Can we improve water quality by changing our leaf collection program?
What if we didn’t regularly collect leaves?
What if we bagged leaves?
What is the impact of spring buds and blossoms vs fall leaves?
This USGS study will answer these and other water quality questions related
to how we collect leaves. The results of the study will be important to both
federal and state agencies who regulate the amount of pollutants (phosphorus
and nitrogen) that reach our lakes and streams. In addition, municipalities will
have a better idea of the importance of a sound leaf collection policy.
Four neighborhoods will be asked to alter their leaf management practices each year of the study in order to measure the impacts of leaves on water quality.
The 4-year scientific monitoring study will begin as soon as fall 2012 due to
a generous funding opportunity from the Fund for Lake Michigan as well as Dane County.
The storm outfalls where each neighborhood drains to (see maps to right) will have monitoring equipment installed by the USGS and a bag will be mounted on the end of the pipe to collect leaves and debris, which will be weighed and analyzed off-site. We will be checking the status of the bags regularly and switching full bags out with empty ones as needed.
We will be relying heavily on the 90+ residents who fall within our different study areas as voluntary participants.
Year 1 (2012) will establish a statistical relationship between the 4 different
neighborhoods - we will provide minimal leaf collection in these areas, which means one leaf collection/ sweeping in mid- to late-November.
Over the next 2 years (2013-2014), two of the neighborhoods will continue
with limited leaf collection to answer the question ”What if we provided minimal leaf collection?" The other two
neighborhoods will receive our current policy ("How beneficial is Madison’s current
program?") in 2013, then be encouraged to bag their leaves with compostable bags that the city will provide ("What if we
bagged most of the leaves?"), along with increased street sweeping, in 2014.
Year 4 (2015), we will continue to have two control neighborhoods receiving only 1 collection in the late fall and an advanced collection strategy in the other two neighborhoods. In Year 5 (2016), we will switch the control and advanced collection strategy neighborhoods. While the final report won’t be written until Year 6 (2017), important data will be posted on the USGS web site. Links to the USGS sample data can be found by clicking the name of your neighborhood:
S Kenosha Dr
Gray Fox Trail
S Kenosha Dr (East)
During the fall of 2012, the USGS installed storm sewer monitoring stations in four residential drainage basins in Madison, Wis. Since then a total of 160 water-quality samples have been collected and analyzed for a variety of nutrients including phosphorus and nitrogen. These samples will be used to measure the response of nutrients in urban runoff through implementation of a city-wide leaf collection program compared to no leaf collection. Although the amount of organic debris on streets is highest during fall, water-quality monitoring will continue through spring and summer to further characterize seasonal patterns in nutrient load.
Collection of water-quality samples representing no active leaf collection was completed in November 2013. As expected, preliminary results indicate phosphorus concentrations can be considerably higher in the fall than in spring or summer. Phosphorus speciation was primarily dominated by the dissolved phase making it highly mobile during runoff events. Total phosphorus yields were as much as 10 times greater than what had been measured in previous studies in Madison with an active leaf collection program (Selbig, 2007). As such, the role of leaf removal from city streets could prove to be a critical element when addressing phosphorus mitigation in the urban environment.
In the spring of 2014, the city of Madison once again began monthly street cleaning operations in the study basins and resumed their normal leaf collection program in October. The lack of rain in October coupled with the early onset of winter in November of 2014 resulted in too few runoff events to measure a change in the amount of phosphorus through leaf collection. Future efforts in 2015 will once again evaluate the benefits of a street cleaning program in the spring; however, the frequency will be increased from monthly to weekly. Similar to 2014, the city will continue their normal leaf collection effort with assistance from the USGS to optimize removal of leaves from streets in the study basins.
Selbig, W.R. and Bannerman, R.T., 2007, Evaluation of street sweeping as a stormwater-quality management tool in three residential basins in Madison, Wisconsin, U.S. Geological Survey Scientific Investigations Report 2007-5156, 120 p.
Answering Water Quality Questions
One of the main outcomes of this study will be an answer to the question of how much phosphorus the City of Madison (and others) are able to capture through leaf collection practices. We generally know that it is beneficial to water quality to keep leaves out of the street because as rainwater flows through leaf piles, it carries nutrients to the nearest waterway. This study will tell us how much phosphorus and nitrogen we are actually capturing and if we need to provide more, in terms of leaf collection services.
The City of Madison and other municipalities are regulated by the EPA and DNR for the amount of nutrients (phosphorus) we discharge into the lakes. A recent regulation, called a Total Maximum Daily Load (TMDL) , calls for the City of Madison to reduce our annual phosphorus loading by 16,000 pounds. To put this in perspective, a new storm pond we are installing in Cherokee Park will capture about 170 pounds of phosphorus per year.
The City of Madison will be partnering with others on an Adaptive Management Pilot Project, which will allow us to pool resources in order to meet the water quality regulations outlined in the TMDL. One method of meeting the requirements will be funding agricultural projects, for example.
This leaf collection study is another component of the larger adaptive management pilot project that will help us meet these goals. At this time, we are not given any credit for the amount of phosphorus we collect through our leaf collection program. This study will enable us to do that, as well as help us determine if we need to do more.
Questions? Contact Greg Fries , (608) 267-1199.