The growth of large coastal cities is putting increasing demand on supplies of potable water as traditional sources are depleted. Increased withdrawal of local groundwater has led to more widespread occurrences of salt-water intrusion and new surface-water supplies are becoming politically and economically difficult to access. As sea level rose and fell over the past million years, the shoreline moved landward and seaward, shifting the boundary between fresh water and salt water with the result that reservoirs of freshwater can often be found offshore. This water could provide a significant reserve for coastal areas if other sources are unavailable. This project will identify the extent of freshwater buried in marine sediments in the continental shelf of New Jersey and in the offshore delta region of Bangladesh. The research will use data from geophysical surveys, sediment deposition, groundwater flow, and solute transport, to develop mathematical models that simulate the accumulation of freshwater in these submarine deposits as sea level rose. The project will also construct simulations of groundwater production from these areas to assess the feasibility of accessing the offshore reservoirs within the next few decades.
The project will assess how sequestration of onshore saltwater and offshore freshwater in coastal environments is influenced by interactions between geomorphic, sedimentological, geodynamic, and hydrologic processes over geologic time scales of one million years or more. The research will develop a new model using the Earth-science community code, Landlab, and apply the code at two field sites with vastly different local sea-level, climate, tectonic and sediment transport regimes: New Jersey and Bangladesh. Calculated sediment type and salinity patterns from these models will be compared to new and existing images from seismic and electromagnetic (EM) data, as well as to available well samples measuring salinity and age of the water. An EM survey will be carried out in Bangladesh to determine the distribution of deep onshore saltwater and freshwater in this active deltaic environment. Along with recently collected EM images from offshore New Jersey, these data will be used to test the Landlab model to elucidate the factors controlling the emplacement of fresh and saline groundwater in coastal regions.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
