Global Journal of Science Frontier Research, H: Environment & Earth Science, Volume 23 Issue 1

Figure 2: Drainage Map of the Study Area (Modified After Geological Survey, 1960) The Ngadda River cuts through the Bama Ridge at Maiduguri in a well-developed channels and flows through a system of braided channels. Further north, the river gradually loses its identity as it fingers out on a marshy plain to form deltas bars which joint the Jere bowl. Upstream from Maiduguri, the Ngadda River passes through Lake Alou, a seasonal lake. The surface area of the Lake Alou is about 4 square kilometres. The Lake receives its water during wet season from delta fans spread from far southern part of the study area without a clear river or channels (Figure 2). While Amanna River, initially flowing to Lake Chad and later, after formation of Bama ridge it diverted its channel into Gongola River. According to Schoeneich (2004), Water present in the study area consists of both atmospheric, surface and groundwater. The atmospheric water is mainly derived from rainfall which progressively falls from 800 mm/a in the southern part of the study to about 400 mm/a to the northern part of the study area. (Schoeneich, 2004) is of the view that, there is no recharge taking place if depth of annual precipitation is less than 700 mm/a (Fig. 3). Hydrochemical Assessment of Surface and Groundwater in Some Selected Communities of Borno and Yobe State 1 Year 2023 57 © 2023 Global Journals Global Journal of Science Frontier Research Volume XXIII Issue ersion I VI ( H )