Delaware’s low elevation makes its groundwater resources particularly vulnerable to salinization. Rising sea levels, increasing coastal flooding, and growing demands on groundwater heighten the risk of saltwater intrusion (SWI) – seawater encroaching into freshwater aquifers. To address this risk, the Delaware Geological Survey, the University of Delaware, and the Delaware Department of Natural Resources and Environmental Control have formed a collaborative partnership to develop a comprehensive groundwater salinity monitoring network.

As an initial phase of the project, the DGS conducted a statewide data gap assessment to evaluate existing groundwater quality datasets. This assessment examined current data for salinity trends and whether existing monitoring infrastructure and testing are adequate for detecting and characterizing SWI risk. The results identify significant spatial and temporal data gaps that limit the state’s ability to assess SWI trends and implement timely responses.

Findings from the data gap assessment have been incorporated into the second phase of the project, which focuses on identifying areas of Delaware that are vulnerable to saltwater intrusion (SWI). The vulnerability analysis integrates groundwater, surface-water, meteorological, and water-use datasets within a geographic information system (GIS) model. This approach enables identification of aquifer-specific areas where salinity is increasing over time, providing a scientific basis for prioritizing monitoring, management, and mitigation efforts to protect Delaware’s groundwater resources.

Next steps include the installation of two new SWI monitoring well clusters. Results of the vulnerability analysis are being used to guide site selection for these new monitoring locations.