HYDROGEOLOGICAL WINDOWS IN THE UPPER AQUIFER OF THE CHAD FORMATION IN THE CHAD BASIN, NORTH-EASTERN NIGERIA

Groundwater is the major source of drinking water in both urban and rural communities around Chad Basin in Northeastern Nigeria. Besides, it is an important source of water for the agricultural and the industrial sector. In this work, hydrogeological windows of the Upper aquifer subzones of the Chad Basin around Bornu sub-basin have been studied. The research involves collection of borehole logs from Borno State Water Board in which the position of each borehole located on a topographic map at scale of 1:500,000. The thicknesses of Upper aquifer subzones at different locations were screened with the top and bottom bed values subtracted from their elevations. Contours of each corresponding values were drawn and contours of recharge windows were demarcated. The results showed that the upper aquifer is divided into ‘a', ‘b' and ‘c' subzones. It also revealed detailed structural behavior of hydrogeological openings that enable the penetration of water from the surface to the three subzones of the Upper aquifer through hydrogeological windows and vice versa. The upper a-subzone is connected to lower upper c-subzone in the upper aquifer that subsequently permit flow of water to the Middle aquifer. These hydrogeological windows are mostly located around Bama, Maiduguri, Damaturu, Monguno, Damasack, Ngala and Kala-Balge. Conclusively, these windows are conduits of recharge into to the upper zones and infiltrate to the Upper b-subzone of the middle aquifer and contribute to balance abstracted water in middle aquifer for economic purposes.