Hydrogeological delineation of groundwater vulnerability to droughts in semi-arid areas of western Ahmednagar district

Groundwater, a renewable and finite natural resource, is a vital source of sustenance for humans and different ecosystems in the semi-arid regions. Rapid population growth in the last three decades has caused a rise in water demand which has inadvertently posed a stress on its availability. Occurrence of groundwater in the Deccan Volcanic Province is governed by the subsurface hydrogeological heterogeneity of basaltic lava flows and by the presence of geological structures like dykes, sills and fractures that influence spatial & vertical groundwater flow. The main objective of this paper is to map and assess areas that are naturally most susceptible to groundwater scarcity and at risk of depletion due to over extraction. The current study involves a field hydrogeological mapping that was integrated with remote sensing and GIS to delineate areas. This technique was based on using different thematic layers viz. lithology, slope, land-use and land cover, lineament, drainage, soil type, depth to groundwater and annual rainfall. Additionally, pumping tests were carried out to classify the study area into different hydrogeological typologies to help delineate communities that are most vulnerable to subsurface heterogeneity. This paper attempts to underline the groundwater scarcity zones based on different influencing thematic layers and provide a robust methodology to prioritize areas vulnerable to groundwater unavailability, by categorizing the study area into different vulnerable class types - extreme, high, moderate and low.