We’re in trouble with fresh groundwater

sciencedaily.com: US groundwater in peril: Potable supply less than thought

The U.S. groundwater supply is smaller than originally thought, according to a new research study that includes a University of Arizona hydrologist.

The study provides important insights into the depths of underground fresh and brackish water in some of the most prominent sedimentary basins across the U.S.

“We found that potable groundwater supplies in the U.S. do not go as deep as previously reported, meaning there is less groundwater for human and agricultural uses,” said Jennifer McIntosh, a University of Arizona Distinguished Scholar and professor of hydrology and atmospheric sciences.

The new research found the average depth of transition from fresh to brackish groundwater in the U.S. overall is about 1,800 feet, which contradicts previous studies suggesting that fresh groundwater extends down to 6,500 feet.

Especially in parts of the eastern U.S., the team found the transition from fresh to brackish water occurs at less than 1,000 feet. In such regions, drilling deeper wells is not a long-term solution to the need for additional fresh water, the team wrote.

“There are a number of cases where potentially you could go a kilometer or so deep for fresh groundwater, but there are other areas of the United States where in maybe a maximum of 200 or 300 metres you would run into saline groundwater — essentially you would be done in terms of water resources,” said Ferguson, an associate professor at the University of Saskatchewan in Saskatoon, Canada.

In addition, the injection of water, chemicals or sand that occurs with hydraulic fracturing, or “fracking,” or the injection of wastewater may drive waters containing hydrocarbons into adjacent areas that contain potable water.