Alimagnet, East Lake projects show quick improvements
Two of the Vermillion River Watershed Joint Powers Organization’s (VRWJPO) projects this year led to quick, significant improvements in their respective water resources – coincidentally, both recreational lakes with city parks.
- Alimagnet Lake, a recreational lake in Apple Valley and Burnsville, was treated with aluminum sulfate (alum) on October 15 to address its phosphorus impairments. Phosphorus is a naturally occurring nutrient, but when there’s too much, it can fuel algae blooms and poor water quality. Alum binds with phosphorus in the water column and forces it to settle. One way to observe lake water quality is by measuring transparency with a Secchi disk. City of Apple Valley water quality volunteers quickly measured results, with transparency increasing from 2.26 ft. pre-treatment to 7.51 ft. following treatment, all the way to the lake’s bottom! That’s a threefold improvement. Our consultant will monitor soil conditions within the lake in 2025, with an additional alum treatment set to take place in spring 2026. Water quality improvements associated with this project are forecasted to last between 15 – 20 years, helping to support improved aquatic habitat within the lake. Check out this video recap!
- East Lake, a shallow recreational lake in Lakeville, had high levels of invasive carp, goldfish, and goldfish hybrids that stir up sediment on the lake bottom and harm water quality. VRWJPO, the City of Lakeville, and Dakota County installed a low-voltage electric fish barrier to keep the fish from leaving the lake via an outlet channel to North Creek-Vermillion River. Once the barrier was operating, our consultant began removing the fish by electrofishing and baited box nets. The first year of removals were quite successful, with 2,798 pounds of fish taken from the lake in an effort to improve water quality. Studies have shown that negative impacts result from carp population densities greater than or equal to 100 lbs/acre – a previous study found carp population density in East Lake to be 192 lbs/ac. With 2024’s efforts, carp and goldfish biomass was reduced to 89.9 lbs/ac. But we can’t celebrate quite yet – we’ve learned that goldfish are the predominant species in the lake. While goldfish are a carp variant, there is no established biomass at which positive water quality impacts are known to be achieved. Fish removals and water quality monitoring will continue in 2025.
Both of these projects were made possible by Clean Water Fund competitive grants from the Minnesota Board of Water & Soil Resources. Learn more about all our projects here.
