Temperatures Rise—And So Do Salt Levels

As temperatures climb and winter fades, snow and ice have disappeared—but what washed away isn’t just water. The road salt applied throughout the winter is now flowing into our lakes, streams, and even drinking water, raising serious concerns about pollution and long-term water quality. 

To better understand the impact, a team led by the Capital Area Regional Planning Commission (CARPC) has been monitoring salt levels in Starkweather Creek alongside our project partners. Eight conductivity meters installed throughout the watershed collect real-time data on salt concentrations and pollution trends. These sensors, funded by a Community-Based Water Research Grant from UW-Madison, show that even in a mild winter, salt continues to wash into waterways during melting events, contributing to long-term environmental damage. 

What the Data Shows 

Our recent monitoring reveals that chloride pollution remains alarmingly high, with salt levels in some areas nearly double the federal toxicity threshold. On February 24 and 26, chloride levels in Starkweather Creek near East Towne Mall spiked to 424 mg/L, exceeding both the Wisconsin DNR’s chronic toxicity limit of 395 mg/L and the federal toxicity threshold of 230 mg/L. While chloride levels are typically highest on the east side of Starkweather Creek, elevated concentrations were also recorded on the west side—demonstrating how widespread and persistent salt pollution has become. 

Why This Matters 

Chloride from salt degrades freshwater ecosystems. Unlike other pollutants, chloride does not break down, making it a lasting threat to aquatic life and drinking water quality. In fact, just one teaspoon of road salt is enough to permanently pollute five gallons of water to a level that is toxic to aquatic life.  

Salt pollution also impacts human health. Recent Wisconsin DNR data shows that over a third of public wells in the state exceed recommended sodium limits for people on low-salt diets. As climate patterns shift and freeze-thaw cycles become more frequent, more salt is applied—even when little snow or ice is present—leading to increased contamination. 

What Can We Do? 

• Sweep up leftover salt from driveways and sidewalks to prevent runoff. 

• In the event of a classic Wisconsin late spring snowstorm, grab a shovel or scraper instead of relying on salt to melt ice and snow. 

• Advocate for #SaltWise practices and start preparing for smarter salting next winter. 

By monitoring salt levels in real time, we’re working to promote better winter maintenance strategies and raise awareness of salt’s lasting impact. The salt we use today doesn’t disappear—it lingers in our water, affecting our lakes, streams, and drinking supply for years to come. 

For more on smart salting practices, visit WI Salt Wise—a program of CARPC.