Scott Watershed Management Organization

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Cedar Lake Fish Kill - June 1, 2020

We have had reports of a fish kill on Cedar Lake over the weekend.  Cedar Lake is a shallow lake (<15 feet deep).  The Star Tribune published an article in January detailing how fish kills occur on shallow lakes.  Fish kills have been occurring on Cedar Lake for decades due to columnaris bacteria or temperature and spawning stress.  Mostly crappies are affected, but the DNR stated the crappie population in Cedar Lake is very good.
If you observe large fish die-offs on any lake, you can report any findings on the U of Mn's fish kill reporting map.  The fish kill map is a tool created by Dr. Nick Phelps to identify fish kills in Minnesota and allows you to identify the date, location, approximate number of fish and condition of the fish and note if anything about the fish looks abnormal. UMN researchers may then investigate the kill and gather specimen samples for the UMN veterinary diagnostics laboratory. UMN staff also share reports with MN DNR staff.

Lake O’Dowd and McMahon (Carl’s) Lake are both getting cleaner!

Good news!  Scott WMO can now definitively say that both Lake O’Dowd and McMahon Lake are getting cleaner.  Lake O’Dowd is located in the Louisville Township and in southwest portions of the City of Shakopee.  McMahon Lake is located in the southeast corner of Spring Lake Township. 

As you can see in the below graphs, Lake O’Dowd has been improving since about 2007.  Lake McMahon has seen mostly improvements since around 2008.  The graphs both show a reduction in the nutrient, Phosphorus.  Phosphorus is one of three parameters used to measure water clarity and cleanliness.  Phosphorus impacts both of the other two parameters: chlorophyll-a levels (chl-a in the graph below) and transparency of the water (secchi in the below graph).  Cholorphyll-a is a plant pigment and is used to measure the amount of algae.  Excess phosphorus causes algae and other plants to overgrow resulting in green and scummy water (high levels of chl-a).  In order for plant and animal communities in lakes to thrive, they need clean water.
The lakes are likely improving because:
  • Landowners surrounding the lakes have participated in both water quality monitoring and lake improvements, like native shoreline stabilizations.  Please see the McMahon (Carl’s) Lake Improvement factsheet for more information.
  • Much of the agricultural land draining to the lakes has been converted to large-lot residential (to view the changes between 1964 and 2015, please use this Land Use Map Viewer).  Large residential lots are better for water quality than both farmland and large urban areas because they maintain longer-living vegetation throughout the year.  Farmlands typically lack vegetation for much of the year.  Bare soil inevitably runs off into waterbodies, adding both sediment and nutrients.  Large urban areas often contain more paved surfaces, like roads and sidewalks, which increase stormwater run-off.  In many cases, stormwater run-off is not filtered prior to draining into lakes and rivers.  So, stormwater drains can directly carry pollutants to our waterbodies.
  • Both lakes are being treated for Curlyleaf Pondweed, which is an invasive plant that adds phosphorus into the lakes when it dies.  Both lakes have reduced levels of the invasive plant compared to ten years ago.  Please see our annual reports for more information on Curly-leaf Pondweed treatment and reduction.
  • Lastly, over ten years ago fertilizers containing phosphorus were banned from use within the metropolitan area.  Fertilizer and lawn clippings can easily run-off into storm drains and collect in lakes and rivers, which can greatly increase phosphorus levels.  The downward trend in phosphorus levels shown in the two graphs above suggest that when residents stopped using fertilizers containing phosphorus, water quality improved in both lakes. 
What happens now?
  • Both Lake O’Dowd and McMahon Lake now meet water quality standards for all three parameters.  Therefore, the Scott WMO requested and was granted removal of both lakes from the Minnesota Pollution Control Agency’s Impaired Waters listing.  
  • We can all enjoy the benefits of clean water: a clear look, healthier plant and animal communities, and probably fewer recreational disruptions (such as restrictions on swimming or fishing due to bacteria outbreaks). 
  • This is clearly a win, and we can all thank those residents living on both lakes for practicing good environmental stewardship.  However, maintaining clean lakes will require continued water quality monitoring and dedication to managing best practices (like native shoreline stabilizations).

Board of Water and Soil Resources rates Scott Watershed Management Organization a “top performer”

Minnesota Board of Water and Soil Resources (BWSR) relies on local government partners, like Scott WMO, to help deliver water conservation programs such as those funded by the Clean Water Fund. Scott WMO uses Clean Water Funds to complete projects ranging from rain gardens to ravine stabilizations along county highways. Each year BWSR audits several partners to test if they deliver effective water management with integrity. This year, Scott WMO was audited.  

BWSR finished the Scott WMO audit on August 24th, 2015. BWSR rates Scott WMO a top performer for water management with only two suggestions for improvement. BWSR commends Scott WMO for meeting 11 out of 12 High Performance Standards. A survey of Scott WMO partners reports that 92 percent believe their relationship with Scott WMO is strong and beneficial. 

A copy of this report is available in our Reports & Documents page.
For more information about Scott WMO clean water projects, please review our annual reports
For more information about BWSR’s auditing process or Clean Water Fund projects, please visit BWSR’s webpage.