Groundwater Vulnerability Map for South Africa

Abstract

Vulnerability of groundwater is a relative, non-measurable and dimensionless property which is based on the concept that some land areas are more vulnerable to groundwater contamination than others. Maps showing groundwater vulnerability assist with the identification of areas more susceptible to contamination than others. They are useful in planning, policy formulation and decision-making for groundwater management and protection. Overlaying these maps with maps showing the location of contamination sources and land use enables the creation of risk maps.
There are various methods for assessing groundwater vulnerability and from these the DRASTIC approach has been highlight in various studies as the most appropriate. This is mainly due to the fact that it is suitable for regional applications and the required input data are readily available. The DRASTIC index can be modified to incorporate anthropogenic influences on groundwater contamination and the modified form is called the DRASTIC Specific Vulnerability Index (DSVI). This paper discusses the creation of a groundwater vulnerability map for South Africa using the DSVI approach. The data used include the depth to groundwater, recharge, aquifer types, soil types, topography, the vadose zone, hydraulic conductivity and land use. These parameters were rated, weighted and combined to create the final map. The result was compared to groundwater quality data and similarities were found between the maps.