Structural control on the occurrence of groundwater in granite gneissic terrain, Purulia, West Bengal

Abstract

Purulia, one of the most drought prone districts of West Bengal, India, is geologically a part of Chotanagpur Gneissic Complex and is mainly a granite gneissic terrain. Scarcity of drinking water has always been a major concern in the area. Thus, a hydrogeological study was carried out in and around Purulia I and Purulia II blocks of the district during lean season. The main objective of the study is to determine the structural control on groundwater flow so that groundwater extraction can be optimised economically in the area. For the purpose, depth to water level zonation map was prepared with flow direction. The lineament data was obtained by analysing satellite imagery of the area and was cross-checked using field data. The orientation of the major joint sets is NE-SW and NW-SE in this area. The NW-SE trending fractures act as conduits and facilitate the flow, while NE-SW trending fractures act as an obstruction to the flow. The lineament density of the area was overlaid on depth to water level map using Surfer and it is observed where fractures form a network, water occurs at shallow level, while in places where fractures are isolated, water flows down to deeper levels. It was interpreted from all the observations that the flow of groundwater in this area depends on the distribution of joints, thus subsurface water being structurally controlled. This type of study has been carried out in various parts of the world but in Purulia district of West Bengal, India, structural control on the occurrence of subsurface water has not yet been established through any major studies. This study will help in divulging structural control on groundwater in this area and identification of areas where constructing tubewells will help in economical extraction of groundwater.