Groundwater pollution vulnerability assessment in the Assin municipalities of Ghana using GIS-based DRASTIC and SINTACS methods

This study has employed the DRASTIC and SINTACS models to assess the groundwater pollution vulnerability potential in the Assin municipalities of Ghana, where agricultural activities, increase in population and industrial activities stand to negatively impact the quality of groundwater, which is the main source of water supply to the populace. Hydrogeological parameters including depth to the water table, aquifer recharge, hydraulic properties of the aquifer, surface topography, and soil properties were utilized in the Geographical Information System (GIS) environment to evaluate the vulnerability of the study area to groundwater pollution. The results indicate that fractured and weathered granites are the main aquifer formations in the area, while the principal soils are mainly clay, clayey sand, loamy and sandy clay, with depth to the water table and hydraulic conductivity ranging between 12–62 m and 0.0031–2.4705 m/day, respectively. In addition, the net recharge range is between 122.80 and 198.20 mm/year, with an average of 163.27 mm/year. DRASTIC model assessment showed that 812.78 km2 (33.62%) of the area has low vulnerability potential with the remaining 1604.22 km2 (66.37%) having moderate vulnerability potential, while 667.76 km2 (27.63%) and 1749.24 km2 (72.37%) of the area were deemed to have low, and moderate vulnerability potentials, respectively, from assessment with the SINTACS model. The moderate groundwater vulnerability zones are generally underlained by undifferentiated biotite granitic rocks, mafic dykes, and the leucogranites, whereas the biotite gneiss and Banket formation underlain the low vulnerable zones. Thus, providing useful information to aid in taking appropriate pollution prevention measures to protect the groundwater resource in the area.