Scientists are digging for answers about the amount and quality of water available underground in central Delaware, where ongoing development will put increasing demands on water supplies in the coming decade.
The Delaware Geological Survey (DGS) is installing 7,700 feet of wells at eight sites in southern New Castle and northern Kent counties to improve groundwater-monitoring efforts, supported by a $600,000 grant from the Delaware Department of Natural Resources and Environmental Control (DNREC). Groundwater is the primary source of drinking water south of the Chesapeake and Delaware Canal, and populations there are projected to continue expanding.
“In response to that, water use is going to at least double in the next 20 years,” DGS Senior Scientist Scott Andres said. “Having a good monitoring infrastructure for groundwater is necessary for determining trends and making projections for the future of the water supply.”
Andres and colleagues from UD, DNREC and the U.S. Geological Survey are constructing the wells from Middletown to Townsend and extracting samples of sediment, called “cores,” to analyze sediment features. Andres expects to find some potentially harmful substances like radon and arsenic and help determine whether they pose a public health concern.
Arsenic has been previously found in Maryland and Delaware in concentrations that exceed drinking water standards in both domestic and public water wells. County ordinances in Maryland now require arsenic testing in new wells.
“Delaware doesn’t do that yet, and we’re hoping to find out if that should be something for Delaware to do,” Andres said.
In addition, the researchers will check for the presence of nitrates, water disinfection bi-products, pharmaceuticals, personal care products and volatile organic compounds (VOCs). They will also gauge groundwater and stream levels to better predict changes associated with increased pumping, helping to avoid over-pumping aquifers, decreasing streamflow or miscalculating water availability.
“At the beginning here we want to get the baseline conditions,” Andres said. “What is it now, and over time does it change?”
Beyond water samples from the wells, sediment cores removed during the project can provide valuable scientific information. DGS staff will use sediment at various depths as clues to determine the direction of water flow underground and water replenishment rates. Clay and silt, for example, do not transmit water as well as more porous deposits.
Paleontologists from Rutgers University will study the microfossils and fossil chemistry of cores that date to the Paleocene-Eocene thermal maximum to come up with sea-level rise rates. Scientists believe that conditions during that period are analogous to what Delaware may experience 100 years from now.
The multi-pronged project came in response to a 2006 Governor’s Water Supply Coordinating Council report identifying a need to evaluate the long- and short-term availability of groundwater in the area with new infrastructure and data collection.
In the future, the researchers hope to unearth significant discoveries about depths down to 3,500 feet below ground at the Potomac aquifers, which are extensively accessed in the northern part of the state but not below the canal. They would like to know where the aquifers become salty, answering questions about long-term groundwater supply options.
“They are potentially the largest single resource in the whole region,” Andres said. “Yet we have almost no information.”
Article and photos by Teresa Messmore