Assessment of groundwater development potential of aquifers within the Ajumako–Enyan–Essiam district of Ghana

The groundwater development potential of the Ajumako–Enyan–Essiam (AEE) District has been assessed using vertical electrical sounding (VES) and borehole drilling data sets. The study aimed to use the available geophysical and hydrogeological data sets to assess the groundwater development potential of the District and also assess the aquifer protective capacity of the overburden rocks in protecting the groundwater from contamination. Twenty-nine VES points were probed up to a maximum electrode separation of 100 m using ABEM Terrameter SAS 1000 on selected sites. VES curves were interpreted quantitatively in terms of true resistivity and thickness manually by the conventional curve matching technique. The results were then improved by the computer using WINRESIST iteration software which gives the resistivity, thickness, and depth of the various layers. Thirteen out of the twenty-nine VES points were selected for drilling boreholes but three produced dry boreholes, while ten produced successful boreholes indicating a success rate of 77%. The ranges of borehole yield, static water level, transmissivity and specific capacity were 13–60 L/min, 7–18.98 m, 0.404–30.744 m²/d and 0.692–18.81 m³/day/m, respectively. There was a good correlation between the VES interpretation and borehole logs. The area was underlain by 3–5 geoelectric layers revealed by the different curves including HK (27.6%), H (20.7%), A (17.2%), K (6.9%), KH (6.9%), HA (6.9%), AK (6.9%), QH (3.4%) and HKH (3.4%). The groundwater development potential and aquifer protective capacity of the area were assessed by the calculation of reflection coefficients (r), longitudinal conductance (S), transverse resistance (T_i), transmissivity (T), and Specific capacity (Sp. Cap). The study showed irregular aquifer characteristics which leads to a heterogeneous hydrogeological environment. The study revealed high groundwater development potential but weak aquifer protective capacity of the study area. This makes the groundwater within the District prone to contamination as a result of the use of agrochemicals for farming, improper waste disposals and galamsey activities. Therefore, there is a need for protecting the groundwater resources from contamination by educating the people on the right ways of agrochemical application, proper waste disposal and use of pit latrine as well as the effects of galamsey activities on the groundwater quality. In addition, the people need to be educated on the need to assess the groundwater quality to ensure they meet the Ghana Standard Authority’s prescribed standard for drinking water before using it for drinking purposes.