Evaluation of the sustainability of deep groundwater as an arsenic-safe resource in the Bengal Basin.
Tens of millions of people in the Bengal Basin region of Bangladesh and India drink groundwater containing unsafe concentrations of arsenic. This high-arsenic groundwater is produced from shallow (<100 m) depths by domestic and irrigation wells in the Bengal Basin aquifer system. The government of Bangladesh has begun to install wells to depths of >150 m where groundwater arsenic concentrations are nearly uniformly low, and many more wells are needed, however, the sustainability of deep, arsenic-safe groundwater has not been previously assessed. Deeper pumping could induce downward migration of dissolved arsenic, permanently destroying the deep resource. Here, it is shown, through quantitative, large-scale hydrogeologic analysis and simulation of the entire basin, that the deeper part of the aquifer system may provide a sustainable source of arsenic-safe water if its utilization is limited to domestic supply. Simulations provide two explanations for this result: deep domestic pumping only slightly perturbs the deep groundwater flow system, and substantial shallow pumping for irrigation forms a hydraulic barrier that protects deeper resources from shallow arsenic sources. Additional analysis indicates that this simple management approach could provide arsenic-safe drinking water to >90% of the arsenic-impacted region over a 1,000-year timescale. This insight may assist water-resources managers in alleviating one of the world's largest groundwater contamination problems.
Michael
Holly A
HA
U.S. Geological Survey, Reston, VA 20192, USA. hmichael@udel.edu
Voss
Clifford I
CI
D001151:Arsenic / Q000032:analysis*; D001459:Bangladesh; D003198:Computer Simulation; D004784:Environmental Monitoring / Q000379:methods*; D005843:Geography; D008962:Models, Theoretical; D015203:Reproducibility of Results; D012987:Soil / Q000032:analysis; D012989:Soil Pollutants / Q000032:analysis*; D014881:Water Supply / Q000032:analysis* / Q000592:standards
D012987:Soil; D012989:Soil Pollutants; D001151:Arsenic