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Water quality test results

Summary, September, 2023 — Bacteria (E. coli) samples from all lake testing sites in June, July and August, 2023 indicate levels well within those considered safe for swimming. Parent Creek levels are extremely high, (* this result was immediately reported to the Municipality and the Campsite, as it could pose a danger to health.) August tests indicate that some pollution continues to come from the area of the campsite.

See "2023 water quality test results" below. Complete results of 2022 water quality tests are also available below.

Each season, our Association's sampling program measures 1) Total Phosphorus (TP) and 2) bacteria (E.coli) levels to determine safety for swimming. This year, the water testing program has been expanded to include: dissolved oxygen and temperature measurements at the deepest parti of the lake taken by ABV des 7, the regional watershed organization.

Enviro Lac Gauvreau is now fully supported by the “Réseau de surveillance volontaire des lacs” (RSVL).

> See the full report below

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2023 water quality test results

Final results for 2023 water quality samples done by Enviro Lac Gauvreau volunteers

LAC GAUVREAU TEST RESULTS FOR JUNE , JULY & AUGUST 2023

INTERPRETATIONS

E.coli - Bacteria (E. coli) samples from all lake testing sites in June, July and August indicate levels well within those considered safe for swimming. (The results from August are higher than before, but still in the ‘Good” range). Parent Creek levels are extremely high, (* this result was immediately reported to the Municipality and the Campsite, as it could pose a danger to health.) The initial E. coli reading in July at Site 5 at the creek's outlet into the lake is low. We have moved this site further into the creek to get a more accurate reading. August tests would indicate that some pollution continues to come from the area of the campsite.

Province of Québec Standards for Swimming (Units: UFC/100ml)

0-20: Excellent
21 -100: Good
101 - 200: Acceptable
201 - +: Not recommended

According to the table below (source), Total Phosphorus (TP) levels place Lac Gauvreau at the threshold between Mesotrophic and Eutrophic. Mesotrophic lakes have an intermediate level of productivity. These lakes are commonly clear water lakes and ponds with beds of submerged aquatic plants and medium levels of nutrients. Eutrophic lakes have high biological productivity with excessive levels of nitrogen and phosphorus that support al abundance of aquatic plants and algae. Occasionally, an excessive algal bloom will occur.

Table - Trophic Status

WHAT IS RSVL?

RSVL is a provincial organization tasked with developing a picture of the health of lakes across the Province by helping members monitor parameters that affect the water quality and degree of aging of their lakes. The program measures levels of total phosphorous (TP), dissolved organic carbon (COD) and chlorophyll A (chl a). Following the RSVL protocol, our volunteers take water samples near the deepest part of the lake (the “pit”). This is done once a month in June, July and August. Transparency measurements are also taken, once every two weeks, using a Secchi disc. RSVL then arranges for pick-up of the samples, analysis and production of reports.

2022 water quality test results

Complete results for 2022 water quality samples done by Enviro Lac Gauvreau volunteers

LAC GAUVREAU TEST RESULTS FOR JUNE, JULY & AUGUST, 2022

INTERPRETATIONS

E.coli - Bacteria (E.coli) samples from all lake testing sites in June, July and August indicate levels well within those considered safe for swimming. Although Parent Creek levels are extremely high, the E.coli reading at Site 5 at the creek's outlet into the lake is low.

Province of Québec Standards for Swimming (Units: UFC/100ml)

0-20: Excellent
21 -100: Good
101 - 200: Acceptable
201 - +: Not recommended

Total Phosphorus (TP) - Sampling from three sites in June indicated a range from 17 to 20 (Hug/L), the highest being in Parent Creek (Site 6).
According to the table below (source), Total Phosphorus (TP) levels place Lac Gauvreau at the threshold between Mesotrophic and Eutrophic. Mesotrophic lakes have an intermediate level of productivity. These lakes are commonly clear water lakes and ponds with beds of submerged aquatic plants and medium levels of nutrients. Eutrophic lakes have high biological productivity with excessive levels of nitrogen and phosphorus that support al abundance of aquatic plants and algae. Occasionally, an excessive algal bloom will occur.

Table - Trophic Status

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ARCHIVED - 2021 water quality test results

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Summary — 2021 water quality test results

Thanks to Municipal funding, a full battery of water quality tests was done last summer, and the results have now been released. Samples were taken on July 5th, August 5th, and mid September, 2021. Volunteers also collected E. Coli samples, done annually, to get a complete profile of Lac Gauvreau's overall health. Following scientific advice and analysis, the results are in! Credit goes to the volunteer test team: Emma Doorly, Barb Booth and Susan Peck. Similar tests will be conducted this summer.

> Report - RAPPEL water quality test results, Lac Gauvreau 2021(translation)

Table - Trophic Status

The Enviro Lac Gauvreau Association has released the final results and interpretations of water quality tests that were conducted during the summer of 2021, using the "RSVL" Water Quality Sampling Protocol. It took until now to publish this report because the 2021 results are difficult to compare with results from earlier years, since samples were not taken in the same places as previously used. Consequently, RSVL has directed Enviro Lac Gauvreau to measure only at the deepest spot (the “pit”) starting in 2022.

Phosphorus levels high

The 2021 phosphorus numbers are roughly the same as in the past. The combination of the different variables analyzed shows that Lac Gauvreau had, even some fifteen years ago, the characteristics of a relatively old lake (i.e. meso-eutrophic).

The lake is significantly enriched with phosphorus (average concentration of 21 ug/L) and the level of chlorophyll A is very high (average concentration of 13.3 ug/L). The water in the lake is very cloudy, with an average transparency of 1.8 meters.

Dissolved organic carbon (DOC) concentration of approximately 8 mg/L was measured a few times in two bays in 2021. Although this was not measured at the pit, it indicates a very strong colouration of water, which could have a major impact on transparency.

Map of the location of the sampling stations at Lac Gauvreau from 2002 to 2021
*Bélisle stream, located north of Parent stream, is not shown here on the map

Swimming is safe in most areas

The average values for the vast majority of sectors are representative of "excellent" or "good" water quality, suitable for swimming, with the exception of Parent and Bélisle creeks. For these sectors, the maximum values observed exceed the criteria allowing indirect contact with water, such as with boating and fishing, because the water is considered unhealthy. The beach at the Whippoorwill Campground is the most effected because of its close proximity to the Parent Creek outlet.

Blue green algae blooms can render perfect swimming water unsafe, even when the e-coli count is very low. So, in the event of a blue green algae bloom, the quality of the water may become unsafe for swimming.

As they do annually, Enviro Lac Gauvreau volunteers collect samples that assess for E. Coli levels at various locations on the lake and in Parent Creek. See the map above where locations A through D indicate Faecal Coliform sampling only. Annual testing has consistently yielded average "Good" to "Excellent" results. The 2021 E. Coli measurements were no exception. The net results of these tests show that Lac Gauvreau continues to be safe for swimming.

Recommendations - Lake health

Enviro Lac Gauvreau must follow the protocols of the Voluntary Lake Monitoring Network (RSVL) in order to assess the health of the lake in the long term.

In order to determine the state of health of a lake, the concentrations of total phosphorus and chlorophyll A, as well as the transparency of the water, must be measured at the lake pit (deepest place) in the first meter of water.
Samples must be taken at a certain frequency. For example, sampling should be done three times during the summer.
Water transparency must be assessed at least ten times between the months of May and October (MELCC, 2022).

The monitoring of Lac Gauvreau as part of the RSVL program in 2022 will make it possible to carry out these analyses.

ARCHIVED - E. Coli Tests