GIS Based Assessment of Groundwater Vulnerability Using Drastic Model

Groundwater has been treated as an important source of water supply due to its relatively low vulnerability to pollution in comparison to surface water, and its huge storage capacity. Because of the known health and economic impacts associated with groundwater contamination, steps to measure the vulnerability of groundwater must be taken for sustainable groundwater protection and management planning. Susceptibility of groundwater refers to the intrinsic characteristics that determine the sensitivity of the water to being adversely affected by an imposed contaminant load. The DRASTIC model is the most extensively used method for identifying the areas where groundwater supplies are most vulnerable to contamination. In this study the DRASTIC model is applied for a part of Kancheepuram district, Tamil Nadu, India, to generate a small-scale map of groundwater vulnerability to contamination. The whole area is classified on a scale of very low, low, moderate and high susceptibility to pollution. The model is considered in relation to groundwater quality data and results have shown a strong relationship between DRASTIC specific vulnerability index and nitrate-as-nitrogen concentrations. A groundwater vulnerability map is developed by using the DRASTIC model in a computer based Geographic Information System. The results show that the central part of the study area is classified as a high vulnerable zone and the south and northeastern parts show medium vulnerable zones, and record higher nitrate values.