Water Quality Division

---

WQ Priority Watershed Projects

 
Fort Cobb Lake 2001-2007

Background
The Fort Cobb Lake watershed covers 314 square miles in southwestern Oklahoma in Caddo, Washita, and Custer Counties. Land use in the watershed is primarily agricultural with wheat, peanuts, sorghum and cotton crops grown in rural communities.

Water Problems
Fort Cobb Reservoir and six stream segments in its watershed are listed on the 1998 303(d) List of Impaired Waters as impaired by nutrients, pesticides, siltation, suspended solids, and unknown toxicity. 

The impairment is thought to be from failing septic systems, runoff from confined animal feeding operations, and agricultural practices that contribute nutrients, silt, phosphorous, pathogens, low dissolved oxygen, and turbidity.

In 2005, the Oklahoma Department of Environmental Quality completed a TMDL for Fort Cobb Reservoir, recommending a 70% decrease in phosphorus from the loading levels documented between 1998 and 2001. Sources of phosphorous included cropland erosion, riparian erosion, septic systems, and livestock waste management. 

Purpose of Project
The purpose of this project is to reduce phosphorous loading to streams and the lake by educating landowners and financially assisting them to implement BMPs that protect riparian areas and reduce nutrients and sediment flowing to streams.

To reduce phosphorous, the project provided technical and cost-share assistance to landowners who installed BMPs to reduce soil erosion and phosphorous runoff from their land. The most popular BMP was converting cropland to pastureland by planting Bermuda grass. 

In total, 128 landowners contributed $522,907 to install 198 BMPs on their property. The project used targeting, planning, education, demonstration, and implementation to focus on the most significant sources of pollution in the watershed. Water quality monitoring data collected throughout and after the project will be analyzed in 2010 to determine water quality improvements.

Project Total =$2,009,254

Map      (pdf)

 

Fort Cobb Project 2005-2008

Building upon the success of the 2001 Ft. Cobb/Cobb Creek Reservoir Watershed Implementation Project, this project is attempting to convert 35,000 acres of tilled cropland to “no-till” cropland in the Fort Cobb watershed. The conversion partially fulfills the TMDL recommendation that 50%, or approximately 51,000 of the 101,000 acres, of cropland need to be no-till to achieve phosphorous load reductions. Implementing no-till could eventually lead to a 12% reduction of phosphorus loading to the watershed.

The TMDL completed for the Fort Cobb Reservoir by ODEQ in 2005 was the first based entirely on nonpoint source pollutants. The practices implemented by projects in the watershed are based on the TMDL, which recommends a 70% reduction in phosphorous loading to the reservoir requiring:

• 50% of the wheat and row crop in the watershed is converted to no-till,
• 20% of the worst cultivated land is converted to pasture,
• 60% of the watershed has riparian buffers,
• 90% of the producers implement nutrient management planning,
• grade stabilization structures are put in place to allow these practices to be effective.

Results from this project are expected to be seen in the 2010 data analysis. As of September 2007, there are $330,000 left to be obligated to BMPs. Publicity and landowner sign-ups are ongoing.

Partners

OK Cooperative Extension Service Deer Creek Conservation District West Caddo Conservation District North Caddo Conservation District Mountain View Conservation District OK Conservation Commission U.S. Department of Agriculture/NRCS Farm Services Agency

OK Corporation Commission OK Dept. of Agriculture/NRCS Bureau of Land Reclamation Agricultural Research Service OK Dept. of Environmental Quality OK Water Resources Board U.S. Environ. Protection Agency Office of the Secretary of the Environ.