Groundwater Quality Vulnerability Assessment Using Water Quality Index and Drastic Model in Araniyar Kosasthalaiyar Watershed, Tamil Nadu, South India
Abstract
This research study has been carried out for the assessment of groundwater quality in the Araniyar-Kosasthalaiyar sub basin for drinking purpose. Twenty seven groundwater samples were collected and analysed for the selected parameters such as such as pH, EC, TDS, TH, Ca, Mg, Na, K, Cl, SO4, NO3 and F. The spatial distribution of Cl, Na, K, EC, TDS and TH. Drinking Water Quality Index (DWQI) derived from the groundwater samples ranges in between 13.37 and 123.45 in Pre-monsoon (PRM) and 16.79 and 131.54 in Post-monsoon (POM) periods. Based on the drinking water quality index, the water has been classified as excellent, good, poor, very poor and unsuitable. Spatially 7.53 % and 7.26 % of study area fall in excellent category in PRM and POM, 31.35 % and 44.33 % fall in very good, 26.60 % and 30.18 % fall in poor, 19.78 % and 17.57 % fall in very poor and 14.74 % and 0.66 % fall in unsuitable categories in PRM and POM periods respectively. The layers such as depth to water-level, recharge rate, aquifer media, soil permeability, topography, impact of vadose zone and hydraulic conductivity were integrated in the DRASTIC model using GIS spatial analysis tools and techniques. Groundwater vulnerability assessment (GWVA) using DRASTIC method was correlated well with the DWQI of groundwater during pre and post monsoon periods in the study area. The GWVA highlighted that the very high vulnerability zones were found in 10.71 % of the area, high vulnerable zones found in 35.89 %, moderate zone and low vulnerable zones spread over 31.30 % and 22.10 % areas respectively. A positive correlation was observed between GWVA and DWQI. GIS application of the DRASTIC model was found to be a suitable method for analyzing the groundwater vulnerability.
