Quirks & Quarks

We're making our fresh water salty by massively changing the landscape

At least one third of U.S. streams and rivers have gotten saltier over the last 100 years

At least one third of U.S. streams and rivers have gotten saltier over the last 100 years

Land use and climate change are leading to increased salinity levels in rivers and streams in the U.S. and other parts of the world. (Mladen Antonov/AFP/Getty Images)
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A new study led by freshwater scientist John Olson, has found that land use and climate change have led to increasing salinity levels in rivers and streams, threatening freshwater resources, biodiversity and ecosystems across the United States.

This is likely happening in other parts of the world as well, including small lakes and streams in Canada, said Olson, an assistant professor in the School of Natural Sciences at California State University.

He estimates that at least one third of U.S. streams and rivers have gotten saltier over the last 100 years, and predicts salinization levels may rise by 50 per cent in half of U.S. streams by the end of the century.

Increased salinity can make freshwater resources no longer suitable for human use such as irrigation or industrial applications.

Human factors

"Salt" in this study refers to ionic compounds formed when an acid reacts with a base in water.

Humans release salts in the form of a variety of ions such as calcium, magnesium, sodium, bicarbonate, sulfate or chloride through activities such as road salting, industrial operations and mining.

Coal extraction exposes the rocks buried underground to air and water, mobilizing the salt in the rock. (Rizwan Tabassum/AFP/Getty Images)

Mining can increase salinity levels, for example, when briny wastewater from fracking gets into the water supply, or when coal extraction exposes the rocks buried underground to air and water, mobilizing the salt in the rock.  

"We're now moving more material around than ever before, exposing new rocks to weathering," explained Olson. "That increase in weathering ends up adding more salt to rivers."

Impact on ecosystems

Olson predicts that 42 per cent of low-salt habitats in the U.S. will be gone by 2100.

"Invertebrates and fish are able to adapt to low-salinity conditions, but future salt levels will be higher than what some animals can adapt to," he cautioned.

Stopping mountaintop removal mining would help with the problem, as well as controlling the amount of water that is produced by oil and gas extractions. But it's a tricky problem because once salt is in the water, it's hard to remove. The best way is to stop salt from getting into the water supply in the first place.