Evaluating Sedimentation Rates and Their Ecological Consequences in Jebba Reservoir, Niger State, North Central Nigeria

Reservoir sedimentation is a major threat to the operational lifespan and ecological function of hydroelectric dams in Nigeria. Jebba Reservoir on the River Niger, a key hydroelectric facility, has been receiving significant sediment loads from its catchment due to upstream deforestation and erosion. This study evaluated sedimentation rates in Jebba Reservoir and assessed associated ecological consequences for aquatic habitats. Sediment samples were collected from twelve transects across the reservoir using a Petersen grab sampler, and sediment depth was measured using acoustic profiling equipment. Grain size distribution, organic matter content, and nutrient levels in deposited sediments were analysed. Fish community surveys using multiple sampling gears were conducted to assess habitat quality and species distribution in areas of varying sediment depth. Results indicated average sedimentation rates of approximately 1.4 centimetres per year across the reservoir, with highest deposition rates in the upstream inflow delta. Shallow sedimented zones supported reduced fish diversity and density, with benthic-feeding species declining in heavily silted areas. Turbidity was significantly elevated in the inflow zone relative to mid-reservoir and dam sections. The study recommends watershed management interventions upstream of Jebba Dam, including reforestation programmes and terracing of cultivated hillslopes, to reduce sediment input and protect the reservoir's ecological and economic value. Keywords: reservoir sedimentation, Jebba Reservoir, fish community, watershed management, Niger State.