Osoyoos Lake reaches this year’s high level, but flood risk abating

By on May 28, 2014
The Zosel Dam at Oroville, WA is operated to control the level of Osoyoos Lake during the summer. During flooding season, however, all its gates are pulled out of the water and the dam doesn’t affect lake levels. When the Similkameen River is high, water can actually back up at the dam. (Richard McGuire file photo)

The Zosel Dam at Oroville, WA is operated to control the level of Osoyoos Lake during the summer. During flooding season, however, all its gates are pulled out of the water and the dam doesn’t affect lake levels. When the Similkameen River is high, water can actually back up at the dam. (Richard McGuire file photo)

Osoyoos Lake reached its highest level this year Sunday night, but barring any unexpected changes in weather, the risk of floods appears to be abating.

On Sunday night and into Monday, the lake’s level was measured at 913.11 feet above sea level, according to the United States Geological Survey (USGS).

This level is still more than a foot lower than last year’s high of 914.19 feet, which forced owners of some low-lying properties to use sandbags.

Last week on May 20, the B.C. River Forecast Centre ended a High Streamflow Advisory affecting a number of South Interior river systems including the Okanagan and Similkameen rivers.

Two days later, on May 22, the River Forecast Centre released its May 15 Snow Survey and Water Supply Bulletin which showed the snow basin index in the Similkameen River basin remained at 181 per cent of normal, although the Okanagan-Kettle basin was only 113 per cent of normal.

“With the warmer weather in early May, the seasonal melt of the snowpack has begun,” the bulletin said. “In mid-elevation watersheds, particularly through the Okanagan, South Interior and Interior Plateau, the majority of snow has now melted, and ongoing flood risk from snowmelt alone is subsiding.”

A period of heavy rain, or higher temperatures leading to rapid snowmelt, could cause the risk to increase again.

Discharge on the Similkameen River near Nighthawk, WA began rising again heading into the weekend, but it hit another peak Saturday evening, reaching 16,700 cubic feet per second.

The flow of the Similkameen River has an impact on the level of Osoyoos Lake because a high volume of water on the Similkameen can force water on the Okanogan River to back up at the Zosel Dam in Oroville, slowing drainage from Osoyoos Lake.

This volume is still well below 2013 volumes, which peaked at 21,700 cubic feet per second.

By Monday at noon, the Similkameen’s volume had dropped again to 13,700 cubic feet per second as recorded by the USGS.

RICHARD McGUIRE

Osoyoos Times

 

 

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