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The following article is from an archived newsletter. See our Shared Waters newsletter.

Drought of 2015 Provides Lessons for Future Water Management - Part 2 of 2

IJC staff
IJC
Water Matters - The Similkameen River

(see Part 1 of 2

The year 2015 created some unusual water management challenges for the International Osoyoos Lake Board of Control, which sets maximum and minimum water level limits in the transboundary lake in accordance with the IJC’s Order of Approval for Zosel Dam. 

“Basically, the drought conditions were felt earlier and more strongly on the Washington state side of the basin than on the British Columbia side,” says Canadian Board Secretary Gwyn Graham. 

This was exemplified by significant differences in drought indicators for Okanagan Lake and the Similkameen River, the two systems the Board considers in determining whether Osoyoos Lake will be managed under special drought-declaration provisions or normal summer-period conditions. In the northern portion of the basin, Okanagan Lake water levels were relatively normal early in the summer and didn’t trigger the drought criteria.

“Because it was warm and dry through the spring and summer, however, Okanagan Lake levels began to decline earlier than usual and less water was available for Osoyoos Lake inflows,” says U.S. Board Secretary Marijke van Heeswijk. 

Credit: Alison Thorpe
The Similkameen River Credit: Alison Thorpe

The operator at Zosel Dam at the outlet of Osoyoos Lake was barely able to meet the ecological streamflow requirements for the Okanogan River downstream of the dam and there were concerns about the operator’s ability to comply with the IJC Order for Osoyoos Lake.

In response to worsening drought conditions on both sides of the border as the summer progressed, the Osoyoos Lake Board of Control recommended that the IJC issue a temporary variance under the Order to allow water levels in Osoyoos Lake prescribed under the drought provisions. This was done at the end of July and provided additional flexibility to the operator of Zosel Dam. 

“This was the first time that the Board has had to use this adaptive management element of the IJC Order and it could well prove useful again next year if we see similar conditions developing,” adds Graham.

(see Part 1 of 2)

Okanagan Lake Water-Surface Levels, January-September, 2015 and 1944-2014 average. Credit: International Osoyoos Lake Board of Control
Okanagan Lake Water-Surface Levels, January-September, 2015 and 1944-2014 average. Credit: International Osoyoos Lake Board of Control

 

IJC staff
IJC

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