Yakubu Mohammed^1,, Ibrahim B. Wulo¹, A. K. Yusuf², Ashe K. Gazali¹

The study was conducted in the Biu plateau with a major objective of elucidating the geomorphic and geologic mechanisms influencing the occurrences and hydrochemistry of surface and ground waters of the area. This was achieved by analyzing surface and groundwater from rivers, lakes, wells and boreholes from different landforms of the plateau. Also, lithologic logs of boreholes and wells from different parts of the plateau were analyzed to give insight to the near surface characteristics of the area. Data on the geology and geomorphology were obtained from field mapping and complimented by secondary sources from journal articles, unpublished thesis and reports on these aspects of the plateau. The plateau with a land mass of 2635.12 Km² is traversed by a total of 14671 streams, with 9814 1^st and 3783 2^nd order streams totaling a length of 6879.5 Km. The drainage pattern of the plateau is dendritic in nature reflecting the uniform nature of the geology and absence of major geologic structures such as faults. The predominant major cation trends in the surface and groundwater samples is in the order of Na⁺ > Ca ²⁺ > Mg²⁺ > K²⁺ and Ca ²⁺ > Mg²⁺ > Na⁺ > K². This reflects the chemical composition of rocks in the plateau which also has a relatively high Mg²⁺, K²⁺, Na⁺ and Ca ²⁺ ionic concentrations. Analysis of lithologic logs of boreholes and hand dug wells from different parts of the plateau indicated that three sources with high groundwater potentials exist in the plateau. The study also found out that the spatial variation in the surface and groundwater hydrochemistry is a reflection of water-rock interaction over space and time.

Biu plateau, geomorphology, hydrochemistry, surface and groundwaters