POLLUTION RISK ASSESSMENT OF GROUNDWATER RESOURCES OF DOON VALLEY, UTTARAKHAND

Abstract

Groundwater vulnerability assessment is an important aspect of determining the risk to groundwater contamination and for developing management options to preserve the quality of groundwater resources. This study aims to provide a spatial analysis of the prevailing subsurface parameters and environmental conditions under which groundwater may get polluted. The DRASTIC model is used here with GIS for finding out the vulnerable zones of groundwater contamination in Doon valley of district Dehradun, Uttarakhand. A vulnerability map of the study area is prepared based on the computed DRASTIC Index (DI) using the ArcGIS 9.3 in order to manage the groundwater resources of the Doon valley. Impact of land use changes on the groundwater vulnerability has also been incorporated in the study by using a DRASTIC-MOD approach. The southern region of the Doon valley aquifer was dominated by "High" vulnerability zone while the elevated eastern and north-eastern region of the study falls in "Low" vulnerability zone. The integrated vulnerability map exhibit the high risk imposed on the southern region of the Doon valley aquifer due to cultivation, high hydraulic conductivity and low depth to groundwater. Higher nitrate concentration is observed in the north-western and middle region of the study area which pertains to moderate to high vulnerability zone and moderate to very high risk zone. Further, a good correlation between DRASTIC and DRASTIC-MOD has been also observed in the study area. Sensitivity analysis of the DRASTIC parameters shows that all the relevant parameters are necessary in order to evaluate the vulnerability of the groundwater resources of the study area. The GIS technique has provided an efficient environment for analyses and handling of large spatial data. The developed groundwater vulnerability and risk map may assist in decision making and future planning of sustainable water resources development of Doon valley