Groundwater depletion in the upper aquifer of the chad formation, Chad basin, North-Eastern Nigeria

Abstract

This paper examines the present groundwater level changes in the Upper aquifer of Chad Formation in Borno basin measured in the year 2007, 2008, 2009, 2011 and 2012. The study involved collection of topographic maps of scale 1:500,000 on Nigerian sheet 4 covering the study area. Previous published literatures on the basin were also collected. Hand dug wells and their elevation were located and measured with satellite navigator. Findings from the results shows that, the Upper aquifer is a phreatic aquifer separated by thin clay layer into “A” sub-zone with depth ranging from 1 to 10 m, “B” sub-zone with depth ranging from 10 to 60 m and “C” sub-zone with depth ranging from 60 to 100 m. From the study, it can be deduced that, the C sub-zone is not recharging from seasonal infiltration of meteoric water or from the horizontal stream flow, it rather shows a depleting groundwater level. It was proved that rain of wet seasons do not recharge Upper C sub-zone to the previous wet season level, and thus the water table in the Upper C zones will be exhausted if the aquifer is not recharged at the present level of abstraction. Keywords: Groundwater, Chad Basin, Phreatic aquifer, Depletion level and Upper aquifer.