Some releases required to preserve storage space for future storms
PORTLAND, Ore. – Large federal reservoirs are seeing the affects of recent back-to-back heavy rainstorms drenching the Willamette Valley, the U.S. Army Corps of Engineers announced today.
However, in a move to preserve adequate storage space for additional storms, the agency will increase water releases from most of its dams this weekend. Agency engineers and water managers continue to work with the National Weather Service to find the right balance of water storage and water release to keep areas rivers below flood stage.
The Corps’ 13 Willamette Valley Project dams continue to store the vast majority of rainwater and snow melt flowing into their reservoirs, significantly reducing river levels downstream. For example, Blue River and Cougar dams on the McKenzie River are releasing only about 4 percent of the 15,200 cubic feet per second flowing into their reservoirs, and less than 2 percent of the total river flow of 31,900 cubic feet per second at the Vida gauge downriver.
In the past two weeks, the Corps’ reservoirs have collectively gone from 0 to 35 percent full, with further substantial rises in reservoir levels expected over the weekend. Willamette Valley Project reservoir and river levels and flows can be seen at http://www.nwp.usace.army.mil/Missions/Water.aspx.
To help maintain adequate storage for a second severe rainstorm expected to arrive over the weekend, Corps reservoir regulators are adjusting releases upwards. Downriver residents can expect to see many rivers the Corps regulates in the Willamette Basin rise above the “action” or “bankfull” levels set by the National Weather Service. The Coast Fork Willamette River at Goshen and the mainstem Willamette River at Harrisburg and Albany are expected to crest at or near flood stage over the next week. Details of current and expected flood conditions are available from the Northwest River Forecast Center at http://www.nwrfc.noaa.gov/rfc/.
The Corps reminds downriver residents that many of its dams’ spillway gates have a risk of not operating properly when reservoir water levels are high. Operating restrictions in place to reduce the risk of a malfunction may mean using the gates earlier and/or opening them wider during and following storm events, potentially increasing water releases. Details of the gates’ status, operation and rehabilitation are at http://www.nwp.usace.army.mil/Missions/Water/Floods.aspx.
The Corps’ 13 dams in the Willamette River basin contribute to a water resource management system that provides flood risk management, power generation, water quality improvement, irrigation, fish and wildlife habitat and recreation on the Willamette River and many of its tributaries. Since their completion, the dams have cumulatively prevented more than $20 billion in flood damages to the Willamette Valley. Learn more at http://www.nwp.usace.army.mil/Locations/WillametteValley.aspx.
For virtually all emergencies, including flooding, county emergency management offices are the first sources of information, the first responders, and the designated authorities for deciding upon and announcing evacuations. Visit http://go.usa.gov/By23 and look under “Be prepared” for contact information. The Corps is closely coordinating with state, tribal and local officials to preparing communities to respond to this event.