America’s freshwater is changing. According to an analysis of 232 sites in streams and rivers over several decades, it has become saltier in some places, and in almost all places, it’s becoming less acidic and more alkaline. These two processes may be related, and researchers have dubbed it “freshwater salinization syndrome.”
There are many likely causes: road salt (particularly in the Midwest and Northeast, where increased freshwater salinity is concentrated), sewage, mining, fertilizers used in agriculture. These continental-scale changes will affect wildlife unused to salty, more alkaline water. It will also likely come around to affect humans and the water we drink.
It’s not just that the water will taste a little saltier—though after a snowy winter in 2014, New Jersey did have to warn residents that its water was too salty for people on sodium-restricted diets. It’s that America’s aging water infrastructure is not built to handle saltier water. Just as road salts rust the metal of your car, dissolved salt in water reacts with the metal in water pipes.
For Sujay Kaushal, a geologist at the University of Maryland who led the recent analysis of 232 sites, this is personal concern. “This affected my house directly,” he says. In 2015, the drinking water in parts of Maryland, where he lives, started to turn brown. The water utility explained the color likely came from manganese, which had been carried out of old pipes by water full of dissolved road salt.
Road salt may have contributed to the lead crisis in Flint, Michigan, too. When the city began drawing water from the Flint River rather than relying on Detroit’s tap water to save money, it also began sending water with eight times as much chloride through its old lead pipes. Chloride can come from road salt (aka sodium chloride), and it corrodes the pipes.