Modelling the Potential Impact of Small-Scale Pumping Near Future Water Supply Wells in a Stressed Aquifer in South Western Bengal Basin on Groundwater Flow

Abstract

This paper highlights the importance and effectiveness of groundwater modelling to water managers to protect stressed aquifer systems and to address conflicting interests and requirements in their decision making process. The study area is located in south western Bengal Basin which is a part of the lower deltaic plain of the River Ganga and lies on the eastern side of the River Hugli, a distributory of River Ganga. The aquifer is sandwiched between two aquitards and is semi-confined in nature. Steady-state model results indicate that groundwater pumping in a proposed housing complex in Kolkata city located just outside the eastern margin of East Kolkata Wetlands (EKW) far outweigh the topographic and geologic controls of the unperturbed groundwater flow system and shifts recharge areas towards the pumping centres. A small part of the groundwater is also recharged from far areas in the south and southwest. Drawdowns due to present and future pumping in the project area extend over a large area which results in interference effect in wells outside the project area. Therefore, part of the city wells will experience an additional fall in the piezometric head. The simulation results indicate that the aquifer is already stressed and therefore it may not be wise to abstract groundwater further. The required water for the housing complex may be obtained from other sources. If other sources of water are not available then as the last resort groundwater may be developed. In such case further groundwater development by wells of high yield around the project area should be avoided. It is also imperative that steps should be taken to artificially recharge the aquifer by roof top rainwater harvesting.