Big snowpack increases region's flood risk

SANDPOINT — Elevated snowpack in watersheds above Lake Pend Oreille has the potential to cause flooding around the lake and downstream of Albeni Falls Dam, according to the U.S. Army Corps of Engineers.

Snow building through February in March in the Lake Pend Oreille, Clark Fork and Flathead basins have increased the snowpack to 130-150 percent of average.

To mitigate the possible flood risk, the corps plans to release about 25,000 cubic feet per second, or full powerhouse capacity, from the dam for the foreseeable future. The operation is meant to keep the lake elevation as close as possible to 2,052 feet above sea level until the dam goes into free-flow operation in late April or early May.

The lake elevation at the end of April is forecasted to be 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-the month minimum elevation.

“Forecasts suggest we could see peak Lake Pend Oreille elevations ranging between 2,062.5 and 2,065 feet in June, and outflows exceeding 100,000 cubic feet per second,” said Joel Fenolio, Upper Columbia Senior Water Manager for the corps.

Free flow is when the hydraulic control point for releases switches from the dam to the natural restriction between Lake Pend Oreille and the dam. This operation is intended 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 and 2,062.5 feet above sea level.

Flooding begins below Albeni Falls Dam when flow through the dam exceeds 100,000 cfs.