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Tuesday 17 October 2017
Local Events
Water Testing 2018
Water testing for next year has been scheduled for Saturday, August 11. Pencil in the date!
Water Quality Report for 2017
Report on water quality at Lake Anne, 2017
Jérôme Rousseau and Madeleine Palmer
Method
The samples were collected on Saturday 12 August between 10 a.m. and noon. Nine sites were tested for fecal coliforms, colour, turbidity, pH, and phosphorus. The samples were taken 10 m from shore (See map at the end of this report). The approximate locations are:
- Near Hunt’s Point
- In front of the Drury Estate
- In Seale Bay
- Near the mouth of Long (a.k.a. Boathouse / Wood’s) Bay
- In front of Nancy Savage
- In front of Guy Biron
- Between Kenneth and Kathleen Hugessen
- Between Reed Drury and Sally McDougall
- At the end of the bay behind Green Mountain
We also tested three sites far from shore for chlorophyll-A and dissolved organic compounds, both of which give information about the effect of rotting organic material on water quality. Taken together, levels of chlorophyll-A, dissolved organic compounds, and phosphorus tell us about the amount of nutrients in the lake.
Results
Fecal coliforms
At 14.2, fecal counts are slightly higher than last year. The last four years have been unusually high. Until 2013 inclusively, the average had been 2.5. For the last four years, it has been 11.7.
The following table shows the variation in fecal coliforms from year to year. High coliform counts can be associated with rains just prior to testing day: e.g., 2003, 2006, 2010, 2013, 2014. 2017 has been a rainy summer. Records indicate 21 mm of rain from 9 to 12 August, but the reason for the increase remains to be established.
According to Public Health norms, untreated lake water is not safe to drink. Drinking water should have zero coliforms, whether fecal or otherwise. However, Lake Anne is in the “Excellent” range for swimming. The lake tests measure only fecal coliforms. Household tests provide information about other coliforms. It is strongly recommended that lake water be treated by boiling or with a UV filter system before drinking. (This is even truer for people at risk, such as children, the elderly, and the sick. For more information on coliforms in drinking water, see http://www2.gnb.ca/content/dam/gnb/Departments/h-s/pdf/en/HealthyEnvironments/water/Coliforme.pdf)
Phosphorus
Phosphorus concentration indicates the amount of nutrients reaching the lake through runoff (This is linked to the risk for algae blooms). Official sources place the threshold for concern at 0.09 mg/l, but Prof. Richard Carignan, a U de M limnologist, draws the line at 0.06 mg/l. After four years of low levels (2011-2014), phosphorus concentrations have been higher for 2015, 2016, and 2017; this may be be a cause for concern.
Chlorophyll A and dissolved organic carbon
The levels of chlorophyll-A and dissolved organic compounds are based on three samples far from shore. (A = The opening of the bay past Green Mountain; B = The opening of Long Bay; C = The middle of the lake--approximately the latitude of the northern tip of the Island and the longitude of the eastern tip of the Presqu’île) The concentration of chlorophyll-A indicates the abundance of phytoplankton (microscopic plants) and helps evaluate the level of eutrophication (the excessive richness of nutrients in a lake or other body of water, which causes a dense growth of plant life and death of animal life from lack of oxygen. Eutrophication often leads to algae blooms.. Phytoplankton is more common if phosphorus levels are high, if the weather is hot, and if water moves slowly. Ministry of Environment norms establish that a concentration below 10 µg/l is acceptable. This year, the tests average 2.41 µg/l, which is excellent.
The quantity of dissolved organic carbon is another factor in eutrophication; it tracks the effects of rotting vegetation and animals. Dissolved organic compounds give a brown colour to water. The average for Lake Anne this year is relatively low at 3.25 mg/l, slightly less than in the previous four years.
Colour and Turbidity
Colour can be caused by natural minerals, vegetable matter, or other organic compounds (For information on measuring colour, see http://www.ceaeq.gouv.qc.ca/methodes/pdf/MA103Col20.pdf). There was a slow increase in colour until 2008, which then appeared to level off. This year, with a level of 19.2, it is higher than the cumulative average (23.94), but less than last year (29.4). In any case, the trend line is not rising significantly.
Turbidity levels above 5 are not a problem for swimming, but untreated water at sites above the norm may not be potable (even without coliforms). This year, it has gone up to 5.38, with 5 of 9 sites above the norm. The trend line shows an increase through the years.
pH
Water is acid below a pH of 7 and alkaline above that number. This year, the pH is 7.16. Overall, there is a trend towards slowly increasing alkalinity, except for the last three years.
Cyanobacteria
Cyanobacteria were not tested in 2017. Notreau’s microbiologist said that the following changes are worth reporting immediately (to Madeleine or Jérôme):
- Dead frogs in the lake, because frogs are particularly sensitive to cyanobacteria.
- An unusual or rapid increase in algae growth, or cloudy water resembling broccoli or pea soup.
Conclusion
This year, three measures are higher than average: fecal coliforms, phosphorus, and turbidity. These changes suggest an increase in dissolved organic substances and material in suspension in the water. These are all associated with a risk for algae blooms. It is too soon to say whether this is a trend, but, if these measures stay at these levels, this will be a cause for concern.
We have a healthy lake where we can swim safely. We will continue to monitor the health of the lake, so that we can be proactive.
We can help maintain the health of our lake by following these guidelines:
- Septic systems need to be cleaned regularly (every two years for frequent residents, every three years for weekenders). They also need to be verified to make sure there are no leaks and leaching fields are functional. ( “An important inspection can be made of your septic system when it is emptied. Here are some things to look for or at least ask the operator to examine: Check the baffles for corrosion or breakage, If water flows from the outlet back into the tank it is an indication that your field may be saturated. If water runs continuously into the tank, there is a leak in your plumbing (probably the toilet) and it could saturate your field. Ask the operator to estimate the level of solids. If the level is 60 cm (2 ft) or less, then your system is working very well; if you have a pre-filter installed at the outlet, this is the time to clean it.” Extracted from the Fall 2010 issue of Information Morin Heights (p. 5)).
- By regulation, the first 15 m of shore line should be covered in bushes and trees to absorb nutrients. Lawns promote run-off which adds to the phosphate load in the lake (The Pépinière Rustique sells indigenous & wild plants (1614 Ch. du Village, St. Adolphe d’Howard, Tel: 819 327 2225, http://www.pepiniererustique.com/francais )
- Avoid churning up the nutrient-rich sediments lying on the bottom of the lake.
- Avoid fertilizers, especially on lawns and steep hills, and anywhere near the lake.
- Use only phosphate-free detergents (both for dishwashers and washing machines).
UV filters
UV filters are an efficient way to make lake water potable, as long as sand filters and UV lights are changed as needed (N.B. UV lights should be changed after 12 months of use. After that, the intensity of UV may be insufficient for disinfection).
- If you drain your system in the winter, it needs to be disinfected with chlorine (Javel) when you start it, including the hot water tank.
- We have been told that if the power is off for more than 3 hours, the pipes may become contaminated; UV system manufacturers recommend purging and treating the pipes and hot water tank with chlorine;
- Chlorine should stand in the pipes for a minimum of 5 hours.
- After purging and treating the pipes after a non-conforming test, Notreau recommends waiting at least two weeks before retesting tap water, because residual chlorine can stay in the pipes and skew the results.
This report is also available on the Lake Anne website, together with spreadsheets of all water-testing data since 1999.
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