Assessment of Groundwater Vulnerability Using GIS-based Modified DRASTIC (DRASTIC-L) Model over Urban and Peri-urban Landscape of an Indian Megacity, Kolkata
Abstract
Groundwater is one of the major sources of freshwater on earth, so its quality, as well as quantity, are important. However, domestic water supply is a serious issue in Indian metro cities due to the enormous growth of population and urban sprawl. This study analyses groundwater vulnerability in an Indian megacity (population >10 million), Kolkata Metropolitan Area (KMA) in eastern India where a total of 40 out of 41 municipalities and 23 panchayat samities (village councils) are dependent on groundwater. Over the past several decades, both the quality and level of groundwater have decreased in the KMA. From 1990 to 2020, built-up areas over KMA have increased about three times, resulting in a decrease in groundwater recharge. Based on the analyses of the last two decades (2000-2020) data from the Central Ground Water Board, the level of groundwater has been depleting substantially towards the east and west of river Ganga. To reduce groundwater contamination and raise groundwater levels, assessment of groundwater vulnerability is essential. The present study focuses on the Geographic Information System-based modified DRASTIC (DRASTIC-L) model for groundwater vulnerability assessment. One additional factor, land use land cover, that is influenced by human activity was added to form the DRASTIC-L model. The ratings of these parameters including depth of water, net recharge, aquifer media, soil media, topography, impact of the vadose zone, hydraulic conductivity, and land-use land-cover, are based on the local environmental condition of the KMA. In addition, the analytical hierarchy process assigns a weight to each parameter in order to reduce the subjectivity of humans in vulnerability assessments. The parameters are integrated and reclassified into five categories, such as very low, low, moderate, high, and very high vulnerability zones. To validate groundwater vulnerability assessment, the accuracy of the results is measured by performing a correlation between groundwater vulnerability index and groundwater quality parameter data. The overall results reveal that the groundwater aquifer in the study area is facing contamination due to land use and land cover changes. Essential remedial measures should be taken in the highly vulnerable zones of the megacity for further prevention of groundwater vulnerability.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMGC41I..01I