P NEAR THE DAM (REDUCTION)................................................................. 70 FIGURE 7-11. TOTAL-P IN THE MIDDLE PART OF THE LAKE (REDUCTION) .................................. 70 FIGURE 7-12. TOTAL-P IN THE UPPER PART OF THE LAKE (REDUCTION)..................................... 70 FIGURE 7-13. SEDIMENT REDUCTION VS. TOTAL-P REDUCTION.................................................. 75 FIGURE 7-14. TOTAL N REDUCTION VS. TOTAL-P REDUCTION.................................................... 76 FIGURE 7-15. SEDIMENT LOAD REDUCTION DUE TO CONVERSION OF CULTIVATED LAND TO PASTURE ................................................................................................................ 77 iv June 26, 2006 List of Tables TABLE 2-1: 1998 303(D) LIST FOR THE COBB CREEK WATERSHED ........................................... 6 TABLE 2-2. 2002 303(D) LIST FOR COBB CREEK WATERSHED ................................................... 7 TABLE 3-1: THRESHOLD VALUES FOR STREAM TOTAL-P AND NO2+NO3 ................................ 10 TABLE 3-2. PUBLISHED LC50 VALUES FROM DIFFERENT SOURCES ......................................... 13 TABLE 4-1. OCC WATER QUALITY MONITORING STATIONS.................................................... 15 TABLE 4-2. SUMMARY OF TSI DATA........................................................................................ 23 TABLE 4-3. LC-50 VALUES AND TARGET CRITERIA FOR PESTICIDES ......................................... 24 TABLE 4-4. LAND USE COMPARISON FOR COBB CREEK AND LAKE CREEK SUB-BASINS........... 26 TABLE 4-5. PESTICIDE LOADINGS (APRIL 1999 – AUGUST 1999)............................................. 26 TABLE 5-1. ESTIMATED POPULATION IN COBB CREEK WATERSHED........................................ 32 TABLE 5-2. PHOSPHORUS LOADING TO LAKES FROM WATERFOWLS........................................ 34 TABLE 5-3. LAND USE COVERAGE IN THE FORT COBB LAKE WATERSHED.............................. 37 TABLE 6-1. SURFACE AREA AND VOLUME OF FORT COBB LAKE ............................................. 43 TABLE 7-1. NUTRIENT REDUCTION RATE ................................................................................. 65 TABLE 7-2. LOAD ALLOCATIONS.............................................................................................. 72 TABLE 7-3. SIMULATED ANNUAL LOADS BY LAND USE FOR THE FORT COBB BASIN FOR THE PERIOD 1990-2000 ................................................................................................ 74 TABLE 7-4. LOAD REDUCTIONS FOR DIFFERENT BMPS ........................................................... 75 TABLE 7-5. RELATIVE EFFECTIVENESS OF NUTRIENT MANAGEMENT ...................................... 78 TABLE 7-6. REDUCTION RATE FOR SEDIMENT AND NUTRIENTS FOR VARIOUS BMPS.............. 79 v June 26, 2006 Executive Summary Cobb Creek watershed includes two HUC 11 watersheds, 11130302120 & 11130302130 and crosses three counties in west-central of Oklahoma. Fort Cobb is located at the lower end of the watershed and there are four tributaries (Cobb Creek, Lake Creek, Willow Creek, and Fivemile Creek) contributing to the lake. The watershed is primarily rural. There is no point source discharge in the watershed. Fort Cobb Lake and four tributaries were listed in the Oklahoma 1998 303(d) list for nutrients, suspended solids, siltation, and pesticides. Fort Cobb Lake, Lake Creek and Willow Creek are listed in the 2002 303(d) list. This TMDL report addresses both the 1998 and 2002 303(d) lists. There are several federal and state agencies collecting water quality data in the watershed. Data used in this project are gathered from U.S. Geological Survey, U.S. Bureau of Reclamation, U.S. Fish and Wildlife Service, Oklahoma Water Resources Board and Oklahoma Conservation Commission. The data were first used to check the status of impairments for all tributaries and Fort Cobb Lake. It was concluded that Cobb Creek, Lake Creek, Willow Creek and Fivemile Creek were not impaired with regard to nutrients and pesticides. It was also concluded that the Fort Cobb Lake was not impaired for pesticides. The Fort Cobb Lake was used as the endpoint in the TMDL project. The TMDL targets were dissolved oxygen, anoxic volume and Trophic State Index (TSI) in the lake. Two water quality models were employed to link pollutant sources to water quality targets. A SWAT (Soil and Water Assessment Tool) model was calibrated to simulate nutrient loads to the lake. A three dimensional EFDC (Environmental Fluid Dynamic Code) model was calibrated and verified to model water quality in Fort Cobb Lake. The calibrated EFDC model was then used to predict how much reduction would be needed to restore the Fort Cobb Lake to meet all Oklahoma water quality standards. As a result, the model called for 78% reduction in nutrient load from the watershed. Due to the BMPs implemented in the recent years, it was estimated by the SWAT model that about 20% nutrient reduction had been achieved as of 2005. In order to achieve the recommended nutrient reduction, sediment load to streams and the lake will also be reduced. Therefore, the suspended solids and siltation impairments in Cobb Creek, Lake Creek, Willow Creek and Fivemile Creek are also addressed by this TMDL. vi FINAL June 26, 2006 1. Introduction 1.1 Latest Revision This TMDL report for Cobb Creek Watershed and Fort Cobb Lake was first drafted in 2004 and went through peer reviews among state agencies. Then, the report was sent to the EPA for technical review. After receiving the EPA’s technical approval, the report was open for public review on November 24, 2004. A public meeting was held in the Town of Fort Cobb on January 13, 2005. The public review period ended on February 25, 2005. Five written comments were received during the public review period. Not all comments are addressed through the response to the comments process because the SWAT model for the watershed was recalibrated which leads to recalibration of the EFDC model for the lake. As a result, the following significant changes have been made to the TMDL reduction goal and this TMDL report: 1). Update on the SWAT Model Since there were many questions on land use, tillage, fertilizer application rate, hydraulic calibration and so on, Oklahoma State University conducted a new survey in the Cobb Creek watershed to collect additional data. A detailed survey was given in 2005 to Oklahoma State University (OSU) Cooperative Extension Service Agents and Specialists to gain an understanding of agricultural practices and land cover that occurred from 1996 to 2001. This survey went into great detail about the different types of crops in the basin along with different tillage practices, common double crops, fertilization rates, cattle stocking rates, and harvest dates. With the newly collected data, OSU recalibrated the SWAT model. A pond option was also added to the SWAT model during the recalibration process. As a result, the SWAT model calibration was greatly improved. The newly calibrated model was used to generate nutrient inputs to the Fort Cobb Lake. It should be emphasized that the SWAT model was calibrated to the conditions when water quality data were collected. Since then, the land cover in the watershed has been changed and certain BMPs have been implemented. In order to evaluate the improvement in nutrient 1 FINAL June 26, 2006 reduction that has occurred in the past few years, OSU also updated the SWAT model with 2005 land cover. The updated SWAT model predicted that on average 20% phosphorus reduction has been achieved since 2001. 2). Update on the EFDC Model Although there is little difference in the average annual total phosphorus loadings (1995-2000) between the current and previous SWAT model, the difference in loadings from year to year ranges from -37% to 43%, especially for the calibration and verification periods of the EFDC model (as shown in red in the following table). The difference is significant enough to require a new calibration of the EFDC model for the Fort Cobb Lake. Year Previous MoTdoetla l P (kg/Cyur)r rent Model Difference 1995 257794 197000 30.9% 1996 34543 50000 -30.9% 1997 93353 104000 -10.2% 1998 75933 53000 43.3% 1999 47922 76000 -36.9% 2000 53741 81000 -33.7% Average 93881 93500 0.4% Trophic State Index (TSI) is the only TMDL target which is not met currently in the Fort Cobb Lake. Thus, TSI is the control factor in determining the reduction goal for this TMDL. A point-to- point comparison between predicted and observed TSI data and R2 which measures the goodness-of-fit were added to the TMDL report in the model calibration. In addition, the same comparison was made for lake elevation and temperature calibration. Vertical temperature profiles were also added to the report to enhance the hydrodynamic calibration. The recalibrated EFDC model was then used to predict the nutrient reduction rate needed to meet all TMDL targets. Due to the significant change in nutrient inputs to the lake, the TMDL reduction goal increased from 65% to 78%. 2 FINAL June 26, 2006 3). Nutrient Input from Migratory Birds One comment suggested that direct defecation by migratory birds or waterfowl might be an important nutrient source. One section was added to this report to address the potential nutrient additions from waterfowl to Fort Cobb Lake. Annual mid-winter waterfowl surveys were obtained from U.S. Fish and Wildlife Service for this assessment. Waterfowl in the lake are primarily ducks and small Canadian geese. The waterfowl phosphorus addition to the lake is estimated less than 2% of non-point source loading and primarily occurs in the winter. Therefore, we believe that waterfowl will have little impact on algae growth in the summer. 4). Other Revisions In addition to the above major updates, many other changes were also made to this report. These changes include annual precipitation plot and EFDC control files etc. The annual rainfall data from 1975 to 2001 were plotted so that one would be able to see the representativeness and appropriateness of the calibration and verification period. The EFDC’s master control files were attached at the end of this report so that those interested in the model parameters could check the final parameters used in the EFDC model. 1.2 Introduction Under Section 303(d) of the Clean Water Act (CWA) as amended by the Water Quality Act of 1987 and the United States Environmental Protection Agency’s (EPA) Water Quality Planning and Management Regulations [Title 40 of the Code of Federal Regulation (40 CFR), Part 130], states, territories, and authorized tribes are required to develop lists for those waters within their boundaries not meeting water quality standards applicable to their designated uses. States are also required to establish priority rankings for waters on the list and develop Total Maximum Daily Loads (TMDLs) for all pollutants violating or causing violation of applicable water quality standards for each identified waterbody in the list. 3 FINAL June 26, 2006 A TMDL specifies the maximum amount of a pollutant that a waterbody can receive while still meeting water quality standards, and allocates pollutant load among all point and nonpoint pollution sources. Such loads are established at levels necessary to meet the applicable water quality standards with consideration given to seasonal variations and margins of safety. The TMDL process establishes the allowable loadings of pollutants or other quantifiable parameters for a waterbody based on the relationship between pollution sources and in-stream water quality conditions. States then establish water quality-based controls and programs to reduce pollution from both point and nonpoint sources and restore and maintain the quality of their water resources [2]. Oklahoma’s 1998 303(d) list identified all major streams (Cobb Creek, Lake Creek, Willow Creek, Fivemile Creek) and Fort Cobb Lake in the Cobb Creek watershed as not supporting their designated beneficial uses due to nutrients, suspended solids, siltation, pesticides, exotic species, unknown toxicity, and/or other habitat alterations. By definition, TMDLs can only be developed for specific pollutants. Exotic species, unknown toxicity and other habitat alterations are not pollutants that cause impairments of water being studied and are not within the scope of this report. This report addresses the remaining pollutants in the Cobb Creek watershed. Cobb Creek watershed includes two HUC 11 watersheds, 11130302120 & 11130302130, which include portions of Caddo, Washita, and Custer counties in Oklahoma (Figure 1-1). At the lower end of the Cobb Creek watershed is Fort Cobb Lake. Land use in the Cobb Creek watershed consists of forest (6%), pasture (41.4%), agricultural land (50.4%), water (2.1%) and urban area (0.1) [17]. The watershed is in one of the most intensive agricultural farming areas of the state. Over half of the state’s peanuts are grown in or near the watershed, along with wheat, alfalfa and many other row crops [6]. The soils are very coarse and fragile, allowing for high infiltration rates and excessive erosion. 4 FINAL June 26, 2006 FIGURE 1-1. COBB CREEK WATERSHED STUDY AREA This study consists of two modeling efforts: a watershed model to estimate non-point source loadings to the Fort Cobb Lake and a lake model to simulate hydrodynamics and water quality conditions in the lake and make comparisons to the applicable water quality criteria. 5 FINAL June 26, 2006 2. Problem Definition Fort Cobb Lake and four streams were included in the Oklahoma 1998 303(d) list due to nutrients, suspended solids, siltation, pesticides, exotic species, unknown toxicity, and/or other habitat alternations. Since exotic species, unknown toxicity and other habitat alterations are not pollutants, they will not be included in this TMDL study and are not included in the following table. TABLE 2-1: 1998 303(d) LIST FOR THE COBB CREEK WATERSHED Waterbody ID Name Area (acres)/ Length (miles) Nutrients Siltation Suspended Solids Pesticide OK310830060020 Fort Cobb Lake 3806 X X OK310830060010 Cobb Creek 17.3 X X X X OK310830060080 Fivemile Creek 12.2 X X X OK310830060040 Lake Creek 16.3 X X X X OK310830060030 Willow Creek 11.0 X X X All stream segments in Table 2-1 were assigned priority 3 in the 1998 Oklahoma 303(d) list. Since there are no permitted point source discharges in the entire watershed, the potential impairments are caused by the non-point sources in the watershed such as agricultural activities, cattle and limited small concentrated animal feeding operations (CAFO) in the watershed. There are two CAFOs in the watershed that are considered to be insignificant in the Soil and Water Assessment Tool (SWAT) model conducted by Oklahoma State University. Because of the way the 303 (d) list was compiled and new information obtained through continuing data collection efforts, the 1998 303(d) list was revisited and reevaluated to determine whether the beneficial uses of waterbodies were still impaired by the listed pollutants. The Oklahoma 2002 Water Quality Assessment Integrated Report indicated that siltation impairments for Cobb Creek, Lake Creek, Willow Creek and Fivemile Creek and suspended solids impairments for Fort Cobb Lake, Cobb Creek, Lake Creek Willow Creek and Fivemile Creek were listed in error based on samples collected under high flow conditions. The siltation and 6 FINAL June 26, 2006 suspended solids impairments for Lake Creek were corrected to turbidity impairment in the Oklahoma’s 2002 303(d) list. The Oklahoma 2002 303(d) list (Table 2-2) shows the latest status of impairments and impairment source codes for streams and lakes in the watershed. The source code of 9000 in Table 2-2 stands for unknown source. The impairments for Cause Unknown and Pathogens are beyond the scope of this study and therefore will not be addressed in this report. The remaining pollutants, together with those in Table 2-1, are re-evaluated in this TMDL report. TABLE 2-2. 2002 303(D) LIST FOR COBB CREEK WATERSHED Waterbody ID Name Cause Unknown Turbidity Phosphorus Low DO Pathogens OK310830060020_00 Fort Cobb Lake 9000 OK310830060040_00 Lake Creek 9000 9000 9000 OK310830060030_00 Willow Creek 9000 Fort Cobb Lake and all the streams in the watershed are designated in Oklahoma Water Quality Standards for the following beneficial uses: • Public and Private Water Supply • Warm Water Aquatic Community • Agriculture • Industrial & Municipal Process and Cooling Water • Primary Body Contact Recreation • Aesthetics • Sensitive Public and Private Water Supply In addition, the Fort Cobb watershed is also classified as a Nutrient Limited Watershed (NLW). 7 FINAL June 26, 2006 3. Applicable Water Quality Standards 3.1 Standards for Streams 3.1.a. Standards for nutrients The Oklahoma Water Quality Standards (OWQS) do not have numerical criteria for nutrients that apply to the streams in the Cobb Creek Watershed. However, they contain the following narrative standard that applies to all streams and lakes in the state: “785:45-5-19 (c) (2) Nutrients. Nutrients from point source discharges or other sources shall not cause excessive growth of periphyton, phytoplankton, or aquatic macrophyte communities which impairs any existing or designated beneficial use”. The rules for implementation of Oklahoma’s Water Quality Standards (OAC 785-46-15) [4] provide a framework that is used in assessing threats to waterbodies or impairments to beneficial uses by nutrients. The implementation rules describe a dichotomous process to be used in determining whether or not a stream is nutrient-threatened. If the dichotomous process indicates a stream is not threatened by nutrients, the stream will be considered not impaired by nutrients. The dichotomous process uses the follow factors to determine if a stream is threatened by nutrients: • Stream order • Stream slope • Total-Phosphorus (P) concentration • Nitrate plus nitrite concentration • Canopy shading • Turbidity The application of this dichotomous process to streams in Cobb Creek watershed was utilized to derive the threshold concentrations for Total-P and nitrate plus nitrite. If the mean value of Total-P and nitrate plus nitrite samples in a stream is below their corresponding threshold value, 8 FINAL June 26, 2006 the stream is considered not threatened by nutrients. Table 3-1 shows stream order, slope and the threshold values for Total-P and nitrate plus nitrite for streams in the Cobb Creek watershed. As shown in Figure 3-1, the stream order is determined using the BASINS rf3 reach file [9]. The stream orders given in Table 3-1 are for those segments where samples were taken. FIGURE 3-1. STREAM ORDER (COBB CREEK WATERSHED) 9 FINAL June 26, 2006 TABLE 3-1: THRESHOLD VALUES FOR STREAM TOTAL-P AND NO2+NO3 Stream Stream Order Slope (ft/mile) Total-P (mg/L) NO2 + NO3 (mg/L) Willow Creek 2 <17 0.15 2.40 Lake Creek 2 <17 0.15 2.40 Trib to Lake Creek 1 ≥ 17 0.24 4.95 Cobb Creek 4 <17 0.36 5.00 3.1.b. Standards for Dissolved Oxygen The Oklahoma Water Quality Standards (OWQS) has the following criteria for dissolved oxygen: Summer (Jun 16 – Oct 15): 4 mg/L Seasonal (Oct 16 – Jun 15): 5 mg/L The dissolved oxygen criteria must be maintained at all time. 3.2 Standards for Fort Cobb Lake The Oklahoma Water Quality Standards do not contain numerical standards for nutrients and suspended solids; only narrative standards for nutrients and suspended solids can be found in the OWQS. However, it is very difficult to use narrative standards as the targets of this TMDL. The targets of a TMDL need to be numerical or quantified in some way. Fort Cobb Lake and its watershed are classified in the OWQS as Nutrient-Limited Watershed (NLW). Nutrient-Limited Watershed, by definition, means a watershed of a waterbody with a designated beneficial use that is adversely affected by excess nutrients as determined by Carlson’s Trophic State Index (using chlorophyll-a) of 62 or greater. According to the Implementation of Oklahoma’s Water Quality Standards [4], the beneficial uses designated for Fort Cobb Lake are presumed to be fully supported but threatened. Since the lake is considered threatened when Carlson’s Trophic State Index (TSI) is 62 or greater, a TSI value less than 62 was chosen as one endpoint of this TMDL. 10 FINAL June 26, 2006 In addition to TSI, dissolved oxygen criteria in the Oklahoma Water Quality Standards and the Implementation of Oklahoma’s Water Quality Standards also apply to Fort Cobb Lake. The following endpoints are identified for this TMDL: • Dissolved Oxygen (DO) for the surface water must meet the following requirements: o Summer (Jun 16 – Oct 15): 4.0 mg/L o Seasonal (Oct 16 – Jun 15): 5.0 mg/L • Anoxic volume of water column in the lake must be less than 50%. The anoxic volume is defined as the vertical water column where the dissolved oxygen concentration is less than 2 mg/L. • Carlson’s Trophic State Index (TSI) must be less than 62. TSI can be calculated as follows: TSI = 9.81 × Ln (chlorophyll-a) + 30.6 The unit of chlorophyll-a is μg/L. Dissolved oxygen criteria must be maintained at all times. Anoxic volume and TSI criteria could not be exceeded more than 10% of the time in order to achieve compliance. 3.3 Pesticide Standards Because Alachlor and Aldicarb were detected in both surface water and streamside seepage samples, pesticides were identified in the1998 303(d) list as a cause of impairment. To determine whether the surface water is actually impaired, water quality criteria for the surface water need to be checked. Review of the pesticide monitoring data for Lake Creek indicates that none of the pesticides tested exceeds any water quality standards. . Oklahoma Water Quality Standards do not have any numerical criteria specifically for Alachlor or Aldicarb. The following requirements for toxic substances in general apply: “For toxicants not specified in Table 2 of Appendix G of this Chapter, concentrations of toxic substances with bio-concentration factors of 5 or less shall not exceed 0.1 of 11 FINAL June 26, 2006 published LC50 value(s) for sensitive representative species using standard testing methods …”. “For toxicants not specified in Table 2 of Appendix G of this Chapter, concentrations of toxic substances with bio-concentration factors greater than 5 shall not exceed 0.01 of published LC50 value(s) for sensitive representative species using standard testing methods …”. Both Alachlor and Aldicarb are not specified in Table 2 of Appendix G of the OWQS. The technical fact sheets of EPA’s National Primary Drinking Water Regulations [12][13] indicate that the bio-concentration factors (BCF) for Alachlor and Aldicarb are 6 and 42, respectively. Since both BCF values are greater than 5, the target values for Alachlor and Aldicarb will be 0.01 of their published LC50 values. Published LC50 values for Alachlor and Aldicarb were found from the following public resources: • EXTOXNET, Extension Toxicology Network[15], which is a pesticide information project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. The USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program provided major support and funding. • Virginia Corporative Extension [14], Virginia Tech and Virginia State University. • PAN Pesticides Database [8], derived from the U.S. EPA AQUIRE (AQUatic toxicity Information REtrieval) Database. 12 FINAL June 26, 2006 TABLE 3-2. PUBLISHED LC50 VALUES FROM DIFFERENT SOURCES Reference Chemical LC50 (μg/L) Name Fathead Minnow Catfish Common, mirror, colored, carp EXTOXNET Extension Alachlor - 6500 - Toxicology Network Aldicarb - - - Virginia corporative Alachlor - - - Extension Aldicarb - - - U.S. EPA AQUIRE Alachlor 5700 15700 5600 Database Aldicarb 2700 23300 1000 Using the general methodology in the Oklahoma Water Quality Standards and the most stringent LC50 values in Table 3.2 for sensitive representative species, the target values for Alachlor and Aldicarb are calculated as 56.0 μg/L and 10.0μg/L, respectively. 3.4 Antidegradation Policy Oklahoma antidegradation policy (OAC 785:45-3) requires protecting all waters of the state from degradation of water quality. The targets of this TMDL, resulting load reduction, and load allocations in this report were set with regard for all elements of the Oklahoma Water Quality Standards which includes the antidegradation policy. With the implementation of this TMDL, the water quality in Fort Cobb Lake and the streams in the watershed will be improving rather than degrading. 13 FINAL June 26, 2006 4. Impairment Assessment & TMDL Targets Oklahoma’s 2002 Water Quality Assessment Integrated Report has concluded that siltation and suspended solids impairments were listed in error for Cobb Creek, Lake Creek, Willow Creek and Fivemile Creek in the Oklahoma’s 1998 303(d) list based on high flow high flow suspended solids and turbidity sampling. The siltation and suspended solids impairments for Lake Creek were corrected to turbidity impairment in the Oklahoma’s 2002 303(d) list. Therefore, siltation and suspended solids will not be addressed in this report. 4.1. Status of Nutrient Impairment in Streams Lake Creek, Willow Creek, Cobb Creek and Fivemile Creek are listed for nutrient impairment in the 1998 303(d) list. The Oklahoma Conservation Commission (OCC) conducted quarterly sampling on Lake Creek and its tributary during 1998 and 1999. The U.S. Geological Survey (USGS) sampled Fort Cobb Lake and its contributing streams during 2000 and 2001. These data are used to determine the status of nutrient impairment for Lake Creek, Willow Creek, and Cobb Creek 4.1.a. Data from OCC The Oklahoma Conservation Commission sampled five (5) sites in Lake Creek from August 1998 to October 1999. Table 2 shows the legal descriptions of the five monitoring sites. Samples were collected monthly at Sites 1 & 4 for nutrients and salt analysis which included nitrate/nitrite, total Kjeldahl nitrogen, total P, sulfate, total suspended solids, chloride, and hardness. Monthly field data were collected concurrently at all five sites. Field monitoring included flow rate, dissolved oxygen, temperature, pH, specific conductivity, turbidity, and alkalinity. In addition to regular monthly monitoring, two high flow events were sampled for water quality and field data at Site 1 on April 25, 1999 and June 21, 1999. 14 FINAL June 26, 2006 TABLE 4-1. OCC WATER QUALITY MONITORING STATIONS Monitoring Sites Latitude Longitude Legal County Lake Creek #1 35° 15’ 30.4” N 98° 31’ 54” W S12, T9N, R13W Caddo Lake Creek #2 35° 18’ 16.6” N 98° 31’ 36.2” W S36, T10N, R13W Caddo Lake Creek #3 35° 20’ 01.2” N 98° 31’ 36.2” W S24, T10N, R13W Caddo Lake Creek #4 35° 21’ 45.7” N 98° 30’ 56.8” W S7, T10N, R12W Caddo Lake Creek #5 35° 24’ 21.9” N 98° 31’ 14.5” W S 25, T11N, R13W Caddo Sampling Site #1 was located on Lake Creek and Site #4 on a tributary to Lake Creek. Figures 4-1 and 4-2 show the total phosphorus (TP) and nitrogen (NO2 + NO3) data and the corresponding threshold values for Lake Creek and its tributary. TP Concentration On Lake Creek (OCC) 0 0.5 1 1.5 2 2.5 4/15/98 7/24/98 11/1/98 2/9/99 5/20/99 8/28/99 12/6/99 3/15/00 Date TP (mg/L) Sit e # 1 Threshold NOx Concentration On Lake Creek (OCC) 0 0.5 1 1.5 2 2.5 3 3.5 4/15/98 7/24/98 11/1/98 2/9/99 5/20/99 8/28/99 12/6/99 3/15/00 Date NOx (mg/L) Site # 1 Threshold FIGURE 4-1. TOTAL-P, NO3/NO2 CONCENTRATION IN LAKE CREEK 15 FINAL June 26, 2006 TP Concentration On Tributary Of Lake Creek (OCC) 0 0.1 0.2 0.3 0.4 4/15/98 7/24/98 11/1/98 2/9/99 5/20/99 8/28/99 12/6/99 3/15/00 Date TP (mg/L) Site # 1 Threshold NOx Concentration On Tributary Of Lake Creek (OCC) 0 1 2 3 4 5 6 7 4/15/98 7/24/98 11/1/98 2/9/99 5/20/99 8/28/99 12/6/99 3/15/00 Date NOx (mg/L) Site # 1 Threshold FIGURE 4-2. TOTAL-P, NO3/NO2 CONCENTRATION IN TRIBUTARY OF LAKE CREEK If the mean of the samples does not exceed the threshold, according to the dichotomous process, the stream is not threatened by nutrients. As shown in Figure 4-1 & 4-2, the mean values of TP or NO2 + NO3 of all samples are well below their corresponding threshold values. Both Lake Creek and its tributary are not nutrient-threatened so they are not nutrient-impaired. 4.1.b. Data from USGS Bi-monthly monitoring was conducted from June 2000 to June 2002 at 26 sites (Figure 4-3). Sixteen sites are located in Fort Cobb Lake and ten sites in three major tributaries, namely Lake 16 FINAL June 26, 2006 Creek, Cobb Creek and Willow Creek. The sites in the lake were designed to characterize the spatial trend of the lake water quality. The sites in the tributaries were intended to determine the source and load of nutrients to the lake. Parameters monitored included temperature, pH, DO, specific conductivity and Oxidation Reduction Potential (ORP), hardness, nitrate/nitrite, ammonia, total nitrogen, total phosphorus, Soluble reactive phosphorus (SRP), particulate organic carbon. FIGURE 4-3. USGS MONITORING STATIONS (PROVIDED BY USGS) 17 FINAL June 26, 2006 TP Concentration On Willow Creek (USGS) 0 100 200 300 400 500 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date TP (ug/L) Threshold Site # 13 Site # 15 Nitrogen Concentration On Willow Creek (USGS) 0 1 2 3 4 5 6 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date NO2+NO3 (mg/L) Threshold Site #13 Site #15 FIGURE 4-4. TOTAL-P, NO3/NO2 CONCENTRATION IN WILLOW CREEK 18 FINAL June 26, 2006 TP Concentration On Lake Creek 0 100 200 300 400 500 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date TP (ug/L) Threshold Site # 18 Site # 20 Nitrogen Concentration On Lake Creek (USGS) 0 0.5 1 1.5 2 2.5 3 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date NO2+NO3 (mg/L) Threshold Site #18 Site #20 FIGURE 4-5. TOTAL-P, NO3/NO2 CONCENTRATION IN LAKE CREEK 19 FINAL June 26, 2006 TP Concentration On Cobb Creek (USGS) 0 100 200 300 400 500 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date TP (ug/L) Threshold Site #25 Site #21 Nitrogen Concentration On Cobb Creek (USGS) 0 1 2 3 4 5 6 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date NO2+NO3 (mg/L) Threshold Site #25 Site #21 FIGURE 4-6. TOTAL-P, NO3/NO2 CONCENTRATION IN COBB CREEK As shown in Figure 4-4, 4-5 & 4-6, the mean values of TP or NO2 + NO3 are well below their corresponding threshold values (Table 3-1). Cobb Creek, Lake Creek and Willow Creek are not nutrient-threatened and therefore are not nutrient-impaired. There is not enough data on Fivemile Creek to assess the status of nutrient impairment. USGS collected only three samples on site 29 & 30. No samples exceeded TP or TN threshold values. In addition, the 2002 Water Quality Assessment Integrated Report [16] indicated that the nutrient impairment for Fivemile Creek was listed in error in the 1998 303(d) list. 20 FINAL June 26, 2006 4.2. Status of Nutrient Impairment in Fort Cobb Lake In addition to the data collected by USGS in Fort Cobb Lake, Oklahoma Water Resources Board (OWRB) and U.S. Fish & Wildlife Service (USFWS) also conducted quarterly sampling in the lake. These data are used to determine the status of nutrient impairment for Fort Cobb Lake. Fort Cobb Lake was not listed in the 1998 303(d) list for nutrient impairment but was included on the 2002 list. The available data support the listing. Oklahoma Water Resources Board has conducted quarterly water quality monitoring at six sites in Fort Cobb Lake from July 1998 to July 1999. Figure 4-7 shows the six sampling sites. The monitored water quality parameters include NH3, NO2, NO3, Total N, Organic N, TKN, Ortho-P, Total P, Settleable and Suspended Solids, Chloride, Chlorophyll-a and Turbidity. Field data include temperature, dissolved oxygen, pH, Conductivity, Total Dissolved Solid (TDS) and other parameters at different depths in the water column. USGS conducted bi-monthly water quality sampling on sixteen sites in Fort Cobb Lake, (Figure 4-3). The sampling started in June of 2000 and ended in June of 2002. Depth profiles of temperature, pH, DO, specific conductivity and Oxidation Reduction Potential (ORP) were conducted for sites in the lake. Water samples for laboratory analysis were collected as a surface composite and analyzed for nutrients (TN, TP, NO2/NO3, NH3, SRP), Chlorophyll-a, particulate organic carbon (POC) and physical chemistry (pH, alkalinity, hardness, turbidity, conductivity, and total dissolved solids). In addition, samples were collected for algae taxonomy. U.S. Fish & Wildlife Service, sponsored by U.S. Bureau of Reclamation, conducted quarterly water quality sampling on sixteen sites on Fort Cobb Lake, its tributaries and outflows (Figure 4- 8). The sampling started in November of 1997 and ended in June of 2000 [11]. 21 FINAL June 26, 2006 FIGURE 4-7. OWRB MONITORING STATIONS IN FORT COBB LAKE The constituents analyzed include conductivity, turbidity, chlorophyll-a, COD, total phosphorus, soluble reactive phosphorus, total alkalinity, chloride, sulfate, total nitrogen, nitrate, nitrite and ammonia. In addition, other constituents such as metals etc. were also analyzed in water samples. However, these parameters are not in the scope of this TMDL. A review of the data for these parameters does not show any violations of water quality standards. 22 FINAL June 26, 2006 FIGURE 4-8. USFWS MONITORING STATIONS The TSI data from USGS, OWRB and USFWS is summarized in Table 4-2. The aesthetics beneficial use for Fort Cobb Lake is considered not threatened with respect to nutrients if planktonic chlorophyll-a samples in the water column indicate a Carlson's Trophic State Index of less than 62. TABLE 4-2. SUMMARY OF TSI DATA Agencies Median TSI Min TSI Max TSI # Of TSI >= 62 Total # Of TSI % Of TSI >= 62 OWRB 63.7 34.0 77.6 21 34 62% USGS 61.2 38.8 85.2 67 158 42% USFWS 61.8 41.7 78.8 34 72 47% 23 FINAL June 26, 2006 Data in Table 4-2 support the 303(d) status that Fort Cobb Lake does not support the Aesthetics beneficial use with respect to nutrients. 4.3. Status of Pesticide Impairment Samples for organics and herbicides were taken by the OCC from August 1998 to June 1999. Immunoassays for pesticides (2,4-D, Alachlor, Aldicarb, Atrazine, Captan, Carbofuran, Chlorothalonil, Chlorpyrifos, Cyanazine, Metolachlor, Metribuzin, Paraquat, Picloram, and Triclopyr) were performed twice monthly during the spring & summer (March – October) and once monthly during fall and winter (November – February). TABLE 4-3. LC-50 VALUES AND TARGET CRITERIA FOR PESTICIDES LC-50 (μg/L) Pesticides Fathead Minnow Channel Catfish Common, mirror, colored, carp Target Criteria (μg/L) 2,4-D 191500 7000 58271 70.0 Alachlor 5700 15700 5600 56.0 Aldicarb 2700 23300 1000 10.0 Atrzine 15000 4982 28467 49.8 Captan 155 78.3 250 0.78 Carbofuran 1264 629 1405 6.29 Chlorothalonil - 81.5 110 0.82 Chlorpyrifos 178.5 457 76.9 0.77 Cyanazine 18630 12862 - 128.6 Metolachlor 8200 4900 - 490.0 Metribuzin - 32540 - 325.4 Paraquat - 100000 78500 785.0 Picloram 64033 13571 135.7 Triclopyr NA for above species, but >1000 for all other tested species 10.0 Table 4-3 shows the target criteria for each pesticide. The target criteria are determined by multiplying the minimum LC50 by 0.01 for each pesticide. The LC50 values are derived from the U.S. EPA AQUIRE database. 24 FINAL June 26, 2006 The pesticide data collected by the OCC were compared with the criteria in Table 4-3 for each pesticide to determine the status of pesticide impairment for Lake Creek. Since no pesticide data exists for Cobb Creek and Fort Cobb Lake, the evaluation of the status of pesticide impairment relies on the comparison of the data for Lake Creek and the prediction of the Soil and Water Assessment Tool (SWAT) model performed by Oklahoma State University. 4.3.a. Lake Creek OCC collected pesticide data on different sites of Lake Creek from August 1998 through October 1999. Alachlor and Aldicarb are the only two pesticides that were detected in both surface water and streamside seepage samples. We believe this is the reason that Alachlor and Aldicarb were listed in the 1998 303(d) list. Alachlor was detected in 13 of the 76 total samples and Aldicarb was detected in 19 of the 62 total samples. The highest concentration measured was 0.26 μg/L for Alachlor and 1.58 μg/L for Aldicarb. Both values are well below the corresponding target values. Other pesticides were screened against the target criteria (Table 4-3). None of the measured data exceeds the corresponding target criteria. Therefore, it can be concluded that pesticides do not impair Lake Creek. 4.3.b. Cobb Creek In addition to Lake Creek, Cobb Creek and Fort Cobb Lake are listed in the 1998 303(d) list for pesticide impairment. No monitoring data are available for either of the water bodies. Oklahoma State University has performed a SWAT model to simulate nutrient and pesticide loadings from the Fort Cobb Watershed [17]. The model is calibrated for flow and nutrients, but it is not calibrated for pesticides because of limited pesticide data. The model is not suitable for predicting the actual pesticide mass loadings from the watershed but is adequate for comparison of the relative pesticide loadings from different sub-watersheds. A comparison of land uses in Lake Creek sub-basin and Cobb Creek sub-basin are made in Table 4-4. Both sub-basins have a majority of land used for agricultural practices where pesticides are normally applied. The percentage of agricultural land in the Lake Creek sub-basin is slightly 25 FINAL June 26, 2006 higher than that in the Cobb Creek sub-basin. The SWAT model was calibrated for pesticides based on data collected in Lake Creek. When the same calibrated parameters are applied to the Cobb Creek sub-basin, the model should give a conservative prediction of pesticides on a relative basis. TABLE 4-4. LAND USE COMPARISON FOR COBB CREEK AND LAKE CREEK SUB-BASINS Land Use Name Cobb Creek Sub-bLaasnidn UseL a(%ke) Creek Sub-basin Urban or Built-up Land 0.3% 0.5% Agricultural Land 85.7% 92.2% Forest Land 0.1% 1.8% Range Land 13.6% 5.5% Barren Land 0.0% 0.0% Water 0.3% 0.0% Pesticide loadings and concentrations from the Cobb Creek sub-basin and the Lake Creek sub-basin as predicted by the SWAT model are shown in Table 4-5. TABLE 4-5. PESTICIDE LOADINGS (APRIL 1999 – AUGUST 1999) Pesticide Loading (kg) Total Accumulative Flow (m3) Average Pesticide Concentration (μg/L) Cobb Creek 394.9 1.42E+07 0.28 Lake Creek 300.4 9.78E+06 0.31 The pesticide loading in Table 4-5 is the loading from April 1999 to August 1999. The loading for other months of the year is negligible because little or no pesticides are applied in these months. As shown in Table 4-5, the predicted pesticide concentration in Cobb Creek is even lower than that in Lake Creek. Because the observed pesticide concentrations in Lake Creek are well below the standards and the pesticide concentrations in Cobb Creek are relatively lower than those in 26 FINAL June 26, 2006 Lake Creek, we can conclude that the pesticide concentration in Cobb Creek is well below the standards. In other words, pesticides do not impair Cobb Creek. 4.3.c. Fort Cobb Lake It is safe to assume that the only source of pesticides to Fort Cobb Lake is pesticides in stream flows of the tributaries to Fort Cobb Lake. Since none of Fort Cobb Lake’s tributaries are impaired by pesticides, a simple mixing model can show that Fort Cobb Lake is not impaired by pesticides. Assume : Vi = volume from stream i, (i = 1,2,…n) V = volume after mixing, V = V1 + V2 + … + Vn Ci = concentration in stream i, (i = 1,2,…n) C0 = critical concentration, C0 > Ci for i = 1,2,…n C = concentration after mixing Based on mass balance, we get: V · C = V1 · C1 + V2 · C2 + … + Vn · Cn Substitute Ci wit
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Title | Watershed based plan fo the Fort Cobb watershed |
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Full text | Page 1 of 38 June 2009 Update WATERSHED BASED PLAN FOR THE FORT COBB WATERSHED Prepared By: Oklahoma Conservation Commission Water Quality Division 4545 N. Lincoln Blvd., Suite 11A Oklahoma City, OK 73105 Page 2 of 38 June 2009 Update FORT COBB WATERSHED BASED PLAN Table of Contents PAGE PREFACE 3 INTRODUCTION 6 CAUSES AND SOURCES 7 LOAD REDUCTIONS 14 CRITERIA 15 NPS MANAGEMENT MEASURES 15 TECHNICAL AND FINANCIAL ASSISTANCE NEEDED 18 IMPLEMENTATION SCHEDULE 21 INTERIM MILESTONES 26 PUBLIC OUTREACH 27 MONITORING PLAN 31 REFERENCES 36 APPENDICES 37 Page 3 of 38 June 2009 Update PREFACE The Fort Cobb Watershed covers 314 square miles in southwestern Oklahoma in Caddo, Washita, and Custer Counties. Ft. Cobb Reservoir’s designated beneficial uses include public and private water supply, warm water aquatic community, agricul-ture, municipal and industrial uses, primary body contact recreation, and aesthetics. The reservoir is the primary drinking water source for the Cities of Anadarko and Chickasha. The watershed is located in the Central Great Plains Ecoregion in southwestern Oklahoma. Landuse in the watershed includes agricultural fields, cattle operations, rural communities, and one hog operation. Most soils in the watershed are highly erodible, sandy clays and loams. The water quality of the reservoir and its tributaries has been of concern for more than a decade with water quality problems identified beginning in 1981. Oklahoma Water Quality Standards list Fort Cobb Reservoir as a Nutrient Limited Watershed (due to high primary productivity) and a sensitive public and private water supply. 1998 Oklahoma Water Resources Board (OWRB) data showed the lake was hypereutrophic and in 1999, eutrophic (OWRB 2002). Studies indicated biological, chemical, and habitat degradation within the Ft Cobb Reservoir Watershed. DDT was detected in fish flesh tissue in 1981. Ft. Cobb Reservoir and six waterbody segments in its watershed were listed on the 1998 303(d) list as being impaired by nutrients, pesticides, siltation, suspended solids, and unknown toxicity (Table 1). The Reservoir and three streams, Cobb, Willow, and Fivemile Creek, are currently listed on the 2008 303(d) list as being impaired (see Table 1; ODEQ 2008). In addition, concerns have been expressed by the Master Conservancy District reservoir managers regarding the nutrient and sediment loads. Page 4 of 38 June 2009 Update Table 1. 303(d) Listed Causes of Impairment in Fort Cobb Watershed. 303(d) list year OK Waterbody ID Name Cause of Impairment 1998 OK 310830050020 Fort Cobb Reservoir pesticides, suspended solids, turbidity 1998 OK 310830060030 Willow Creek nutrients, siltation, suspended solids 1998 OK 310830060040 Lake Creek unknown toxicity, pesticides, nutrients, siltation, other habitat alterations, suspended solids 1998 OK 310830060050 Cobb Creek pesticides, nutrients, siltation, suspended solids 1998 OK 31080060080 Fivemile Creek nutrients, siltation, suspended solids 1998 OK 31080060130 Crowder Lake nutrients, organic enrichment/D.O., suspended solids 2002 OK310830050020 Fort Cobb Reservoir phosphorus 2002 OK 310830060030 Willow Creek pathogens 2002 OK 310830060040 Lake Creek low dissolved oxygen1, turbidity 2004 OK310830050020 Fort Cobb Reservoir phosphorus 2004 OK 310830060030 Willow Creek Fecal coliform, Enterococcus, E. coli 2004 OK 310830060040 Lake Creek selenium 2006 OK310830050020 Fort Cobb Reservoir phosphorus, turbidity 2006 OK 310830060030 Willow Creek Fecal coliform, Enterococcus, E. coli 2006 OK 310830060040 Lake Creek selenium 2006 OK 31080060130 Crowder Lake turbidity, dissolved oxygen 2008 OK310830050020 Fort Cobb Reservoir turbidity 2008 OK 310830060030 Willow Creek Fecal coliform, Enterococcus, E. coli 2008 OK 310830060050 Cobb Creek ammonia, Enterococcus, E. coli 2008 OK 31080060080 Fivemile Creek Enterococcus, E. coli 2008 OK 31080060130 Crowder Lake turbidity, chlorophyll-a, dissolved oxygen Considerable efforts have been made to identify the causes, sources, and extent of water quality threats and impairments in the basin, and extensive remedial efforts have occurred in the past several years. Previous studies of the reservoir and watershed were conducted by the U.S. Fish and Wildlife Service (USFWS), the Bureau of Reclamation (BOR), and the U.S. Geological Survey (USGS). These studies identified the causes, extent, and some of the sources of water quality impairment in the watershed. 1 Listing for D.O. later determined to be in error during TMDL development. In 2006, the Oklahoma Department of Environmental Quality (ODEQ) released the final draft of a TMDL for phosphorus loading to Fort Cobb Reservoir (Appendix A). This TMDL recommended a 78% phosphorus load reduction to restore beneficial use support to the reservoir. Because there are no point source dischargers in the watershed, this reduction must come entirely from nonpoint sources in the watershed. Page 5 of 38 June 2009 Update The TMDL was based on watershed data collected between 1990 and 2001; therefore, loading reduction recommendations are based upon loading during that period. Since that period, many changes have taken place in the watershed which suggests that Oklahoma is making significant progress towards the TMDL goal. These efforts include, but are not limited to, a decrease in peanut production in the watershed following the loss of government subsidies of peanut production, a 2001 §319 Project focused on education and demonstration of practices to reduce sediment and nutrient pollution in the watershed, a 2005 §319 Project focused on no-till, and continued effects of previous NPS education programs in the watershed which have resulted in the voluntary implementation of best management practices such as riparian zones, nutrient management, and conservation tillage. Additional work in the watershed includes education programs developed by the Oklahoma Cooperative Extension Service (OCES), the Deer Creek, West Caddo, North Caddo, and Mountain View Conservation Districts, the Natural Resources Conservation Service (NRCS), and the Oklahoma Conservation Commission (OCC), and various programs to reduce nonpoint source loading in the watershed. As a result of these efforts, Lake Creek was delisted for pesticides and unknown toxicity in 2002. A Conservation Reserve Enhancement Program (CREP) is planned for the Fort Cobb watershed, which will further address sediment and nutrient loading. This watershed based plan (WBP) discusses the efforts which have already occurred as well as those necessary to expand the programs ongoing in the watershed to reach the load reduction goals established by the TMDL and to restore beneficial use support to Fort Cobb Reservoir and the waterbodies in its watershed. Page 6 of 38 June 2009 Update INTRODUCTION In 1997, on the 25th anniversary of the 1972 Federal Clean Water Act, Vice President Al Gore initiated development of a nationwide strategy to protect water quality. This initiative resulted in the development of the Clean Water Action Plan (CWAP), which established goals and implementation schedules for numerous strategies dealing with point and nonpoint sources. Oklahoma’s Office of Secretary of Environment (OSE) was designated as the state lead agency to implement the provisions of the CWAP in Oklahoma. Under OSE’s leadership, Oklahoma has successfully met the CWAP requirement to establish a Unified Watershed Assessment (UWA) strategy. Oklahoma’s UWA is a written document whose development and implementation relied upon input from the state’s UWA Work Group. Through the UWA process, the Work Group identified “Category I” watersheds in Oklahoma that were recognized as significantly impaired and in need of immediate federal and state funding to target restoration activities. Fort Cobb Watershed was one of these high priority watersheds (Figure 1). EPA’s Nonpoint Source Program and Grants Guidelines for States and Territories for FY 2004 and Beyond requires a Watershed-Based Plan (WBP) to be completed prior to implementation using incremental funds. The guidance defines the 9 key components to be addressed in a watershed-based plan, much of which builds from the strategies outlined in a Watershed Restoration Action Strategy (WRAS). These components are: 1) identification of causes and sources that will need to be controlled to achieve load reductions, 2) estimate of load reductions expected from the management measures described, 3) a description of the management measures that will need to be implemented to achieve load reductions, 4) an estimate of the amounts of technical and financial assistance needed, associated costs, and/or the sources or authorities who will bear responsibility, 5) an information/education component that will be used to enhance public understanding of the project and encourage early participation in the overall program, 6) a schedule for implementing the Non-Point Source (NPS) management measures identified in this plan that is reasonably expeditious, 7) a description of interim, measurable milestones for determining whether control actions are being implemented, 8) a set of criteria that can be used to determine whether loading reductions are being achieved over time and substantial progress is being made or whether the Watershed Plan or Total Maximum Daily Load (TMDL) needs to be revised, and 9) a monitoring component to evaluate the effectiveness of the implementation efforts over time. The WBP for the Fort Cobb Watershed has been developed as a dynamic document that will be revised, when necessary, to incorporate the latest information, address new strategies, and define new partnerships between watershed shareholders following this initial documentation. Also, it is understood that the water quality goals set forth in this WBP, as well as the technical approach to address the goals, may not be comprehensive and it may be necessary to revise or expand them in the future. Page 7 of 38 June 2009 Update Figure 1. Fort Cobb Watershed. West Caddo CD Mountain View CD Deer Creek CD North Caddo CD Fivemile Creek Lake Creek Cobb Creek Willow Creek Federal and state funding allocations for future water quality projects designed to address the Fort Cobb Watershed problems should not be based solely upon their inclusion in this WBP, rather the WBP should be considered a focal point for initial planning and strategy development. In order for this WBP to become an integral part of the entire watershed restoration program, it must be amenable to revision and update. It is anticipated that at least biannual revisions may be necessary, and that the responsibility for such revisions will rest primarily with the OCC with support from the Office of the Secretary of the Environment (OSE) and the NPS Working Group. CAUSES AND SOURCES Causes Currently, Fort Cobb Reservoir, Willow Creek, Cobb Creek, and Fivemile Creek are impaired by turbidity (reservoir), bacteria (all creeks), and ammonia (Cobb Creek) (Table 1). The Fort Cobb TMDL (ODEQ 2006) focuses on phosphorus as the primary cause of impairment in Fort Cobb Reservoir and suggests that the dissolved oxygen listing for Lake Creek was in error. In addition, it confirms that pesticide impairments cited by the 1998 303(d) list are no longer present, as indicated by current water quality and biological data (Appendix A). Page 8 of 38 June 2009 Update Sources Point Sources The TMDL verified that there were no permitted point source dischargers in the Fort Cobb Watershed. However, there are two Concentrated Animal Feeding Operation (CAFO) farms in the watershed, both with total retention NPDES permits. Permits on these farms, one a cattle farm with 2700 animal units, and the other a swine farm with 800 animal units allow overflows only under 25 year, 24 hour storm events. According to the TMDL, these provisions are determined sufficient to protect the waters in the Cobb Creek watershed. The TMDL recommends no additional measures for these CAFO farms. In order to rule out effects of these facilities on nearby stream health, the relative load contribution attributable to these facilities should be considered by the State to verify that these facilities are not significant contributors to local or watershed-wide water quality problems. Based on these findings, the TMDL may need to be revised. Nonpoint Sources In rural settings, the primary sources of nutrients may include runoff of applied fertilizer and manure to agricultural land, runoff of animal wastes associated with the erosion of sediments in grazing fields, runoff from concentrated animal operations, failing septic tanks, and contributions from wildlife. The TMDL used the Soil and Water Assessment Tool (SWAT) model to estimate NPS loadings from landuse in the watershed (Appendix B). This is the same model and model runs that were used to target NPS implementation with an FY 2001 §319 project in the Fort Cobb Watershed. The model subdivided the basin into 90 subbasins, based on 10-meter USGS Digital Elevation Model data for the basin (Figure 3). Loading estimates for these 90 subbasins as predicted by SWAT are seen in Table 2. Loading estimates from Fort Cobb landuses as predicted by SWAT are seen in Table 3. Figure 4 displays the SWAT predictions related to phosphorus loading from subbasins in the Fort Cobb watershed. The darkest red basins produce the highest phosphorus in runoff. The SWAT model estimated a total sediment load to the lake (excluding roads) of 276,000 metric tons per year and a total phosphorus load of approximately 70,000 kg P/year. Typical landuse in the Fort Cobb Watershed (photo courtesy of Storm et al. 2003). Page 9 of 38 June 2009 Update Figure 1. Sub-basin layout used in the Cobb Creek SWAT model (Storm et al. 2003). Figure 3. Total phosphorus loading by sub-basin as predicted by SWAT (Storm et al. 2003). Page 10 of 38 June 2009 Update Table 2. SWAT Estimated Sub-basin Loading. Sub-basin AREA (km2) Surface Runoff (mm) Baseflow (mm) Total Water Yield (mm) Sediment (mg/ha) Organic Nitrogen (kg/ha) Organic P (kg/ha) Nitrate in surface runoff (kg/ha) Soluble Mineral P (kg/ha) Sediment bound mineral P (kg/ha) Total P (kg/ha) 1 1.92E+01 27.198 21.307 51.494 3.02 4.895 0.603 0.106 0.009 0.452 1.064 2 2.12E+01 44.085 35.825 84.136 6.228 6.636 0.803 0.308 0.005 0.828 1.636 3 1.86E+01 45.708 41.17 91.644 4.087 7.324 0.917 0.139 0.015 0.589 1.521 4 8.41E+00 59.531 54.213 121.906 3.919 6.681 0.814 0.173 0.01 0.589 1.413 5 1.51E+01 59.522 35.941 105.415 1.371 9.323 1.123 0.21 0.119 0.951 2.193 6 1.15E+01 54.575 44.673 104.907 1.299 10.146 1.179 0.153 0.092 0.869 2.14 7 7.76E-01 64.588 93.128 175.716 4.213 3.414 0.427 0.221 0.006 0.538 0.971 8 1.18E+01 83.927 68.263 158.491 5.242 7.35 0.92 0.285 0.03 0.837 1.787 9 1.48E+01 50.333 41.2 94.889 2.573 4.644 0.576 0.149 0.012 0.465 1.053 10 2.92E+01 31.725 28.935 64.179 3.398 6.12 0.763 0.081 0.007 0.482 1.252 11 8.49E+00 49.722 43.356 100.008 4.762 7.552 0.933 0.143 0.014 0.688 1.635 12 3.92E-01 81.615 63.218 150.528 4.692 4.613 0.591 0.288 0.008 0.637 1.236 13 4.08E+00 57.373 45.845 109.125 4.154 5.687 0.689 0.172 0.012 0.647 1.348 14 1.49E+01 51.162 45.908 101.745 3.902 6.746 0.844 0.145 0.016 0.619 1.479 15 6.40E-01 67.495 56.309 133.605 4.144 3.42 0.445 0.244 0.006 0.555 1.006 16 1.04E+01 66.203 48.74 118.653 5.349 7.315 0.898 0.219 0.007 0.786 1.691 17 3.25E+00 65.768 53.966 125.363 3.876 5.338 0.673 0.233 0.007 0.628 1.308 18 8.27E+00 61.75 65.052 135.163 4.894 6.626 0.815 0.238 0.009 0.844 1.668 19 2.34E+00 63.825 41.101 109.131 3.083 4.99 0.623 0.227 0.007 0.557 1.187 20 1.56E+01 52.451 43.091 98.176 4.097 6.665 0.816 0.174 0.006 0.643 1.465 21 1.17E+01 62.091 37.157 119.144 2.322 3.437 0.384 0.103 0.026 0.413 0.823 22 1.58E+01 54.363 47.485 112.845 5.096 7.144 0.845 0.14 0.03 0.761 1.636 23 1.54E-01 57.438 54.933 119.686 5.707 6.978 0.85 0.235 0.006 0.7 1.556 24 2.58E+01 63.747 38.638 116.515 1.651 3.385 0.38 0.135 0.035 0.413 0.828 26 8.30E+00 55.895 41.336 102.702 3.631 6.642 0.812 0.148 0.013 0.595 1.42 27 3.16E-01 70.184 82.381 159.887 3.497 3.602 0.441 0.251 0.006 0.47 0.917 28 1.11E+01 58.754 90.282 162.144 3.27 4.629 0.573 0.157 0.01 0.497 1.08 29 1.33E+00 60.497 53.606 127.77 3.833 4.113 0.503 0.207 0.005 0.525 1.033 30 1.63E+01 56.704 79.111 143.377 4.087 5.737 0.709 0.168 0.006 0.602 1.317 31 1.56E+01 59.96 35.11 96.799 3.669 5.706 0.705 0.214 0.008 0.694 1.407 32 1.60E+01 44.063 49.617 102.287 4.17 3.912 0.497 0.155 0.004 0.559 1.06 33 9.64E+00 45.049 45.392 95.578 4.119 5.626 0.685 0.162 0.004 0.61 1.299 Page 11 of 38 June 2009 Update Sub-basin AREA (km2) Surface Runoff (mm) Baseflow (mm) Total Water Yield (mm) Sediment (mg/ha) Organic Nitrogen (kg/ha) Organic P (kg/ha) Nitrate in surface runoff (kg/ha) Soluble Mineral P (kg/ha) Sediment bound mineral P (kg/ha) Total P (kg/ha) 34 1.38E+01 42.272 36.619 82.554 4.841 7.858 0.943 0.14 0.018 0.752 1.713 35 8.03E+00 45.779 47.536 103.311 4.865 5.756 0.713 0.147 0.015 0.648 1.376 36 1.63E+01 41.155 36.611 81.13 5.508 8.637 1.034 0.123 0.016 0.808 1.858 37 7.86E+00 71.821 93.901 178.555 3.963 4.737 0.582 0.301 0.009 0.714 1.305 38 6.23E-01 60.379 52.918 117.398 10.491 8.53 1.027 0.221 0.005 1.078 2.11 39 2.97E+01 51.589 100.085 167.169 3.579 4.675 0.575 0.184 0.018 0.599 1.192 40 1.10E+01 32.863 32.221 66.38 3.782 6.5 0.791 0.094 0.003 0.554 1.348 41 2.39E-01 37.573 89.244 141.895 1.859 2.549 0.322 0.117 0.003 0.256 0.581 42 9.76E+00 35.479 57.285 99.696 2.994 5.537 0.682 0.104 0.014 0.562 1.258 43 5.64E+00 50.394 37.238 90.2 2.031 3.753 0.47 0.159 0.007 0.432 0.909 44 2.39E-01 68.272 51.862 126.06 1.636 2.306 0.328 0.197 0.005 0.257 0.59 45 3.41E-01 54.859 69.637 137.479 0.968 1.207 0.175 0.151 0.003 0.149 0.327 46 1.08E+01 44.676 82.178 133.882 2.73 3.618 0.436 0.141 0.005 0.472 0.913 47 3.17E+01 67.633 71.945 148.966 5.84 6.645 0.821 0.233 0.007 0.844 1.672 48 9.09E+00 72.984 51.113 128.756 4.478 6.09 0.747 0.267 0.008 0.694 1.449 49 1.56E+01 48.316 64.608 122.413 2.924 4.499 0.556 0.148 0.018 0.534 1.108 50 7.69E+00 59.272 119.231 185.652 2.76 3.342 0.397 0.198 0.007 0.509 0.913 51 4.69E-01 52.32 99.866 172.358 0.875 0.793 0.11 0.14 0.003 0.14 0.253 52 4.18E-01 72.596 53.314 139.115 4.258 4.933 0.624 0.248 0.006 0.58 1.21 53 4.18E-01 51.149 59.582 117.475 5.527 3.89 0.455 0.164 0.005 0.634 1.094 54 1.02E+01 51.24 42.769 97.537 4.672 5.997 0.734 0.157 0.005 0.678 1.417 55 3.56E+00 55.822 69.517 133.307 3.071 3.307 0.396 0.186 0.006 0.494 0.896 56 1.80E+00 56.706 56.26 120.711 2.619 3.573 0.456 0.177 0.005 0.413 0.874 57 8.04E+00 50.824 75.133 131.671 2.129 3.164 0.4 0.172 0.006 0.418 0.824 58 2.83E+01 37.324 73.863 116.036 1.448 3.002 0.372 0.105 0.01 0.297 0.679 59 2.56E-04 29.149 122.047 151.789 5.553 8.264 0.982 0.258 0.009 0.686 1.677 60 1.20E+01 43.583 55.189 103.275 2.564 4.431 0.551 0.138 0.006 0.494 1.051 61 5.99E-02 92.043 48.162 145.011 1.77 2.39 0.302 0.375 0.009 0.366 0.677 62 1.11E+01 34.114 31.551 67.489 5.613 7.922 0.949 0.099 0.003 0.739 1.691 63 3.92E+00 61.29 95.521 171.36 3.253 3.11 0.386 0.206 0.007 0.551 0.944 64 9.31E+00 45.097 120.841 184.917 3.077 2.532 0.3 0.148 0.005 0.492 0.797 65 1.03E+01 45.126 41.258 88.964 2.588 5.11 0.63 0.123 0.016 0.505 1.151 66 1.57E+01 53.374 106.726 177.098 2.706 3.754 0.457 0.168 0.014 0.48 0.951 Page 12 of 38 June 2009 Update Sub-basin AREA (km2) Surface Runoff (mm) Baseflow (mm) Total Water Yield (mm) Sediment (mg/ha) Organic Nitrogen (kg/ha) Organic P (kg/ha) Nitrate in surface runoff (kg/ha) Soluble Mineral P (kg/ha) Sediment bound mineral P (kg/ha) Total P (kg/ha) 67 3.85E+00 59.375 71.051 137.048 2.903 4.243 0.522 0.191 0.005 0.466 0.993 68 8.70E-03 43.584 63.164 112.436 0.007 0.009 0.001 0.094 0.001 0.001 0.003 69 1.80E+00 44.714 46.247 95.734 2.079 3.344 0.417 0.135 0.004 0.344 0.765 70 1.30E+01 26.598 126.714 163.971 1.14 1.639 0.199 0.077 0.003 0.215 0.417 71 7.55E+00 37.126 32.073 71.802 2.793 4.819 0.579 0.094 0.007 0.482 1.068 72 1.40E+00 53.081 82.98 143.678 3.572 5.059 0.614 0.176 0.005 0.548 1.167 73 3.34E+00 45.478 55.954 107.349 1.931 3.024 0.382 0.129 0.004 0.336 0.722 74 8.29E+00 59.304 81.656 151.916 3.641 4.695 0.59 0.187 0.005 0.512 1.107 75 1.24E+01 55.807 87.467 155.92 4.042 5.144 0.618 0.183 0.014 0.651 1.283 76 2.75E+00 96.8 81.318 192.216 12.309 9.954 1.204 0.411 0.012 1.557 2.773 77 1.13E+00 70.043 55.222 132.27 6.565 7.172 0.872 0.246 0.006 0.836 1.714 78 2.70E+00 68.549 64.252 144.007 4.496 5.311 0.699 0.259 0.008 0.717 1.424 79 1.25E+00 68.765 58.196 139.176 4.478 4.673 0.581 0.235 0.006 0.63 1.217 80 1.36E+01 40.901 125.391 186.441 2.599 3.061 0.369 0.132 0.004 0.408 0.781 81 3.33E-01 47.632 90.536 159.356 4.14 4.9 0.674 0.138 0.003 0.388 1.065 82 1.71E-02 35.8 84.674 120.944 1.205 2.99 0.397 0.09 0.004 0.207 0.608 83 9.91E+00 40.605 55.685 99.948 2.405 4.03 0.499 0.123 0.005 0.432 0.936 84 5.80E-01 49.712 86.352 148.054 1.111 1.33 0.175 0.132 0.003 0.17 0.348 85 9.08E+00 53.278 124.399 194.81 2.157 2.228 0.262 0.185 0.021 0.465 0.748 86 1.68E+00 33.15 34.701 69.55 1.149 2.413 0.299 0.092 0.004 0.242 0.545 87 1.96E-01 53.203 84.646 154.727 0.935 1.425 0.2 0.137 0.002 0.121 0.323 88 7.79E+00 39.372 118.206 168.503 1.84 2.465 0.3 0.125 0.005 0.342 0.647 89 8.69E+01 26.772 81.711 113.273 1.679 2.725 0.336 0.076 0.003 0.292 0.631 90 1.62E+01 53.325 61.977 120.823 2.375 4 0.494 0.197 0.006 0.423 0.923 Page 13 of 38 June 2009 Update The SWAT model predictions are subject to the following limitations: • Loads are subject to all the same limitations as those presented in the report: Fort Cobb Basin – Modeling and Land Cover Classification 2003; • The loads are from upland sources only and do not consider bank or stream bed erosion, instream nutrient processes, or deposition of sediment in reservoirs or flood control structures on main channels; • These data contain significantly more uncertainty than absolute load predicted to the lake or basin outlet. With limited calibration data, these data would be best utilized to relatively rank subbasins in terms of their nutrient contributions. Although these predictions are subject to limitations, the estimates provide valuable information about areas contributing most significantly to watershed loading and suggest areas where incentives and other implementation programs should be targeted to have the greatest impact on water resources. These high priority subwatersheds (highest contributing watersheds as depicted in Figure 3) account for approximately 66.17 or 20% of the 329.35 square miles in the watershed and about 30% of the load. Including the next highest contributing set of subwatersheds increases the area to 210.83 square miles or 47% of the watershed and approximately 61% of the load. The TMDL estimated phosphorus loading from septic tanks to be 3,608 kg/year, assuming all watershed residents used septic systems and using a worst case scenario where: • All septic tanks were failing, • Every household was assumed to have one septic tank, equaling 1,124 septic tanks in the watershed, • Effluent from the tanks (11.6 mg P/L) drained directly to streams and lakes, • Persons in the watershed produced 75 gallons of wastewater per day. This loading would be approximately five percent of the total phosphorus loading to the watershed. Given that this is an over estimate of the loading from the current systems, the TMDL determined that loading from septic tanks was insignificant. The primary crops grown in the watershed are wheat (80% of cropland), peanuts, sorghum, and cotton (Storm et. al 2003). Wheat, peanuts, and sorghum are the landuses that provided the highest nutrient and sediment loading in the watershed (Table 3); croplands, which are about 50.4% of the total land in the watershed, account for 90.4% of total P load. With the loss of peanut subsidies, peanut pro-duction has declined in the watershed, and many formerly peanut fields have been con-verted to cotton fields. The SWAT model esti-mated that the conver-sion of peanuts to cotton without BMPs to address cotton could result in increased phosphorus and sediment loading to the lake (Table 4). Cotton is one of the row crops produced in the Fort Cobb Watershed (photo courtesy of Storm et al. 2003). Page 14 of 38 June 2009 Update Table 3. SWAT simulated loads by land cover for the Fort Cobb Basin for the period 1/1990 - 10/2001 (from Storm et al. 2003). Land Cover Fraction of Basin (%) Surface Runoff (mm) Total Stream Flow (mm) Sediment (Mg/ha) Total N (kg/ha) Total P (kg/ha) Forest 6.0% 23.98 178.98 0.01 2.20 0.01 Pasture-Range 41.4% 40.34 105.36 1.61 3.60 0.62 Peanut 7.1% 61.76 147.15 4.06 7.74 1.87 Sorghum 2.8% 96.02 161.33 3.16 6.95 1.20 Urban 0.1% 87.60 100.95 0.05 1.20 0.09 Water 2.1% 0.00 0.00 0.00 0.00 0.00 Wheat for Grain 30.8% 57.58 121.60 5.88 9.90 1.91 Grazeout Wheat 9.7% 56.10 118.77 5.16 8.69 1.81 Basin Average --- 48.47 118.46 3.36 6.26 1.19 Table 4. Load summary for Fort Cobb Basin as predicted by the SWAT model (from Storm et. al 2003). Crop Scenario Runoff (CMS) Total Water Yield (CMS) Sediment (Mg/yr) Total P (kg/yr) Total N (kg/yr) Current 1.37 3.05 301,277 108,031 543,615 Peanuts converted to cotton 1.28 2.95 307,131 110,103 543,461 Further details about the estimation of causes and sources in the Fort Cobb Watershed can be found in the TMDL (ODEQ 2006) and SWAT model reports (Storm et. al. 2003). LOAD REDUCTIONS The draft TMDL estimated that a 78% phosphorus load reduction2 would be necessary to restore beneficial use support to Fort Cobb reservoir. This sets a goal of reducing phosphorus loading from 70,000 kg/yr to 15,400 kg/yr. The TMDL addresses both phosphorus and turbidity impairment to the reservoir because most phosphorus is found attached to sediment, one of the primary causes of turbidity. The TMDL reasons that if phosphorus is reduced to meet water quality standards, then turbidity levels in contributing streams will also be reduced to a level that will meet the turbidity standard. Fortunately, BMPs recommended by the TMDL will also work to address the other sources of impairment in watershed streams including pathogens. The TMDL also estimates that every 1.0% reduction in phosphorus will correspond to a 1.33% reduction in total nitrogen and a 1.5% reduction in sediment delivery to the lake. Further explanation of the methodology for arriving at the 78% load reduction can be found in the TMDL and SWAT model reports (ODEQ 2006; Storm et. al 2003). 2 This includes the load reduction to allow for a margin of safety and potential growth in the watershed. Page 15 of 38 June 2009 Update CRITERIA Fort Cobb Reservoir’s designated beneficial uses include public and private water supply, warm water aquatic community, agriculture, municipal and industrial uses, primary body contact recreation, and aesthetics. The reservoir is the primary drinking water source for the Cities of Anadarko and Chickasha. The goal of the TMDL is to reduce the 1998 – 2001 loading to the lake of approximately 70,000 kg P/year to 15,400 kg P/year. That load reduction is based on the following endpoints, based on Oklahoma’s Water Quality Standards (OWRB 2004a, b): • Trophic State Index (chlorophyll-a based) for Fort Cobb Reservoir less than 62 • Dissolved Oxygen (surface water) o Summer (June 16 – October 15): 4.0 mg/L o Seasonal (October 16 – June 15): 5.0 mg/L • Anoxic volume in Fort Cobb Reservoir less than 50% of water column. Additional criteria that apply to causes of impairment in the watershed are (OWRB 2004): • Turbidity (only applicable during baseflow) 25 NTU for lakes 50 NTU for streams • Coliform bacteria Monthly geometric mean <5000 colonies/100 ml at point of intake • <5% of total samples in any 30 day period will total coliform exceed 20,000 colonies/100 ml • Enterococci bacteria Geometric mean of 33 colonies/100 ml • Escherichia coli (E. coli) Geometric mean of 126 colonies/100 ml • Warm Water Aquatic Community IBI = 22 These criteria stem from Oklahoma’s Water Quality Standards (OWRB 2004a). The procedures by which the data must be collected and analyzed to verify whether or not these criteria have been met are identified in Oklahoma’s Use Support Assessment Protocols (OWRB 2004b). Both of these documents fall under the jurisdiction of the Oklahoma Water Resources Board. NPS MANAGEMENT MEASURES According to the TMDL, croplands account for about 90% of the phosphorus loading in the watershed; therefore, load reduction efforts should focus on cropland (Table 3). The TMDL SWAT modeling applied various scenarios relative to landuse and BMPs used in the watershed to estimate the possible solutions to achieve the recommended 78% phosphorus load reduction. As shown in Table 5, below, the TMDL evaluated the Page 16 of 38 June 2009 Update effectiveness of various BMPs to achieve a phosphorus load reduction. No single BMP type will fully address the required load reduction; a combination of BMPs will be necessary. Table 5. Load reductions for different BMPs (from ODEQ 2006). Practice % Reduction In Total Basin Load Sediment Total N Total P No-till wheat and row crops -51.10% -42.80% -34.40% No winter cover on row crops 9.20% 11.10% 6.80% Worst 1% of cultivated land to pasture -6.00% -3.20% -4.40% Worst 2.5% of cultivated land to pasture -11.50% -8.10% -8.00% Worst 5% of cultivated land to pasture -18.00% -13.90% -12.30% Worst 7.5% of cultivated land to pasture -23.00% -18.30% -15.50% Worst 10% of cultivated land to pasture -26.50% -21.40% -17.90% Worst 15% of cultivated land to pasture -33.00% -27.10% -22.10% Worst 20% of cultivated land to pasture -37.50% -31.10% -25.10% Worst 25% of cultivated land to pasture -41.50% -34.70% -27.70% Worst 35% of cultivated land to pasture -48.00% -40.40% -32.00% Riparian Buffer -75% to -90% -35% to -55% -40% to -60% Nutrient Management -15% -35% In addition to the BMPs mentioned above, grade stabilization structures are necessary in this watershed due to the highly erodible soils; damage is already evident in the watershed with extensive gullying and rill erosion being relatively common. The SWAT model could not predict areas where grade stabilization structures would be necessary, nor could it predict the loading reduction that would result from installation of these structures. Such a prediction would require extensive reconnaissance in the watershed and ultimately, a conservation plan for every producer. However, an estimate of the need can be roughly extrapolated from the need demonstrated with the FY 2001 §319 project, where approximately 25% of the cooperators required grade stabilization structures to reduce erosion. The FY 2001 §319 project funded a targeting exercise based on the SWAT model that was later expanded into the TMDL. Results of that exercise were used to focus implementation into areas of origin for the bulk of the sediment and phosphorus loading. Subsequently, the OCC used these results in conjunction with the recommendations of the TMDL as part of a FY 2005 §319 project. Figure 6 displays results of the 2003 targeting effort. Implementation of BMPs in the red areas was expected to reduce nutrient loading to the watershed by approximately 50%. Implementation of BMPs in the yellow areas could reduce nutrient loading by an additional 30%. Page 17 of 38 June 2009 Update Figure 6. Location of areas in Fort Cobb Watershed most likely contributing the greatest portions of total sediment, and therefore phosphorus loading. Page 18 of 38 June 2009 Update TECHNICAL AND FINANCIAL ASSISTANCE NEEDED The amounts of technical and financial assistance needed are closely tied to one another. All programs to implement NPS BMPs outlined in the above section require technical assistance in the form of a plan writer, certified by the NRCS. Such a position typically costs a total of $42,000 - $61,000 per year, including benefits. NRCS funds this technical support for their own programs (mainly EQIP in this watershed), but programs like a Conservation Reserve Enhancement Program or §319 must fund technical support through some other means. In addition, part-time help may be required to address the needs of the tri-county area. Any staff that provides technical support would be best served to work through the local conservation district and NRCS offices, as these are the places local landowners are most comfortable in going to for technical support. Therefore, it is beneficial to provide assistance to these districts to help support the program. Funding necessary to implement the BMPs recommended by the TMDL is estimated using a combination of best professional judgment, based on experience in the watershed, and use of the PRedICT model. These values are seen in Table 6. An initial value of approximately $16 million has been estimated as necessary to implement the TMDL recommended practices. However, this value will likely change as the programs evolve and the Watershed Based Plan is updated. The actual amount of funding for BMP implementation in each of the OCC’s projects is given below: 2001 Fort Cobb project (2001-2005): 128 cooperators $1,386,611 of practices installed, total: $365,650 from State funds $498,054 from Federal 319 funds $522,907 from landowners (38%) 2005 Fort Cobb project (2005-2008): 60 cooperators $865,403 of practices implemented, total: $502,556 from State funds $290,250 from Federal 319 funds $72,597 from landowners (8%) Table 7 provides some estimates of funding planned or already implemented for technical support in the watershed. Some of these are multi-year efforts, and some are single-year efforts. At a minimum, around $160,000 is required for technical support each year to provide support to the conservation districts and personnel to meet with landowners and draft conservation plans. Table 8 estimates funding necessary to support monitoring needs in the watershed. Not all information is available at this time regarding monitoring costs for USGS or Bureau of Reclamation; however, available information suggests that at least $230,000 is needed every five years. Page 19 of 38 June 2009 Update Table 6. Funding Needs for Technical Support for Implementation of BMPs. Project/Funding Source Task Federal State Cost Share Funds Total FY 2001 §319 Fort Cobb Project- five year period On-Site Coordinator $225,000 $225,000 Plan Writer $80,000 $80,000 District Support $75,000 FY 2005 §319 Fort Cobb TMDL Implementation Project- salaries and support for 2 years beyond 2001 project On-Site Coordinator $121,000 $121,000 District Support $15,000 $15,000 Conservation Reserve Enhancement Program (CREP)- funding for 2-3 years of technical support Plan Writer $94,000 - $312,000 $94,000 - $312,000 NRCS District Conservationists (3) $52,000 - $85,0003 $52,000 - $85,000 Total $609,800 - $642,800 $94,000 - $312,000 $703,000 - $954,800 3 Estimated from GS 9/11 salary range + benefits. Page 20 of 38 June 2009 Update Table 7. Funding Necessary to Implement TMDL Recommended Practices to Restore Beneficial Use Support to Fort Cobb Reservoir. Load Reduction TMDL Recommended BMP Project/Funding Source TMDL Federal State/Local Total target Anticipated from this project 17% 7% No-till in 50% of wheat and other row crop FY 2005 §319 Fort Cobb TMDL Implementation $672,380 $586,754 $1,259,1344 10% CSP, EQIP $930,000 25% Convert 20% of worst cultivated land to pasture FY 2001 §319 Fort Cobb Project EQIP, CSP $2,050,0005 30% 1% Riparian Areas in 60% of watershed FY 2001 §319 Fort Cobb Project $38,802 $25,867 $64,669 15% 2010 CREP $4,726,790 $945,358 $5,672,148 14% EQIP, CRP, CSP $4,235,204 $1,058,801 $5,294,005 31.5% 31.5% Nutrient Management Plans for 90% of producers FY 2001 and 2005 §319 Programs, EQIP, CRP, CSP $375,0006 ??? ??? Grade Stabilization Structures FY 2001 §319 Fort Cobb Project $92,804 $61,870 $154,674 ??? EQIP,??? Total $15,799,630 4 Represents an estimated start-up costs for no-till on 39% of cropland based on purchase of no-till drills for the 4 conservation districts, 30% cost-share on purchase of 10 drills for landowners, and $10/acre incentive payment (rate recommended by Fort Cobb WAG) for a three year period. Does not include technical support costs seen in Table 3. 5 Assumes a cost of $51 per acre (based on pasture costs in 20% of cultivated land (40,192 acres) 6 $5.00/acre/year for 90% of all crop and pastureland in the watershed, based on annual incentives offered through other State 319 programs, plus annual cost of soil testing. Most likely would only need to apply to all cropland, as few producers fertilize pasture, which would reduce costs to $250,000 annually. Page 21 of 38 June 2009 Update Table 8. Monitoring Funding Needs Associated with Fort Cobb Watershed. Monitoring Program Parameters assessed State Federal Total OCC Rotating Basin Stream water quality, biological community, habitat, hydraulic budget, riparian condition, landuse / landcover, $10,000 - $30,000 every 5 years $10,000 - $30,000 every 5 years OWRB BUMP Program Lake Water Quality $10,000 annually $10,000 annually Watershed modeling (OSU, ODEQ, ARS) Landuse / Land Cover, BMP implementation, Load reduction $150,000 every 5 years USGS Groundwater/Surface Water Quality, Load reduction ??? ??? Bureau of Reclamation ??? ??? ??? IMPLEMENTATION SCHEDULE The TMDL recommends a 78% load reduction from loading seen between 1998 and 2001. Implementation towards this load reduction has progressed with formal programs such as the FY 2001 and 2005 §319 Projects and passive changes resulting from the loss of peanut subsidies. Measures of water quality changes as a result of those efforts are not fully available at this time; however, information is available on the implementation completed through the FY 2001 and 2005 programs such that an estimate of potential load reductions attributed to the project activities thus far has been estimated. These reductions are seen in Table 7 under the “Load Reduction” column under “Anticipated from this project”. These efforts are initial steps towards full implementation of the TMDL recommendations. Table 9 presents a schedule towards implementation of the remaining TMDL recommendations. Included in table 9 is a column that schedules the evaluation of each program. Failure of the programs to meet planned implementation level or load reduction goals will result in adaptations, as possible during the program period or, as necessary, with follow-up, supplemental programs until the load reduction goals have been met. The ARS CEAP program provides an excellent opportunity to evaluate the progress of these programs towards the TMDL-established goals. The Watershed Based Plan will be updated following the completion of the ARS effort in 2010 to summarize its findings and to make necessary adaptations to reach the TMDL load reduction goals. Page 22 of 38 June 2009 Update Table 5. Schedule for Implementation of TMDL-Recommended Practices. TMDL-recommended practice Program proposed to implement Begin Date Completion Date Date to evaluate Agency(ies) / Group(s) involved No-till 50% of row crops and wheat pasture FY 2005 §319 Project October 2005 January 2009 Annually during project, and following completion of the CEAP program. OCC, conservation EQIP, CSP, ??? Immediate Ongoing districts, USDA Convert 20% worst cultivated land to pasture FY 2001 §319 Project7 October 2001 September 2006 Annually during the project, and following completion of the CEAP program. OCC, conservation districts, USDA USDA Programs such as EQIP, CRP, etc. ongoing ongoing following completion of the CEAP program NRCS, FSA, ARS, Conservation Districts Riparian Buffers in 60% of Watershed FY 2001 §319 Fort Cobb Project October 2001 September 2006 Annually during the project, and following completion of the CEAP program. OCC, conservation districts, USDA 2010 CREP 2010 2025 Annually during the project period FSA, NRCS, OCC, Conservation Districts EQIP, CRP, CSP, and ??? ongoing ongoing following completion of the CEAP program NRCS, FSA, ARS, Conservation Districts Nutrient Management Plans for 90% of Producers FY 2001 and 2005 §319 Programs, EQIP, CRP, CSP, and ??? ongoing ongoing Annually during the projects, & following completion of the CEAP program NRCS, FSA, ARS, Conservation Districts, OCC Grade Stabilization Structures FY 2001 §319, EQIP, CSP, and ??? ongoing ongoing Annually during the project & following completion of the CEAP program NRCS, FSA, ARS, Conservation Districts, OCC 7 The project did not implement much of this conversion; however, based on recommendations of the TMDL, the Project Coordinator attempted to contact landowners of the worst-cultivated lands to encourage them towards pasture conversion using either the 319 program or USDA programs. Page 23 of 38 June 2009 Update The following is a summary of the implementation achieved through the OCC’s 2001 and 2005 §319 projects (2001-2008): 21,086 acres of no-till farming 32 grade stabilization structures 8 diversions, 7 grassed waterways, and 2 terraces 230 acres of riparian area exclusion fencing 1 stream crossing 10,767 acres of cropland converted to pasture 957 acres of grass planting for pasture improvement 35,030 linear ft of cross-fencing 4 wells 4 septic systems Visible improvements from no-till implemented through the §319 program are obvious throughout the watershed. Often, large piles of sandy soil accumulate along fence lines and in fields when dry and windy conditions occur in this area. No-till helped to hold moisture in the soil and reduce the amount of soil lost by wind and rain erosion, as seen in the photos below (Figure 7). The first two photos are of a no-till field, while the next two photos are of an adjacent, conventional till field. Much of the wheat in the conventional till field has been covered by soil which blew or washed over the plants. No-till wheat field Fence along no-till wheat field Figure 7. Two adjacent wheat fields, the top in no-till and the bottom in conventional till. Conventional till wheat field Fence along conventional till wheat field Eroded soil mounded along fence line Eroded soil covering wheat in field Fence along conventional till Conventional till wheat field wheat field Page 24 of 38 June 2009 Update The OCC’s no-till program has resulted in implementation of almost 30% of the TMDL goal for no-till. An additional 30% of row crops have been converted to conservation tillage, so at least 60% of the row crop acreage in the watershed is now in some form of conservation tillage (Table 10). In addition, approximately 63% of the TMDL goal for converting row crops to pasture has been achieved through the §319 program. NRCS EQIP has provided funding for both no-till and conservation tillage as well, so additional progress toward the overall TMDL goal has been made. Table 10. OCC §319 progress toward TMDL goals, 2001-2008. Total conventional row crop in basin at start of project: 98,289 acres BMP Total Amount Implemented (acres) Goal for TMDL (acres) % Towards TMDL Goal Row Crop Converted to No-Till 16,401 58,973 27.8 Row Crop Converted to Conservation Tillage 17,286 58,973 29.3 Convert Worst Row Crop to Pasture 12,462 19,658 63.4 Establish Riparian Buffers 169 8,547 2.0 A phosphorus load reduction of approximately 20% has already been accomplished since 2001 due to a dramatic change in crop production in the watershed (ODEQ 2006). Specifically, many acres that were used for peanut production have now been converted to wheat production or pasture. According to the SWAT watershed model (Storm et al. 2006), if there was 100% conversion of row crops and wheat to no-till, total phosphorus loading would be expected to decrease by 34%. Based on the conversion of 16,000 acres to no-till, total phosphorus loading should be reduced by approximately 6%. The maturation of other BMPs, installed as part of the 2001 and 2005 projects, will further reduce the phosphorus loading in the watershed. Approximately one-third of the implementation from 2001-2008 occurred in areas that were expected to be contributing high levels of phosphorus, according to the SWAT model: • Of the 9,188.6 acres that were in the top 10% of phosphorus load supplying areas, 32% now have BMPs on them; • Of the 10,033.2 acres in the next 10% of high phosphorus areas, 27% have BMP implementation. Figure 8, below, shows the overlay of implementation and targeting. Further details about the OCC implementation projects can be found in the final reports associated with the 2001 and 2005 projects. Page 25 of 38 June 2009 Update Figure 8. Overlay of regions of high phosphorus loading (targeted regions) onto areas of BMP implementation through the §319 program, 2001-2008. A Conservation Reserve Enhancement Program (CREP) is planned for the Fort Cobb watershed beginning in 2010. This project aims to restore stable riparian vegetation and riparian buffers and to reduce livestock access to floodplains. This will result in reduced overland flow of pathogens and phosphorus to the streams and will lessen streambank erosion by stabilizing stream banks. Overall, this will lead to better water quality, lower maintenance requirements to the road and highway system, and will help to preserve existing floodplain cropland, pasture, and rangeland. The WBP will be updated at the conclusion of the CREP signup to estimate the load reductions expected from this implementation. Page 26 of 38 June 2009 Update INTERIM MILESTONES Interim milestones towards addressing the recommendations of the TMDL will continue to be developed as activities are implemented under the Watershed Based Plan. Some of these have already been completed through various project workplans, others are ongoing or planned. Project Description Responsible Party Target Date Complete TMDL Compile watershed loading model and link to lake model ODEQ, OSU 2003 X Calibrate model to water quality monitoring data ODEQ 2003 X Develop draft TMDL ODEQ 2004 X Solicit public input to draft TMDL ODEQ 2005 X Submit to EPA ODEQ 2005 X 2001 §319 Project Hire Local staff- project and education coordinators and plan writer OCC, Conservation Districts (CDs) 2002 X Establish agreements with CDs OCC, CDs 2001 X Establish a WAG and EdWAG CDs 2001 X Complete GIS-Based Targeting OCC, WAG 2001 X WAG selection of BMPs and cost-share rates WAG, OCC 2001 X Watershed Implementation Plan OCC 2002 X BMP Demonstration OCC, CDs 2002 – 2006 X Develop education program to educate producers and other watershed citizens about problems and solutions EdWAG 2002 X Identify oil and gas related sources in the watershed Corp. Comm 2001 - 2002 X Hire companies to plug abandoned wells Corp. Comm. As needed Ongoing Educate current operators and when necessary take enforcement actions Corp. Comm. As needed Ongoing Sample creeks, streams, and agricultural lands in watershed for pesticides and fertilizer-related parameters ODAFF8 2002 X Conduct pesticide education programs ODAFF 2001 - 2003 Ongoing Summary of Project Activities including estimation of load reduction due to practices implemented and comparison of implementation to TMDL recommendations OCC, ODAFF, Corp. Comm. 2006 X 8 Oklahoma Department of Agriculture, Food, and Forestry Page 27 of 38 June 2009 Update Project Description Responsible Party Target Date Complete 2005 §319 Project Further delineate targeted areas based on TMDL recommendations OCC 2006 X Implement no-till practices OCC, CDs 2006 - 2008 X Update WBP OCC 2008 X Follow-up GIS evaluation of implementation OCC 2008 - 2009 X Instream Habitat Monitoring to Support ARS CEAP Project and evaluate success of BMPs OCC 2006 - 2008 X CEAP Water Quality monitoring, watershed modeling, and compilation of BMPs implemented in watershed to evaluate impacts of BMPs ARS, NRCS, OCC 2005 - 2010 Ongoing CREP Develop program plan with FSA and NRCS OCC, FSA, NRCS 2003 – 2005 X Secure State match and Governor’s approval OCC, OSE 2007 X Submit plan to USDA OCC, FSA, NRCS 2009 Planned Begin implementation OCC, FSA, NRCS 2010 - 2013 Planned EQIP Explore possibility of declaring watershed a special emphasis area to secure higher funding level FSA, NRCS, CDs Annually Ongoing Continue to implement EQIP practices annually in watershed CSP Designate watershed as a CSP priority watershed FSA, NRCS, CDs ??? ??? WBP Update Watershed Based Plan and evaluation of progress towards TMDL goals with watershed modeling at least every five years or more frequently upon completion of major tasks/projects OCC, WAG 2012 Ongoing Continue water quality monitoring to identify sources, causes, and progress towards TMDL goals OWRB, Bureau of Recl., USGS, OCC, ARS Annually Ongoing PUBLIC OUTREACH Many local efforts, as well as efforts by state and federal agencies and other organizations, are collectively contributing to the Public Outreach efforts in the Fort Cobb Watershed. Public outreach will need to be continued in order to reach the water quality goals of restoring beneficial use support and attaining water quality standards in the watershed. This section identifies those agencies, organizations, and services that are active in the Page 28 of 38 June 2009 Update watershed (in no particular order). To varying degrees, these groups have been, and will continue to be, active in development and expansion of the Watershed Based Plan and other planning efforts in the watershed. The roles of these groups and programs are summarized below: 1. Deer Creek, West Caddo, North Caddo, and Mountain View Conservation Districts These agencies are critical to ensuring participation of local landowners in water quality improvement programs. Local Conservation Districts are generally the most effective means to bring a large federal or state program to private citizens because the local agencies know the local people. Local agencies often have the most accurate knowledge concerning current land management practices and local needs. In addition, these agencies have existing programs and mechanisms directed towards the goals of the WBP. The Conservation Districts, partnered with the OCC, NRCS, and Cooperative Extension, have been among the primary agencies responsible for public outreach in the watershed. The districts and NRCS work one-on-one with citizens of the watershed to reduce pollution and educate about the importance of protecting water resources. These groups also organize or participate in seminars, training sessions, and meetings to interact with local people and provide technical assistance and information. The Deer Creek Conservation District has a very active education program through its outdoor classroom. This program targets mainly elementary school children and teaches them about environmental issues. In addition, Deer Creek has housed the Education Coordinator for the FY 2001 and 2005 §319 Fort Cobb Projects and served as the hub for education activities of that project. 2. Watershed Advisory Group (WAG) and Education Watershed Advisory Group (EdWAG) The success of water quality protection programs in the Fort Cobb Watershed depends on the approval and cooperation of the local landowners and various government agencies. The WAGs were made up of local shareholders in the watershed (including private citizens, representatives of local industries, and local government) who provided guidance in delivering the §319 programs based on information supplied to them by technical agencies in conjunction with their knowledge of the needs of the watershed residents. The WAGs were developed to help insure that the programs most effectively worked towards reducing water quality impacts, but, at the same time, met the needs of and were acceptable to the local producers and other landowners. The WAG recommended the practices and cost-share rates to reduce the NPS pollution problems in the watershed. The EdWAG considered the issues in the watershed and recommended an education program to help inform watershed citizens about those issues using a “show and tell” approach. 3. The Oklahoma Conservation Commission (OCC) With the 2001 project, the OCC devoted almost $2.3 million towards a program to educate citizens and implement best management practices to reduce nonpoint source pollution in the watershed. A portion of these funds support the WAG, a portion is devoted to Page 29 of 38 June 2009 Update identifying the major sources in the watershed and monitoring the success of the program, another portion is devoted towards education, but the majority of the funds provides cost-share assistance to farmers to implement WAG-recommended and OCC-approved BMPs to protect the water resources of the watershed. This effort was extended through the FY 2005 program, which focused on recommendations of the TMDL, primarily no-till. The OCC’s main function is to provide oversight for successful completion of the program. To do this, they provide technical guidance and final approval to the WAG and local conservation districts for implementation of the BMPs. The OCC implemented an education program targeted towards citizens of the watershed whose change in behavior could have the most substantial impacts on water quality. The OCC is also responsible for monitoring the success and providing administrative support for the §319 projects, and working with NRCS and FSA to implement a CREP Program in the watershed. In addition, Blue Thumb, OCC’s education program, is active in the Fort Cobb watershed. Streams are monitored by volunteers and school groups are taught about water quality through this program. 4. Oklahoma Cooperative Extension Service (OCES) The Oklahoma Cooperative Extension Service (OCES) is another leader in promoting water quality education efforts in the State, working closely with the conservation districts and the NRCS to promote water quality awareness. The OCES provides one-on-one meetings and education with landowners along with group presentations and other forms of technical assistance to improve awareness in the watershed. The OCES also develops and utilizes test plots and demonstration sites to educate producers about the effectiveness of certain best management practices. One such set of test plots, developed by the Oklahoma State University Cooperative Extension Service, was utilized to demonstrate methods of integrated pest management and effectiveness of more managed fertilizer application in wheat production. The OCES also holds public meetings and workshops to educate landowners on topics such as pesticide and fertilizer management, animal waste issues, and general BMPs. 5. NRCS Local Offices and FSA (USDA) The United States Department of Agriculture Natural Resource Conservation Service (USDA/NRCS) and Farm Services Agency (FSA) in Oklahoma have several programs active in or that could be expanded in the Fort Cobb Watershed. These programs include the Environmental Quality Incentives Program (EQIP), Conservation Reserve Program (CRP) and Conservation Reserve Enhancement Program (CREP), Wildlife Habitat Incentives Program (WHIP), and the Wetlands Reserve Program (WRP). These programs are employed by the USDA to help landowners protect natural resources. 6. Oklahoma Corporation Commission (Corp. Comm.) Corp. Comm., as the state agency with jurisdiction over oil and gas mining activities, has Page 30 of 38 June 2009 Update ongoing efforts in the watershed to identify and reduce impacts from oil and gas activities. These include efforts to identify location and severity of erosion related to well sites and pipelines, followed by cleanup by the operators and pipeline companies. Corp. Comm. will begin additional work in the watershed to further identify problem areas in the watershed and initiate educational and other actions for site operators. These efforts range in extent from informing landowners about who to contact in the case of pollution occurring at well sites or exploration sites to what best management practices can be utilized during exploration and operation of oil and gas sites. Another focus of additional planned Corp. Comm. activities includes efforts to reduce impacts from abandoned oil and gas activities. 7. Oklahoma Department of Agriculture, Food, and Forestry (ODAFF) The ODAFF has an ongoing project aimed at reducing impacts of fertilizers and pesticides to surface and groundwater in the watershed. The program has attempted to locate sources or likely sources of contamination from these fertilizers or pesticides and conduct educational programs to reduce the impact of those sources. 8. Bureau of Reclamation Fort Cobb Reservoir is owned by the Bureau of Reclamation, which has played an active role in the watershed with cooperative efforts towards water quality monitoring, land management, and education. 9. Agricultural Research Service (ARS) The ARS is currently pursuing a project to evaluate the success of BMPs implemented in the watershed through the Conservation Effects Assessment Project (CEAP). This program will involve water quality monitoring, watershed modeling, and cooperation with local conservation districts, NRCS, OCC and similar agencies to obtain current information on management practices in the watershed. Information will be shared regarding the success of programs and can be used to improve efficiency with cost-share and other implementation programs, as well as to evaluate progress towards meeting the goals of the TMDL. Youth education is a significant effort pursued by OCES, NRCS, and the conservation districts. Most youth education activities focus on general water quality maintenance and improvement and include activities such as 4-H group water quality monitoring and education, “Earth-Day-Every-Day” activities fair where hundreds elementary school children and some of their parents are exposed to environmental education, and various other training sessions. Newspaper articles and other media are a method that can be used to inform citizens of the watershed about programs focused on water quality. The OCES, Conservation Districts, and NRCS often contribute articles that were released to local papers, covering a wide range of topics related to water quality, and more specifically, advertising education Page 31 of 38 June 2009 Update events and programs. Many articles serve as promotions for various upcoming trainings or other events. Other media related activities such as radio spots and logo contests can be used to further the efforts of the program. However, in using media and advertising in education programs, efforts must focus on measurable results. An information article about water quality is not enough; the article must be associated with some additional effort that is likely to change behaviors. Information alone doesn’t often change people’s behaviors; people must be persuaded to change their behavior. Persuasion is more likely to occur as part of a program of repeated contact and interaction than as the result of a well-written article in a newspaper. Current outreach programs in the watershed will need to expand and perhaps partially redirect their public outreach efforts to work towards more measurable results. Although current education efforts are valuable programs, efforts may need to be expanded to insure that the target audience is being reached. The target audience is the people whose change of behaviors could have the most substantial benefits to water quality. In other words, the target audience in the Fort Cobb Watershed should include people such as county commissioners and road maintenance crews, agricultural producers, and people in the oil and gas industry, among others. Existing and planned outreach programs will need to coordinate among themselves and with other ongoing efforts in the watershed in order to educate more watershed citizens and more importantly, change behaviors of land users in the watershed. Public Outreach to assure support of this and future evolutions the Watershed Based Plan will come from: • Conservation District Newsletter and/or website • Continued support the WAG or a similar group • Public meetings and listening sessions held throughout the local communities (and eventually, throughout the watershed) • Regular media coverage of activities/issues (both at local and State levels) • Education programs such as the ones developed in the 2001 and 2005 §319 projects that involve segments of the community ranging from school children to agricultural producers to homeowners and lakeside residents • Programs that encourage local citizens to experience “ownership and understanding” of environmental issues such as volunteer monitoring, clean-up events, and other educational grassroots efforts to address the problem MONITORING PLAN Every Watershed Based Plan requires a monitoring plan to gage overall success of restoration and remediation efforts. The goal of the monitoring plan for this WBP will be to expand current monitoring efforts into a long-range monitoring program with clearly defined milestones that will oversee the progress towards the TMDL recommended load reductions, restoration of the beneficial use support in the watershed, and preservation of natural resources for future generations. Page 32 of 38 June 2009 Update The monitoring plan for this WBP provides for development of individual monitoring plans and associated quality assurance plans and Standard Operating Procedures for each underlying project or effort working toward the ultimate goal of restoration of beneficial use support. These monitoring efforts must be based on Oklahoma’s Water Quality Standards and Use Support Assessment Protocols, which define the process by which beneficial use support can be determined. Technical assistance in developing these plans can come from various sources including the Oklahoma State Agency peer review process, and the Oklahoma Water Quality Monitoring Council. In addition, local stakeholders need to be involved in developing these plans to ensure that the plans address monitoring needs identified by stakeholders and that stakeholders remain informed about watershed monitoring activities. Monitoring methodologies specified in this WBP have been selected to provide: 1) a quantifiable measure of changes in parameters of concern, 2) success measures that can be easily understood by cooperators and stakeholders with a variety of technical backgrounds, and 3) consistent, compatible information throughout the watershed. As the WBP evolves, it is anticipated that this list will expand and contract. Monitoring will focus on the primary causes of impairment, as listed in the 303(d) list, but will also consider related causes that may exacerbate the impacts of the primary causes or may ultimately reach impairment levels without improved management. The primary types of monitoring to be conducted in the Fort Cobb Watershed include: • Surface water quality: nutrients, sediments, suspended solids, fecal bacteria, dissolved oxygen, temperature, pH, conductivity, alkalinity, hardness, turbidity, chlorophyll-a, pesticides, BOD • Hydraulic budget: in-stream flows, infiltration rates, aquifer recovery, groundwater levels • Groundwater quality: nutrients, metals, pesticides, pH • Landuse/Land cover: acreage in different landuses, quality and type of land cover, timing and other variables of associated management practices • Riparian Condition: extent and quality of riparian zones in the watershed, to include quality and type of vegetation, degree of impact or stability, condition of streambanks, and primary source of threat or impact • Aquatic Biological Communities: assessment of the condition of fish and benthic macroinvertebrate communities related to reference streams and biocriteria • BMP and other implementation effort coverages: type, extent, and when possible, specific location of practices to include an estimate of the potential load reduction effected by implementation • Behavioral change: participation in Watershed Based Plan-related activities and behavioral changes of affected communities • Sediment quality: nutrients, pesticides, other organics of concern With each WBP-related program, as well as for the WBP as a whole, baseline conditions will be established and monitored prior to implementation. A monitoring schedule and Quality Assurance Project Plan (QAPP) will be developed based on the type of project and Page 33 of 38 June 2009 Update timing of its implementation. Monitoring results will be reported to appropriate local, state, and federal entities as defined in the QAPPs. Baseline Data The baseline data to evaluate progress in the Fort Cobb Watershed has been established by the draft TMDL. This includes watershed data from primarily the period between 1998 – 2001. Specifically, this data is listed below: • 2000 census data to estimate watershed population and septic tank loading in the watershed • SWAT model used: o Land use was determined using data retrieved from June 10, 2001 30 m resolution Landsat TM imagery, a crop type breakdown based on 1999-2001 Oklahoma Agricultural Statistics Service data, and center pivot irrigation locations tagged from aerial photos. o 1 meter resolution Digital Orthophoto Quarter Quads (DOQQ) from 1995 for the entire Fort Cobb Basin were used in ground-truthing the Landsat data. o Soil test phosphorus for common agricultural land covers was derived from OSU county level averages for the period 1995-1999. o The model was calibrated for flow for the period January 1990 through October 2001 and validated for flow in Cobb Creek for the period 1975 – 1989. o 10 m USGS DEM o 200 m NRCS MIADS Soils Data o EPA Reach3 Streams o National Inventory of Dams o County level National Agricultural Statistics Service (NASS) cattle estimates for the period 1996-2000 were combined with land cover data to estimate the number of cattle within the basin. o Approximate CAFO locations and animal numbers were taken from an Oklahoma Department of Agriculture coverage available at the ODEQ website. The metadata are listed at the following address: http://www.deq.state.ok.us/deqmap/help/CAFO.htm. o Few stream gage data were available to calibrate the SWAT Model for the period Jan 1990 - Oct 2001. The only suitable gage was Cobb Creek near Eakley (USGS 07325800). The hydrologic calibration was performed almost entirely with data from this gage. Another gage downstream of the Fort Cobb Reservoir was also utilized as a check of the calibration. • OWRB and USFWS lake data collected in 1998-1999 was used to calibrate the model, and USGS and USFWS data collected in 2000–2001 was used to validate the model. • Atmospheric deposition of nutrients was based on annual data for Oklahoma downloaded from National Atmospheric Deposition Program’s web site. The average of the data from 1998 to 2001 was used in the model. • Hourly weather data, daily flow data, and daily loadings (from the SWAT model) to the lake were also used in the model. Weather data was obtained from Oklahoma Mesonet for the Fort Cobb station. The data includes hourly atmosphere pressure, Page 34 of 38 June 2009 Update air temperature, wind speed and direction, relative humidity, rainfall, and solar radiation. The hydraulic data was downloaded from Army Corps Of Engineer's web site (http://www.swtwc.usace.army.mil/FCOBcharts.html). The data includes daily inflow, release, pool elevation, and evaporation. Once again, 1998 – 1999 data was used in calibration, and 2000 – 2001 data was used in validation. Data Collection Responsibilities for Current and Future Monitoring Responsibility for the collection of additional data of the types described above will reside with project managers of the individual projects as spelled out their individual work plans. These project managers will be responsible for ensuring that the data is submitted to the ODEQ for inclusion in the Oklahoma State Water Quality Database, which will ultimately be uploaded to the National STORET database. Data reporting under individual workplans will also be the responsibility of the project managers. Monitoring results will be made public through the ODEQ’s website, at a minimum. In addition, project and monitoring results should be presented locally with a public meeting or to the WAG or similar group. In addition to those monitors to be identified in the workplans of the individual projects under this WBP, the following groups, at a minimum, will be involved in monitoring activities: • Oklahoma Water Resources Board: Beneficial Use Monitoring Program and Oklahoma Water Watch Monitoring Program • Oklahoma Conservation Commission: Rotating Basin Monitoring Program, Priority Watershed Project Monitoring, and Blue Thumb Project Monitoring • U.S. Geological Survey: Surface and Groundwater quality and quantity monitoring and special studies • Oklahoma Department of Agriculture, Food, and Forestry: soil sampling associated with CAFO regulations • ARS: CEAP associated monitoring • US Bureau of Reclamation Currently, the OCC has two sites in the Fort Cobb watershed which are part of the Rotating Basin monitoring program. These sites were sampled every five weeks from 2004-2006 and will be sampled again from 2009-2011. The parameters measured include water temperature, dissolved oxygen, pH, specific conductance, alkalinity, turbidity, instantaneous discharge, nitrate, nitrite, orthophosphate, total phosphorous, total Kjeldahl nitrogen (TKN), ammonia, chloride, sulfate, total suspended solids, total dissolved solids, 5-day biochemical oxygen demand (BOD5), and total hardness, as well as biological (fish and macroinvertebrates) and habitat data. The OWRB has 6 sites in the reservoir from which physico-chemical data are collected quarterly. The parameters measured include turbidity, true color, dissolved oxygen, metals, chloride, sulfates, total dissolved solids, pH, nutrients, temperature, and chlorophyll-a. The USGS has 5 “real time” gauging stations in streams in the Fort Cobb watershed, as Page 35 of 38 June 2009 Update well as one reservoir station and a meteorological station from which data may be accessed. The parameters collected include temperature, instantaneous discharge, conductivity, dissolved oxygen, pH, nutrients, suspended sediments, and alkalinity. The ARS has been monitoring 15 sites in the Fort Cobb watershed since 2004 as part of a national CEAP Watershed Assessment Study. Fortunately, Fort Cobb is included within one of the 12 benchmark watersheds in the US, and as a result, ARS, working collaboratively with the Great Plains RC&D, will complete an extensive bi-weekly water quality monitoring program. This program includes monitoring of the following paramters: pH, dissolved oxygen, conductivity, salinity, total dissolved solids, temperature, turbidity, oxygen reduction potential, nitrate concentration, ammonia concentration, suspended sediment, and phosphorus. The Great Plains RC&D will work collaboratively with ARS to contact farmers to obtain conservation and production management information relevant to the assessments. Benefits of the Monitoring Plan Implementation of this monitoring plan will enable Fort Cobb partners to meet the goals of the WBP, which is ultimately to restore beneficial use support to waters of the Fort Cobb Watershed. Implementation of the monitoring plan will help further define areas of the watershed where restoration activities should be focused to realize the optimum benefit for the investment as well as evaluating the impacts (realized and potential) of implementation efforts. Collection of the data described under this monitoring plan will help define the relative contributions from various sources in the watershed and the processes contributing to water quality degradation in the watershed. And finally, continued collection of this data and evolution of the monitoring plan for the watershed will allow the program to adapt to meet the changing needs of watershed protection in the Fort Cobb Watershed. Page 36 of 38 June 2009 Update REFERENCES ODEQ. 2008. The State of Oklahoma 2008 Water Quality Assessment Integrated Report. Oklahoma Department of Environmental Quality, Oklahoma City, OK. ODEQ. 2006. TMDL Development for Fort Cobb Creek Watershed and Fort Cobb Lake: FY 99 Section 319(h) Grant #C9996100-07 Final Report. Oklahoma Department of Environmental Quality, Oklahoma City, OK. OWRB. 2002. 2002 Report of Oklahoma Beneficial Use Monitoring Program. Oklahoma Water Resources Board, Oklahoma City, OK. OWRB. 2004a. Oklahoma Water Quality Standards, Oklahoma Administrative Code, Chapter 45. Oklahoma Water Resources Board, Oklahoma City, OK. OWRB. 2004b. Implementation of Oklahoma’s Water Quality Standards, Oklahoma Administrative Code, Chapter 46. Oklahoma Water Resources Board, Oklahoma City, OK. Storm, D. E., M.J. White, and S. Stoodley. 2003. Fort Cobb Modeling and Land Cover Classification Final Report. Oklahoma State University Biosystems and Agricultural Engineering. Stillwater, OK. Page 37 of 38 June 2009 Update APPENDIX A: TMDL Development For Cobb Creek Watershed And Fort Cobb Lake FY99 Section §319(h) Grant #C9996100-07 FINAL REPORT 2006 TMDL Development For Cobb Creek Watershed And Fort Cobb Lake FY99 Section 319(h) Grant #C9996100-07 FINAL REPORT Prepared by Paul Yue Oklahoma Department of Environmental Quality June 26, 2006 June 26, 2006 Table of Contents EXECUTIVE SUMMARY …………………………………………………………………….vi 1. INTRODUCTION................................................................................................................... 1 1.1 LATEST REVISION.................................................................................................................. 1 1.2 INTRODUCTION..................................................................................................................... 1 2. PROBLEM DEFINITION...................................................................................................... 6 3. APPLICABLE WATER QUALITY STANDARDS............................................................. 8 3.1 STANDARDS FOR STREAMS.................................................................................................... 8 3.1.a. Standards for nutrients ................................................................................................ 8 3.1.b. Standards for Dissolved Oxygen................................................................................ 10 3.2 STANDARDS FOR FORT COBB LAKE ..................................................................................... 10 3.3 PESTICIDE STANDARDS ....................................................................................................... 11 3.4 ANTIDEGRADATION POLICY ................................................................................................ 13 4. IMPAIRMENT ASSESSMENT & TMDL TARGETS...................................................... 14 4.1. STATUS OF NUTRIENT IMPAIRMENT IN STREAMS ................................................................ 14 4.1.a. Data from OCC.......................................................................................................... 14 4.1.b. Data from USGS ........................................................................................................ 16 4.2. STATUS OF NUTRIENT IMPAIRMENT IN FORT COBB LAKE................................................... 21 4.3. STATUS OF PESTICIDE IMPAIRMENT .................................................................................... 24 4.3.a. Lake Creek ................................................................................................................. 25 4.3.b. Cobb Creek ................................................................................................................ 25 4.3.c. Fort Cobb Lake .......................................................................................................... 27 4.4. STATUS OF DISSOLVED OXYGEN IMPAIRMENT FOR LAKE CREEK ....................................... 27 4.5. ENDPOINT AND TARGETS FOR FORT COBB TMDL.............................................................. 28 5. SOURCE ASSESSMENT ..................................................................................................... 29 5.1. ASSESSMENT OF POINT SOURCES ....................................................................................... 29 5.2. ASSESSMENT OF NONPOINT SOURCES ................................................................................ 31 5.2.a. Septic Systems ............................................................................................................ 31 5.2.b. Migratory Birds ......................................................................................................... 33 5.2.c. SWAT model for Nonpoint Source Loadings ............................................................. 36 6. MODEL DEVELOPMENT.................................................................................................. 41 6.1. MODEL SELECTION ............................................................................................................ 41 6.2. MODEL SETUP.................................................................................................................... 42 6.2.a. Watershed Representation ......................................................................................... 42 6.2.b. Lake Representation................................................................................................... 42 6.2.c. Selection of Model Simulation Period........................................................................ 43 6.2.d. Model Inputs .............................................................................................................. 45 6.3. MODEL CALIBRATION ........................................................................................................ 46 i June 26, 2006 6.3.a. Hydrodynamics .......................................................................................................... 46 6.3.b. Water Quality............................................................................................................. 47 6.4. MODEL VERIFICATION ....................................................................................................... 57 6.4.a. Hydrodynamics .......................................................................................................... 57 6.4.b. Water Quality............................................................................................................. 57 7. NUTRIENT REDUCTION................................................................................................... 64 7.1. LOAD REDUCTION .............................................................................................................. 64 7.2. MARGIN OF SAFETY AND LOAD ALLOCATION.................................................................... 71 7.3. BEST MANAGEMENT PRACTICES........................................................................................ 73 7.3.a. Effectiveness of Best Management Practices............................................................. 73 7.3.b. Options for Implementing BMPs ............................................................................... 80 8. PUBLIC PARTICIPATION................................................................................................. 82 9. REFERENCES...................................................................................................................... 84 10. APPENDIX A....................................................................................................................... 88 ii June 26, 2006 List of Figures FIGURE 1-1. COBB CREEK WATERSHED STUDY AREA................................................................. 5 FIGURE 3-1. STREAM ORDER (COBB CREEK WATERSHED).......................................................... 9 FIGURE 4-1. TOTAL-P, NO3/NO2 CONCENTRATION IN LAKE CREEK ......................................... 15 FIGURE 4-2. TOTAL-P, NO3/NO2 CONCENTRATION IN TRIBUTARY OF LAKE CREEK ................ 16 FIGURE 4-3. USGS MONITORING STATIONS (PROVIDED BY USGS) .......................................... 17 FIGURE 4-4. TOTAL-P, NO3/NO2 CONCENTRATION IN WILLOW CREEK .................................... 18 FIGURE 4-5. TOTAL-P, NO3/NO2 CONCENTRATION IN LAKE CREEK ......................................... 19 FIGURE 4-6. TOTAL-P, NO3/NO2 CONCENTRATION IN COBB CREEK......................................... 20 FIGURE 4-7. OWRB MONITORING STATIONS IN FORT COBB LAKE........................................... 22 FIGURE 4-8. USFWS MONITORING STATIONS........................................................................... 23 FIGURE 5-1 STORM WATER DISCHARGES ................................................................................. 30 FIGURE 5-2. 2000 U.S. CENSUS BLOCKS IN COBB CREEK WATERSHED .................................... 32 FIGURE 5-3. SUBBASIN LAYOUT USED IN THE COBB CREEK SWAT MODEL ............................. 39 FIGURE 5-4. LAND USE COVERAGE ........................................................................................... 40 FIGURE 6-0. ANNUAL PARTICIPATION FOR FORT COBB WATERSHED........................................ 44 FIGURE 6-1. BATHYMETRIC AND COMPUTATIONAL GRID OVERLAY - FORT COBB LAKE.......... 44 FIGURE 6-2. COMPARISON OF MODELED AND OBSERVED LAKE ELEVATION............................. 48 FIGURE 6-3. TEMPERATURE PROFILE NEAR THE DAM................................................................ 49 FIGURE 6-3A. TEMPERATURE PROFILE NEAR THE DAM................................................................ 50 FIGURE 6-4. CHLOROPHYLL-A CONCENTRATION NEAR THE DAM............................................. 51 FIGURE 6-5. CHLOROPHYLL-A IN THE MIDDLE PART OF THE LAKE ........................................... 51 FIGURE 6-6. CHLOROPHYLL-A IN THE UPPER PART OF THE LAKE.............................................. 51 FIGURE 6-7. TROPHIC STATE INDEX NEAR THE DAM ................................................................. 52 FIGURE 6-8. TROPHIC STATE INDEX IN THE MIDDLE PART OF THE LAKE................................... 52 FIGURE 6-9. TROPHIC STATE INDEX NEAR IN THE UPPER PART OF THE LAKE............................ 53 FIGURE 6-10. DISSOLVED OXYGEN NEAR THE DAM .................................................................... 53 FIGURE 6-11. DISSOLVED OXYGEN IN THE MIDDLE PART OF THE LAKE...................................... 54 FIGURE 6-12. DISSOLVED OXYGEN IN THE UPPER PART OF THE LAKE ........................................ 54 FIGURE 6-13. TOTAL-P NEAR THE DAM....................................................................................... 54 FIGURE 6-14. TOTAL-P IN THE MIDDLE PART OF THE LAKE ........................................................ 55 FIGURE 6-15. TOTAL-P IN THE UPPER PART OF THE LAKE........................................................... 55 FIGURE 6-16. LAKE ELEVATION (2000)....................................................................................... 59 FIGURE 6-17. WATER TEMPERATURE NEAR THE DAM (2000)..................................................... 59 FIGURE 6-18. TROPHIC STATE INDEX NEAR THE DAM (2000)...................................................... 60 FIGURE 6-19. TROPHIC STATE INDEX IN THE MIDDLE PART OF THE LAKE (2000) ....................... 60 FIGURE 6-20. TROPHIC STATE INDEX IN THE UPPER PART OF THE LAKE (2000).......................... 60 FIGURE 6-21. CHLOROPHYLL-A NEAR THE DAM (2000)............................................................... 61 FIGURE 6-22. CHLOROPHYLL-A IN THE MIDDLE PART OF THE LAKE (2000) ................................ 61 FIGURE 6-23. CHLOROPHYLL-A IN THE UPPER PART OF THE LAKE (2000)................................... 61 FIGURE 6-24. DISSOLVED OXYGEN NEAR THE DAM (2000) ......................................................... 62 FIGURE 6-25. DISSOLVED OXYGEN IN THE MIDDLE PART OF THE LAKE (2000) .......................... 62 iii June 26, 2006 FIGURE 6-26. DISSOLVED OXYGEN IN THE UPPER PART OF THE LAKE (2000)............................. 62 FIGURE 6-27. TOTAL-P NEAR THE DAM (2000) ........................................................................... 63 FIGURE 6-28. TOTAL-P IN THE MIDDLE PART OF THE LAKE (2000)............................................. 63 FIGURE 6-29. TOTAL-P IN THE MIDDLE PART OF THE LAKE (2000)............................................. 63 FIGURE 7-1. CARLSON’S TSI NEAR THE DAM (REDUCTION)...................................................... 67 FIGURE 7-2. CARLSON’S TSI IN THE MIDDLE PART OF THE LAKE (REDUCTION) ....................... 67 FIGURE 7-3. CARLSON’S TSI IN THE UPPER PART OF THE LAKE (REDUCTION).......................... 67 FIGURE 7-4. CHLOROPHYLL-A NEAR THE DAM (REDUCTION).................................................... 68 FIGURE 7-5. CHLOROPHYLL-A IN THE MIDDLE PART OF THE LAKE (REDUCTION) ..................... 68 FIGURE 7-6. CHLOROPHYLL-A IN THE UPPER PART OF THE LAKE (REDUCTION)........................ 68 FIGURE 7-7. DISSOLVED OXYGEN NEAR THE DAM (REDUCTION) .............................................. 69 FIGURE 7-8. DISSOLVED OXYGEN IN THE MIDDLE PART OF THE LAKE (REDUCTION) ............... 69 FIGURE 7-9. DISSOLVED OXYGEN IN THE UPPER PART OF THE LAKE (REDUCTION) .................. 69 FIGURE 7-10. TOTAL-P NEAR THE DAM (REDUCTION)................................................................. 70 FIGURE 7-11. TOTAL-P IN THE MIDDLE PART OF THE LAKE (REDUCTION) .................................. 70 FIGURE 7-12. TOTAL-P IN THE UPPER PART OF THE LAKE (REDUCTION)..................................... 70 FIGURE 7-13. SEDIMENT REDUCTION VS. TOTAL-P REDUCTION.................................................. 75 FIGURE 7-14. TOTAL N REDUCTION VS. TOTAL-P REDUCTION.................................................... 76 FIGURE 7-15. SEDIMENT LOAD REDUCTION DUE TO CONVERSION OF CULTIVATED LAND TO PASTURE ................................................................................................................ 77 iv June 26, 2006 List of Tables TABLE 2-1: 1998 303(D) LIST FOR THE COBB CREEK WATERSHED ........................................... 6 TABLE 2-2. 2002 303(D) LIST FOR COBB CREEK WATERSHED ................................................... 7 TABLE 3-1: THRESHOLD VALUES FOR STREAM TOTAL-P AND NO2+NO3 ................................ 10 TABLE 3-2. PUBLISHED LC50 VALUES FROM DIFFERENT SOURCES ......................................... 13 TABLE 4-1. OCC WATER QUALITY MONITORING STATIONS.................................................... 15 TABLE 4-2. SUMMARY OF TSI DATA........................................................................................ 23 TABLE 4-3. LC-50 VALUES AND TARGET CRITERIA FOR PESTICIDES ......................................... 24 TABLE 4-4. LAND USE COMPARISON FOR COBB CREEK AND LAKE CREEK SUB-BASINS........... 26 TABLE 4-5. PESTICIDE LOADINGS (APRIL 1999 – AUGUST 1999)............................................. 26 TABLE 5-1. ESTIMATED POPULATION IN COBB CREEK WATERSHED........................................ 32 TABLE 5-2. PHOSPHORUS LOADING TO LAKES FROM WATERFOWLS........................................ 34 TABLE 5-3. LAND USE COVERAGE IN THE FORT COBB LAKE WATERSHED.............................. 37 TABLE 6-1. SURFACE AREA AND VOLUME OF FORT COBB LAKE ............................................. 43 TABLE 7-1. NUTRIENT REDUCTION RATE ................................................................................. 65 TABLE 7-2. LOAD ALLOCATIONS.............................................................................................. 72 TABLE 7-3. SIMULATED ANNUAL LOADS BY LAND USE FOR THE FORT COBB BASIN FOR THE PERIOD 1990-2000 ................................................................................................ 74 TABLE 7-4. LOAD REDUCTIONS FOR DIFFERENT BMPS ........................................................... 75 TABLE 7-5. RELATIVE EFFECTIVENESS OF NUTRIENT MANAGEMENT ...................................... 78 TABLE 7-6. REDUCTION RATE FOR SEDIMENT AND NUTRIENTS FOR VARIOUS BMPS.............. 79 v June 26, 2006 Executive Summary Cobb Creek watershed includes two HUC 11 watersheds, 11130302120 & 11130302130 and crosses three counties in west-central of Oklahoma. Fort Cobb is located at the lower end of the watershed and there are four tributaries (Cobb Creek, Lake Creek, Willow Creek, and Fivemile Creek) contributing to the lake. The watershed is primarily rural. There is no point source discharge in the watershed. Fort Cobb Lake and four tributaries were listed in the Oklahoma 1998 303(d) list for nutrients, suspended solids, siltation, and pesticides. Fort Cobb Lake, Lake Creek and Willow Creek are listed in the 2002 303(d) list. This TMDL report addresses both the 1998 and 2002 303(d) lists. There are several federal and state agencies collecting water quality data in the watershed. Data used in this project are gathered from U.S. Geological Survey, U.S. Bureau of Reclamation, U.S. Fish and Wildlife Service, Oklahoma Water Resources Board and Oklahoma Conservation Commission. The data were first used to check the status of impairments for all tributaries and Fort Cobb Lake. It was concluded that Cobb Creek, Lake Creek, Willow Creek and Fivemile Creek were not impaired with regard to nutrients and pesticides. It was also concluded that the Fort Cobb Lake was not impaired for pesticides. The Fort Cobb Lake was used as the endpoint in the TMDL project. The TMDL targets were dissolved oxygen, anoxic volume and Trophic State Index (TSI) in the lake. Two water quality models were employed to link pollutant sources to water quality targets. A SWAT (Soil and Water Assessment Tool) model was calibrated to simulate nutrient loads to the lake. A three dimensional EFDC (Environmental Fluid Dynamic Code) model was calibrated and verified to model water quality in Fort Cobb Lake. The calibrated EFDC model was then used to predict how much reduction would be needed to restore the Fort Cobb Lake to meet all Oklahoma water quality standards. As a result, the model called for 78% reduction in nutrient load from the watershed. Due to the BMPs implemented in the recent years, it was estimated by the SWAT model that about 20% nutrient reduction had been achieved as of 2005. In order to achieve the recommended nutrient reduction, sediment load to streams and the lake will also be reduced. Therefore, the suspended solids and siltation impairments in Cobb Creek, Lake Creek, Willow Creek and Fivemile Creek are also addressed by this TMDL. vi FINAL June 26, 2006 1. Introduction 1.1 Latest Revision This TMDL report for Cobb Creek Watershed and Fort Cobb Lake was first drafted in 2004 and went through peer reviews among state agencies. Then, the report was sent to the EPA for technical review. After receiving the EPA’s technical approval, the report was open for public review on November 24, 2004. A public meeting was held in the Town of Fort Cobb on January 13, 2005. The public review period ended on February 25, 2005. Five written comments were received during the public review period. Not all comments are addressed through the response to the comments process because the SWAT model for the watershed was recalibrated which leads to recalibration of the EFDC model for the lake. As a result, the following significant changes have been made to the TMDL reduction goal and this TMDL report: 1). Update on the SWAT Model Since there were many questions on land use, tillage, fertilizer application rate, hydraulic calibration and so on, Oklahoma State University conducted a new survey in the Cobb Creek watershed to collect additional data. A detailed survey was given in 2005 to Oklahoma State University (OSU) Cooperative Extension Service Agents and Specialists to gain an understanding of agricultural practices and land cover that occurred from 1996 to 2001. This survey went into great detail about the different types of crops in the basin along with different tillage practices, common double crops, fertilization rates, cattle stocking rates, and harvest dates. With the newly collected data, OSU recalibrated the SWAT model. A pond option was also added to the SWAT model during the recalibration process. As a result, the SWAT model calibration was greatly improved. The newly calibrated model was used to generate nutrient inputs to the Fort Cobb Lake. It should be emphasized that the SWAT model was calibrated to the conditions when water quality data were collected. Since then, the land cover in the watershed has been changed and certain BMPs have been implemented. In order to evaluate the improvement in nutrient 1 FINAL June 26, 2006 reduction that has occurred in the past few years, OSU also updated the SWAT model with 2005 land cover. The updated SWAT model predicted that on average 20% phosphorus reduction has been achieved since 2001. 2). Update on the EFDC Model Although there is little difference in the average annual total phosphorus loadings (1995-2000) between the current and previous SWAT model, the difference in loadings from year to year ranges from -37% to 43%, especially for the calibration and verification periods of the EFDC model (as shown in red in the following table). The difference is significant enough to require a new calibration of the EFDC model for the Fort Cobb Lake. Year Previous MoTdoetla l P (kg/Cyur)r rent Model Difference 1995 257794 197000 30.9% 1996 34543 50000 -30.9% 1997 93353 104000 -10.2% 1998 75933 53000 43.3% 1999 47922 76000 -36.9% 2000 53741 81000 -33.7% Average 93881 93500 0.4% Trophic State Index (TSI) is the only TMDL target which is not met currently in the Fort Cobb Lake. Thus, TSI is the control factor in determining the reduction goal for this TMDL. A point-to- point comparison between predicted and observed TSI data and R2 which measures the goodness-of-fit were added to the TMDL report in the model calibration. In addition, the same comparison was made for lake elevation and temperature calibration. Vertical temperature profiles were also added to the report to enhance the hydrodynamic calibration. The recalibrated EFDC model was then used to predict the nutrient reduction rate needed to meet all TMDL targets. Due to the significant change in nutrient inputs to the lake, the TMDL reduction goal increased from 65% to 78%. 2 FINAL June 26, 2006 3). Nutrient Input from Migratory Birds One comment suggested that direct defecation by migratory birds or waterfowl might be an important nutrient source. One section was added to this report to address the potential nutrient additions from waterfowl to Fort Cobb Lake. Annual mid-winter waterfowl surveys were obtained from U.S. Fish and Wildlife Service for this assessment. Waterfowl in the lake are primarily ducks and small Canadian geese. The waterfowl phosphorus addition to the lake is estimated less than 2% of non-point source loading and primarily occurs in the winter. Therefore, we believe that waterfowl will have little impact on algae growth in the summer. 4). Other Revisions In addition to the above major updates, many other changes were also made to this report. These changes include annual precipitation plot and EFDC control files etc. The annual rainfall data from 1975 to 2001 were plotted so that one would be able to see the representativeness and appropriateness of the calibration and verification period. The EFDC’s master control files were attached at the end of this report so that those interested in the model parameters could check the final parameters used in the EFDC model. 1.2 Introduction Under Section 303(d) of the Clean Water Act (CWA) as amended by the Water Quality Act of 1987 and the United States Environmental Protection Agency’s (EPA) Water Quality Planning and Management Regulations [Title 40 of the Code of Federal Regulation (40 CFR), Part 130], states, territories, and authorized tribes are required to develop lists for those waters within their boundaries not meeting water quality standards applicable to their designated uses. States are also required to establish priority rankings for waters on the list and develop Total Maximum Daily Loads (TMDLs) for all pollutants violating or causing violation of applicable water quality standards for each identified waterbody in the list. 3 FINAL June 26, 2006 A TMDL specifies the maximum amount of a pollutant that a waterbody can receive while still meeting water quality standards, and allocates pollutant load among all point and nonpoint pollution sources. Such loads are established at levels necessary to meet the applicable water quality standards with consideration given to seasonal variations and margins of safety. The TMDL process establishes the allowable loadings of pollutants or other quantifiable parameters for a waterbody based on the relationship between pollution sources and in-stream water quality conditions. States then establish water quality-based controls and programs to reduce pollution from both point and nonpoint sources and restore and maintain the quality of their water resources [2]. Oklahoma’s 1998 303(d) list identified all major streams (Cobb Creek, Lake Creek, Willow Creek, Fivemile Creek) and Fort Cobb Lake in the Cobb Creek watershed as not supporting their designated beneficial uses due to nutrients, suspended solids, siltation, pesticides, exotic species, unknown toxicity, and/or other habitat alterations. By definition, TMDLs can only be developed for specific pollutants. Exotic species, unknown toxicity and other habitat alterations are not pollutants that cause impairments of water being studied and are not within the scope of this report. This report addresses the remaining pollutants in the Cobb Creek watershed. Cobb Creek watershed includes two HUC 11 watersheds, 11130302120 & 11130302130, which include portions of Caddo, Washita, and Custer counties in Oklahoma (Figure 1-1). At the lower end of the Cobb Creek watershed is Fort Cobb Lake. Land use in the Cobb Creek watershed consists of forest (6%), pasture (41.4%), agricultural land (50.4%), water (2.1%) and urban area (0.1) [17]. The watershed is in one of the most intensive agricultural farming areas of the state. Over half of the state’s peanuts are grown in or near the watershed, along with wheat, alfalfa and many other row crops [6]. The soils are very coarse and fragile, allowing for high infiltration rates and excessive erosion. 4 FINAL June 26, 2006 FIGURE 1-1. COBB CREEK WATERSHED STUDY AREA This study consists of two modeling efforts: a watershed model to estimate non-point source loadings to the Fort Cobb Lake and a lake model to simulate hydrodynamics and water quality conditions in the lake and make comparisons to the applicable water quality criteria. 5 FINAL June 26, 2006 2. Problem Definition Fort Cobb Lake and four streams were included in the Oklahoma 1998 303(d) list due to nutrients, suspended solids, siltation, pesticides, exotic species, unknown toxicity, and/or other habitat alternations. Since exotic species, unknown toxicity and other habitat alterations are not pollutants, they will not be included in this TMDL study and are not included in the following table. TABLE 2-1: 1998 303(d) LIST FOR THE COBB CREEK WATERSHED Waterbody ID Name Area (acres)/ Length (miles) Nutrients Siltation Suspended Solids Pesticide OK310830060020 Fort Cobb Lake 3806 X X OK310830060010 Cobb Creek 17.3 X X X X OK310830060080 Fivemile Creek 12.2 X X X OK310830060040 Lake Creek 16.3 X X X X OK310830060030 Willow Creek 11.0 X X X All stream segments in Table 2-1 were assigned priority 3 in the 1998 Oklahoma 303(d) list. Since there are no permitted point source discharges in the entire watershed, the potential impairments are caused by the non-point sources in the watershed such as agricultural activities, cattle and limited small concentrated animal feeding operations (CAFO) in the watershed. There are two CAFOs in the watershed that are considered to be insignificant in the Soil and Water Assessment Tool (SWAT) model conducted by Oklahoma State University. Because of the way the 303 (d) list was compiled and new information obtained through continuing data collection efforts, the 1998 303(d) list was revisited and reevaluated to determine whether the beneficial uses of waterbodies were still impaired by the listed pollutants. The Oklahoma 2002 Water Quality Assessment Integrated Report indicated that siltation impairments for Cobb Creek, Lake Creek, Willow Creek and Fivemile Creek and suspended solids impairments for Fort Cobb Lake, Cobb Creek, Lake Creek Willow Creek and Fivemile Creek were listed in error based on samples collected under high flow conditions. The siltation and 6 FINAL June 26, 2006 suspended solids impairments for Lake Creek were corrected to turbidity impairment in the Oklahoma’s 2002 303(d) list. The Oklahoma 2002 303(d) list (Table 2-2) shows the latest status of impairments and impairment source codes for streams and lakes in the watershed. The source code of 9000 in Table 2-2 stands for unknown source. The impairments for Cause Unknown and Pathogens are beyond the scope of this study and therefore will not be addressed in this report. The remaining pollutants, together with those in Table 2-1, are re-evaluated in this TMDL report. TABLE 2-2. 2002 303(D) LIST FOR COBB CREEK WATERSHED Waterbody ID Name Cause Unknown Turbidity Phosphorus Low DO Pathogens OK310830060020_00 Fort Cobb Lake 9000 OK310830060040_00 Lake Creek 9000 9000 9000 OK310830060030_00 Willow Creek 9000 Fort Cobb Lake and all the streams in the watershed are designated in Oklahoma Water Quality Standards for the following beneficial uses: • Public and Private Water Supply • Warm Water Aquatic Community • Agriculture • Industrial & Municipal Process and Cooling Water • Primary Body Contact Recreation • Aesthetics • Sensitive Public and Private Water Supply In addition, the Fort Cobb watershed is also classified as a Nutrient Limited Watershed (NLW). 7 FINAL June 26, 2006 3. Applicable Water Quality Standards 3.1 Standards for Streams 3.1.a. Standards for nutrients The Oklahoma Water Quality Standards (OWQS) do not have numerical criteria for nutrients that apply to the streams in the Cobb Creek Watershed. However, they contain the following narrative standard that applies to all streams and lakes in the state: “785:45-5-19 (c) (2) Nutrients. Nutrients from point source discharges or other sources shall not cause excessive growth of periphyton, phytoplankton, or aquatic macrophyte communities which impairs any existing or designated beneficial use”. The rules for implementation of Oklahoma’s Water Quality Standards (OAC 785-46-15) [4] provide a framework that is used in assessing threats to waterbodies or impairments to beneficial uses by nutrients. The implementation rules describe a dichotomous process to be used in determining whether or not a stream is nutrient-threatened. If the dichotomous process indicates a stream is not threatened by nutrients, the stream will be considered not impaired by nutrients. The dichotomous process uses the follow factors to determine if a stream is threatened by nutrients: • Stream order • Stream slope • Total-Phosphorus (P) concentration • Nitrate plus nitrite concentration • Canopy shading • Turbidity The application of this dichotomous process to streams in Cobb Creek watershed was utilized to derive the threshold concentrations for Total-P and nitrate plus nitrite. If the mean value of Total-P and nitrate plus nitrite samples in a stream is below their corresponding threshold value, 8 FINAL June 26, 2006 the stream is considered not threatened by nutrients. Table 3-1 shows stream order, slope and the threshold values for Total-P and nitrate plus nitrite for streams in the Cobb Creek watershed. As shown in Figure 3-1, the stream order is determined using the BASINS rf3 reach file [9]. The stream orders given in Table 3-1 are for those segments where samples were taken. FIGURE 3-1. STREAM ORDER (COBB CREEK WATERSHED) 9 FINAL June 26, 2006 TABLE 3-1: THRESHOLD VALUES FOR STREAM TOTAL-P AND NO2+NO3 Stream Stream Order Slope (ft/mile) Total-P (mg/L) NO2 + NO3 (mg/L) Willow Creek 2 <17 0.15 2.40 Lake Creek 2 <17 0.15 2.40 Trib to Lake Creek 1 ≥ 17 0.24 4.95 Cobb Creek 4 <17 0.36 5.00 3.1.b. Standards for Dissolved Oxygen The Oklahoma Water Quality Standards (OWQS) has the following criteria for dissolved oxygen: Summer (Jun 16 – Oct 15): 4 mg/L Seasonal (Oct 16 – Jun 15): 5 mg/L The dissolved oxygen criteria must be maintained at all time. 3.2 Standards for Fort Cobb Lake The Oklahoma Water Quality Standards do not contain numerical standards for nutrients and suspended solids; only narrative standards for nutrients and suspended solids can be found in the OWQS. However, it is very difficult to use narrative standards as the targets of this TMDL. The targets of a TMDL need to be numerical or quantified in some way. Fort Cobb Lake and its watershed are classified in the OWQS as Nutrient-Limited Watershed (NLW). Nutrient-Limited Watershed, by definition, means a watershed of a waterbody with a designated beneficial use that is adversely affected by excess nutrients as determined by Carlson’s Trophic State Index (using chlorophyll-a) of 62 or greater. According to the Implementation of Oklahoma’s Water Quality Standards [4], the beneficial uses designated for Fort Cobb Lake are presumed to be fully supported but threatened. Since the lake is considered threatened when Carlson’s Trophic State Index (TSI) is 62 or greater, a TSI value less than 62 was chosen as one endpoint of this TMDL. 10 FINAL June 26, 2006 In addition to TSI, dissolved oxygen criteria in the Oklahoma Water Quality Standards and the Implementation of Oklahoma’s Water Quality Standards also apply to Fort Cobb Lake. The following endpoints are identified for this TMDL: • Dissolved Oxygen (DO) for the surface water must meet the following requirements: o Summer (Jun 16 – Oct 15): 4.0 mg/L o Seasonal (Oct 16 – Jun 15): 5.0 mg/L • Anoxic volume of water column in the lake must be less than 50%. The anoxic volume is defined as the vertical water column where the dissolved oxygen concentration is less than 2 mg/L. • Carlson’s Trophic State Index (TSI) must be less than 62. TSI can be calculated as follows: TSI = 9.81 × Ln (chlorophyll-a) + 30.6 The unit of chlorophyll-a is μg/L. Dissolved oxygen criteria must be maintained at all times. Anoxic volume and TSI criteria could not be exceeded more than 10% of the time in order to achieve compliance. 3.3 Pesticide Standards Because Alachlor and Aldicarb were detected in both surface water and streamside seepage samples, pesticides were identified in the1998 303(d) list as a cause of impairment. To determine whether the surface water is actually impaired, water quality criteria for the surface water need to be checked. Review of the pesticide monitoring data for Lake Creek indicates that none of the pesticides tested exceeds any water quality standards. . Oklahoma Water Quality Standards do not have any numerical criteria specifically for Alachlor or Aldicarb. The following requirements for toxic substances in general apply: “For toxicants not specified in Table 2 of Appendix G of this Chapter, concentrations of toxic substances with bio-concentration factors of 5 or less shall not exceed 0.1 of 11 FINAL June 26, 2006 published LC50 value(s) for sensitive representative species using standard testing methods …”. “For toxicants not specified in Table 2 of Appendix G of this Chapter, concentrations of toxic substances with bio-concentration factors greater than 5 shall not exceed 0.01 of published LC50 value(s) for sensitive representative species using standard testing methods …”. Both Alachlor and Aldicarb are not specified in Table 2 of Appendix G of the OWQS. The technical fact sheets of EPA’s National Primary Drinking Water Regulations [12][13] indicate that the bio-concentration factors (BCF) for Alachlor and Aldicarb are 6 and 42, respectively. Since both BCF values are greater than 5, the target values for Alachlor and Aldicarb will be 0.01 of their published LC50 values. Published LC50 values for Alachlor and Aldicarb were found from the following public resources: • EXTOXNET, Extension Toxicology Network[15], which is a pesticide information project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. The USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program provided major support and funding. • Virginia Corporative Extension [14], Virginia Tech and Virginia State University. • PAN Pesticides Database [8], derived from the U.S. EPA AQUIRE (AQUatic toxicity Information REtrieval) Database. 12 FINAL June 26, 2006 TABLE 3-2. PUBLISHED LC50 VALUES FROM DIFFERENT SOURCES Reference Chemical LC50 (μg/L) Name Fathead Minnow Catfish Common, mirror, colored, carp EXTOXNET Extension Alachlor - 6500 - Toxicology Network Aldicarb - - - Virginia corporative Alachlor - - - Extension Aldicarb - - - U.S. EPA AQUIRE Alachlor 5700 15700 5600 Database Aldicarb 2700 23300 1000 Using the general methodology in the Oklahoma Water Quality Standards and the most stringent LC50 values in Table 3.2 for sensitive representative species, the target values for Alachlor and Aldicarb are calculated as 56.0 μg/L and 10.0μg/L, respectively. 3.4 Antidegradation Policy Oklahoma antidegradation policy (OAC 785:45-3) requires protecting all waters of the state from degradation of water quality. The targets of this TMDL, resulting load reduction, and load allocations in this report were set with regard for all elements of the Oklahoma Water Quality Standards which includes the antidegradation policy. With the implementation of this TMDL, the water quality in Fort Cobb Lake and the streams in the watershed will be improving rather than degrading. 13 FINAL June 26, 2006 4. Impairment Assessment & TMDL Targets Oklahoma’s 2002 Water Quality Assessment Integrated Report has concluded that siltation and suspended solids impairments were listed in error for Cobb Creek, Lake Creek, Willow Creek and Fivemile Creek in the Oklahoma’s 1998 303(d) list based on high flow high flow suspended solids and turbidity sampling. The siltation and suspended solids impairments for Lake Creek were corrected to turbidity impairment in the Oklahoma’s 2002 303(d) list. Therefore, siltation and suspended solids will not be addressed in this report. 4.1. Status of Nutrient Impairment in Streams Lake Creek, Willow Creek, Cobb Creek and Fivemile Creek are listed for nutrient impairment in the 1998 303(d) list. The Oklahoma Conservation Commission (OCC) conducted quarterly sampling on Lake Creek and its tributary during 1998 and 1999. The U.S. Geological Survey (USGS) sampled Fort Cobb Lake and its contributing streams during 2000 and 2001. These data are used to determine the status of nutrient impairment for Lake Creek, Willow Creek, and Cobb Creek 4.1.a. Data from OCC The Oklahoma Conservation Commission sampled five (5) sites in Lake Creek from August 1998 to October 1999. Table 2 shows the legal descriptions of the five monitoring sites. Samples were collected monthly at Sites 1 & 4 for nutrients and salt analysis which included nitrate/nitrite, total Kjeldahl nitrogen, total P, sulfate, total suspended solids, chloride, and hardness. Monthly field data were collected concurrently at all five sites. Field monitoring included flow rate, dissolved oxygen, temperature, pH, specific conductivity, turbidity, and alkalinity. In addition to regular monthly monitoring, two high flow events were sampled for water quality and field data at Site 1 on April 25, 1999 and June 21, 1999. 14 FINAL June 26, 2006 TABLE 4-1. OCC WATER QUALITY MONITORING STATIONS Monitoring Sites Latitude Longitude Legal County Lake Creek #1 35° 15’ 30.4” N 98° 31’ 54” W S12, T9N, R13W Caddo Lake Creek #2 35° 18’ 16.6” N 98° 31’ 36.2” W S36, T10N, R13W Caddo Lake Creek #3 35° 20’ 01.2” N 98° 31’ 36.2” W S24, T10N, R13W Caddo Lake Creek #4 35° 21’ 45.7” N 98° 30’ 56.8” W S7, T10N, R12W Caddo Lake Creek #5 35° 24’ 21.9” N 98° 31’ 14.5” W S 25, T11N, R13W Caddo Sampling Site #1 was located on Lake Creek and Site #4 on a tributary to Lake Creek. Figures 4-1 and 4-2 show the total phosphorus (TP) and nitrogen (NO2 + NO3) data and the corresponding threshold values for Lake Creek and its tributary. TP Concentration On Lake Creek (OCC) 0 0.5 1 1.5 2 2.5 4/15/98 7/24/98 11/1/98 2/9/99 5/20/99 8/28/99 12/6/99 3/15/00 Date TP (mg/L) Sit e # 1 Threshold NOx Concentration On Lake Creek (OCC) 0 0.5 1 1.5 2 2.5 3 3.5 4/15/98 7/24/98 11/1/98 2/9/99 5/20/99 8/28/99 12/6/99 3/15/00 Date NOx (mg/L) Site # 1 Threshold FIGURE 4-1. TOTAL-P, NO3/NO2 CONCENTRATION IN LAKE CREEK 15 FINAL June 26, 2006 TP Concentration On Tributary Of Lake Creek (OCC) 0 0.1 0.2 0.3 0.4 4/15/98 7/24/98 11/1/98 2/9/99 5/20/99 8/28/99 12/6/99 3/15/00 Date TP (mg/L) Site # 1 Threshold NOx Concentration On Tributary Of Lake Creek (OCC) 0 1 2 3 4 5 6 7 4/15/98 7/24/98 11/1/98 2/9/99 5/20/99 8/28/99 12/6/99 3/15/00 Date NOx (mg/L) Site # 1 Threshold FIGURE 4-2. TOTAL-P, NO3/NO2 CONCENTRATION IN TRIBUTARY OF LAKE CREEK If the mean of the samples does not exceed the threshold, according to the dichotomous process, the stream is not threatened by nutrients. As shown in Figure 4-1 & 4-2, the mean values of TP or NO2 + NO3 of all samples are well below their corresponding threshold values. Both Lake Creek and its tributary are not nutrient-threatened so they are not nutrient-impaired. 4.1.b. Data from USGS Bi-monthly monitoring was conducted from June 2000 to June 2002 at 26 sites (Figure 4-3). Sixteen sites are located in Fort Cobb Lake and ten sites in three major tributaries, namely Lake 16 FINAL June 26, 2006 Creek, Cobb Creek and Willow Creek. The sites in the lake were designed to characterize the spatial trend of the lake water quality. The sites in the tributaries were intended to determine the source and load of nutrients to the lake. Parameters monitored included temperature, pH, DO, specific conductivity and Oxidation Reduction Potential (ORP), hardness, nitrate/nitrite, ammonia, total nitrogen, total phosphorus, Soluble reactive phosphorus (SRP), particulate organic carbon. FIGURE 4-3. USGS MONITORING STATIONS (PROVIDED BY USGS) 17 FINAL June 26, 2006 TP Concentration On Willow Creek (USGS) 0 100 200 300 400 500 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date TP (ug/L) Threshold Site # 13 Site # 15 Nitrogen Concentration On Willow Creek (USGS) 0 1 2 3 4 5 6 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date NO2+NO3 (mg/L) Threshold Site #13 Site #15 FIGURE 4-4. TOTAL-P, NO3/NO2 CONCENTRATION IN WILLOW CREEK 18 FINAL June 26, 2006 TP Concentration On Lake Creek 0 100 200 300 400 500 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date TP (ug/L) Threshold Site # 18 Site # 20 Nitrogen Concentration On Lake Creek (USGS) 0 0.5 1 1.5 2 2.5 3 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date NO2+NO3 (mg/L) Threshold Site #18 Site #20 FIGURE 4-5. TOTAL-P, NO3/NO2 CONCENTRATION IN LAKE CREEK 19 FINAL June 26, 2006 TP Concentration On Cobb Creek (USGS) 0 100 200 300 400 500 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date TP (ug/L) Threshold Site #25 Site #21 Nitrogen Concentration On Cobb Creek (USGS) 0 1 2 3 4 5 6 3/15/00 6/23/00 10/1/00 1/9/01 4/19/01 7/28/01 11/5/01 2/13/02 5/24/02 9/1/02 Date NO2+NO3 (mg/L) Threshold Site #25 Site #21 FIGURE 4-6. TOTAL-P, NO3/NO2 CONCENTRATION IN COBB CREEK As shown in Figure 4-4, 4-5 & 4-6, the mean values of TP or NO2 + NO3 are well below their corresponding threshold values (Table 3-1). Cobb Creek, Lake Creek and Willow Creek are not nutrient-threatened and therefore are not nutrient-impaired. There is not enough data on Fivemile Creek to assess the status of nutrient impairment. USGS collected only three samples on site 29 & 30. No samples exceeded TP or TN threshold values. In addition, the 2002 Water Quality Assessment Integrated Report [16] indicated that the nutrient impairment for Fivemile Creek was listed in error in the 1998 303(d) list. 20 FINAL June 26, 2006 4.2. Status of Nutrient Impairment in Fort Cobb Lake In addition to the data collected by USGS in Fort Cobb Lake, Oklahoma Water Resources Board (OWRB) and U.S. Fish & Wildlife Service (USFWS) also conducted quarterly sampling in the lake. These data are used to determine the status of nutrient impairment for Fort Cobb Lake. Fort Cobb Lake was not listed in the 1998 303(d) list for nutrient impairment but was included on the 2002 list. The available data support the listing. Oklahoma Water Resources Board has conducted quarterly water quality monitoring at six sites in Fort Cobb Lake from July 1998 to July 1999. Figure 4-7 shows the six sampling sites. The monitored water quality parameters include NH3, NO2, NO3, Total N, Organic N, TKN, Ortho-P, Total P, Settleable and Suspended Solids, Chloride, Chlorophyll-a and Turbidity. Field data include temperature, dissolved oxygen, pH, Conductivity, Total Dissolved Solid (TDS) and other parameters at different depths in the water column. USGS conducted bi-monthly water quality sampling on sixteen sites in Fort Cobb Lake, (Figure 4-3). The sampling started in June of 2000 and ended in June of 2002. Depth profiles of temperature, pH, DO, specific conductivity and Oxidation Reduction Potential (ORP) were conducted for sites in the lake. Water samples for laboratory analysis were collected as a surface composite and analyzed for nutrients (TN, TP, NO2/NO3, NH3, SRP), Chlorophyll-a, particulate organic carbon (POC) and physical chemistry (pH, alkalinity, hardness, turbidity, conductivity, and total dissolved solids). In addition, samples were collected for algae taxonomy. U.S. Fish & Wildlife Service, sponsored by U.S. Bureau of Reclamation, conducted quarterly water quality sampling on sixteen sites on Fort Cobb Lake, its tributaries and outflows (Figure 4- 8). The sampling started in November of 1997 and ended in June of 2000 [11]. 21 FINAL June 26, 2006 FIGURE 4-7. OWRB MONITORING STATIONS IN FORT COBB LAKE The constituents analyzed include conductivity, turbidity, chlorophyll-a, COD, total phosphorus, soluble reactive phosphorus, total alkalinity, chloride, sulfate, total nitrogen, nitrate, nitrite and ammonia. In addition, other constituents such as metals etc. were also analyzed in water samples. However, these parameters are not in the scope of this TMDL. A review of the data for these parameters does not show any violations of water quality standards. 22 FINAL June 26, 2006 FIGURE 4-8. USFWS MONITORING STATIONS The TSI data from USGS, OWRB and USFWS is summarized in Table 4-2. The aesthetics beneficial use for Fort Cobb Lake is considered not threatened with respect to nutrients if planktonic chlorophyll-a samples in the water column indicate a Carlson's Trophic State Index of less than 62. TABLE 4-2. SUMMARY OF TSI DATA Agencies Median TSI Min TSI Max TSI # Of TSI >= 62 Total # Of TSI % Of TSI >= 62 OWRB 63.7 34.0 77.6 21 34 62% USGS 61.2 38.8 85.2 67 158 42% USFWS 61.8 41.7 78.8 34 72 47% 23 FINAL June 26, 2006 Data in Table 4-2 support the 303(d) status that Fort Cobb Lake does not support the Aesthetics beneficial use with respect to nutrients. 4.3. Status of Pesticide Impairment Samples for organics and herbicides were taken by the OCC from August 1998 to June 1999. Immunoassays for pesticides (2,4-D, Alachlor, Aldicarb, Atrazine, Captan, Carbofuran, Chlorothalonil, Chlorpyrifos, Cyanazine, Metolachlor, Metribuzin, Paraquat, Picloram, and Triclopyr) were performed twice monthly during the spring & summer (March – October) and once monthly during fall and winter (November – February). TABLE 4-3. LC-50 VALUES AND TARGET CRITERIA FOR PESTICIDES LC-50 (μg/L) Pesticides Fathead Minnow Channel Catfish Common, mirror, colored, carp Target Criteria (μg/L) 2,4-D 191500 7000 58271 70.0 Alachlor 5700 15700 5600 56.0 Aldicarb 2700 23300 1000 10.0 Atrzine 15000 4982 28467 49.8 Captan 155 78.3 250 0.78 Carbofuran 1264 629 1405 6.29 Chlorothalonil - 81.5 110 0.82 Chlorpyrifos 178.5 457 76.9 0.77 Cyanazine 18630 12862 - 128.6 Metolachlor 8200 4900 - 490.0 Metribuzin - 32540 - 325.4 Paraquat - 100000 78500 785.0 Picloram 64033 13571 135.7 Triclopyr NA for above species, but >1000 for all other tested species 10.0 Table 4-3 shows the target criteria for each pesticide. The target criteria are determined by multiplying the minimum LC50 by 0.01 for each pesticide. The LC50 values are derived from the U.S. EPA AQUIRE database. 24 FINAL June 26, 2006 The pesticide data collected by the OCC were compared with the criteria in Table 4-3 for each pesticide to determine the status of pesticide impairment for Lake Creek. Since no pesticide data exists for Cobb Creek and Fort Cobb Lake, the evaluation of the status of pesticide impairment relies on the comparison of the data for Lake Creek and the prediction of the Soil and Water Assessment Tool (SWAT) model performed by Oklahoma State University. 4.3.a. Lake Creek OCC collected pesticide data on different sites of Lake Creek from August 1998 through October 1999. Alachlor and Aldicarb are the only two pesticides that were detected in both surface water and streamside seepage samples. We believe this is the reason that Alachlor and Aldicarb were listed in the 1998 303(d) list. Alachlor was detected in 13 of the 76 total samples and Aldicarb was detected in 19 of the 62 total samples. The highest concentration measured was 0.26 μg/L for Alachlor and 1.58 μg/L for Aldicarb. Both values are well below the corresponding target values. Other pesticides were screened against the target criteria (Table 4-3). None of the measured data exceeds the corresponding target criteria. Therefore, it can be concluded that pesticides do not impair Lake Creek. 4.3.b. Cobb Creek In addition to Lake Creek, Cobb Creek and Fort Cobb Lake are listed in the 1998 303(d) list for pesticide impairment. No monitoring data are available for either of the water bodies. Oklahoma State University has performed a SWAT model to simulate nutrient and pesticide loadings from the Fort Cobb Watershed [17]. The model is calibrated for flow and nutrients, but it is not calibrated for pesticides because of limited pesticide data. The model is not suitable for predicting the actual pesticide mass loadings from the watershed but is adequate for comparison of the relative pesticide loadings from different sub-watersheds. A comparison of land uses in Lake Creek sub-basin and Cobb Creek sub-basin are made in Table 4-4. Both sub-basins have a majority of land used for agricultural practices where pesticides are normally applied. The percentage of agricultural land in the Lake Creek sub-basin is slightly 25 FINAL June 26, 2006 higher than that in the Cobb Creek sub-basin. The SWAT model was calibrated for pesticides based on data collected in Lake Creek. When the same calibrated parameters are applied to the Cobb Creek sub-basin, the model should give a conservative prediction of pesticides on a relative basis. TABLE 4-4. LAND USE COMPARISON FOR COBB CREEK AND LAKE CREEK SUB-BASINS Land Use Name Cobb Creek Sub-bLaasnidn UseL a(%ke) Creek Sub-basin Urban or Built-up Land 0.3% 0.5% Agricultural Land 85.7% 92.2% Forest Land 0.1% 1.8% Range Land 13.6% 5.5% Barren Land 0.0% 0.0% Water 0.3% 0.0% Pesticide loadings and concentrations from the Cobb Creek sub-basin and the Lake Creek sub-basin as predicted by the SWAT model are shown in Table 4-5. TABLE 4-5. PESTICIDE LOADINGS (APRIL 1999 – AUGUST 1999) Pesticide Loading (kg) Total Accumulative Flow (m3) Average Pesticide Concentration (μg/L) Cobb Creek 394.9 1.42E+07 0.28 Lake Creek 300.4 9.78E+06 0.31 The pesticide loading in Table 4-5 is the loading from April 1999 to August 1999. The loading for other months of the year is negligible because little or no pesticides are applied in these months. As shown in Table 4-5, the predicted pesticide concentration in Cobb Creek is even lower than that in Lake Creek. Because the observed pesticide concentrations in Lake Creek are well below the standards and the pesticide concentrations in Cobb Creek are relatively lower than those in 26 FINAL June 26, 2006 Lake Creek, we can conclude that the pesticide concentration in Cobb Creek is well below the standards. In other words, pesticides do not impair Cobb Creek. 4.3.c. Fort Cobb Lake It is safe to assume that the only source of pesticides to Fort Cobb Lake is pesticides in stream flows of the tributaries to Fort Cobb Lake. Since none of Fort Cobb Lake’s tributaries are impaired by pesticides, a simple mixing model can show that Fort Cobb Lake is not impaired by pesticides. Assume : Vi = volume from stream i, (i = 1,2,…n) V = volume after mixing, V = V1 + V2 + … + Vn Ci = concentration in stream i, (i = 1,2,…n) C0 = critical concentration, C0 > Ci for i = 1,2,…n C = concentration after mixing Based on mass balance, we get: V · C = V1 · C1 + V2 · C2 + … + Vn · Cn Substitute Ci wit |
Date created | 2011-06-14 |
Date modified | 2011-10-28 |
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