Abstract: Sandy aquifers deposited > 12,000 years ago, some as shallow as 30 m, have provided a reliable supply of low-arsenic (As) drinking water in rural Bangladesh. This study concerns the potential risk of contaminating these aquifers in areas surrounding the city of Dhaka where hydraulic heads in aquifers > 150 m deep have dropped by 70 m in a few decades due to municipal pumping. Water levels measured continuously from 2012 to 2014 in 12 deep ( > 150 m), 3 intermediate (90-150 m) and 6 shallow ( < 90 m) community wells, 1 shallow private well, and 1 river piezometer show that the resulting drawdown cone extends 15-35 km east of Dhaka. Water levels in 4 low-As community wells within the 62-147 m depth range closest to Dhaka were inaccessible by suction for up to a third of the year. Lateral hydraulic gradients in the deep aquifer system ranged from 1.7 × 10 -4 to 3.7 × 10 -4 indicating flow towards Dhaka throughout 2012-2014. Vertical recharge on the edge of the drawdown cone was estimated at 0.21 ± 0.06 m/yr. The data suggest that continued municipal pumping in Dhaka could eventually contaminate some relatively shallow community wells.
Recommended citation: Knappett, P. S. K., Mailloux, B. J., Choudhury, I., Khan, M. R., Michael, H. A., Barua, S., et al. (2016). Vulnerability of low-arsenic aquifers to municipal pumping in Bangladesh. Journal of Hydrology, 539, 674–686. https://doi.org/10.1016/j.jhydrol.2016.05.035