Measurement of the Remaining Storage and Rate of Siltation of Tagwai Impounding Reservoir, Niger State, Nigeria

Measurement of the Remaining Storage and Rate of Siltation of Tagwai Impounding Reservoir, Niger State, Nigeria

Water resources planning and management is a major challenge to most developing nations in their struggle to secure water. Depending on the availability of water, which is increasingly becoming a scarce resource in most developing nations, Resersvoirs are created by construction of dams across rivers to impound and capture runoff water.Sediment accumulation due to erosion of soils in the drainage basin has decreased the storage capacity of reservoirs. A field study of Tagwai reservoir was carried out in Tagwai drainage basin, Niger State, Nigeria. A total of 141 points were taken with their coordinates to outline the perimeter of the reservoir (open watersurface), while a total of 415 depth measurements from the open water surface accompanied with their corresponding coordinates were measured in a slowly moving boat with a weighted line, metric tape, and Global Positioning System (GPS); from which area and storage were calculated. The remaining storage in the year 2010 was the same as the total storage of the reservoir. This is because the dead storage has been already silted up. Remaining storage was in year 2010, 21,650,648 m³ which is 76.5 % of the original storage. Average rate at which the storage shrunk from 1978 and 2010 is 207,792 m³/year. Losses to siltation are 6,649,352 m³ during a period of 32 years, which is 0.73% per annum. The reservoir will be completely silted up in 136 years from the date of its impoundment i.e. in the year 2114, if the rate of siltation is not reduced.