Groundwater quality trends in the Dupi Tila aquifer of Dhaka, Bangladesh: sources of contamination evaluated using modelling and environmental isotopes

Dhaka, capital of Bangladesh, is a megacity dependant on groundwater for the majority of its water supply, pumped from 420 boreholes distributed throughout the city. Recharge to the groundwater aquifer is insufficient to balance abstraction, groundwater levels are in decline and water quality is compromised by seepage from areas of urban and industrial contamination and leakage from polluted rivers. The strategic importance of the naturally high-quality groundwater resource demands a targeted programme of aquifer protection. Repeated surveys at over 100 boreholes demonstrate the patterns and trends of deteriorating groundwater quality. Groundwater modelling and environmental isotope distributions have been used independently to evaluate the significance of potential sources of pollution. Both approaches identify the polluted River Buriganga as the main threat to groundwater quality, indicating priorities for monitoring and aquifer protection.