Snow building through February and March in the two major watersheds above Lake Pend Oreille, Clark Fork River and Flathead basins, have increased the snowpack to 130-150 percent of average. The elevated snowpack has the potential to cause flooding around the lake and downstream of Albeni Falls Dam.
To mitigate possible flood risk, the U.S. Army Corps of Engineers plans to release about 25,000 cubic-feet-per-second, or full powerhouse capacity, from Albeni Falls Dam for the foreseeable future. This operation is intended to keep lake elevation as close to elevation 2,052 feet as possible, as measured at the Hope Gage, until the dam goes into free flow usually by late April or early May.
The end of April minimum elevation of Lake Pend Oreille is 2,054 feet. If free flow has not occurred, or is not projected to in the near future, a decision will be made mid-month to begin filling the lake to its end-of-month minimum elevation.
“Forecasts suggest we could see peak Lake Pend Oreille elevations ranging between 2,062.5 and 2,065.0 feet in June, and outflows exceeding 100,000 cubic feet per second,” said Joel Fenolio, Upper Columbia Senior Water Manager for the Army Corps of Engineers.
Free flow is when the hydraulic control point for releases switches from Albeni Falls Dam to the natural restriction between Lake Pend Oreille and the dam. This operation is meant to help keep the Lake level down and to mitigate for some of the potentially high releases through the spring. Lake Elevations could be above 2,062.5 feet for several weeks. Areas downstream of Lake Pend Oreille, such as Cusick, Newport, and Usk could be affected by high releases from Albeni Falls Dam while the dam is on free flow. The normal maximum elevation for Lake Pend Oreille during the summer is between 2,062.0 and 2,062.5 feet above sea level. Flooding begins below Albeni Falls Dam when flow through the dam exceeds 100,000 cfs.
Given the above normal snowpack, people residing in flood-prone areas should take precautions this spring and be prepared for flooding.
The Corps is closely monitoring weather and snowpack conditions, lake inflow, forecasted releases and the level of Lake Pend Oreille. The Corps will continue to operate Albeni Falls Dam to minimize flood damage.
A public information meeting for Albeni Falls Dam operations is scheduled at the Priest River High School cafeteria at 6 p.m., April 22.