Wisconsin fresh water is becoming increasingly salty. Forty-seven rivers and lakes in our state are impaired due to high chloride concentrations (WDNR). Elevated salt levels in lakes, streams, and wetlands, threaten our fisheries, tourism, economy, quality of life, and the health of our aquatic ecosystems. Road salt is the primary culprit, followed by salt from conventional water softening systems.
Over 500,000 tons of salt (sodium chloride) are applied to Wisconsin roadways annually. Deicing salt does its job by dissolving into snow and ice; once it’s dissolved it goes where the snowmelt goes – often into storm sewers and directly into our lakes and streams.
The 40-lb bags of salt that we pour into our water softeners brine also end up in our freshwater either through infiltration from private septic systems or direct discharge from the sewage treatment plants that are unable to desalinize wastewater. Whether these salts are shuttled straight to surface waters or slowly infiltrate into groundwater, all the salt that we bring into Wisconsin ends up in our fresh water.
We’re salting our surface water
Salt is a permanent pollutant in lakes, streams, and wetlands. Elevated salt levels stress plants and animals that have adapted to freshwater environments. Before reaching lethal levels, chloride (Cl–, the negative ion in sodium chloride, NaCl), has a variety of direct and indirect impacts on the health of organisms in aquatic ecosystems. Fish experience decreased rates of growth, frogs are more susceptible to parasites, and the embryonic survival of salamanders declines as salt concentrations increase. Researchers hypothesize that the young of many species are impacted before the adults because the organs that help with osmoregulation (kidneys, gills, etc.), the regulation of salts in the body, are not yet fully formed. As salt levels go up, the one winner is algae. Expect greener, murkier waters as water gets saltier because the zooplankton that eat algae are highly sensitive to salt. (A review of the species, community, and ecosystem impacts of road salt salinisation in fresh waters, 2019.)
The Southeastern Wisconsin Regional Planning Commission (SEWRPC) is investigating the inputs and impacts of chloride in regional watersheds. Initial SEWRPC study results include chloride concentrations above 3,000 mg/L in freshwater streams in southeastern Wisconsin. This is 10 times greater than the EPA limit for chronic exposure (230 mg/L) and over three times the EPA limit for acute exposure (860 mg/L).
We’re salting our groundwater
Surface water is not the only victim of unchecked salting. In our capital, salt pollution of both upper and lower aquifers is forcing the Madison Water Utility to prepare for the closure of one drinking water well in the next 10-15 years and another 10-15 years after that. Elevated concentrations of sodium (Na+, the positive ion in NaCl) in drinking water are a concern for individuals on low-sodium diets. According to private well water data from the University of Wisconsin – Steven’s Point, drinking water across the state has elevated levels of chloride; it’s likely that sodium levels are elevated as well, but it is not often tested. We do know, throughout most of the state, that our water now comes to our taps pre-salted. Additionally, now that our groundwater is salted, our lakes and streams are recharged with salty water during the summer months. In the SEWRPC study referenced above, monthly chloride grab samples indicate that some stream chloride concentrations are elevated above the chronic toxicity limit year-round.
The cost of salt keeps rising
Beyond the very clear impacts to our freshwater resources, oversalting is a costly endeavor. By weakening metal, concrete, brick, and stone, one ton of road salt causes between $800 and $3,300 in damages as it prematurely ages our roads, bridges, and vehicles. Nationwide, we spend $5 billion annually to repair salt damage to roads and bridges and we’re not keeping up. (Impacts of Chemical Deicers on Roadway Infrastructure, 2018.)
There is a better way
Forward-thinking municipalities across the state are rethinking winter maintenance. They are ditching the outdated mindset around salt that “more is better” and embracing precision applications of salt combined with a renewed focus on mechanical removal. Educating operators, calibrating equipment, and incorporating salt brine are several of the methods that are enabling communities to reduce salt use by 30-70%. Read about improvements by Salt Wise Champion Municipalities on our website at www.wisaltwise.com/Municipal-Champions.
As individuals we can support our municipal public works staff by staying off roads during winter storms as pressure from constituents often drives the over-use of salt. We can also improve personal practices around our homes and places of work by using winter salt wisely and making sure our water softener is not a salt hog. Get tips on how you can be Salt Wise at www.wisaltwise/TakeAction. A quality ice scraper could preempt your need for deicing salt. A salt-free water treatment device may solve hardwater scale issues equally as well as a salt-based softener. Whatever steps you take, your local freshwater lake or stream, and the freshwater species that call it home, will appreciate it!