What is the problem?
Lake Independence was added to the Minnesota impaired water list in 2002 due to an excess of phosphorus (more information on the water page under Info). LICA, Three Rivers Park, Hennepin County Environmental Services, the DNR and many other patrons of the lake have been working since then to reduce the amount of phosphorus in the lake to improve water quality.
Ardmore Watershed projects funded
The Pioneer Sarah Creek Watershed Management Commission (PSCWMC) and the City of Medina have approved an agreement with Hennepin County to pay part of the cost for three projects recommended in the 2016 Sub-Ardmore Watershed study. The City of Medina Public Works Dept will do the construction.
The Sub-Watershed cover 472 acres that drain into Lake Ardmore, which subsequently drains into Lake Independence. The approved projects are intended to reduce the amount of sediment and phosphorous flowing into both lakes.
The first project involves stabilizing the stream bank between the two lakes to reduce the amount of erosion occurring at a sharp curve in the streams path. Sharp curves encourage erosion because they accelerate stormwater flow.
The second project is the installation of a carp barrier (photo above) on the stream between the two lakes, to prevent carp from migrating upstream from Lake Independence to Lake Ardmore, particularly during spawning season. Carp contribute to lake impairment by rooting around on the lake bottom, stirring up sediment and phosphorous.
The other project is for shoreline restoration around the Independence Beach boat launch.
Funding for these projects will be provided by a Hennepin County Natural Resources grant, the PSCMC, the City of Medina and LICA.
What is the solution?
Reduce the amount of phosporus, entering the lake from all sources in order to reduce the growth of algae bloom (that is where the TMDL-Total Maximum Daily Load-comes in, it's to total ammount of phosphorous that can enter the lake per day without overfilling) and other aquatic invasive species.
After all sources of phosphorous loading have been controlled, the lake can begin to heal and a whole lake alum treatment to boost clarity can be considered.
Secchi Depth Measurements on Lake Independence
by LICA members Jim and Kim Klancke
Kim and I are volunteer lake quality monitors for the MN Pollution Control Agency (MPCA) Citizens Lake Monitoring Program. We collect water quality data using a Secchi disk - an 8-inch circular black and white plate attached to a calibrated rope. The disk is slowly lowered into the lake and a reading is taken at the point the white disk is no longer visible. Then the disk is lowered further and slowly raised, noting the reading when the disk re-appears. We submit the readings to the MPCA at the end of each monitoring season.
The Secchi disk measures transparency, which is an excellent indicator of water quality. Water transparency indicates the amount of light penetration and indirectly shows the amount of suspended material in the water, which may include sediment and plant nutrients such as algae. Plant nutrient sources include septic tanks and lawn and farm fertilizer. Sources of sediment include shore erosion, farm fields and storm runoff. By measuring Secchi depth throughout the season and from year-to-year, transparency trends (and by extension water quality trends) can be observed.Over time, the collected data helps detect water degradation.
This graph combines data from Secchi measurements taken on Lake Independence during spring and summer from May, 2009 to October, 2019. The data are plotted as 7-day moving average measurements to smooth the data to better see the trend in water clarity throughout the spring and summer collectively, as individual readings have some variability based on a number of factors such as sunlight, waves, recent rainfall, etc. For example, the data point on Day 32 is the average of readings from 2009-2019 in the seven day period surrounding June 1. Typically, water quality gradually decreases beginning in June, stabilizing around the 4th of July and holding through August.
Because the water quality fluctuates throughout the spring and summer, taking an average of one year’s measurements is not particularly useful. Trends only emerge when data is collected and compared over a number of years. To date, the MPCA is reporting no detectable trend in water quality. The summary for Lake Independence can be found on the MPCA website.