Everything from hot weather to improperly diapered toddlers can cause the bacterial readings at Valley beaches to spike and force Island Health to declare them unsafe for swimming.
Recently three beaches have been on and off the list: Fuller Lake, Kin Beach in Chemainus and the boat launch area at Maple Bay.
According to Kellie Hudson, Island Health’s media relations manager, the list of possible causes is long.
“Things that can increase the presence of E.coli or Enterococci are presence of water fowl, wildlife, dogs, etc., in the area; improper diapering of children/toddlers; live-aboard boats and/or other boats with facilities; runoff from land which could be affected by onsite sewerage systems or agricultural properties,” she said.
When a small enclosed lake like Fuller Lake is involved, the effect of the factors listed above can be exacerbated by the weather, and even its depth.
“Higher water temperatures can also play a role in increasing the proliferation and/or increased survival of bacteria,” she said, adding, “Something to remember is: hot weather results in lower lake levels, and increased use by wildlife and recreational swimmers.”
Wide-open beaches on big lakes, like those on Cowichan Lake, can still be affected by any combination of those factors, Hudson explained.
When it comes to sampling water at Cowichan Valley beaches, Island Health’s sampling program is based upon the Guidelines for Canadian Recreational Water Quality, a Health Canada document, she said.
“Immediate water quality issues are identified with a single sample. Chronic water quality issues that could be causing unsatisfactory bacteriological results are identified through the average of multiple samples over a set period of time.”
Several local beaches have been the focus of warnings already this summer, though none are still under an advisory at this time.
“In the case of Maple Bay, Kin Beach, and Fuller Lake, it was a single sample that initiated the postings.”
A single reading showing a spike in the number of E. coli or Enterococci can be an indicator of ongoing contamination or it may be the result of something as localized as a waterbird stopping for a rest near a sampling site.
“We don’t have a sense at this point that there are chronic issues at any of these beaches,” Hudson said.
Because beach advisories can be issued from single sample results, which indicate an issue at a point-in-time, sampling is continuous to provide the best idea of water quality at the beach.
Island Health’s beach sampling results can be viewed at: www.viha.ca/mho/recreation/beach_reports.htm. The Cowichan Valley is considered a “Central Island” area.