Water Quality Update 2020
Five times each year, volunteers take water samples from specific areas of Wabedo Lake (NE bay and SW bay), Little Boy Lake and Cooper Lake. Volunteers also do Secchi disc readings which gives us data regarding water clarity. RMB Environmental Laboratories (RMBEL) records the data on its website and can easily be accessed. The following information is from the RMBEL website https://www.rmbel.info/data/
TP or Total Phosphorus: A nutrient needed for plant growth. Phosphorus can enter a lake through run-off from manure and fertilizer or through seepage from leaking septic and holding tanks. It can also show up due to the bottom of the lake being stirred up. Wake boats, motor traffic, and heavy waves can cause this action.
Chla or Chlorophyll- a: The pigment that makes plants and algae green. Chlorophyll-a is measured in lakes to determine algal concentration or in other words, how green the water is.
TSI or Trophic State Index: A measurement of overall lake productivity (nutrient enrichment). The overall TSI of a lake is the average of the TSI for phosphorus, chlorophyll-a and secchi depth. Trophic State Index, Phosphorus, Chlorophyll-a (algae concentration) and Secchi depth are related. When phosphorus increases, that means there is more food available for algae, so algal concentrations increase. When algal concentrations increase, the water becomes less transparent and the Secchi depth decreases.
Secchi or Secchi Depth: A measure of water clarity that can indicate the overall health of a lake. A black and white metal disc is lowered into the water on a rope until it can’t be seen anymore and raised to the point it can be seen. The depth of the disk to the surface of the water is the Secchi Depth.
Looking at the data over the past ten years, we can ascertain the following:
Little Boy Lake: The phosphorus (TP), chlorophyll –a(Chla)and secchi disc readings are within the expected range. Phosphous ranges from 9 – 46; the mean is 18.3. Cholorphyll-a ranges from .9-28; the mean is 5.7. Trophic State Index (TSI) is 44.6. Since 2017 only two spikes of higher phosphorus was recorded. No significant change.
Cooper Lake: TP ranges from 8-38; the mean is 6.5. The Chla range is 0.4-7.6; the mean is 3. Secchi ranges from 9’-18’: the mean is 14.9. In the past five years the Secchi reading has been 15’ or higher. The TSI is 40.3. No significant trend.
Wabedo (SW Bay): TP ranges from 10-100; 21.2 is the mean. Over the past five years, the phosphorus data shows a decline. The Chla range is 2.2-16; the mean is 6.2. Data from August and September showed spikes. Secchi readings range from 5.3-16; the mean is 10. TSI is 46.3 and improving.
Wabedo (NE Bay): TP ranges from 10-30; mean is 19. Chla ranges from 1 – 14.7; the mean is 6.2. Secchi ranges from 5.5 – 14; the mean is 9.4. TSI is at 46.4 which indicates a decline.
The association has been sending data on Stony Creek, Spring Creek, the inlet and outlet of Little Boy for many years. That information can be accessed on the WLBCR website. The lakes filter out the phosphorus and data indicates it moves from Stony Creek to the outlet of Little Boy. The color changes as well.
We are curious about why the Wabedo NE bay is declining when our other lakes are holding steady. This will be a topic we will research for future newsletters. Developing ways to improve the NE bay will also be a topic.
Thank you for creating a 20 foot ‘no mow’ zone along parts of your shoreline.
Thank you for not using lawn chemicals.
Thank you for not burning fires near the lake.
Thank you for being a member.
Submitted by Kathy Wagner, Water Quality Chair
Water Quality and Clarity
Water transparency is a quick and easy measurement that tells scientists a lot about a lake's water quality. First it indicates the amount of light penetration into a lake. Second, Secchi transparency provides an indirect measure of the amount of suspended material in the water, which in many cases is an indication of the amount of algae in the water.
Click on the Lakes Monitoring or Secchi Readings tab in the left drop down menu for more information and links to our water quality data.
Volunteers collect water transparency data using an 8-inch, circular, all-white metal plate attached to a calibrated rope. This tool is called a Secchi disk. About once a week during the summer, volunteers boat to a designated spot on their lakes to collect transparency readings. The volunteer lowers the disk into the water until it is no longer visible and notes that depth from the markings on the rope. The disk is then lowered a little further and then raised back up until it is just visible. This second depth reading is averaged with the first, and the final number is recorded.
Phosphorous and chorophyll readings are taken by gathering a water sample and sending it to a laboratory for analysis. RMB Labs has performed our water analysis since 2007. These readings indicate the quality of the water body by indicating how much of these pollutants are present. For example, too much phosporous in the water body can cause green algae bloom. The sources for phosphorous could be fertilizer run-off from lawns, failing septic systems, and other sources. We monitor these indicators to ensure our lakes continue to be healthy.
The association has volunteers that perform these readings and gather water samples. We pay for the laboratory analysis, but some of the costs are reimbursed through grants or other measures.
We would like to extend a huge "Thank You" to these volunteers who commit a great deal of time to these efforts.
Cooper - Russ Link (Camp Olson) gathers the water samples.
Little Boy - Randy Helland gathers the water samples and also performs the secchi readings.
Wabedo (NE basin) - Joe and Irene Maertens gather and perform the water samples, Joe Bloch performs the secchi readings.
Wabedo (SW Basin) - Tom and Pam Fields perform the secchi readings and gather the water samples.
Spring Creek - Tom and Pam Fields perform the secchi readings and gather the water samples.
Little Boy inlet and outlet, Wabedo Creek - Kathy Wagner gathers the water samples.
Little Boy River (Sioux Camp Road) - Kathy Wagners performs bi-weekly water tests and submits information to the MNPCA.
In addition, the association also monitors lake levels. This reading is taken from a post on the Little Boy bridge. Mary Jane Black performs these readings.
In 2008, we also started tested inlet/outlet streams for phosphorous. The streams are Wabedo Creek and Spring Creek which feed into Wabedo Lake and the inlet/outlet to Little Boy. In the results below you can see Spring Creek has a much higher phosphorous reading than Wabedo Creek. We believe this is due to Spring Creek draining more wetland areas and thus the higher readings may be normal (higher phosphorous levels found naturally in wetlands). Please note the table also shows data from 1994 when the inlet streams were also tested during the Middle Boy River Project. Another interesting observation - in 14 years the phosphorous level in Wabedo Creek has varied dramatically but the last few readings are similar to 1994 (not sure why?). Another piece of good news - the outlet readings for Little Boy from 1994 compare favorably to our recent test results.
And one last tidbit - water coming from Wabedo into Little Boy has more phosphorous than the water going out of Little Boy. This indicates Little Boy is "cleaning" the water before it leaves (the phosphorous is being trapped in the lake bottom). This also indicates you should not cause the lake bottom to be disturbed. Those bigger motors should be run slowly in the shallow areas.
Another interesting statistic for water quality information is the "Water Residence Times". This is an estimate of the time it would take for the water in the lake basin to be replaced and the nutrients flushed out. (This information was found in the lake association files from a study in the early 1990's).