SEATTLE -- To sustain current Lake Pend Oreille elevations and mitigate lakeshore flood risk, U.S. Army Corps of Engineers’ officials removed a spill gate May 14, and reduced powerhouse flows to achieve the desired total outflow.
During this operation, powerhouse flows were reduced to regulate the total flow increase to 5,000 cubic feet per second and the gate was removed without incident.
Spill operations remain restricted at Albeni Falls Dam in Oldtown, Idaho, while USACE officials respond to the discovery of base metal flaws and defects identified on a spillway gate undergoing rehabilitation. The flaws were discovered in April 2024 as part of a major gate rehabilitation contract initiated in June 2023.
USACE officials are minimizing spill gate movements, so rather than moving multiple gates to regulate lake elevation, a single gate was fully removed.
Current hydrologic modeling indicates maintaining current Lake Pend Oreille elevation until late May might be necessary. Officials are monitoring real-time weather, streamflow trends and updating modeling predictions daily.
Once lakeshore flood risk passes, USACE will operate to meet normal summer pool elevations as quickly as possible.
Even with lower-than-normal snowpack recorded in the basin, there still is significant uncertainty in the inflow forecasts both in terms of total volume and snowpack runoff timing.
The Corps is closely monitoring upstream storage projects, streamflow, snowpack and weather forecasts, and officials are adjusting operations in real-time as conditions allow.
“We need to keep storage space available to guard against the potential for rain or snow events that can lead to sudden spring high inflows,” said Albeni Falls Dam Operating Project Manager Amanda Smith. “The basin is extremely large so there is a lot to consider when monitoring the conditions. These rain events can happen in any year, so we are being cautious during refill operations.”
To receive email notifications for Albeni Falls Dam outflow changes and near-term lake elevation projections, email uppercolumbiawm@usace.army.mil and request to be added.