A freedom of information request by the BC Wildlife Federation has found that an early drawdown of Okanagan Lake has compromised a significant portion of the lake’s shore-spawning kokanee salmon population.
The Wildlife Federation’s director of fisheries restoration is worried that the kokanee kill-off could set restoration efforts back years, if not decades.
A drawdown is when water levels are lowered by dams or other structures, usually to prevent flooding, during spring and early summer.
“Our infrastructure isn’t set up to manage the changes that we are experiencing in terms of run-off in the spring,” said Jesse Zeman, who is frustrated with the water-level management of Okanagan Lake.
In fact, Zeman said when he noticed low water levels this spring, he became concerned about the kokanee salmon population.
So, he put in a freedom information request with the provincial government.
“What we found in (the documents) was that the lake level had been brought down early. It had been flagged the Okanagan Nation Alliance, by provincial biologists,” said Zeman.
“They stopped reducing the water, but the province went out and did some sampling and found that in those areas and 75 per cent of the eggs and alevin in those areas had been killed by the drawdown.”
The BCWF said with snowpacks above normal earlier this year, the Ministry of Environment began to lower Okanagan Lake in February in anticipation of a substantial spring freshet in order to mitigate the risk of flooding to properties surrounding the lake.
The BCWF then said according to documents released under the Freedom of Information and Protection Privacy Act, “early in March, government biologists and First Nations partners became concerned that the annual drawdown was prematurely exposing shoreline spawning areas, stranding unhatched kokanee eggs and immature fry.”
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In citing the Freedom of Information documents, the BCWF said an excavation of the shoreline led by a government biologist found mainly dead eggs in the 25-centimetre vertical drawdown zone.
The provincial ministry responsible for maintaining the water levels in Okanagan Lake admits better science is needed in order to make informed decisions that prevent flooding and also preserve fish stocks.
“When it comes to lake level drawdown, it’s really based on our inflow forecast,” said Shaun Reimer of the Ministry of Forests and Lands.
“And we have struggled with that, with the impacts of climate change that we are already seeing and the kind of extreme weather events.”
In the meantime, Zeman worries this kokanee kill-off could set restoration efforts back by decades
“After the kokanee collapsed in the 1990s, last year was the first return since the 1970s where we had well north of 300,000 fish,” said Zeman.
He suggests an interim solution would be drawing the lake level down during spawning season in October.
The wildlife organization says the dam in Penticton can only lower Okanagan Lake by 1.75 cm per day, but noted that climate change spring runoff can raise the lake’s level as many as 7-8 cm.
“The interim solution for the kokanee is to draw down the lake before October, so that spawners lay their eggs further down the shoreline,” said Zeman.
“In the short term, B.C. needs a watershed security fund and strategy to deal with the earlier and more intense spring runoff followed by the dry summers we’re currently experiencing.
“In the long term, Okanagan valley homes and buildings are going to have to be built or moved further from the lake and stream edges so that these unprecedented runoff and drought cycles do not continue to flood people’s property.”
Zeman added “that sounds like a radical solution, I know, but the climate is changing and we have to adapt to a new reality.”
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