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DGS issues report on groundwater discharge areas

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RI74 Locating Ground-Water Discharge Areas In Rehoboth And Indian River Bays And Indian River, Delaware Using Landsat 7 Imagery
April 7, 2008

The Delaware Geological Survey (DGS) at the University of Delaware has released a new technical report that identifies locations of groundwater discharge to estuaries and determines locations of discharge into the Inland Bays. Using satellite imagery, the report identifies potential discharge locations by analyzing processed thermal images along with the panchromatic and near-infrared spectral bands.

The report, “Locating Ground-Water Discharge Areas in Rehoboth and Indian River Bays and Indian River, Delaware, Using Landsat 7 Imagery,” was prepared by Lillian Wang, geographic information systems specialist and cartographer at DGS, Thomas McKenna, associate professor of geological sciences and associate scientist at DGS, and Tracy DeLiberty, chairperson and associate professor of geography at UD.

"If the discharging groundwater is hotter or colder than the surface water that it discharges into, a thermal anomaly may be detectable in the surface water" Wang said. "In this study, we observed a signature of warmer groundwater discharging into cooler ambient surface water in satellite images collected during the winter."

The new report, also known as Report of Investigations No. 74 covers Delaware's Inland Bays in southeastern Sussex County, which are valuable natural resources supporting ecology, tourism, community-based recreation, and fisheries. Nitrogen loading from groundwater discharge to the bays is one of the most difficult environmental problems to quantify.

Wang said groundwater discharge areas were successfully located on the north shore of Rehoboth Bay west of the Lewes and Rehoboth Canal, on Herring and Guinea creeks on the north shore of Indian River and on the north shore of Indian River Bay near Oak Orchard.

“Locating groundwater discharge areas is a critical step towards identifying potential pathways of excess nutrient transport thereby facilitating development of remediation strategies to reduce nutrient loads to the bays,” Wang said.

The report is part of the Delaware Geological Survey's ongoing mission to understand hydrologic systems and to advise, inform and educate Delawareans about the results of such investigations for use in such areas as water resources, agriculture, public health, economic development, land-use planning, geologic hazards, environmental protection, energy and mineral resources, emergency management and recreation.

Report of Investigations No. 74 is available in PDF format. Additional information may be requested by contacting DGS at (302) 831-2833 or via e-mail to [delgeosurvey@udel.edu].

For questions and information, contact DGS at
delgeosurvey@udel.edu, 302-831-2833