Analysis of Geophysical Methods for Groundwater Prospecting in the Semi-Arid Environment of Yobe State

Groundwater is the primary source of potable water for the majority of rural communities in Yobe State, North East Nigeria, yet aquifer delineation in the region's semi-arid basement complex terrain requires reliable geophysical prospecting methods adapted to local geological conditions. This study evaluates the comparative effectiveness of electrical resistivity sounding and seismic refraction methods for groundwater prospecting at fifteen selected sites across Yobe State. Resistivity surveys employed the Schlumberger electrode array with electrode spreads reaching 300 meters, and data were processed using iterative one-dimensional inverse modeling. Seismic refraction surveys used a sledgehammer source and 24-channel geophone spread, with first arrival picks processed using time-term inversion. At each site, geophysical predictions were validated against borehole lithological logs and pumping test data from the Yobe State Rural Water Supply and Sanitation Agency. Results indicate that resistivity sounding correctly predicted saturated zone depth within 15 percent accuracy at 11 of 15 sites, while seismic refraction accurately mapped weathered layer thickness at 13 of 15 sites. Integration of both methods reduced false positive aquifer predictions from 27 percent for single-method surveys to 8 percent for combined surveys. The study provides cost-benefit analysis comparing the two methods and their combination and recommends an integrated prospecting protocol for the Yobe State rural water development program. Keywords: groundwater prospecting, electrical resistivity, seismic refraction, Yobe State, semi-arid hydrogeology