City Cast

How Leaf-Free Streets Lead to Cleaner Lakes

Hayley Sperling
Hayley Sperling
Posted on September 20
Two mason jars are side by side. the left one hold wet leaves while the right one holds brown water.

An example of "leaf tea" shows how rain soaked leaves creates phosphorus-laden water that ends up in our lakes. (City of Madison / YouTube)

The air is crisp, trees are changing colors, and pumpkin spice lattes are on the menu — it’s officially fall on Saturday. And while there are plenty of things to enjoy about this time of year, the season also brings an unwelcome guest to our lakes and streams: phosphorus.

According to the city, fall accounts for more than half of the phosphorus leaving a neighborhood.

As rain soaks the leaves that have drifted from their branches onto yards, sidewalks, and streets, it dissolves the phosphorus in them and carries it into our waterways. You can think of the leaves as tea bags brewing phosphorus as it steeps.

Too much phosphorus can lead to murky waters, toxic algae growth, and depletion of oxygen in water, which results in the death of aquatic animals.

To combat the problem, the city cleans leaves from the streets before storms and offers yard waste collection in the fall. Clearing streets of leaves can reduce harmful phosphorus concentrations in stormwater by more than 80%, according to a joint study from the City of Madison and U.S. Geological Survey. And you can help, too.

What You Can Do

  • Rake leaves from the street before it rains. Dane County residents can sign up for text alerts that will remind you when rain is on the way and it’s time to take action.
  • Mulch your leaves. Using a mulching lawn mower to grind up leaves that fall on your lawn will return nutrients to the soil, providing a source of organic fertilizer to your lawn. It’s a win-win!
  • Follow the yard waste pickup rules. Yard waste includes items like leaves, weeds, grass and garden trimmings, pumpkins, and pine cones. It’s different from brush, which is typically woody material cut from a tree. The city prefers you use compostable leaf bags to collect yard waste.
  • Yard waste pickup dates are now available for 2023. You can find yours by entering your address here.
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