ASSESSMENT OF GROUNDWATER POTENTIAL OF RISHA PART OF AKWANGA SHEET 209NE, NORTH CENTRAL NIGERIA

A geological traverse was undertaken in Risha, part of Akwanga Sheet 209NE North-Central Nigeria to appraise the rock types and their structural patterns that might enhance prospect for water. Three rock types; schistose-gneiss, granite-gneiss and pegmatite, with their main structural pattern were discovered, trending mostly NW-SE. Analysis of twenty-three Vertical Electrical Resistivity Soundings (VES) carried out in the area using the Campus Ohmega digital resistivity meter showed that the field curves were of H, KH, HK, A and K types. There were majorly four to five geoelectrical layers consisting of topsoil (sand/clay) with depth range of 0.3-2.4m and resistivity value of 66-2850Ωm. The second layer is lateritic clay with depth range of 0.4-5.7m and resistivity range of 222- 3575Ωm. The third layer had a depth range of 1.2-8.6m with resistivity of 40-4591Ωm, while the fourth layer, weathered rocks or regolith, has a depth range of 3-33m and resistivity range of 49-23668Ωm. Two locations gave six lithological layers/units being partially fractured/fresh basement with resistivity values of 1028-4574Ωm and depth range of 11.4- 24m. The water potential of the area may be classified as poor, moderate, good and very good and varied from location to location. The groundwater potential area varies with high potential around Risha, Tidde and Ridam compared to Ade-Katako, Ngazzu,AngwanDorowa, Ngakide and Adande. Based on the textures, structural pattern and well measurement interpretations, the granite gneiss was observed to have more water prospectivity than the schistose gneiss.