The annual International Osoyoos Lake Board of Control public meeting was held last week on Oct. 14 and covered lake water levels, operations of the Zosel Dam, and several other updates.
“2021 is a very significant year for the board because it’s the 75th anniversary for our Board of Control that was established in 1946,” said Dave Hutchinson, chair of the Canadian section of the board. He also noted that it is the 75th anniversary of the Town of Osoyoos.
The boundary waters treaty was signed in 1909 and is a treaty between the United States and Great Britain, outlining the principles and procedures and mechanisms to prevent and resolve water disputes between the shared watersheds and waters between Canada and the U.S.
It also established the International Joint Commission (IJC) which oversees and resolves these conflicts. The board additionally communicates hydrologic conditions and Zosel Dam operations to the IJC and the public.
Ted White, board member in the Canadian section provided an update of the 2021 hydrology overview and compliance with the IJC order.
In reviewing the temperature and precipitation over the last year, White mentioned that in December there was normal precipitation, but in February, it went below normal precipitation. There was also minimal rain.
As for drought conditions this year, White said, “as you all experienced, it was a dry year. Drought monitors that monitor drought levels in both B.C. and Washington reflect this and it was pretty severe.”
The Okanagan Lake’s net inflow was above average in April but hit its peak four weeks earlier than normal while showing a low cumulative net inflow this year which was similar to 2015 and 2019.
Osoyoos Lake elevation has been within the prescribed rule curve for the year; it’s in compliance.
“In February, there was a bump in elevation (during the cold spell) which led to some ice-related effects that caused an increase in lake levels. Otherwise, it’s a fairly smooth and unremarkable curve that went through no pressure-driven peak,” said White.
On the topic of the Zosel Dam, White touched on the backwater effect this year. The backwater effect can occur when the Similkameen River is at high flow.
“This year, although the river did exceed its level a little, there was no effect of the dam and there was no corresponding decrease in Okanogan river flow and rise in Osoyoos Lake levels,” he said.
The meeting also outlined some special projects spearheaded by different members of the board.
Martin Suchy, secretary of the board, talked about the Similkameen Hydrologic Model.
“In recent years, we’ve either seen high runoff with flooding or low runoff with drought/low flow concerns,” said Suchy. The purpose of the hydrologic model is to assess the climate change impacts of IJC orders for Osoyoos Lake.
The model was completed earlier this year and projects a significant shift in the hydrologic regime of the river by 2100.
Some of the other projects the board is working on involve the Osoyoos Lake Bathymetry to map the Canadian portion of the Okanagan Basin. It helps to understand the wave run-ups in future flooding, explained board member Anna Warwick Sears.
Mapping of the Osoyoos Lake has been undertaken as most of the area has been mapped out including the underwater areas on both sides of the border to have a much better idea of how the water will work under different flow conditions related to climate change.
“It’s a really exciting project, and it’s with cutting edge technology… we’re just going to have a much better basis of science in order to understand what these future flows are going to be. It was a great team project,” said Sears.
