Hydrological Assessment Of Water Resources And Environmental Impact On An Urban Lake: A Case Study Of Eleyele Lake Catchment, Ibadan, Nigeria

Abstract

Previous assessment of the effect of land use changes on water quality of Eleyele lake Ibadan, Nigeria revealed that pollutants are being washed by rainfall runoff into the lake which indicated the need for further study. In this study, Universal Soil Loss Equation (USLE) was used to estimate the quantity of soil that is being lost into the lake using parameters derived from an earlier study.  The result revealed that 2080 kg of soil is being washed into the lake annually. Tests to determine the water quality of the two streams that flow into the lake and, the outflow were done. The results showed that between 6 and 95% of the pollutants washed into the lake were retained or converted to sediments which may cause it to eutrophicate in the future. To compute water accounting for the lake watershed, precipitation over the area was calculated, discharge measurements on the two rivers that empty into the lake and outflow from the lake were done, and also, the evaporation/evapotranspiration were determined. The results showed that 59% of the gross inflow was available for potable water supply while 30.3% of the total outflow was uncommitted. Evapotranspiration (including lake surface evaporation), municipal/industrial and total outflow were 1.0, 59 and 31% respectively. Management plan and useful recommendations have been suggested to improve the reliability of the lake.