Crystal Lake - Excess Nutrients: TMDL Project

Lake Crystal blue-green algae bloom, September 9th, 2004 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.

Crystal Lake Blue-green algae bloom June 13, 2007The 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.

PDF icon Map of Crystal Lake within the Minnesota River Basin

Map of Lake Crystal and Crystal Loon Mills Watershed

TMDL report and implementation plan

Other documents and online information


Information contact

Paul Davis, Project Manager
Minnesota Pollution Control Agency
12 Civic Center Plaza, Suite 2165
Mankato MN 56001

Bryan Spindler
Minnesota Pollution Control Agency
12 Civic Center Plaza, Suite 2165
Mankato, MN 56001