The Madison lifestyle is built on the fact that the city is sandwiched between two large lakes, creating opportunities for recreation, habitat for animals and a unique capitol identity — but our way of life is contributing to water pollution.
Runoff from stormwater, tree leaves and agricultural sources is polluting the five lakes in the Yahara watershed — Mendota, Monona, Wingra, Waubesa and Kegonsa — with phosphorus, which triggers algae blooms each year, harming wildlife and forcing municipalities, including Madison, to temporarily close public beaches and strongly advise against swimming in the lakes.
Michael Smale, the watershed programs specialist for Clean Lakes Alliance, said phosphorus enters the lakes from leaves, which are a primary carrier of phosphorus. When leaves are swept or flooded into stormwater sewers, they enter the lakes and increase algae growth.
While the majority of phosphorus in the lakes flows from agricultural sources located largely north of the Mendota watershed, leaf or urban leaf phosphorus inflows are “far the largest urban source of phosphorus” going to our lakes.
The pavement that makes the city of Madison so walkable and accessible for students and residents contributes to the crisis. Pavement runoff promotes blue-green blooms, called cyanobacteria, that end up in the lakes, causing some of the most-used beaches to close each summer.
“So now when it rains, it hits pavement, asphalt, and then all the water gets shunted right off the landscape and into waterways and into our lakes,” Smale said. Instead of dust, oil or other contaminants soaking into soil, “it all [gets] washed off along with the water into the lakes.”
Although algae is a natural environmental phenomenon, too much cyanobacteria creates blooms that produce cyanotoxins in the water and make swimming and recreation dangerous, Smale said.
Smale said that Clean Lakes Alliance has found that $200 million of economic activity in the region is attributed directly to the lakes, so while closing the beaches may benefit the people of Madison’s physical health, it will hurt the economy.
Outside of urban areas, when leaves fall onto the ground in autumn, they decompose and get recycled into the vegetation the following year. But because of Madison’s condensed streets and pavement, it doesn’t happen that way.
When leaves fall onto pavement and decompose, “leaking out” phosphorus when it rains, “hat fosters litter-water” that, instead of going into the soil and getting absorbed, “just gets whisked away into the lakes and that becomes an algae and then it becomes an algae concern the next year,” Smale said.
The Madison Streets Department currently has nine street sweepers, according to Bryan Johnson, the strategic initiative coordinator and public information officer for the city’s Streets and Urban Forestry Division.
It is against city ordinances to place leaves in the streets, so residents are directed to put leaves and yard waste at the curb to be picked up by leaf crews, which are followed by the street sweepers, Johnson said.
“We run [the street sweepers] as much as we possibly can during [the fall] and try to keep them behind the leaf crews, but there’s so many more leaf crews than sweepers,” Johnson said, adding that funding limits how much they can operate.
Greg Fries, assistant city engineer for City of Madison Engineering, said the city has changed its leaf collection policies to more efficient at collecting leaves prior to having water run through the leaves and into the stormwater system.
Fries said Madison has intensified upgrades to its systems for flood control since 2018, but stormwater management and leaf runoff is not the main concern.
While urban land does contribute to stormwater runoff, it is not the main catalyst for the algae blooms and phosphorus in the Yahara lakes, Fries said — agriculture is. Madison participates in adaptive management, an agreement to minimize phosphorus discharge by working with landowners, municipalities and counties to target sources of the runoff.
Fries said the city works with farmers to reduce the amount of phosphorus that ends up in the lakes. Madison is subject to the state Department of Natural Resources’ total daily maximum load — the amount of a pollutant a body of water can receive and still meet water quality standards — and pays farmers to implement practices to curb runoff.
The city of Madison is working toward solutions for stormwater management, leaf runoff and agricultural sources, but Smale said “everybody has a role to play” in reducing the amount of phosphorus that gets into the lakes — including those in urban areas that contribute less to the total amount.
“It doesn’t mean the lakes turn clear the next day. It’s a long-term commitment, and it takes everybody. It’s not just the city of Madison, it’s everybody around the watershed,” Smale said.
