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15th April 2017
By: Kevin Mathews
April 14, 2017

Don’t look now, but the U.S.’s biggest bodies of freshwater are gradually getting saltier. In the first-of-its-kind massive study of North American lakes, researchers found that 44 percent of them were becoming salinized over time.

The Global Lake Ecological Observatory Network enlisted fifteen researchers to test a total of 371 freshwater lakes. They’ve been recording the salt levels of these lakes for at least 10 years, and therefore are able to chart the increases in saltiness.

While none of the lakes have lost their freshwater status, some have tested as high as having 240 milligrams of salt per liter (though most are well under that mark.) The EPA stipulates that potable water should have less than 250 milligrams of salt in it.

What’s the Culprit?

Scientists have a pretty good grasp on what’s making these lakes saltier: road salt thrown on the ground to make driving on ice less slippery. Currently, North America throws down about 23 million metric tons of salt each winter to help melt ice and snow.

Though the researchers can only chart a correlation rather than causation, the correlation is certainly strong. For starters, the lakes’ salt levels are highest in the winter months. Second, the closer the lake is to a roadway or parking lot, the more likely it is to become salinized.

Road salt is intended to seep into the ground rather than nearby bodies of water, but some areas aren’t conducive to that. In areas where the ground is paved all the way, or nearly all the way, to the lake, the water is significantly more likely to be salty. In those cases, water just slides the salt over the asphalt and into the lake. Even a small point of exposure is enough to boost a lake’s salt levels.

Why Does This Matter?

The threat of salt to freshwater should not be ignored. Humans frequently rely on these lakes as a source of drinking water, and losing these sources could prove devastating over time. 14 of the 371 lakes studied are on track to be too salty to drink within the next few decades.

Heck, the salt in the water is more immediately devastating to non-human forms of life. Academics working on tangential research have found that young amphibians have difficulty surviving in water tainted with road salt. Freshwater fish are seeing their ecosystems change as the concentration of salt increases with each passing winter.

The accumulation of salt is one of the scariest parts. While streams and rivers can push the salt out to the ocean, the stationary nature of lakes means that salt collects in them for long periods of time. Unaddressed, road salt will continue to pose problems.

“We need to manage and monitor lakes to ensure they are kept “fresh” and protect the myriad of services they provide, from fisheries and recreation to drinking water supplies,” said Kathleen Weathers, a coauthor of the study.

Are There Alternatives?

Count the salinization of freshwater as just one reason humans should try to wean themselves off road salt. It may keep drivers safe on the road, but it leaves us less safe in other ways.

Fortunately, green-minded folks have begun to discover alternatives to the traditional salt. Particularly in Wisconsin, government officials have begun to dump cheese brine on the roads instead, which is a cheaper and more effective way of keeping the streets safe.

Other areas have found good results from other types of food waste. Beet juice, pickle juice and potato juice have all been used in different parts of the continent to de-ice the roads.