Exploring hydrogeology and groundwater dynamics in a lateritic terrain of West Bengal, India, under limited data conditions

Abstract

This study aimed at investigating hydrogeology and groundwater dynamics in a lateritic terrain of West Bengal, India, under limited data conditions. A field setup was developed comprising six observation wells, two onfarm reservoirs and three artificial excavations. Groundwater levels, groundwater quality and water levels of surface water bodies were monitored during 2003–2005 period. Regression and correlation analyses of groundwater levels with rainfall and surface water levels were performed to study rainfall–groundwater dynamics and surface water–groundwater interaction. Depth-wise geologic samples of six sites were subjected to grain-size analysis (GSA) and stratigraphy analysis. Hydraulic conductivities (K) of subsurface formations at different depths were estimated by three GSA models, and finally groundwater recharge was estimated. Stratigraphy analyses revealed that besides shallow aquifers, deep confined aquifers of 5–16 m thickness exist at 54–96 m depths in the study area. Significant correlation of groundwater levels with the water levels in excavations and the ‘potential recharge’ of 1.90–2.99 cm/day from excavations indicate that the excavations can serve as promising low-cost recharge structures for augmenting groundwater resources. Nitrate concentration in the groundwater beyond maximum permissible limit at most sites renders it unsuitable for drinking purpose. Furthermore, the Hazen, Harleman, and Alyamani and Sen models yielded reasonable K values of subsurface formations. Average hydraulic conductivity and transmissivity values of the deep aquifer system vary from 3 to 129 and 27 to 1161 m2 /day, respectively, which suggest significant aquifer heterogeneity. Seasonal groundwater recharge in the study area was found to be in the range of 4.32–15.24 cm.