Hydrogeophysical Framework for Assessing Managed Aquifer Recharge Potential in the Kano Alluvial Aquifer

This study develops a hydrogeophysical framework for assessing the potential and optimising the design of managed aquifer recharge schemes in the Kano alluvial aquifer, Kano State, North West Nigeria. Rapid urbanisation and agricultural intensification have created severe groundwater stress in the Kano metropolitan area, with water level declines of 0.8 to 1.2 metres per year documented in monitoring wells. Managed aquifer recharge using treated surface water or storm runoff offers a potential solution, but the selection of optimal recharge sites requires detailed knowledge of aquifer hydraulic properties, vertical connectivity, and unsaturated zone characteristics. This study applies an integrated geophysical investigation combining time-lapse electrical resistivity tomography, frequency-domain EM profiling, and seismic MASW along 15 kilometres of profiling across the Kano River floodplain and adjacent alluvial fans. In-situ permeameter tests at 24 points calibrate geophysical estimates of hydraulic conductivity. Available borehole logs and pumping test data from the Kano River Basin Authority database provide hydrogeological validation. A 2D flow model simulates recharge mound propagation under different injection scenarios at geophysically-selected sites. Findings reveal that the highest hydraulic conductivity zones (greater than 15 metres per day) correspond to clean gravelly sand bodies with resistivity above 180 ohm-metres, located along the Kano River paleo-channels identified in the MASW and ERT sections. The unsaturated zone is thinnest at these locations, minimising recharge lag time. Three priority MAR sites are delineated with modelled recharge capacity of 5,000 to 12,000 cubic metres per day each. The study provides the first quantitative MAR feasibility framework for the Kano alluvial system.

Keywords: managed aquifer recharge, hydrogeophysics, Kano alluvial aquifer, time-lapse ERT, groundwater stress.