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

Figure 3: Map of Annual Depth of Rainfall in Nigeria (After Schoeneich, 2004) The groundwater in the research area is contained mainly in the Chad Formation with the greater part of the groundwater (7817km 3 ) is salty water with only the upper most part consisting of 1713km 3 being fresh water according to (Schoeneich, 2001). This fresh water occurs mainly in the Chad Formation within three geologic formations namely the Upper, Middle and Lower Aquifers (Fig. 4) Figure 4: Map of Hydrogeological Cross-Section A-B of Chad Formation Showing the Three Aquifer, (Upper, Middle and Lower Aquifer) the Middle Aquifer is Separated into A and B Subzone (After Sani, 2016) Hydrochemical Assessment of Surface and Groundwater in Some Selected Communities of Borno and Yobe State © 2023 Global Journals 1 Year 2023 58 Global Journal of Science Frontier Research Volume XXIII Issue ersion I VI ( H )