In 2015, staff of the Water Supply Section of the Delaware Department of Natural Resources and Environmental Control (DNREC) informed the DGS of their concerns about overpumping of the unconfined Columbia aquifer in an area east of Dover (Figure 1). In this area, the City of Dover’s Long Point Road Wellfield (LPRW) and numerous irrigation systems pump water from the shallow Columbia aquifer. Overpumping is a cause for concern because it may 1) increase the risk for saltwater intrusion into the aquifer from saline tidal creeks and marshes and, 2) induce extra drawdown that could reduce the transmissivity of the aquifer and decrease well yields. The potential for overpumping will become more significant when an electric generating station served by the LPRW is expected to increase capacity and requires more water.
This report summarizes monitoring and modeling that were conducted to investigate the potential impacts of overpumping. Automated water level and salinity sensors were installed and operated in three monitoring wells, and a digital groundwater flow model was constructed. The model was run in both steady-state and transient modes. As is the case with most models, many assumptions and simplifications had to be made because of data limitations. The model was calibrated to a spatially limited set of data. Consequently, model outputs are meant to inform how the aquifers behave given the assumptions and simplifications and will not represent precise predictions of water pressures in the area represented by the model. Additional data are now being collected in the model domain to refine the accuracy and precision of model results.
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