Lake Mendota and Lake Monona form a central part of Madison’s identity. They enhance the surrounding area’s appeal and draw people to the beauty, recreation and vibrancy they create, according to Between Two Lakes.
But underneath their glistening surfaces, the lakes tell a murkier story.
Even with the Federal Clean Water Act’s implementation around 50 years ago, Mendota and Monona are classified as impaired, much like the rest of the 55% of lake acres studied in recent years in the United States. According to the Environmental Integrity Project, these lakes aren’t safe as sources of food and drinking water or as sources of recreation.
The 1972 Clean Water Act set industry wastewater standards and enabled the legal implementations of water pollution control guidelines, making it unlawful for any party to emit any pollutant from a direct, or point source into “navigable waters” without a permit.
The Clean Water Act has addressed point sources of pollution since its adoption, according to Paul Dearlove, deputy director and senior science officer with Clean Lakes Alliance, a non-profit organization dedicated to the protection and improvement of inland water and wetlands in Wisconsin’s Yahara River Watershed.
While the act has addressed direct pollutant discharge, Dearlove said the problem has “morphed” since then.
According to Dearlove, today’s lakes face pollution from nonpoint sources. These include both urban and agricultural runoff, according to the United States Environmental Protection Agency. Anytime a significant disturbance or change occurs, there is potential for environmental harm from large amounts of runoff draining into surrounding water bodies via a watershed.
Dearlove also noted how Wisconsin deals with this same type of nonpoint source pollution: runoff, specifically excess nutrient runoff from agricultural activity.
Dearlove acknowledged Wisconsin's status as a “major dairy production presence,” especially in northern Dane County at the helm of the Yahara River Watershed. This geography contributes significantly to the nutrient runoff into the Yahara lakes, including Mendota and Monona.
“We have 60,000-plus units of livestock in our watershed, and that is equivalent to about 2.7 million people,” Dearlove said.
This massive livestock population contributes a massive amount of manure, which gets washed into groundwater sources as agricultural runoff.
Manure used to be treated more as a sustainable resource that was spread across the land before large industrial farms replaced traditional small and spread-out ventures, according to Dearlove. This balanced spread enabled farmers to utilize the nutrients phosphorus and nitrogen stored in manure for crop health.
“With pressures on the industry to get bigger and consolidate, you have now fewer farms,” Dearlove said. “They're bigger, they're more industrial, and you have these high concentrations of animals on a small piece of land”.
“The negative effect is that you have massive amounts of manure being generated in fewer and fewer areas,” he added.
The excess manure results in an overloading of nutrients into the soil, saturating it with phosphorus and nitrogen that wash into surface waters.
According to the Clean Lake Alliance’s 2022 “State of the Lakes” report, phosphorus concentration trends in Mendota and Monona are considered fair, by the Wisconsin Department of Natural Resources’ standards.
“If we have too much phosphorus in the system, it can lead to algal blooms, which we see commonly in the Madison lakes,” said Ellen Albright, a postdoctoral researcher at the University of Wisconsin-Madison Center for Limnology.
Albright’s research focuses on what happens to pollutants when already in the lake. As a part of her doctoral work, Albright studied a process called “internal-phosphorus loading,” referring to how a nutrient is cycled and recycled when already in lake water.
“What my research illuminates is that once pollutants or something undesirable is in a lake, it's really hard to get it out, especially things like phosphorus,” Albright said. “These nutrients can be held in sediments and recycled in between sediments and water for a long time.”
Albright also pointed to how other pollutants used in consumer goods, such as perfluorooctane sulfonic acid (PFOS), associate with sediments on lake floors to become “sticky in the system.” These pollutants settle in the lake’s sediments and recycle when the sediments are disturbed.
Albright’s current research also focuses on aquatic plants and the role they play in structuring a lake’s ecosystem. She described large, vascular lake plants, called macrophytes, as “ecosystem engineers.” Albright said macrophyte roots stabilize lake sediment and slow down water disturbances with their biomass.
However, nutrient pollutants in lake water threaten this role by spurring the excess growth of phytoplankton near the water’s surface. This blocks sunlight from reaching macrophytes and hinders their growth.
Albright also pointed to how aquatic plants like macrophytes prevent shoreline erosion by keeping pollutants in lake sediment from getting disturbed and distributed through the water.
“If you're a property owner along the lake, all those waves are slowly eroding away your shoreline, and your land is washing out into the lake,” Albright said. “But if you have healthy aquatic vegetation, it's gonna slow down that wave action and prevent shoreline erosion.”
Grace Roper, UW-Madison senior and president of the Wisconsin Hoofers Scuba Club, attests to the impacts of lake pollution on human communities and initiatives.
Roper said pollution and toxic algal blooms in Lake Mendota make diving near-impossible and limit other recreational activities in shallower areas.
“There’s been a lot of algae problems right outside of the Hoofers by the Union. It becomes unswimmable because the algae is toxic,” Roper said.
According to Roper, the water quality in Lake Mendota deters diving expeditions from happening there despite a community of local divers existing in Madison.
“It’s pretty unfortunate because we have a lake right here, but we don’t really use it. That is because of the water quality,” Roper said.
Roper added that lake clean-up initiatives, or “clean-up dives,” are also put in jeopardy because of unswimmable conditions. In addition to clean-up dives, UW-Madison’s Center for Limnology utilizes divers for research purposes.
According to Albright, research plays a central role in informing decision-making in areas around lakes. The decision-makers include property owners and members of every level of government among others.
“This application of research has become particularly important as we're facing an increasingly uncertain future,” Albright said. “Looking at different projections or scenarios gives us a better idea of how our lakes are going to be responding to different climate conditions and how we can adapt our decisions to this.”
As the battle against lake pollution ensues, Dearlove acknowledged there are countervailing headwinds against the progress being made. While communities increasingly adopt green infrastructure and better manure management techniques, a wetter climate favors pollutant accumulation.
“It's a good thing that we're doing the work that we're doing as a community,” Dearlove said.
“But we need to do a heck of a lot more of it in order to start to see actual, sustained water quality improvements in the lakes.”