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Online tool provides Mille Lacs Lake water quality data captured by satellite

Since 2002, the University of Minnesota has used Landsat 8 and European Sentinel-2 satellites to remotely measure water clarity, dissolved organic matter, and chlorophyll-a in Mille Lacs and other state lakes.

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Mille Lacs Lake waters. Contributed / John Pearson

MILLE LACS LAKE — Water quality monitoring of Mille Lacs Lake and its surrounding watershed is ongoing with water sample collection pursued annually by the Mille Lacs Band Department of Natural Resources and carried out on a 10-year cycle by the Minnesota Pollution Control Agency.

But not all studies are done using water sampling. Since 2002, the University of Minnesota has used Landsat 8 and European Sentinel-2 satellites to remotely measure water clarity, dissolved organic matter, and chlorophyll-a in Mille Lacs and other state lakes. Their findings can be explored using the online tool, the Minnesota LakeBrowser, available at tinyurl.com/4jkkkd2f .

The satellite imagery provides snapshots of information from moments in time as well as options to view seasonal cycles and long-term trends. The LakeBrowser covers more than 10,500 lakes measured 11 times from 1975-2018. It also includes searchable maps of chlorophyll concentrations and colored dissolved organic matter levels for several recent years.

Changes can be seen over time: Mille Lacs Lake water clarity has increased from about 2 to 3 meters in 1975 to 2 to 4-plus meters in 2020. Colored dissolved organic matter variations can be viewed during the year with concentrations around Mille Lacs’ bays, shorelines and nearby small lakes increasing as the summer wears on. Chlorophyll-a also shows seasonal variation from a low of about 4 micrograms/liter in the spring of 2020 to 16 micrograms/liter in the fall.

Although these studies show Mille Lacs water quality is good overall, caution is advised in interpreting this data.

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“Remember that continued protection of our priceless natural gift of Mille Lacs is critical,” Mille Lacs Lake Watershed Management Group officials stated in a news release.

The Minnesota LakeBrowser site provides links to additional information from the Minnesota DNR and the Minnesota Pollution Control Agency, including regional summaries by ecoregion, county or watershed.

The Minnesota Pollution Control Agency’s Water Quality Monitoring Strategy 2021-31 publication is available for download at tinyurl.com/y3zus73y .

The Mille Lacs, Aitkin and Crow Wing soil and water conservation districts and members of the Mille Lacs Lake Watershed Management Group have also collected data over the years; summaries of results are available on Mille Lacs Lake Watershed Management Group’s website at tinyurl.com/2p8mr47h .

Visit MilleLacsWatershed.org to learn more about supporting a healthy lake environment.

The Mille Lacs Lake Watershed Management Group helps area landowners manage their property in ways that support the water quality of Mille Lacs Lake and its surrounding area. Formed in 1997, it connects interested citizens with local and state agency experts and resources, provides educational materials, and inspires simple actions that can have a positive impact on the area’s land and waters.

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