Assessing the vulnerability of aquifer systems in the Volta river basin: a case-study on Afram Plains, Ghana

Groundwater is the main water resource which supplies more than half of the residents of Afram Plains. Recent studies show that the aquifer is subject to deteriorating quality from several anthropogenic activities. The aquifer vulnerability to contamination was assessed using the widely known DRASTIC model. This paper aimed to determine the depth-to-water table, identification of the various soil types, topography, recharge rate, and major lithological units in the area. The degree of vulnerability was identified by an index which is computed by superimposition of all the parameters considered for the model. Based on the vulnerability assessment, it was found that, 20.72% (1044.28 km2), 49.78% (2508.91 km2) and 29.50% (1486.80 km2) of the total area was classified as low, moderate and high, respectively. The final vulnerability index was largely influenced by the depth-to-water table, impact of the vadose zone, net recharge and aquifer media parameters. The model was validated with on-ground nitrate concentrations in groundwater in the study area. The DRASTIC model exhibits highly correlated areas in mapping vulnerable regions. The maps produced in this study could be used as a general guide to vulnerability by planners, groundwater managers and decision-makers on the implementation of measures aimed at the protection of this vulnerable resource. © 2017, Springer International Publishing AG.