Study: South Florida susceptible to underground mix of salt water with freshwater

The journal Science published a new study showing 9 percent of U.S. coastal areas are susceptible to a contaminated underground mix of fresh water and salt water, including southeastern Florida.

The study features the first map of underground water flows ever developed. The technical name for these flows is “submarine groundwater discharge.” These flows bring fresh groundwater beneath the United States into contact with salt water from the oceans.

Southeastern Florida, Southern California and Long Island , New York, are among the metropolitan areas with water supplies at risk of contamination by seawater, the study found.

Ohio State University hydro-geologist Audrey Sawyer, lead author of the study, said only a minor amount of seawater will make drinkable water undrinkable. As rivers and streams flow into oceans, freshwater and salt water mix constantly without posing a public threat. But Sawyer said unseen subterranean mixing can lead to salt water intrusion that contaminates underground freshwater aquifers.

Hydrologist Cedric David of NASA’s Jet Propulsion Laboratory, which was involved in the study, told USA Today it  “removed the cloak from hidden groundwater transfers between land and sea.” [USA Today] — Mike Seemuth