Water testing results
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 every year at the location on the map. Your association membership fees and donations pay for the water testing.
2021 water testing results summary - Lac Notre Dame on August 3rd - Usher Lake - August 9th
Phosphorus/phosphates - target levels are below .005 mg/L Natural run-off from minerals, erosion and stormwater, and run-off from fertilizers and waste can act as a fertilizer for plants and algae in the lake, and can reduce the oxygen content.
Prevention: naturalized shorelines, reduced boat wakes, restricted use of fertizers and phosphate-containing detergents
- 2021 Phosphorus levels: Lac Notre Dame has no sites below the target level of 0.005 (in 2020 there were 4 sites below the target). As usual, one of highest levels is at Ch. des Generation location 6 off Ch. des Generations, and also this year, around the island.
- Usher Lake: all Phosphorus levels are higher than the target level
Nitrogen and nitrates - target levels below 0.5 Nitrogen occurs naturally and from fertilizers leaching into the water. High levels make the water unsafe for drinking and upset the natural ecosystem. We report on Total Kjeldahl Nitrogen (TKN) - the sum of nitrogen in bound in organic substances, nitrogen in ammonia (NH3-N) and in ammonium (NH4+-N).
- 2021: TKNTP Total Nitrogen levels: Levels increased slightly to 0.25 to 0.33 from 2020's 0.23 to 0.29 on Lac Notre Dame. These levels, especially given the rainfall, are fairly normal for the lake and within the expected range.
- Usher Lake levels range from 0.33 to 0.39.
E.coli bacterium - target levels below 10 E coli can cause severe illness. The presence of E. coli in water is a strong indication of recent sewage or animal waste (beavers, geese!) 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.
- 2021: E-coli levels are lower this year with only 1 location at 10 (in 2020, 4/9 locations had levels above 10), perhaps a combination of the rain, better septic system maintencance & fewer geese.
- Usher Lake: Also lower than last year. Only location 1's sample was below 10.
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.
- 2021: Not yet completed but expected to be poor based on high algae levels and rainfall. August 7 2020 were measured at 4.4 meters - down from 2019's 4.75m. Still an improvement over 2017's measurements of 3.75 meters. The rain and high spring water levels brought in a lot of sediment from wash and erosion.
Eurasian Milfoil is an invasive aquatic plant that usually grows at depths of 1 to 4 metres and can form a dense carpet on the lake’s surface. This association was founded to fight the harm milfoil caused in the early 2000's - it formed such a dense mat on much of the lake that people weren't able to boat through it at all. It's a Zombie weed - each cut bit can form a new weed so we place buoys to keep boats out of the dense areas.
- 2020: Milfoil levels were similar this year to last year. We placed the new yellow buoys in mid July. Unfortunately, it was clear that boat motors were chopping up the milfoil in mid August, as the water was full of floating fragments. Boats need to stay clear of those areas. See Milfoil tips and history
Biologist Paul Hamilton says about 2019, when native weeds recolonized previously heavy milfoil patches:
"the initiation of growth for the milfoil in the spring was stressed by limited sunlight, and colder temperatures (less likely nutrients). The higher water levels 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."
We continue to encourage people to cut milfoil near your shore and remove the cuttings.
View spreadsheet of water testing results by map location
- All water testing results by date and location for E-coli, phosphates and nitrogen from 2005 (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.
* Map of water testing locations.
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. 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. Lac Notre Dame was characterized as between oligotrophic and the next stage of mesotrophic.
To understand the in-depth results, these Canadian Water Quality Guidelines for the Protection of Aquatic Life provide some target levels.