Identifying multiple deep aquifers in the Bengal Basin: Implications for resource management

Abstract In the Bengal Basin of Bangladesh and West Bengal (India), where arsenic (As) and salinity adversely affect groundwater in shallow aquifers (<150 m deep), consumers increasingly turn to “the deep aquifer” as a source of low‐As and low‐salinity water. We show that “the deep aquifer,” which has traditionally been regarded as a single entity, can be divided into at least eight deep aquifer units each with distinctive chemical, isotopic, hydraulic, and piezometric characteristics. Except in the rapidly subsiding Sylhet Basin, the deep aquifers are largely As‐safe (<50 μg/L and mostly <10 μg/L) but differ in terms of iron (Fe), manganese (Mn), salinity, stable isotopic composition, groundwater age, and in their piezometric response to pumping. We use isotopic data to…