Hydrodynamics of Groundwater Flow in the Arsenic-Affected Areas of the Gangetic West Bengal, India
Hydrostratigraphy and groundwater flow in a ~21,000 km2 area of the arsenic-contaminated districts of West Bengal [Murshidabad, Nadia, North 24 Parganas and South 24 Parganas (including Calcutta)], India, have been delineated. Based on 143 lithologs, a re
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Abstract Hydrostratigraphy and groundwater flow in a *21,000 km2 area of the arsenic-contaminated districts of West Bengal [Murshidabad, Nadia, North 24 Parganas and South 24 Parganas (including Calcutta)], India, have been delineated. Based on 143 lithologs, a regional hydrostratigraphic model has been developed to a depth of 300 m below mean sea level. Lithologic interpolations that were done manually and by computer models (resolution: 1000 m 1000 m 2 m) demonstrate a near-continuous, unconfined to semi-confined aquifer dominated by sand underlain by a thick clay aquitard. The aquifer thickens toward basin center in Bangladesh, toward south and east. Toward the Bay of Bengal, at the southern boundary, several heterogeneous aquitard layers of clay sub-divide the primary aquifer, into several deeper, regionally-discontinuous but laterally-connected, confined to semi-confined aquifers. Eight 21-layer regional groundwater models are based on observed topography and hydrostratigraphy. Groundwater flows were simulated in the pre-monsoon, monsoon and post-monsoon seasons with presence (2001) and absence (pre-1970s) of irrigation pumping and projected pumping for pre-monsoon seasons of 2011 and 2021. Modeling results indicate topographically dominated, seasonally variable, continuos regional-scale groundwater flow, which have been largely distorted by pumping. Groundwater flow is predominantly in the upper *100 m of the aquifer but occurs to a depth of *200 m. Keywords West Bengal Groundwater flow
Hydrostratigraphy Numerical modeling
A. Mukherjee (&) Department of Geology and Geophysics, Indian Institute of Technology (IIT), Kharagpur, Kharagpur 721302, India e-mail: [email protected]; [email protected] © Springer Nature Singapore Pte Ltd. 2018 D. Saha et al. (eds.), Clean and Sustainable Groundwater in India, Springer Hydrogeology, https://doi.org/10.1007/978-981-10-4552-3_19
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1 Introduction More than 120 million (2% of global population) lives in *200,000 km2 in eastern parts of India (West Bengal state) and most of Bangladesh. This area known as the Bengal basin (BB) or Ganges–Brahmaputra–Meghna river basin is considered to be the world’s largest fluvio-deltaic system (Coleman 1981; Alam et al. 2003). The rivers and surface water bodies have been indiscriminately used as sewerage and industrial waste discharge by the residents of the Bengal basin, thereby making the surface water unsafe. Further, intense irrigation of groundwater for high-yielding dry-season rice (Boro) (Harvey et al. 2005) largely increased the water-demand in the area. During the early 1970s, this resulted to the change of water-usage policy to groundwater from surface water in both West Bengal and Bangladesh, resulting to installation of millions of wells that range from low discharge hand-pumped wells to motor-driven, high-discharge wells (Smith et al. 2000; Kinniburgh and Smedley 2001; Harvey et al. 2005; Horneman et al. 2004). However, unfortunately, wide areas of the groundwater of BB were found to be pol
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