Browsing by Author "Koneshloo, Mohammad"
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Item Impact of topography on groundwater salinization due to ocean surge inundation(American Geophysical Union, 2016-08-05) Yu, Xuan; Graf, Thomas; Koneshloo, Mohammad; O'Neal, Michael A.; Michael, Holly A.; Yang, Jie; Xuan Yu, Jie Yang, Thomas Graf, Mohammad Koneshloo, Michael A. O'Neal, Holly A. Michael; Yu, Xuan; Koneshloo, Mohammad; O'Neal, Michael A; Michael, Holly A.Sea-level rise and increases in the frequency and intensity of ocean surges caused by climate change are likely to exacerbate adverse effects on low-lying coastal areas. The landward flow of water during ocean surges introduces salt to surficial coastal aquifers and threatens groundwater resources. Coastal topographic features (e.g., ponds, dunes, barrier islands, and channels) likely have a strong impact on overwash and salinization processes, but are generally highly simplified in modeling studies. To understand topographic impacts on groundwater salinization, we modeled a theoretical overwash event and variable-density groundwater flow and salt transport in 3-D using the fully coupled surface and subsurface numerical simulator, HydroGeoSphere. The model simulates the coastal aquifer as an integrated system considering overland flow, coupled surface and subsurface exchange, variably saturated flow, and variable-density groundwater flow. To represent various coastal landscape types, we simulated both synthetic fields and real-world coastal topography from Delaware, USA. The groundwater salinization assessment suggested that the topographic connectivity promoting overland flow controls the volume of aquifer that is salinized. In contrast, the amount of water that can be stored in surface depressions determines the amount of seawater that infiltrates the subsurface and the time for seawater to flush from the aquifer. Our study suggests that topography has a significant impact on groundwater salinization due to ocean surge overwash, with important implications for coastal land management and groundwater vulnerability assessment.Item Megacity pumping and preferential flow threaten groundwater quality(Nature Publishing Group, 2016-09-27) Khan, Mahfuzur R.; Koneshloo, Mohammad; Knappett, Peter S.K.; Ahmed, Kazi M.; Bostick, Benjamin C.; Mailloux, Brian J.; Mozumder, Rajib H.; Zahid, Anwar; Harvey, Charles F.; van Geen, Alexander; Michael, Holly A.; Mahfuzur R. Khan, Mohammad Koneshloo, Peter S.K. Knappett, Kazi M. Ahmed, Benjamin C. Bostick, Brian J. Mailloux, Rajib H. Mozumder, Anwar Zahid, Charles F. Harvey, Alexander van Geen & Holly A. Michael; Khan, Mahfuzur R.; Koneshloo, Mohammad; Michael, Holly A.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.Item Megacity pumping and preferential flow threaten groundwater quality(Nature Publishing Group, 2016-09-27) Khan, Mahfuzur R.; Koneshloo, Mohammad; Knappett, Peter S.K.; Ahmed, Kazi M.; Bostick, Benjamin C.; Mailloux, Brian J.; Mozumder, Rajib H.; Zahid, Anwar; Harvey, Charles F.; van Geen, Alexander; Michael, Holly A.; Mahfuzur R. Khan, Mohammad Koneshloo, Peter S.K. Knappett, Kazi M. Ahmed, Benjamin C. Bostick, Brian J. Mailloux, Rajib H. Mozumder, Anwar Zahid, Charles F. Harvey, Alexander van Geen & Holly A. Michael; Khan, Mahfuzur R.; Koneshloo, Mohammad; Michael, Holly A.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.