PORTLAND, Ore. -- The Portland District, U.S. Army Corps of Engineer is increasing controlled water releases at most Willamette Valley dams as rain and melting snows are projected to fill reservoirs to near 100% capacity in the coming days.
The flows include water release at historic rates from Dorena Reservoir, and the Corps has worked in partnership with Lane County Emergency Management, which has issued evacuation notices for those in the Row River Floodplain and the Coast Fork Floodplain of the Willamette River.
“We are managing flows in a way to protect the downstream public from flood to the extent we are able, and to maintain space in the reservoirs to avoid uncontrollable releases,” said Ross Hiner, Portland District Dam Safety Program Manager.
“However, inflows are so high that we are having to increase our releases to minimize the overall flooding risk,” he said.
This releases mean that the Corps is maximizing reservoir storage within safe limits.
Prior to this rain event, below-average precipitation in the Willamette Valley contributed to low reservoir levels throughout the system of dams, while snow levels in the basin were above average.
“We are currently experiencing an atmospheric river coupled with melting snow,” said Salina Hart, Portland District Chief of Reservoir Regulation and Water Quality.
The Corps reservoirs are able to capture a portion of the flood waters in order to reduce downstream flows, but will not be able to eliminate all of its impacts. Water managers expect levels in the Willamette Valley to be at flood stage now through the middle of the week at several gauges, including Goshen and on the main stem of the river at Harrisburg and Albany.
Additionally, forecasts show Salem near flood stage Wednesday.
A flood stage will result in water inundating areas that are not normally covered by water, and teams at the Portland District are running forecasting models multiple times a day in conjunction with the Northwest River Forecast Center. The models are used to assess forecasted inflows to Willamette Valley reservoirs and flows from unregulated tributaries to plan reservoir outflows for downstream flood risk management.
The models are rerun with updates to the forecast and the latest information on projected operations is shared with local emergency managers.
Residents in affected areas should follow the instructions of local emergency managers as unregulated flows from tributaries continue to contribute to water levels.
For the most up to date official river flow information, refer to the Northwest River Forecast Center at www.nwrfc.noaa.gov/rfc/