Assessment of groundwater vulnerability using analytical hierarchy process and evidential belief function with DRASTIC parameters, Cuddalore, India

Groundwater is the most consistent source of fresh water throughout the year, regardless the monsoon. However, due to tremendous changes in climate patterns and anthropogenic activities, threats to groundwater quality and quantity have been increased. To protect the available resources from quality deterioration, it is necessary to identify the zones vulnerable to contamination. Several vulnerability mapping models were evolved to serve this purpose, but selecting the apt one based on the study area characteristics and the aquifer properties is a challenging task. By carrying out few modifications in the conventional DRASTIC method, two groundwater vulnerability mapping methods, viz., Analytical Hierarchy Process AHP-DRASTIC and Evidential Belief Function EBF-DRASTIC methods, were applied to Cuddalore District, India, which is at its alarming stage of groundwater contamination. To gather data and to create the required thematic maps pertaining to the seven DRASTIC parameters (Depth to water table [D], Net recharge to the aquifer [R], Aquifer media [A], Soil media [S], Topography [T], Impact of vadose zone [I], Conductivity [C] advent of Remote Sensing (RS) and Geographic Information System (GIS) were used. The results obtained from these two methods were categorized into five classes say Very High, High, Moderate, Low, and Very Low range of vulnerability. The models were validated by generating the receiver operating characteristic curve (ROC) using R. Based on the value of area under the curve (AUC) 0.866 for EBF and 0.744 for AHP; the EBF-DRASTIC model with comparatively highest AUC is considered to be the best suited model for the selected study region.