Evaluation of Groundwater Potential Index (GWPI) Using Geophysical Survey in Kallar Watershed, Tamil Nadu, India

The increasing demand for water has brought immense pressure on groundwater resources in the regions where groundwater is prime source. In the present study an attempt has been made to evaluate groundwater potential index (GWPI) for understanding the hydro geological condition of Kallar Watershed, South India. Vertical Electrical Sounding (VES) was carried out at 17 locations within and around the study area. The interpretation of the data obtained from the VES revealed that three non-aquifer geo-electrical layers overlie the un-fractured basement. The first layer has an average thickness of about 0.5 m and resistivity of 83 Ohm-m. The thickness of the second layer is about 0.7 m and resistivity of 438 Ohm-m. The third layer is about 3.4 m thick and has resistivity of about 63 Ohm-m. Aquifer resistivity and thickness interpreted from VES data is used to generate the corresponding thematic maps. Weights are assigned to different ranges of resistivity and thickness values based on their position on geological map. Finally the weighted maps are integrated using a GIS based aggregation method to evaluate the groundwater potential index of the area.