Edina
Background:
Lake Cornelia and Lake Edina are shallow lakes with poor water quality that are on the state’s impaired waters list for excess nutrients. The Nine Mile Creek Watershed District is working to control nutrient levels (specifically phosphorous) in Lake Cornelia and Lake Edina.
Project Updates:
A new monitoring buoy has been deployed in North Cornelia Lake to help us better understand what’s happening beneath the surface. The buoy measures lake level, water temperature, and dissolved oxygen (DO) and sends readings to a web-based monitoring portal three times a day, as long as cell service is available.
dissolved oxygen in the water.
This information will give NMCWD staff a better picture of changing conditions and help inform decisions about how to improve fisheries.
One of the most interesting things the buoy measures is dissolved oxygen—the oxygen available in the water for fish and other aquatic life.
During the day, dissolved oxygen typically increases as plants and algae use sunlight to photosynthesize and release oxygen into the water. After sunset, photosynthesis stops, and plants and algae continue to respire, using oxygen from the water. As a result, dissolved oxygen levels generally decline throughout the night and reach their lowest point in the early morning hours.
Also, as the water is warmer on these hot days and stretches of days, the lake water has a tougher time holding onto oxygen. More dissolved oxygen can dissolve in cooler water. The giant swings in dissolved oxygen can be one indication of an algal bloom since essentially more percentage of the lake is filled with photosynthesizing biomass, as compared to lakes with low algal presence and fewer plants.
The buoy will remain in North Cornelia through the winter, allowing us to monitor oxygen levels when the lake is covered by ice. This will help us determine if and when dissolved oxygen levels drop low enough to stress native fish and whether a water agitator should be installed to help introduce additional oxygen into the lake.
Here is the link to the dashboard
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Since May, the watershed district has conducted weekly goldfish and carp removal efforts in North and South Cornelia Lakes. Curly-leaf pondweed (CLP) treatment was applied this spring, and aquatic plant surveys are planned for August to assess vegetation in both lakes. The survey results will help determine whether additional treatment for hybrid watermilfoil is needed and, if so, the appropriate extent of that treatment.
Staff are also compiling data to quantify the number of fish removed through box-netting efforts so far this season.
Community Engagement:
Join NMCWD and the City of Edina for a informal community meeting on August 24th 5:30-7:30p at the City of Edina Public Works building at 7450 Metro Blvd (please use the parking lot entrance off of 74th Street to enter through the front door of the building)
Learn about current lake conditions, upcoming recommended projects, potential timelines, and how these projects could affect the lakes. We willalso walk you through the public hearing process, which happens before a project is ordered, including how it works, what to expect, and how you can participate.
For more information about this meeting contact Jordan Wein, NMCWD Water Resources Project Manager at jwein@ninemilecreek.org or 952.737.8155
Project Timeline:
The Nine Mile Creek Watershed District (District) and City of Edina are completing a multi-phased project to improve the health of Lake Cornelia and Lake Edina. As part of the overarching project, the District and City of Edina have completed several projects:
- 2017-2022: the City of Edina conducted annual lake herbicide treatments on Lake Cornelia to control curly leaf pondweed
- 2020: NMCWD ordered an in-lake alum treatment on Lake Cornelia
- 2021: The District installed a stormwater filtration vault located in Rosland Park
- 2023: The District and the City of Edina retrofitted Lynmar Basin to hold and treat more stormwater before it reaches Lake Edina
- 2024: The District took over the Endothall treatment
- 2024: Water Quality Monitoring Report: Lake Cornelia’s North Basin
- 2024 Water Quality Monitoring Report: Lake Cornelia’s South Basin
- 2025: The District switched to the herbicide Galleon. (Galleon is a selective herbicide which means it targets a specific species of aquatic plant. Galleon was chosen for this herbicide treatment to minimize impacts on the native plants growing Lake Cornelia)
- 2026: Spring, herbicide treatment was applied.
Beyond this, the District is working with WSB and Associates to manage goldfish in the Lake Cornelia system. The District will also assess the need to improve oxygen conditions in the lake, after evaluating monitoring data.
Project Details:
Goldfish Management
To help improve water quality and the ecological health of Lake Cornelia and Lake Edina, the District is undertaking goldfish management.
Goldfish are an invasive species of fish that cause water quality problems due to their bottom feeding behavior. They stir up lake bottom sediments which reduces water clarity and releases phosphorus. They also uproot aquatic vegetation, destroying habitat for waterfowl and aquatic communities.
The goldfish population was likely started with the release of pet goldfish into one or more of the lakes within the system. Awareness and public education are needed to prevent this from happening in any small ponds that could perpetuate the invasive goldfish population in the Cornelia chain.
A 2018 fish summary indicated that while there were carp, another invasive bottom-feeding fish, in the Lake Cornelia system, they were not abundant. Goldfish, on the other hand, were plentiful and at a level where management of the population is recommended for water quality purposes.
A follow-up goldfish and carp study was completed in 2020 to assess goldfish and carp levels, track inter-waterbody movement through the Lake Cornelia system and test management/removal methods. Surveyors found a large number of young of the year goldfish in the lake, indicating successful goldfish recruitment (survival to the juvenile stage).
The District will continue to study and manage the goldfish population in the Lake Cornelia system, to determine the best methods for goldfish removal and population management.
The District received grant funding for the goldfish studies on Lake Cornelia from the Minnesota Board of Water and Soil Resources through the Clean Water, Land and Legacy Amendment and from Hennepin County through their Aquatic Invasive Species Prevention program.
Cornelia Lake System fisheries assessment for 2020 Report
District Goldfish Study Featured In the News:
In summer 2025, the District partnered with the Minnesota Zoo to provide collected goldfish and invasive carp as food for zoo animals — a unique collaboration that even caught the attention of WCCO the Star Tribune.
In this Minnesota Bound episode (filmed in 2020) you can see the goldfish research team in action starting at around 1:20, as they collect information on goldfish in the Lake Cornelia system in Edina.
The City of Edina takes a look at water quality in Lake Cornelia and goldfish in this featured video.
How can you help Lake Cornelia and Lake Edina?
If you have unwanted aquarium fish or plants, never dump them in a lake, creek or pond. Always surrender them at a re-home event.
You can also Adopt a Drain to keep pollution from entering the water in the first place. Learn more at mn.adopt-a-drain.org.
Studies and Reports
Visit the Lake Cornelia and Lake Edina Study page to read the lake water quality study and feasibility reports.
Questions?
Contact Jordan Wein, Water Resources Project Manager, at 952-800-8307 jwein@ninemilecreek.org