Carole Doré has been volunteering as the Association water tester for years. Thank her when you see her! She collects and delivers the water samples on a regular basis for phosphorus, nitrogen and also for e-coli bacterial contamination. Your association membership fees pay for the water testing.
2019 water testing results summary
Phosphate run-off from fertilizers, detergents and waste can act as a fertilizer for plants and algae in the lake, and can reduce the oxygen content. Target levels for Phosphorus in an uncontaminated lake are below .005 mg/L. Our lakes are rarely in that uncontaminated range but are holding fairly steady.
- 2019 Phosphorus levels in August: Lac Notre Dame is at 0.005 to 0.009 mg/L with one high sample of 0.012 at location 6 off Ch. des Generations. We may go speak to property owners there to check in about using phosphate-free soaps and detergents. Usher Lake levels are slightly higher than Lac Notre Dame as usual at .007 to 0.008.
Nitrogen and nitrates occur naturally in soil and water, but lawn and garden fertilizers leaching into the water can make it unsafe for drinking and upset the natural ecosystem. Our water testing reports measure Total Kjeldahl Nitrogen (TKN) - the sum of nitrogen in bound in organic substances, nitrogen in ammonia (NH3-N) and in ammonium (NH4+-N). Guidelines suggest levels between 0.100 to 0.500.
- 2019 TKNTP Total Nitrogen levels in August: ranged from 0.22 to 0.31 on Lac Notre Dame which is fairly normal for the lake and within the expected range. In Usher Lake, levels are 0.24 to 0.39, again consistent with previous years.
E.coli bacterium that can cause severe illness. The presence of E. coli in water is a strong indication of recent sewage or animal waste contamination. The safety target for e-coli in drinking water is a level of 4 CFU or below (CFU = Colony Forming Units in 100 ml of water). For swimming, the safety limit is 100 - 200 CFU.
- 2018 E-coli levels in Lac Notre Dame on August 11 were slightly higher than previous years when almost all samples had no detectable colonies. This year, 7 of the 10 locations tested had levels at or above 10 CFU. Locations 1 and 9b were at 20 and 30 respectively. In contrast, most years there are usually only one or two locations with results above 10. This may be associated with the presence of the geese on the lake for the second year.
- In Usher Lake, there is some continuing evidence of contamination at the culvert and the associated inlet at location 11 (16 CFU) but overall results are lower than other summer tests.
Transparency/Clarity is an indicator of lake health - clear, more transparent water is a sign of a healthy lake. Water transparency is tested with a Secchi disk. Poor transparency of less than 3 meters can be a warning sign of eutrophication. In the dry summer of 2015 (only 40mm of rain), an excellent 7m measurement was recorded.
- 2019: water transparency tests on August 2 were measured at 4.75 meters. Like 2018, water levels were extremely high in the spring and all the way through July. Both years are an improvement over 2017’s measurements of 3.75 meters with record-level rainfall (249.8mm). The spring rains brought in a lot of sediment, and high water levels eroded the shoreline as well.
Eurasian Milfoil Again this year, there are no mats of milfoil on the surface of the lake, and so little evidence of milfoil that we did not place the buoys. It’s not the weather that is causing our low milfoil and replacement with native weeds - other lakes nearbye are thickly choked this year. Our consulting biologist has this to say about the spring high water and our very low milfoil situation:
At least in the short term good results for your lake. We call what you have observed an “alternate state”. The sudden switch from one state to another. With respect to the milfoil (and cyanobacteria for that matter), we have no real consistent explanation for the sudden change in lakes. Why your lake and not others in the area for example. Although I have no scientific proof, I tend to agree with you that it was the spring conditions (colder, more rain) and the higher water levels that likely impacted the milfoil.
My argument for this is simple, the initiation of growth for the milfoil in the spring was stressed by limited sunlight, and colder temperatures (less likely nutrients). The higher water level will impede the light getting to the bottom of the lake (a requirement for milfoil spring growth). Then the growth of spring algae further blocked the sunlight and the summer development of the lake started. Again this is good news. I am however further surprised that you do not have cyanobacteria (blue green algae growth) replacing the milfoil. This is also good news, but for how long this will maintain this state I don’t know.
We continue to encourage people to cut milfoil near your shore and remove the cuttings.
View a spreadsheet of water testing results by map location
- All results by date and location for E-coli, phosphates and nitrogen from 2005 to 2019 (Google Sheet)
Association volunteers collect water samples at specific locations where water enters and exits the lakes. Note these locations are not the same as the Municipality of La Peche’s test locations referenced in the ABV-7 report.
2014 ABV-7 Report and recommendations
In 2014, the Municipality of La Pêche, with the Association, worked with ABV-7 to produce a report on the shoreline and water of Lac Notre Dame. A translated summary is provided below - the report is in French.
ABV-7 was mandated in June 2014 by the Municipality of La Pêche to characterize the shoreline of Lake Notre-Dame, assess the physico-chemical quality of the water and delimit the milfoil meadows on the lake. This information provided a picture of the current situation in order to slow down the eutrophication of the lake and combat its invasion by Eurasian water milfoil.
Eutrophication is the gradual process of a lake becoming too rich in nutrients like nitrogen and phosphorus. The nutrients feed the cycle of plant and algae growth, which over time, can result in oxygen depletion.
The protocol of the Ministry of Sustainable Development, Environment and Parks (MDDEP) (currently MDDELCC) and the Laurentian Regional Environment Council (CRE Laurentides) (2007) was used to characterize the riparian strip. With respect to the assessment of water quality, ABV des 7 collected and analyzed data on total phosphorus and Escherichia coli (E. coli) provided by the Notre-Dame Lakes Association. and Usher (2005 to 2011 and 2013) as well as by the municipality (2008 to 2013). In addition, ABV des 7 collected and analyzed data on the concentration and dissolved oxygen saturation, pH, depth and conductivity of water acquired during field visits on 17 July 2014. L ABV des 7 subsequently identified and mapped the water-milfoil meadows on 3 September 2014.
Old detailed reports including other minerals, alkalinity and nitrites
To understand the in-depth results, these Canadian Water Quality Guidelines for the Protection of Aquatic Life provide some target levels.