Osoyoos residents have received their strongest warning to date to prepare for flooding later this week that could go beyond what has already occurred and perhaps even to record levels.
The Regional District of Okanagan-Similkameen (RDOS) fears the lake’s level could rise beyond 917 feet and perhaps even higher, based on weekend forecasts.
“(The Similkameen) is expected to flow high enough to push as much as several feet of additional water back into Osoyoos Lake,” the Regional District said in a release this morning delivered through the Town of Osoyoos.
That estimate was confirmed this afternoon by Dave Campbell, head of the BC River Forecast centre.
Osoyoos Lake, the Regional District noted, is already flooding low-lying properties with a peak of 916.42 feet — as measured at the US Geological Service’s Oroville station — with 53 homes and one lakefront hotel in Osoyoos and 17 properties in rural Electoral Area ‘A’ evacuated.
The lake’s water level currently sits at 916.10 feet.
“When we see (the Similkameen’s) flow coming into Osoyoos Lake, it’s going to get fairly high,” explained the Regional District’s Cameron Baugham. “We looked at the worst-case scenario on Friday and Saturday and that was pushing about one to two feet of water back into Osoyoos Lake.
Two feet would take the lake’s level beyond 918 feet.
“There are no controls on the water coming from below. Zosel Dam is pretty much out of commission in terms of control and the water is going to go where it’s going to go and it’s going to push back into Osoyoos Lake.”
The forecast is based on warming temperatures and a high snowpack leading to rising water in the Similkameen through the Long Weekend.
The Similkameen River collects water from as far away as Manning Park and the Coquihalla Highway.
“We have seen it rising the last couple of days after a bit of easing,” said Mr. Campbell of the Similkameen’s flow. “That suggests that there is enough snow there to drive levels up to or above what we’ve experienced already.”
At Nighthawk, Wa., the Similkameen reached a peak discharge of 32,000 cubic feet per second last week before falling off to 23,900 cubic feet per second. Discharge started to climb again early this morning and now sits at 24,400 cubic feet per second.
The province measures the Similkameen’s flow at Hedley.
“Our current flow projection has the potential of getting up to about 800 cubic metres per second (about 28,250 cu. ft. per second),” said Mr. Campbell. “So far we’ve reached about 600, so that’s going up another 20 percent above that.”
Mr. Campbell cautioned, however, that it would be difficult to draw an exact relationship between the Hedley measurements and the Osoyoos Lake water level.
“The dynamics at Osoyoos Lake are a little bit outside of the scope of what I can respond to,” he said. “We can measure the changes of the river gauge near Hedley, but kind of extrapolating what the river would do in terms of rise by the time we get down to the confluence with the Okanogan system is a bit of a stretch.
“(It’s) beyond the kind of tools I’ve got to answer that.”
Osoyoos residents may get more answers tomorrow evening when the Town of Osoyoos — accompanied by the Regional District and provincial agencies — hosts an information session at the Sonora Community Centre.
The event is scheduled to begin at 6:30 p.m.