Geophysical Delineation of Aquifer Systems for Municipal Water Supply Planning in Makurdi, Benue State, North Central Nigeria

Makurdi's municipal water supply capacity is chronically below demand, and the Benue State Rural Water Supply and Sanitation Agency has identified the expansion of groundwater abstraction from alluvial and sedimentary aquifers as the most cost-effective short-term strategy to bridge the supply deficit. This professional study delineates the productive aquifer systems available for municipal-scale groundwater development in Makurdi metropolis using a combination of vertical electrical sounding, two-dimensional resistivity profiling, and hydrochemical analysis. Forty-two VES stations were distributed across the urban area using a spatially stratified design that covers all major geological formations, including Quaternary alluvium, Maastrichtian sediments, and the Basement Complex. VES interpretation and cross-section construction identify three distinct aquifer systems at progressively greater depths: an unconfined alluvial aquifer at 5 to 20 metres, a confined Campanian sandstone aquifer at 40 to 80 metres, and a fractured basement aquifer at 80 to 130 metres. Pumping test data from 14 existing boreholes were used to calibrate transmissivity estimates derived from geoelectric parameters. Hydrochemical data from 22 water samples confirm the chemical acceptability of water from all three aquifer systems for municipal supply with standard treatment. The study presents a phased abstraction development plan targeting the most productive and water-quality-compliant aquifer zones, with an estimated maximum sustainable yield of 12,000 cubic metres per day from the combined aquifer systems. Keywords: aquifer delineation, municipal water supply, VES, Makurdi, hydrochemistry