Groundwater vulnerability to pollution in the semi-arid Vattamalaikarai River Basin of south India thorough DRASTIC index evaluation

Abstract

Pollution risk assessment is an important task for sustainable management of groundwater resources. In this pilot study, we demarcated areas of different pollution vulnerabilities within the Vattamalaikarai River Basin (ca.435 km2) of south India using the DRASTIC index and involving the combined geospatial techniques of remote sensing, geographical information system and global positioning system. Seven major hydrogeological factors such as depth to water level, net recharge, aquifer media, soil characteristics, topography, impact of vadose zone and hydraulic conductivity, gathered from well inventory, were considered as variables in this model. Additionally, we took into account the rainfall, geology, digital elevation model (DEM) and borehole lithology data to understand the above variables. Our vulnerability map divided the study area into zones of ‘high’, ‘moderate’ and ‘low’ groundwater pollution risks. Most of the basin is under the moderate pollution risk, and the regions of “high” vulnerabilities are associated with the shallow and permeable aquifer formations. The partial validation of this modelling with respect to the spatial distribution of nitrate in groundwater suggests that studies similar to ours in other regions can provide quick information to decision makers for better groundwater resource management and protection.