Technical Abstract: The Fort Cobb Reservoir in southwestern Oklahoma is an artificial impoundment constructed by the Bureau of Reclamation for water supplies, flood control, and recreation. Success of best-management practices in reducing inflows of sediments and phosphorus to the reservoir prompted the U.S. Department of Agriculture in 2003 to designate the watershed for study as part of the Conservation Effectiveness Assessment Project to quantify environmental benefits derived from agricultural conservation programs. The U.S. Geological Survey, as part of the Central Region Integrated Science Program, studied land uses, soils, geology, and water quality in the watershed through field and remote sensing investigations in collaboration with the Agricultural Research Service from 2004 to 2007. These investigations indicated that though progress has been made in reducing inflows of sediment and nutrients in the basin, targeting best-management practices to small intermittent streams draining to the reservoir and to the Cobb Creek subwatershed may effectively augment efforts to improve eutrophic to hypereutrophic conditions that continue to affect the reservoir. Multidisciplinary data gathered for this report provide information about interactions between land uses, geologic features, other watershed properties, and eutrophication of a major reservoir that would not otherwise have been provided by more limited investigations of water quality or aquatic ecology.