Lower than average snowfalls in Washington have that state’s Department of Ecology planning to bring Osoyoos Lake to “its maximum mandate operational level” of 912 feet earlier this spring.
That would have the lake rising a month earlier than normal.
“[L]ess than average snow levels are being reported in all watersheds in the region and temperatures are on the rise,” the department is reporting. “Because of this, the agency will raise the lake earlier than usual to avoid water shortages and low flows later in the summer.
“The goal is to bring the lake to its maximum mandated operational level of 912 feet by early May, rather than by June 1 as usual.”
The department regulates the lake’s levels by opening or closing gates at Zosel Dam near Oroville.
Lake levels are mandated by the International Joint Commission of the Boundary Waters Act and administered by a joint board, made up of representatives from the United States and Canada.
North of the border, releases from Okanagan Lake and snowpack runoff also impact lake levels at Osoyoos. The Similkameen River, which joins the Okanogan River near Oroville, can also play a role in the lake’s level as water backs up into Osoyoos Lake.
A spokesperson for the department suggested the dam’s action would not have an impact on flooding north of the border.
During the snowpack runoff season, the level of the lake can rise sharply and the lake could rise beyond 913 feet and can reach as high as 915 feet, explained Al Josephy, with Ecology’s Water Resources Program.
But, he added, “this phenomenon is driven by snowpack and temperatures, and cannot be controlled by Zosel Dam.
“Although the very high levels are rare, we’re reminding lake residents that it can cause inconvenience and occasional flooding to property owners along the lake and down to the site of the dam itself.”
British Columbia’s River Forecast centre is reporting current snowpack levels in both the Okanagan and Nicola at about 80 percent of normal — well below the levels reported in 2018.
“However, seasonal snowpack can still change significantly with one to two more months of possible snow accumulation left in winter/spring 2019,” the forecast centre reports in a March 1 bulletin.
“While snow is one significant aspect to seasonal flooding in BC, weather during the freshet season also plays a key role, and flooding is possible in years with near normal snowpack.”
Last spring, Osoyoos Lake crested at 916.32 feet in mid-May. It currently sits at just over 910 feet.