A joint study by the Ohio State University and NASA’s Jet Propulsion Laboratory recently published in the journal Science revealed that there are water exchanges underground where fresh water and ocean water mix.
The study revealed previously uncovered sources of pollution along 20% of the US coastline.
It further sheds light on the dynamics of water exchange under the ground to and from the ocean, which has implications on terrestrial water pollution, as well as ocean pollution.
Audrey Sawyer, assistant professor of earth sciences at The Ohio State University and leader of the study, noted that scientists have long been aware of such exchanges, but little has been hitherto known about them.
This exchange is called submarine groundwater discharge. "Freshwater flows out to sea, and vice versa. Urbanization, agricultural development, climate, and topography all affect how much water flows in either direction and the exchange has a big impact on both onshore groundwater that we drink and offshore seawater where we swim and fish."
Going one way, water from land could seep to oceans, contaminating them with waste water from septic tanks and fertilizer runoff. Once in the ocean, nutrients from ground water could cause hazardous algal blooms to form, restricting oxygen supply in the water. This contamination poses a threat to fisheries and coral reefs, as well as tourism activities.
In another direction, ocean water could seep to freshwater supply, threatening the safety and potability of drinking water.
"It takes only a small amount of saltwater to render drinking water non-potable, so saltwater invasion is a big concern for water resource management in coastal areas," Sawyer said. "That's why we hope others will use our analysis to better plan strategies for coastal land development and groundwater management that help preserve water quality.”
