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Photo Series of Ruiru Reservoir in Nairobi Kenya.


Reservoir Sedimentation Measurement and Assessment in Kenya

As part of the U.S. government's global hunger and food security efforts, USDA is building collaborative scientific partnerships with several organizations to help water management officials sustain safe and affordable water supplies from Africa's water reservoirs, and ensure enough water for drinking, irrigation, and power generation.

USDA Agricultural Research Service (ARS) scientists Daniel Moriasi, Jean Steiner, and Jeff Arnold are passionate about water and sharing knowledge to keep poor East African communities supplied with plenty of it. "With rapidly expanding population, extended drought, and projected long-term climate change, water resources are increasingly limited in East Africa. Mismanaged reservoirs can fill up with sediment, and become shallow or even dry up," Moriasi explains. 

USDA's Soil and Water Assessment Tool, or "SWAT" simulates hydrolic processes and predicts management impacts on soil and water resources using a technique called Rapid Geomorphic Assessment (RGA) to measure sediment flows with aerial and ground surveys of feeder streams. Measurement accuracy affects SWAT predictions. Multifrequency acoustic profiling (APS) is a new, cheaper method using sound waves to measure the capacity, or degree and rate of reservoir sedimentation. Moriasi and colleagues at ARS Grazing Lands Research Lab, and ARS Grassland Soil and Water Lab tested it at Cobb Creek sub-watershed in Oklahoma's Fort Cobb Reservoir, using APS and RGA measures for SWAT predictions. The experiment convinced the team APS could work in Africa to measure sedimentation rates cost-effectively.

In the first year, U.S. and African partners will set up the APS equipment in the Ruiru Reservoir, in Nairobi Kenya, to serve as a teaching lab for Africans to learn to use the equipment for measuring, modeling, and using data across Africa. The long-term vision for the project is an African regional/continental reservoir and watershed sediment assessment center staffed by African experts.