By Ruby Pratka

Local Journalism Initiative

A local environmental group has good news about Cowansville’s drinking water. Last year, the Comité de sauvegarde du bassin versant du lac Davignon (CSBVLD; Lake Davignon watershed safeguarding committee) completed a two-year water quality sampling campaign covering multiple areas of the lake. The resulting report, which will be presented to the public at the CSBVLD annual general meeting on April 2, shows broadly encouraging results for the lake, which has provided drinking water and much-appreciated swimming and boating and outdoor recreation opportunities for Cowansville residents since soon after it was dug in 1965.

Sampling was carried out in 2022 and 2023 at 20 locations in and around the lake and along its tributary streams. The samples were collected by CSBVLD volunteers and analyzed by biologists and field technicians from the Organisme du bassin versant de la Yamaska (OBV-Yamaska; Yamaska watershed organization).

The 2022-2023 campaign is a follow-up to an initial sampling campaign conducted from 2010 to 2012. “Analyses of data collected in 2022 and 2023 show that the good overall water quality in the Lake Davignon watershed observed between 2010 and 2012 continued through 2023 and even improved for fecal coliforms. All stations demonstrated good water quality for phosphorus, fecal coliforms, ammonia nitrogen, pH and dissolved oxygen,” OBV-Yamaska analysts wrote in a summary of the report. The majority of the samples received an “A” (good quality for most uses, including swimming) rating for most contaminants, although there were a few isolated “B” (generally satisfying quality for most uses) ratings for nitrates and nitrites and suspended particles, and two “C” (suspect, may compromise some uses) ratings for chlorophyll.

The authors cautioned that continued surveillance was needed to monitor levels of chlorophyll, nitrates and nitrites, and suspended particles (sediment) in the water.

They also noted that three specific sites, at the Cowansville beach and the Ruisseau marsh, and in the stream between Brome and Cowansville, had lower overall water quality and had been singled out for further analysis.  “Water quality improvement efforts should prioritize” these areas, according to the report’s authors. They also note that the water quality at sampling stations on the beach is “generally good,” even if it is lower than that observed at other stations.

The authors recommended that the town of Cowansville prioritize runoff reduction and “renaturalization” efforts in the targeted areas; continue to monitor targeted pollutants and continue to monitor fecal coliform and acidity (pH) levels at the beach specifically; start to plan a long-term response to the gradual filling in of the lake with sediment; and plan a similar sampling campaign in ten years.

“We are pleased to see that the majority of the analysis results show good water quality. This indicates that the improvement work carried out in the watershed (e.g., sediment traps that filter runoff and capture sediment) in recent years by the Brome-Missisquoi MRC and the municipalities concerned has borne fruit,” said Gérard Houle, vice-president of the CSBVLD and volunteer responsible for the sampling campaign.

“These results are good, and they show that what has been done over the past ten years [to control runoff] is working, but with climate change and extreme weather, there are a lot more downpours, and we need to think about what’s going down our gutters and into our streams to end up in our drinking water,” Jonathan B-Mailhot, president of the CSBVLD, told the BCN in an interview. “Having the data helps us go to officials and say, ‘This is what you need to do to protect our drinking water.’”

The City of Cowansville had not responded to a request for comment by press time.

Mailhot noted that the water sampling results aren’t the only encouraging trend in lake conservation. “Every year around Earth Day [mid-April], we go and clean the banks of the lake, and every time we go, there is less and less rubbish down there.” He asked residents and people who spend a lot of time around the lake to inform the CSBVLD if they notice anything unusual in or around the water.

Anyone who wants to attend the presentation of the water quality report on April 2 at the Salle Arthur-Fauteux of the MRC Brome-Missisquoi office is advised to reserve their seat in advance at lacdavignon.org/echantillonnage.