Measurement of remaining storage, rate of siltation, and rate of erosion of the Ahmadu Bello University Farm Lake drainage Basin in Zaria

Abstract

Ahmadu Bello University Teaching Hospital at Shika, 547 beds and water demand 154 m³/d, suffers from inadequate and irregular water supply. But there is a nearby abandoned impounding reservoir constructed around 1966, with original storage capacity 636,300 m³. The authors propose to use this reservoir as the main source of water for Shika Hospital. However, it is not known whether after 43 years of siltation, the reservoir still contains enough water to meet water demand from the hospital. To determine, how much water is still available in the impounding reservoir after many years of siltation, the authors embarked a boat and measured the remaining storage of the reservoir as 349,911 m³. Thereafter calculated rate of siltation between years 1966 and 2009 as 6,600 m³/y, rate of erosion in the drainage basin during the same period as 0.559 mm/y, and safe yield during 176 days of hydrological dry season as non existing, because after deduction of losses to evaporation calculated as 194,560 m³/y and deduction of 272,700 m³ of environmental reserve - minimum necessary to preserve aquatic wildlife, there is no active storage left. Since there is no active storage, there is also no safe yield and there is no water for Shika Hospital. The authors conclude that the University Farm Lake cannot serve as source of water for Shika Hospital, unless it is dredged to its original storage capacity. The impounding reserve will soon be lost. In some year to come there will be little or no more water in it because it will completely be silted up as there will even be no trace of it seen on the maps. @JASEM