Decipherment of potential zones for groundwater occurrence: a study in Khatra Block, Bankura District, West Bengal, using geospatial techniques

Groundwater is considered as one of the most valuable natural resources as it supports human civilization. Freshwater is considered as an important natural resource which occurs partially on the surface and dominantly beneath the surface. The resource is declining drastically owing to the rapid increase in population and its management in an improper way. The occurrence of groundwater in hard rock terrain still behaves as enigmatic. Various terrain parameters control the movement and storage of groundwater. Accordingly geoscientists are using various techniques to explore the potential zone amongst which multi-criteria evaluation (MCE) technique seems to be more precise. Application of remote sensing and geographic information system (GIS) has come out as very effective tools in deciphering groundwater potential zone by modeling terrain features specially in hard rock arid regions. The present study is aimed to find out groundwater potential zones in Khatra Block of Bankura District, West Bengal, India characterized by hard granitic terrain and semi-arid climatic condition. In the present study various thematic maps viz., geomorphology, geology, lineament density, drainage density and slope have been prepared. For these, IRS Resources at LISS-4 with 5.8m spatial resolution digital data, CARTOSAT-1 digital elevation model, CartoDEM with 2.5m spatial resolution, along with other data sets such as Survey of India toposheets (73J/13, 73I/16, 73I/12), GSI Map have been used. Digitized vector maps relating to chosen parameters, were converted to raster data using 30mx30m grid cell size. Different theme weight and class rank have been assigned to these raster maps. Each theme weight has been multiplied by its respective class rank and all the raster thematic layers have been summed up in a linear combination equation in Arc GIS Raster Calculator module. Similarly, the weighted layers have been statistically modeled to get the areal extent of groundwater prospects. This integrated approach, helped in classifying the groundwater availability in the study area into five categories, viz. very good, good, moderate, poor and very poor. Finally, it can be stated that the modeling assessment method proposed in this study forms an effective tool for delineating groundwater potential zones for proper development and management of groundwater resources in hard rock terrains.