By Don Urquhart, Times Chronicle
In response to drought conditions on both sides of the border the International Joint Commission (IJC), responsible for overseeing issues related to Osoyoos Lake, has approved a request for a temporary variance to how Osoyoos Lake levels are managed this summer.
The temporary variance allows the operator of Zosel Dam, the Washington State Department of Ecology, more flexibility to operate lake levels than under non-drought conditions.
The temporary limits allow Osoyoos Lake levels to range between 910.5 (23.13 m) and 912.5 feet (23.18 m), which is an extra half foot (15.24 cm) above and below the normal summer level range.
The variance will remain in effect from June 20, 2025 until November 1, 2025, or until weather and water supply conditions improve, the IJC said.
The operator plans to gradually increase Osoyoos Lake levels during the next few weeks towards the new temporary upper limit of 912.5 feet.
“The additional stored water will help to augment late summer water supplies and support downstream flows in the Okanogan River, which is crucial for endangered fish and other aquatic species,” it said.
The IJC said the move was necessitated by the “unusual weather and water conditions the Okanagan and Similkameen basins experienced in early 2025.”
Normally, Osoyoos Lake levels are kept between 911.5 and 912 feet from May 1 to September 15 in non-drought years. While the conditions for a drought year – according to the IJC definition – haven’t been officially met this year due to what it says was ”proactive water management in the Okanagan Basin, low winter snowpack, coupled with early snowmelt due to warm temperatures,” have heightened water supply concerns for the late summer months in the basin.
Okanagan Lake, upstream of Osoyoos Lake, peaked on June 1, 2025, and is being rapidly drawn down, leading to less water flowing into Osoyoos Lake, it said. The Similkameen sub-basin is experiencing significantly reduced flows, at only 47 per cent of normal.
British Columbia has reported Drought Level 2 for the Okanagan Basin, and Washington State has declared a drought emergency for Okanogan County, signaling the water stress felt on both sides of the border.
Osoyoos Lake levels are managed by Zosel Dam under the authority of the IJC, which involves equal representation from the US and Canada. Details about the drought and non-drought conditions are outlined in IJC Orders.
