Downstream from Lake Okanagan and upstream from where the Similkameen enters the lake that bears its name, the community of Osoyoos is threatened by rising water from two directions.
But Janette Van Vianen says there’s little the Town of Osoyoos can do as the lake level starts to rise except preach preparation.
“At this point, we’re not flooding,” she said. “People are seeing a rise in the lake and we’re telling them they may want to take some preliminary measures and start doing some sand-bagging if they feel they’re going to experience some flooding.
“Everybody has their different flood plain elevations. Some people might start seeing some flooding at 912.5 or 913, where others won’t see it until it gets a little higher.”
As of Monday morning, the lake level, as measured by the US Geological Survey, was at 911.84 feet
“Where we peaked last year was at 914.88 feet,” said Ms. Van Vianen. “So that’s like another three feet or so. It still flooded before the 914.88, but that was the peak of where we hit before it started receding last year.”
As states of emergency and evacuation alerts are issued elsewhere, the Town’s Corporate Services director keeps an eye on water levels and checks in with various agencies across the province.
Her focus is on both the Okanagan River, which enters Lake Osoyoos from the north, and the Similkameen River, which drains just south of the lake.
The lake’s water level, she notes, is determined by a number of factors, including the operation of Zosel Dam in Washington State, the operation of Okanagan Dam in Penticton, stream-flow into Okanagan River between Penticton and Osoyoos, and the flow levels of the Similkameen River, which joins Okanagan River south of the US/Canada border.
It’s a complicated watch. Wet weather elsewhere in the system can have just as much impact in Osoyoos as rain falling locally and warmer temperatures at higher elevations will accelerate the snowpack melt.
And, as occurred over the weekend, cooler temperatures can bring additional snow.
“I’m in constant contact with (the provincial) River Forecast (Centre) and getting updates from them as to what they’re seeing in different areas as well,” said Ms. Van Vianen.
Much of the flow in both the Okanagan and Similkameen is predicated on snowpack melt. Current monitoring has “snow pillows” in both areas at above 150 per cent of normal.
“If it comes down slowly, we’re probably not going to see a lot of flooding,” said Ms. Van Vianen. “But that’s something that we can’t predict; it’s out of our control.
“It really depends on what Mother Nature does; it’s what the weather is going to do.”
The heavy spring runoff has several areas within the Regional District of Okanagan-Similkameen either in a state of emergency and/or facing evacuation. Closest to Osoyoos is an area just north of Oliver.
The runoff has also brought mud slides to the region. Hwy. 3A remains closed near Yellow lake — about 18 km east of Keremeos — due to a mud slide. A similar slide temporarily closed Hwy. 33 north of Rock Creek Sunday.