Groundwater potential zoning of a peri-urban wetland of south Bengal Basin, India

Abstract

Demand for groundwater for drinking, agricultural, and industrial purposes has increased due to rapid increase in population. Therefore, it is imperative to assess the groundwater potential of different areas, especially in a fragile wetland ecosystem to select appropriate sites for developing well fields to minimize adverse environmental impacts of groundwater development. This study considers East Calcutta Wetlands (ECW)--a freshwater peri-urban inland wetland ecosystem located at the lower part of the deltaic alluvial plain of South Bengal Basin and east of Kolkata city. This wetland is well known over the world for its resource recovery systems developed by local people through ages, using wastewater of the city. The subsurface geology is completely blanketed by the Quaternary sediments comprising a succession of silty clay, sand of various grades, and sand mixed with occasional gravels and thin intercalations of silty clay. Groundwater occurs mostly under confined condition except in those places where the top aquitard has been obliterated due to scouring action of past channels. The groundwater in the study area is being over-extracted at the rate of 65 × 10(3) m(3)/day. Overlay analysis in Geographic Information System platform using multiple criteria such as water quality index, hydraulic conductivity, groundwater velocity, and depth to piezometric surface reveals that in and around ECW, there are five groundwater potential zones. About 74% of the aquifer of this area shows very poor to medium groundwater potential. Management options such as minimization of groundwater abstraction by introducing the treated surface water supply system and the implementation of rainwater harvesting and artificial recharge in high-rise buildings and industries are suggested for different potential zones.