Sustainable management of erosion prone areas of upper watershed of Kainji hydropower dam, Nigeria

Abstract

Reservoir sedimentation has been a major concern to stakeholders around the world in the implementation of sustainable management of hydropower dams. Not only that it reduces the storage capacity of reservoirs, several sediment related problems such as reduction in water quality and acceleration of abrasion of underwater parts can impair the primary purpose of which the reservoir is built. Therefore, sustainable management of watersheds upstream of hydropower dam is necessary to combat the issues of sedimentation and to extend its useful life. In this study, Soil and Water Assessment Tool (SWAT) was interfaced with MapwindowGIS to model and predict sediment yield and concentration into sub-basins of the upper watershed of Kainji hydropower dam in Nigeria which has an area of 30,350 km2. The model was run daily for 30 years and performance evaluation was carried out using Coefficient of Determination (R2) and Nash Sutcliffe Efficiency (NSE). Model calibration and validation as well as identification of erosion prone areas were equally achieved. The results showed that average annual sediment yield and concentration were 35.29 t/ha/year and 11,903.7 mg/l respectively. Application of filter strips on critical erosion prone region showed that sediment yield and concentration could be reduced up to 37% and 34% respectively. Also, construction of stone bunds in the watershed showed a reduction of up to 75% and 84% for sediment yield and concentration respectively. The outcome of this study could allow control effort to be focused effectively on an area identified as extreme cases and could also be used by relevant authorities in prioritizing implementation of Best Management Practices (BMPs) for the area.