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United States Department of Agriculture

Agricultural Research Service

Title: Environmental effects of agricultural conservation: A framework for research in two watersheds in Oklahoma's Upper Washita River Basin

Authors
item Steiner, Jean
item Starks, Patrick
item Daniel, John
item Garbrecht, Jurgen
item Moriasi, Daniel
item McIntyre, Sherwood
item Chen, Jin Song

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 10, 2008
Publication Date: November 1, 2008
Citation: Steiner, J.L., Starks, P.J., Daniel, J.A., Garbrecht, J.D., Moriasi, D.N., Mcintyre, S.C., Chen, J. 2008. Environmental effects of agricultural conservation: A framework for research in two watersheds in Oklahoma's Upper Washita River Basin. Journal of Soil and Water Conservation. 63(6):443-452.

Interpretive Summary: Agriculture in the Upper Washita River Basin represents mixed crop-livestock systems of the Southern Plains. Research was established in two sub-watersheds, the Little Washita River Experimental Watershed and the Fort Cobb Reservoir Experimental Watershed, to quantify interactive effects of variable climate, land use, and management on hydrologic processes and water quality and quantity. The Little Washita watershed provides opportunities to explore impacts of a large number of small flood retarding impoundments within a watershed. The Fort Cobb watershed exhibits high trophic state in the reservoir, is the focus of an Oklahoma Conservation Commission 319 Water Quality Project, and provides opportunities to study effects of conservation practices on a large eutrophic reservoir. Dominant conservation practices in the Fort Cobb watershed include conservation tillage, stream fencing, and conversion of cropland to perennial cover. Climate, soils, land management, hydrology, stream channel stability, and water quality data and results are discussed in this manuscript. Analysis of the 1940-2005 precipitation, runoff, and suspended sediment data on the Fort Cobb watershed showed that precipitation increased 33%, corresponding runoff increased 101%, and sediment yield increased 183% when comparing multi-year dry periods to multi-year wet periods. Preliminary results show that depth to groundwater exhibits seasonal and inter-annual variation. A rapid geomorphic assessment indicated that unstable stream channels dominate the stream networks in both watersheds. Preliminary analysis indicated that average total phosphorus concentration was most strongly related to the contributing area and length of stream above the stream sampling sites. Anticipated outcomes of this research are improved understanding of environmental effects of conservation practices, new approaches to enhance mitigation of water quality problems in Fort Cobb Reservoir, and tools to support strategic placement of conservation practices on the landscape to achieve desired environmental endpoints.

Technical Abstract: Agriculture in the Upper Washita River Basin represents mixed crop-livestock systems of the Southern Plains. Research was established in two sub-watersheds, the Little Washita River Experimental Watershed and the Fort Cobb Reservoir Experimental Watershed, to quantify interactive effects of variable climate, land use, and management on hydrologic processes and water quality and quantity. The Little Washita sub-watershed provides opportunities to explore impacts of a large number of small flood retarding impoundments within a watershed. The Fort Cobb sub-watershed exhibits high trophic state in the reservoir, is the focus of an Oklahoma Conservation Commission 319 Water Quality Project, and provides opportunities to study effects of conservation practices on a large eutrophic reservoir. Dominant conservation practices in the Fort Cobb sub-watershed include conservation tillage, stream fencing, and conversion of cropland to perennial cover. Climate, soils, land management, hydrology, stream channel stability, and water quality data and results are discussed in this manuscript. Analysis of the 1940-2005 precipitation, runoff, and suspended sediment data on the Fort Cobb sub-watershed showed that precipitation increased 33%, corresponding runoff increased 101%, and sediment yield increased 183% when comparing multi-year dry periods to multi-year wet periods. Preliminary results show that depth to groundwater exhibits seasonal and inter-annual variation. A rapid geomorphic assessment indicated that unstable stream channels dominate the stream networks in both watersheds. Preliminary analysis indicated that average total phosphorus concentration was most strongly related to the contributing area and length of stream above the stream sampling sites. Anticipated outcomes of this research are improved understanding of environmental effects of conservation practices, new approaches to enhance mitigation of water quality problems in Fort Cobb Reservoir, and tools to support strategic placement of conservation practices on the landscape to achieve desired environmental endpoints.

Last Modified: 11/23/2014
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