Learn more about the watershed, sediment, and the nutrient management for Lake Decatur & why it is important.
What is the Lake Decatur Watershed Management Program?
Lake Decatur’s water comes from a watershed (or drainage area) that is 925 square miles in size and includes parts of 7 counties in east central Illinois. In order to preserve the recently completed $92 million Lake Decatur dredging project investment and improve the lake’s water quality, in February 2020, the Decatur City Council authorized a comprehensive long-term watershed management program. The program has grown significantly, and is now nationally recognized as a model for sustainable watershed management.
In addition to dedicated city funding and grants secured through the Illinois Environmental Protection Agency, Decatur was the recipient of a $9.8-million-dollar United States Department of Agriculture (USDA) Regional Conservation Partnership Program (RCPP) award focused on improving water quality in key areas across the watershed. The 5-year program provides substantial cost-share and flexibility to landowners and growers for certain practices aimed at reducing sediment and nutrient losses to the lake. Funding and non-USDA technical assistance is being directed to key counties, drainage areas and fields within a set proximity to the reservoir. Priority Counties in the initial years include Macon, Piatt and DeWitt.
Cool, but what is a watershed?
We’re glad you asked. A watershed, or a drainage basin, is an area of land that channels rainfall, snowmelt, and runoff into a common body of water. Healthy watersheds provide critical services, such as clean drinking water, productive fisheries, and outdoor recreation, that support our economies, environment, and quality of life. (Source: EPA)
Got it. Now, what is sediment?
Sediment is made up of solid material that settles at the bottom of the lake. This may include things like clay, organic debris, and chemical precipitates. Sediment entering the lake reduces the storage capacity and increases drought vulnerability.
A single storm can add thousands of tons of sediment (!!!), which is why we must do our part to help reduce sediment levels including prevention strategies like shoreline management, land management, and nutrient control, as well as sediment removal strategies like dredging.
Tell me more about our local watershed and Lake Decatur.
Lake Decatur was created in 1920-1923 and serves as the water supply for Decatur, grain processing firms ADM and Primient, and the Village of Mt. Zion.
Our local watershed management program covers approximately 592,000 acres and spans seven counties including Macon County. It aims to improve water quality and reduce sediment delivery to the 3,090-acre Lake Decatur. If you’re a local boater, you may have seen fresh rock on Basin 1. Here are some reasons rock is needed:
1. Eroding shorelines contribute an estimated sediment load of 285 tons per year, or roughly 18 dump trucks worth. With this comes 446 pounds of nitrogen and 149 pounds of phosphorus which can lead to algal blooms.
2. The vast majority of the entire sediment originates from only 2% of the banks.
3. Those segments established in Basin 1 have reduced 115 tons of sediment entering the lake each year, in addition to 120 pounds of nitrogen and 62 pounds of phosphorus.
4. The shorelines were stabilized using a breakwater technique that places rock out from the bank to allow for a space where vegetation can establish to create a natural wetland habitat. Check out the before and after photos below of a recent shoreline stabilization of Segment 6 of Lake Decatur. Approximately 80% of the watershed consists of cultivated crops, further illustrating the great benefits of the RCPP grant program that helps incentivize landowners and growers.
How can I help?
There are several ways you can help:
- If you are a property owner in the watershed, please let us know if you have an erosion problem. We may be able to fix the problem at little out-of-pocket cost to you.
- If you are a farmer with low-lying, marginal farmland, please consider converting it to switchgrass as a cash crop. Perennial grasses do a great job of keeping sediment and nutrients out of the watershed.
- If you are a business with compostable waste, please work with us to divert that waste from the landfill to a composting operation. The compost can be used to replenish the soils in the watershed.
Where can I learn more?
Check out the links below to learn more about the Lake Decatur Watershed Management project:
Regional Conservation Partnership
2023 Lake Decatur Watershed Monitoring
Lake Decatur Watershed Fact Sheet
