By Steve Hubrecht
A report on recreational impact and sediment quality in Lake Windermere showed elevated levels of arsenic, copper and lead in the lake, as well as very high densities of an algal-bloom forming and potentially toxic phytoplankton cyanobacteria at Kinsmen Beach.
The report was conducted in 2022 by environmental consultants Ecoscape Ltd. and was commissioned by the Lake Windermere Ambassadors. It was completed earlier this year and made public by the Ambassadors last week, during the Tuesday, May 9 Invermere council meeting.
The study was meant to assess the impact of recreation on environmental values (such as habitat disruption and lakeshore erosion), on sediment quality and suspension; and on drinking water (as plumes containing contaminants can travel from disturbed areas to drinking water intakes on the lake).
“Wake turbulence is particularly concerning given the extensive shallow areas, or littoral zone, of Lake Windermere. Fine organic and silty sediments accumulated on these shallows are easily re-suspended with wake turbulence from prop wash, which can be exacerbated when large ballasts are present in boats to create larger wakes,” read the report.
Part of the study included taking measurements at nine sites throughout the lake: by the Athalmer boat launch; at Kinsmen Beach; at a ‘deep site’ at the deepest point of the lake (roughly halfway between Windermere and Invermere); along the northern part of the lake’s western shore; by each of three marinas on the eastern side of the lake; by Lake Windermere Provincial Park; and at a control site in the middle of the far south end of the lake.
Sediments cores taken during these measurements found elevated arsenic, copper and lead, to a level exceeding the 80 per cent of maximum allowable concentration warning threshold.
“Of these, only arsenic exceeded the B.C. sediment quality guideline…with seven of the nine sites exceeding the guideline by as much as double the deep and control sites,” read the report.
Phytoplankton densities were also measured. They were moderate in the southern half of the lake, but very high at the two northernmost sites (the Athalmer boat launch and Kinsmen Beach). The phytoplankton was predominately Anacystis sp — a type of cyanobacteria that it potentially toxic and is associated with algal blooms.
“The beach sample contained 21,410 cells per millilitre of cyanobacteria, a concerning result for a popular swimming area. While this is unlikely to lead to acute cyanotoxicity, chronic low dose exposure cannot be ruled out,” read the report.
The study also developed a method of assessing boat density, with recommendations for a full year of data collection to determine which parts of the lakes see the most recreational use. Once that is complete, the reports outlines that recommendations can be made on which are the most appropriate areas of the for recreational use.
The report was presented to council by Lake Windermere Ambassadors employee Amy Baxter, patching in via video link.
“The findings have raised concerns about water quality and drinking water,” said Baxter.
Baxter pointed out that wake from ballasted wake boats can have considerable impact on bodies of water up to eight metres deep. “The majority of the lake (Windermere) is three or four metres deep, and its deepest point has a maximum depth of six metres, so the whole lake is susceptible to these impacts,” she said, adding a 25 per cent increase in the level of phosphorus can be measured after just two wake boat passes.
She noted that although a full-year of data has not yet been crunched “the carrying capacity for boating is likely exceeded on busy weekends.”
Baxter outlined that there has been a trend of increasing phosphorus in Lake Windermere over the last seven years. At the same time, over the past 11 years, the average summer lake temperature has increased 1.7 degrees Celsius, she explained.
These two trends, she pointed out, could spell trouble, since high levels of phosphorus and warming water conditions are both associated with excessive algal blooms.
Baxter did explain that cyanobacteria can be a confusing organism. It can be present when there are no algal blooms to be seen. Conversely, there can be extremely visible cyanobacteria-related algal blooms, but the cyanobacteria present may not be toxic. And, just to complicated things further, non-toxic cyanobacteria can change and become toxic cyanobacteria.
She said the highest levels of cyanobacteria were measured at Kinsmen Beach in September and suggested that perhaps the prevailing winds and the comparatively more stagnant water in the Taynton Bay might explain the high measurements. (The winds tend to come from the south helping ‘trap’ the water in Taynton Bay, while the rest of the lake has a relatively high flushing rate, since it is really just a widening of the Columbia River).
Baxter recommended the District of Invermere put up ‘Watch Your Wake’ signs, develop a cyanobacteria response plan for Kinsmen Beach and incorporate Green Shore for Homes principles into the Athalmer Neihgbourhood Plan.
Invermere councillor Gerry Taft suggested there could be resistance to restrictions on boating, unless the Ambassadors engage the boating community right from the start, saying “my fear is there could be a fight,” especially if a final outcome is a map showing areas where boating should and shouldn’t occur.
Baxter countered that other places that have created such maps (such as Kalamalka Lake in the Okanagan) have seen a positive response, rather than a negative one.
“I truly think that if we get maps into the hands of people, they will do their best to stay in the areas deemed to best for boating from an ecological and water quality standpoint,” she said.
Others councillors did not share Taft’s quibble, and were eager to implement Baxter’s recommendations.
“We need a (cyanobacteria response) plan,” said councillor Kayja Becker, adding the district also needs a way to inform residents and visitors when cyanobacteria levels at Kinsmen Beach are particularly high “so they’re not just swimming and have no idea…That would be scary to not having anything, if these kinds of events (cyanobacteria) are going to continue to get worse.”
Baxter concurred that would be a good idea, and added “I was not expecting those (cyanobacteria) numbers to be that high.”