Some minor modifications will be made to how water levels on Osoyoos Lake are managed after the International Joint Commission issued an Order of Approval to renew Washington State's authority to operate Zosel Dam.
The Dam, located in the southern portion of the lake near Oroville, WA., is subject to international jurisdiction because it regulates the outflow from Osoyoos Lake, and backs water across the border into BC.
“Thanks to the active participation in the process by watershed residents and input from the State and Province, the IJC was able to thoroughly vet the issues affecting both countries before revising this Order,” said Commissioner Lyall Knott of the IJC.
In a June 2012 report, the board concluded that the current orders have adequately enabled water levels to stay within reason to benefit agriculture, tourism, municipal interests, and fisheries protection in the area. The board recommended only minor modifications to the rule curve that sets Osoyoos Lake upper and lower target water levels for different times of the year.
The previous rule curve had specified that the lake be maintained within a half-foot range (911.0 to 911.5 feet) from April through October during normal conditions, and be allowed to rise to 913.0 feet during drought years.
The Board recommended that the maximum elevation be reduced to 912.5 feet with the flexibility to regulate within a two-foot range every year, thereby eliminating the need for drought declarations. It was also recommended in the boards June 2012 report that a more gradual transition in water levels be implemented during the spring and fall.
Public hearings were conducted with the IJC in Oroville and Osoyoos in July of last year; they also met with the Osoyoos Indian Band. Several shoreline residents in Canada voiced concern that a sustained maximum lake level of 912.5 feet would be too high because of concerns about flooding, erosion, riparian habitat, endangered species and navigation and adjustments were made.
The Commissioners decided that the rule curve would include a one foot-range with a 912-foot maximum in the summer under normal conditions, and a two-foot range with a 912.5-foot maximum during drought years.