Megacity pumping and preferential flow threaten groundwater quality
Date
2016-09-27
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Publisher
Nature Publishing Group
Abstract
Many of the world’s megacities depend on groundwater from geologically complex aquifers
that are over-exploited and threatened by contamination. Here, using the example of Dhaka,
Bangladesh, we illustrate how interactions between aquifer heterogeneity and groundwater
exploitation jeopardize groundwater resources regionally. Groundwater pumping in Dhaka
has caused large-scale drawdown that extends into outlying areas where arseniccontaminated
shallow groundwater is pervasive and has potential to migrate downward. We
evaluate the vulnerability of deep, low-arsenic groundwater with groundwater models that
incorporate geostatistical simulations of aquifer heterogeneity. Simulations show that
preferential flow through stratigraphy typical of fluvio-deltaic aquifers could contaminate
deep (4150 m) groundwater within a decade, nearly a century faster than predicted through
homogeneous models calibrated to the same data. The most critical fast flowpaths cannot be
predicted by simplified models or identified by standard measurements. Such complex
vulnerability beyond city limits could become a limiting factor for megacity groundwater
supplies in aquifers worldwide.
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Citation
Khan, M.R. et al. Megacity pumping and preferential flow threaten groundwater quality. Nat. Commun. 7:12833 doi: 10.1038/ncomms12833 (2016).