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MPCA Report – Lake Crystal – Excess Nutrients

This article from the Minnesota Pollution Control Agency concisely explains  Total Maximum Daily Loads and how this has affected our area lakes.

Minnesota’s Impaired Waters and TMDLs


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

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

Crystal Lake, adjacent to the city of Lake Crystal in 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 Crystal, Loon and Mills lake system. 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. Four landowners disputed parts of the TMDL and submitted a request for a contested case hearing during the public comment period. Due to this contested case request, the completion of the TMDL process is on hold while the state prepares a response.

Meanwhile, local citizens devoted to restoring the lake have formed a group called the Crystal Waters Project (CWP). “The mission of the CWP to restore a healthy watershed that would improve the water quality of area lakes. To promote good stewardship and better management practices throughout the entire Lake Crystal watershed.”

The MPCA has drafted a lake crystal implementation plan that will be finalized once the TMDL report is finalized. 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

Lake Crystal is part of the Crystal Loon Mills watershed. Crystal Loon Mills watershed is located in Blue Earth County in the Minnesota River – Mankato watershed in the Minnesota River basin.

Sources: Esri, HERE, DeLorme, USGS, Intermap, INCREMENT P, NRCan, Esri Japan, METI, Esri China (Hong Kong), Esri Korea, Esri (Thailand), MapmyIndia, NGCC, © OpenStreetMap contributors, and the GIS User Community


Map of Lake Crystal and Crystal Loon Mills Watershed

TMDL report and implementation plan

Other documents and online information


Meetings and events

See the TMDL Meetings, Events and News page for notices of general interest and event-related information on impaired waters/TMDLs.


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