Problems of sedimentation in small dams in Zambia
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An inventory of small dams in Zambia and the results of a preliminary analysis of sediment loads for rivers and reservoirs are reported. A regression approach was used to determine relationships between drainage area and sediment load for 21 rivers based on available sediment concentration and discharge data. The resulting regression equation was applied to the drainage areas of 66 small dams located in Southern Province and rates of sediment input to the reservoirs were computed. By assuming 95% trap efficiency for sediment by the dams, the expected useful life of the reservoirs was also calculated. Calculated annual rates of sedimentation in small dams were found to range from 2 to 183 m3 year1 with a mean of 24.6 m3 year1. The estimates of reservoir useful life ranged from 200 tp 5100 years with a mean of 7314 years. Anthropogenic factors contributing to sediment generation and sedimentation in. reservoirs, community participation in dam construction and rehabilitation efforts together with conservation measures embarked on in the country are discussed. Qualitatively, it is concluded that sedimentation in the dams of Southern Province is serious. This calls for detailed quantitative research to assess the problem and to find ways of minimizing adverse impacts of soil erosion on environment and society.
Human Impact on Erosion and Sedimentation