Abstract
A steady state numerical groundwater flow model has been calibrated to characterize the spatial distribution of a key hydraulic parameter in a crystalline aquifer in southwestern Ghana. This was to provide an initial basis for characterizing the hydrogeology of the terrain with a view to assisting in the large scale development of groundwater resources for various uses. The results suggest that the structural entities that control groundwater occurrence in the area are quite heterogeneous in their nature and orientation, ascribing hydraulic conductivity values in the range of 4.5 m/d to over 70 m/d to the simulated aquifer. Aquifer heterogeneities, coupled possibly with topographical trends, have led to the development of five prominent groundwater flowpaths in the area. Estimated groundwater recharge at calibration ranges between 0.25% and 9.13% of the total annual rainfall and appears to hold significant promise for large-scale groundwater development to support irrigation schemes. However, the model suggests that with reduced recharge by up to 30% of the current rates, the system can only sustain increased groundwater abstraction by up to 150% of the current abstraction rates. Prudent management of the resource will require a much more detailed hydrogeological study that identifies all the aquifers in the basin for the assessment of sustainable basin yield.
Highlights
Groundwater resources constitute arguably the most reliable buffer against the unremitting effects of climate change/variability and the concomitant ramifications on sustainable agriculture especially in the developing world
A good match between model computed and observed hydraulic heads is obvious in Figure 2, suggesting that the model is reasonably calibrated within the limits of the data used and is representative of the hydrogeological conditions prevailing in the terrain
In regional hydrogeological studies, the use of numerical groundwater models is very much recommended for achieving the goals of aquifer characterization
Summary
Groundwater resources constitute arguably the most reliable buffer against the unremitting effects of climate change/variability and the concomitant ramifications on sustainable agriculture especially in the developing world. This is so because groundwater is mostly protected from high surface temperatures and the corresponding high evapotranspiration rates that affect surface flows and impoundments and render them ineffective sources of irrigation water supply to sustain large-scale irrigation activities. There are various approaches available for regional hydrogeological investigations and for providing the necessary information required for optimal aquifer and basin yield management [1] They include the application of remote sensing aerial photography, surface geological field investigations, application of advanced geophysical methods, and subsequent drilling to access aquifers. The use of models will continue to provide useful leads to the effective management of flow and solute transport in aquifers, especially where climate change/variability and its attendant effects on the spatial
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