Evaluation of the sustainability of deep groundwater as an arsenic-safe resource in the Bengal Basin

doi:10.1073/pnas.0710477105

Evaluation of the sustainability of deep groundwater as an arsenic-safe resource in the Bengal Basin

Holly A. Michael*,^† and
Clifford I. Voss*

U.S. Geological Survey, Reston, VA 20192

Edited by William A. Jury, University of California, Riverside, CA, and approved April 4, 2008
↵*H.A.M. and C.I.V. contributed equally to this work. (received for review November 5, 2007)

Abstract

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.

Footnotes

^†To whom correspondence should be sent at the present address:
Department of Geological Sciences, University of Delaware, Newark, DE 19716.
E-mail: hmichael{at}udel.edu
Author contributions: H.A.M. and C.I.V. designed research; H.A.M. performed research; H.A.M. analyzed data; and H.A.M. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0710477105/DCSupplemental.