Crystal Lake, adjacent to the city of Lake Crystal (Blue Earth County), is a popular recreational area. However, recreation on Crystal Lake is not advised at times because of algal blooms caused by excess phosphorus. A major concern is blue-green algae, which can contain the toxic chemical microcystis. In 2004, the Minnesota Pollution Control Agency (MPCA) found microcystis levels 7,000 times the World Health Organization’s acceptable exposure level in Crystal Lake. Again in 2007, microcystis levels were several thousand times the acceptable exposure level. Since then, algae blooms have occurred every year.
Crystal Lake is 355 acres with a contributing watershed of 13,900 acres, including the lake system that includes Crystal, Loon and Mills Lakes. Of the total watershed area, 15% of the watershed consists of lakes and wetlands while 85% of the watershed is dry land. Of the dry land, roughly 90% is in agricultural cultivation and 10% is in urban/residential development based on the 2011 land use inventory. The lake drains to Minneopa Creek and then to the Minnesota River.
The MPCA found that Crystal Lake was “impaired” for phosphorus following a Total Maximum Daily Load (TMDL) analysis. The TMDL incorporated hundreds of water quality samples, years of continuous flow measurement, and supplemental lake modeling. The TMDL found that the lake receives about four times more phosphorus than it can handle. Much of the water and phosphorus contributed to Crystal Lake comes from the County Ditch 56 watershed, with additional contributions from the Loon Lake watershed and direct runoff to Crystal Lake. Additionally, internal phosphorus adds to the problem. This internal phosphorus is “legacy” that has built up inside the lake after decades of excess watershed contributions.
The TMDL report was available for public comment in 2012. Two requests for contested case hearings were submitted during the public comment period and denied. One of these was appealed and heard by the state Court of Appeals, where it was reviewed and again denied; the Minnesota Supreme Court refused to hear an appeal of this decision. Documentation of these actions is included in the final report submitted to the EPA.
Meanwhile, local citizens devoted to restoring the lake formed a group called the Crystal Waters Project (CWP). CWP's mission is to restore a healthy watershed and promote good stewardship and better management practices throughout the entire Lake Crystal watershed.
Implementation planning for Lake Crystal will be included as part of the Minnesota River-Mankato Watershed WRAPS process. Restoration will require improved management within the cropped and urban landscape to minimize phosphorus contributions to the lake. After these phosphorus sources are minimized, the in-lake phosphorus should be addressed.
Map and location
Crystal Lake is part of the Crystal Loon Mills watershed (Blue Earth County) in the Minnesota River - Mankato watershed.
Map of Crystal Lake within the Minnesota River Basin
TMDL report and implementation plan
- Crystal Lake Excess Nutrients TMDL (wq-iw7-37e) (EPA approval 5/16/2019)
- Crystal Lake Excess Nutrients TMDL: EPA approval letter (wq-iw7-37g)
- Findings of Fact: Crystal Lake TMDL (wq-iw7-37o)
- Crystal Lake: Appendix A comment letters (wq-iw7-37n)
- Crystal Lake TMDL Court of Appeals Decision (wq-iw7-37p)
- Crystal Lake TMDL State Supreme Court Denial (wq-iw7-37q)
- Draft implementation plan for Crystal Lake
Other documents and online information
- Nutrients: Phosphorus, Nitrogen Sources, Impact on Water Quality
- Assessing and Listing Impaired Waters
- Technology helps farmers protect water quality
- Minnesota River — Mankato watershed
Links
Information contact
Paul Davis, Project Manager
Minnesota Pollution Control Agency
12 Civic Center Plaza, Suite 2165
Mankato MN 56001
507-344-5246
Bryan Spindler
Minnesota Pollution Control Agency
12 Civic Center Plaza, Suite 2165
Mankato, MN 56001
507-344-5267