Groundwater Risk Assessment for Shallow Aquifers within the Atankwidi Basin of (Ghana)

Abstract

This study reveals the potential risk to the quality of shallow groundwater aquifers from the application of agro-chemicals in upscaling crop production to ensure food security within the Atankwidi basin of Ghana, using the combination of DRASTIC and Arc GIS methods. The DRASTIC indices ranged from 41 to 117, representing the lowest to highest vulnerable areas. 34.4, 93.3 and 63.9 km2 representing 20, 48.8 and 33.2% of the area had low, moderate and high vulnerabilities with indices ranging between 41–71, 71–88 and 88–117, respectively. The moderate and high vulnerable areas, which constituted approximately 80% of the area, were underlain by clay-loam and sandy-loam soils, respectively, where major farming takes place. The most vulnerable areas were in the highest elevated areas (recharge), with the shallowest depth to water-table and the highest permeability values. Sensitivity analysis using a map removal approach revealed influential parameters in the order of Hydraulic conductivity (C) ˃ Soil type (S) ˃ Depth to water table (D) ˃ Net Recharge (R) ˃ Influence of vadose zone (I) ˃ Topography (T) ˃ Aquifer material (A). The validation of the model using heavy metals measured in shallow aquifers showed the highest values within the most vulnerable areas and the lowest values in the least vulnerable ones.