Arsenic pollution study in Yamuna sub-basin, Nadia and North 24-Paraganas districts, West Bengal

Abstract

Occurrence of Arsenic in groundwater and their areal spreading in a linear track of 470 Km in the Ganga-Brahmaputra delta covering 8 districts in West Bengal are serious concern among users and beneficiaries, groundwater managers, and also to the researchers. Earlier investigations and available literature indicate different opinions on sources of Arsenic but show a common argument about its activation, which is suspected to be due to the excessive exploitation of groundwater environment. Many researchers have explained the sources are of geologic origin, however, their geo-chemical processes of activation are yet to be established. The study of "Arsenic Pollution in the Yamuna sub-basin, West Bengal" presented in this report is a joint effort of the National Institute of Hydrology and the Central Ground Water Board, Eastern Region, Calcutta. The objectives of the study which were conceived as: i) understanding and prediction of contaminants transport in the saturation zone, and ii) quantification of remedial measures to arrest spreading. These objectives have been addressed through development of a groundwater flow model, and a transport model for the study area. The USGS 3-dimensional finite difference model, MODFLOW and MT3D compatible with MODFLOW have been used as tools for flow and transport modelling. The flow modelling has been carried out considering unsteady state of model boundaries and variable external stresses and so is the case for transport modelling. A 3-dimensional groundwater flow and contaminants transport model has been developed considering semi-confined unconfined aquifer system.