Storm passes, weather cools and Osoyoos gets temporary reprieve from flood threats

By on May 15, 2017
Water is high and strong at a weir on the Okanagan Channel north of Osoyoos Lake. (Richard McGuire photo)

Water is high and strong at a weir on the Okanagan Channel north of Osoyoos Lake. (Richard McGuire photo)

The threat of floods in the South Okanagan has diminished in recent days, but a sudden change in weather could again increase the risk.

Temperatures have fallen, slowing the melt of higher elevation snowpacks, and last Thursday a threatened thunderstorm passed through leaving little rain.

Nonetheless, snowpacks in the Okanagan and Similkameen basins remain much higher than normal and Environment Canada issued weather alerts for snowfalls at higher elevations on Monday night and into Tuesday.

A return of temperatures to the high 20s or 30s could again result in rapid melting.

Flood watches affecting the South Okanagan were lifted on Friday, but water levels in rivers and lakes remain high.

The Town of Osoyoos, which took precautionary measures last week, is still making sand bags available at the public works yard in the industrial park and sand is available across Highway 3 from Dairy Queen.

The level of Osoyoos Lake reached 913.5 feet above sea level on Saturday and it has stayed around that level through the weekend and into Tuesday.

The situation is still menacing further north where Okanagan Lake was just 35 centimetres below the flood mark as of late Sunday afternoon, Central Okanagan Emergency Operations said in a news release on Monday.

Boaters were warned about floating debris in the water and were warned to stay away from shorelines and reduce speeds as additional wave action could cause disturbance to banks and beaches.

Last week Okanagan Lake was rising at a rate of three centimetres a day as water flowed into the lake much faster than it could flow out. Many homeowners next to waterways in Kelowna were busy sandbagging.

One positive sign for Osoyoos is that flows on the Similkameen River have diminished again after reaching a peak of 14,500 cubic feet per second on Friday at Nighthawk, WA. As of Tuesday morning, the discharge had fallen to 9,690 cubic feet per second.

The volume of water in the Similkameen River is a major factor affecting the level of Osoyoos Lake, because when water backs up from the confluence of the Similkameen and Okanogan Rivers at Oroville, water can’t drain effectively from the lake at the Zosel Dam.

Al Josephy, the official with Washington State Department of Ecology who oversees the Zosel Dam, said Monday that the Similkameen River is not currently backing up into the Okanogan.

Nonetheless, the gates at Zosel Dam, except for one that has been malfunctioning, are all raised to allow the maximum outflow of water from Osoyoos Lake, Josephy said. The malfunctioning one is partly opened and is expected to be working later this week.

Josephy said he would not be surprised to see the level of Osoyoos Lake reach 914 feet, but he said that level is not extreme and has been experienced in the past decade.

“It’s really hard to predict, but it doesn’t look like anything extreme is on the way here,” Josephy said. “Now a sudden rainstorm could change that, suddenly going up to (24 C to 27 C) could change that, but I don’t see any of that in the forecast now.”

The situation on Lake Okanagan is worse, he said, and that could result in water management challenges downriver later.

“But we’re on top of it,” he said. “All things are moving ahead. It’s spring.”

RICHARD McGUIRE

Osoyoos Times

Water is high and strong at a weir on the Okanagan Channel north of Osoyoos Lake. (Richard McGuire photo)

Water is high and strong at a weir on the Okanagan Channel north of Osoyoos Lake. (Richard McGuire photo)

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