FROM SURFACE TO SUBSURFACE: CONNECTING DEPOSITIONAL PROCESSES AND SURFACE FEATURES TO SUBSURFACE ARCHITECTURE AND CONTAMINANT TRANSPORT IN DELTAIC AQUIFERS

The subsurface architecture of deltaic aquifer systems is complex and difficult to characterize, yet the nature and connectedness of the sedimentary strata are critical controls on groundwater flow and contaminant transport. As deltaic aquifers are the primary water source for hundreds of millions of people, it is essential that we use all available information to characterize these systems. Building on surface-subsurface connectivity insights from a companion presentation, we use a series of numerically-simulated synthetic deltas and groundwater flow and solute transport modeling to show that the nature of the surface depositional system has a strong control on both the connection properties of the static media and the flow and transport properties of the aquifer systems. We illustrate how these controls vary depending on the spatial distribution of contaminant source and groundwater flow direction relative to the depositional system. Lastly, we use densely distributed lithologs from three areas of the Ganges-Brahmaputra-Meghna Delta to illustrate how surface network information can be used to improve both subsurface characterization and contaminant transport prediction. The insights gained have implications for the management of complex aquifers and providing sustainable clean water to a large portion of the global population.