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Driving Mechanisms and Timescales of Saltwater Intrusion near Dover, DE

IWRA 2020 Online Conference - Addressing Groundwater Resilience under Climate Change
THEME 1. Groundwater Natural Resouces Assessment Under Climate Change
Author(s): Mary Hingst, Rachel McQuiggan, Chelsea Peters, A. Scott Andres, Holly Michael

Mary Hingst1, Rachel McQuiggan2, Chelsea Peters1 ,  A. Scott Andres2 , Holly Michael1

1 University of Delaware,
2 Delaware Geological Survey



Groundwater is the main source of freshwater for irrigation and drinking water in Dover, Delaware. Growing demand for groundwater combined with proximity to the coast and low elevation puts Dover at high risk of groundwater contamination from saltwa ter intrusion. Saltwater intrusion can occur both rapidly, via surface inundation, and gradually from sea level rise and increased groundwater pumping. Most of the developed land east of Dover is row crop agriculture . Many of these agricultural operations are fringed by saline tidal creeks and salt marshes which means irrigation wells and ponds are likely to be the first locations affected by sa ltwater intrusion.

The aim of this study is to assess the driving mechanisms of saltwater intrusion around Dover , the timescales of contamination, to characterize level of risk. A combination of field monitoring data and a variable density SEAWAT groundwater flow and salt transport model are being used to complete the study. Water level and sp ecific conductivity data which were recorded in irrigation ponds, marshes , tidal creeks and monitoring wells, indicate change s in groundwater flow patterns in response to irrigation, tidal fluctuations, and inundation from storm events.

During the irrigation season and certain tidal events, specific conductivity levels increased above the tolerance threshold of planted crops. Forecasted i ncreased pumping for public water supply and power generation is expected to increase saltwater intrusion. Because mall increases in salinity could have large economic impacts on area farmers, it is essential to better understand the potential
impacts and risks of drivers and mechanisms of saltwater intrusion.

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