Characterisation of groundwater flow and recharge in crystalline basement rocks in the Talensi District, Northern Ghana

Abstract

A numerical groundwater flow model, calibrated under equilibrium conditions to characterise the spatial variation of key hydraulic parameters and groundwater flow pattern in a crystalline aquifer in the Upper East Region of Ghana has been developed. The development of groundwater flow model was to provide the baseline information to assist in assessing the impacts of population growth and climate change scenarios on large scale development of groundwater resources for various uses. The results revealed an apparent dominant northeast– southwest flow pattern influenced mainly by the hydraulic conductivity field, with estimated values ranging between 0.001 and 58 m/day, and local flow systems which are controlled mainly by local variations in the topography in the area. The estimated average groundwater recharge from the calibrated model and chloride mass balance technique: 2.00% and 2.07% of the annual precipitation respectively has a direct positive correlation with elevation. The low recharge rate is evident in the high evaporation rates as revealed by stable isotope (δ2H and δ1⁸O) analysis of sampled water sources. The study also reveals the aquifer is being partly recharged by the White Volta River. This gives an indication that the area holds good groundwater fortunes for potential commercial groundwater development as predicted by scenario analysis which suggests that the aquifer can sustain increased abstractions by more than 100% of the current rate provided the current recharge rate is maintained. However, for the aquifer to sustain large scale abstractions beyond 100% of the current rate under conditions of reduced vertical recharge by more than 40% of the current rate, deliberate efforts would have to be made to enhance artificial vertical recharge to augment the natural recharge.