Fort Cobb Reservoir Watershed, Oklahoma and Thika River Watershed, Kenya twinning pilot project
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The Fort Cobb Reservoir Watershed (FCRW) (830 km2) is a watershed within the HELP Washita Basin, located in Caddo and Washita Counties, OK. It is also a benchmark watershed under USDA’s Conservation Effects Assessment Project, a national project to quantify environmental effects of USDA and other conservation programs. Population in south-western Oklahoma, in which FCRW is located, is sparse and decreasing. Agricultural focuses on commodity production (beef, wheat, and row crops) with high costs and low margins. Surface and groundwater resources supply public, domestic, and irrigation water. Fort Cobb Reservoir and contributing stream segments are listed on the Oklahoma 303(d) list as not meeting water quality standards based on sedimentation, trophic level of the lake associated with phosphorus loads, and nitrogen in some stream segments in some seasons. Preliminary results from a rapid geomorphic assessment results indicated that unstable stream channels dominate the stream networks and make a significant but unknown contribution to suspended-sediment loadings. Impairment of the lake for municipal water supply, recreation, and fish and wildlife are important factors in local economies. The Thika River Watershed (TRW) (867 km2) is located in central Kenya. Population in TRW is high and increasing, which has led to a poor land-population ratio with population densities ranging from 250 people/km2 to over 500 people/km2. The poor land-population ratio has resulted in land sub-division, fragmentation, over-cultivation, overgrazing, and deforestation which have serious implications on soil erosion, which poses a threat to both agricultural production and downstream reservoirs. Agricultural focuses mainly on subsistence and some cash crops (dairy cattle, corn, beans, coffee, floriculture and pineapple) farming. Surface and groundwater resources supply domestic, public, and hydroelectric power generation water. Thika River supplies 80% of the water for the city of Nairobi. A dam was constructed in 1994 with a water reservoir of 70 million m3. Thika River also supplies water to Masinga Reservoir to supply the seven forks dams, which together supply 75% of the nation’s electricity. The quantity of water in rivers and reservoirs is decreased due to sedimentation while water quality is degraded by sediments, and sediment-borne nutrients and pesticides. The focus of this pilot twinning project is watershed erosion and reservoir sedimentation assessment. This will be accomplished by (1) a rapid watershed/catchment erosion assessment using ground based measurements and remote sensing/GIS techniques, 2) use of Acoustic Profiling Systems (APS) for reservoir sedimentation measurement studies, and 3) advanced water quality modeling using the soil and water assessment tool (SWAT) model. Data acquired will be used for sediment transport modeling to1) determine sediment “hot spots” and management practices that will minimize sediments into reservoirs in order to 2) maintain the reservoirs on which many farmers depend for their livelihood and a cleaner environment. This project will provide an opportunity for 1) sharing knowledge and experience among the stakeholders, 2) building capacity through formal and informal education opportunities through reciprocal hosting of decision makers and water experts, and 3) technology transfer of pilot results with recommended management practices to reduce reservoir sedimentation rates.