Arsenic in Deep Groundwater: InSAR and Hydromechanical Modeling in the Mekong Delta
2013 Fall Cyberseminar Series
- Laura Erban / Stanford University
Throughout the arsenic-prone basins of South and Southeast Asia, contamination tends to be most severe in shallow wells, rarely affecting wells in deeper aquifers. Deep aquifers are now sought out as presumed pathogen- and arsenic-free sources of water, though the processes that may compromise their long-term viability remain in question. In the Mekong Delta, a large cluster of deep contaminated wells (nearly 900 wells, 200-500m deep) in a heavily-pumped region prompted me to reconsider their arsenic source. Here I develop integrated lines of evidence based on interpretation of well observations, 3D hydromechanical modeling and Interferometric Synthetic Aperture Radar (InSAR) analysis that support a previously unrecognized mechanism causing deep arsenic contamination in the Mekong Delta: expulsion of solutes from compacting clays induced by excessive pumping. Over-exploitation of groundwater threatens not only to exacerbate arsenic contamination, but also induce land subsidence and saline intrusion in this highly vulnerable region. Recommendations are given for future research aimed at informing responsible water resources management in the Delta and other similar systems.