Mathematical Analysis of Groundwater Flow Dynamics in the Chad Basin Aquifer System, North East Nigeria

This study applies mathematical analysis to groundwater flow dynamics in the Chad Basin aquifer system, with focus on the North East Nigerian portion of the basin encompassing Borno, Yobe, and Bauchi states, a region where declining groundwater levels threaten the water security of millions of people dependent on shallow and deep aquifer systems for domestic and irrigation water supply. The Chad Basin Multi-Aquifer System is among the most important regional groundwater resources in sub-Saharan Africa, and the combined effects of reduced Lake Chad surface water recharge, increasing groundwater extraction for irrigation, and climate change-driven precipitation deficits have produced measurable aquifer drawdown over the past two decades. The governing equations of saturated groundwater flow are formulated using Darcy's law and the storage equation, and the resulting partial differential equations are solved numerically using the finite difference method within the MODFLOW-6 groundwater modelling code. Aquifer parameter data including hydraulic conductivity, specific yield, and specific storage are sourced from borehole completion logs compiled by the Lake Chad Basin Commission and the Geological Survey of Nigeria. Steady-state and transient groundwater models are calibrated against observed water level hydrographs from monitoring wells. Predictive simulations over a 30-year horizon under baseline and increased extraction scenarios quantify projected drawdown and the spatial extent of zones approaching critical water level thresholds. Keywords: groundwater flow, Chad Basin aquifer, MODFLOW, Darcy's law, North East Nigeria