Retrogressive Implications of Reservoir Sedimentation and Siltation on Water Storage and Other Socio-Economic Activities in Arid and Semi-Arid Regions of Nigeria

Sedimentation and siltation are jeopardizing water resources in Nigeria’s arid regions, threatening livelihoods and ecosystem. Sediment deposit is one of the principal and most serious technical challenge facing reservoirs today. Year-in, year-out, various dams are gradually losing their ability to store water for the purpose for which they were built, due to sedimentation and siltation. It is against this background that the National Water Resources Institute (NWRI), Kaduna, embarked on the study of reservoir sedimentation and siltation situated within the Arid and Semi-arid regions of Nigeria by the use of bathymetric surveys to ascertain their siltation levels. The study also looked at reported research findings from published works in the area of sedimentation and siltation to complement the findings from the field. The results indicated a substantial reduction in the storage capacities (i.e., original design depths) of all the reservoirs assessed by NWRI from 2012 to 2021 due to siltation and sediment transportation, and further supported by reported research findings from published works. This is not unconnected to their susceptibility to erosional features within and along the course of the main rivers and the tributaries feeding them, including climate change phenomenon. This decrease in storage capacity has also affected the diverse socio-economic activities which these reservoirs offer in these regions. This study intensifies the urgency of adopting sediment management strategies, including dredging, and erosion control, as this would improve water conservation, preserve reservoir functionality and sustain their diverse socio-economic benefits.