Madison collects about 18,000 tons of leaves each year, mostly during late October and early November when residents rake and pile them curbside for city pickup.
Keeping those leaves out of the street is the most important thing urban dwellers can do to protect Madison’s lakes, new research shows.
The U.S. Geological Survey has been studying leaves and runoff in Madison, with initial findings suggesting fallen leaves (and to a lesser extent soil, lawn clippings and pet waste) accounted for 56 percent of the phosphorus pollution last year that washed into our lakes from urban areas.
The research also has determined that careful timing of leaf removal from curbs can reduce that pollution by as much as 80 percent.
Unfortunately, too many homeowners and renters still rake their leaves into the streets, in violation of city ordinance. Those leaves then wash down the street and clump at storm sewer grates when it rains. The water soaks the mass of leaves like a tea bag, leeching out the phosphorus, which runs into the lakes. The phosphorus then feeds weed and algae growth in the water, filling the shoreline with green muck each summer and closing beaches.
Most of the phosphorus pollution entering Madison’s lakes comes from manure that’s stored and spread on farms. But city residents and businesses still have a responsibility to control the runoff from their properties, too, which accounts for about 30 percent of the overall problem.
Farmers are doing more to stem the erosion of animal waste into our lakes. Similarly, city and suburban residents must try harder to stop leaves from getting into street gutters and grates.
William Selbig, a hydrologist for the U.S. Geological Survey, said Tuesday his team now plans to study how much varying municipal practices for picking up leaves in the fall reduces the amount of phosphorus that’s released into the lakes. They’ll study the impact of using trucks, sweepers and large vacuum tubes to collect leaves from curbs.
But any collection system still will require help from the public so leaves don’t wash away when it rains.
The best way to keep leaves out of the streets and our lakes is to mulch or compost them in your yard. Yet most residents want their leaves picked up from the curb. That’s fine — so long as the leaves are piled a few feet from the street so they stay put during a storm.
Another tip for Madison residents is to look at the city’s website to learn when crews will be picking up leaves in their neighborhood. That way, the leaves don’t sit for weeks on the curb, killing grass and potentially eroding away.
Tips for how to rake, collect and store your leaves in communities across Dane county, including Madison, can be found at www.cleanlakesalliance.org/leaves.
Please do your part to protect our lakes by keeping your leaves out of the street. Now is the most critical time for prevention.