Corps to provide update on refilling reservoirs

After a historically dry start to the refill season, water managers with the Portland District, U.S. Army Corps of Engineers are optimistic about refilling most Willamette Valley reservoirs after increased rainfall and snowmelt in April.

To help explain the nuances of this water year, including refill and the conservation forecast, Corps staff will host a virtual public information session at https://usace1.webex.com/meet/erik.s.petersen from 5 to 6 p.m. Thursday, May 11. Participants may also access the session by calling 1-844-800-2712. The access code is 1999-18-2318 #.

The Corps encourages questions during the meeting and asks participants to either send them using the chat function in WebEx during the meeting or email them beforehand to the Portland District Public Affairs Office at [email protected].

“The last few years have been a hydrologic roller coaster, and this year is no exception,” said Salina Hart, chief of water management for the Corps. “Spring rains are essential for refilling reservoirs and fortunately, we saw a substantial improvement in April.”

The Corps reports the Willamette Valley system of dams and reservoirs is 62% full as of May 2.

Weather is one critical factor among a host of other criteria that influence the way the Corps approaches water management in the Willamette Valley system.

In February, water managers begin the “delicate dance” of balancing the many Congressional purposes of both the reservoirs and the dams that impound them.

One primary purpose of the system’s dams and reservoirs is flood risk management: Water managers must keep reservoir elevations low to maintain storage space in them through the spring to capture seasonal rains and prevent flooding downriver. This must be balanced with what sometimes seems to be conflicting purposes: refilling the reservoirs for irrigation, hydropower generation, water quality improvement and recreation.

The balancing act doesn’t end there: The Corps must also meet minimum water releases according to the requirements of the 2008 Biological Opinion, which define minimum releases, or “beneficial flows,” from the reservoirs to improve downstream habitat for endangered species.

Additionally, this year, water managers will continue to operate under the constraints of a 2021 court injunction that aims to improve conditions for endangered species. The injunction orders have called on the Corps to delay reservoir refills this spring at Cougar and Fall Creek and begin early fall drawdowns of the reservoirs at Lookout Point and Green Peter, which will impact recreational access as the reservoirs release water sooner to provide fish passage.

Water managers forecast that Foster Lake will remain full for Memorial Day through Labor Day. Several smaller reservoirs are currently full or nearing full levels. The remaining larger reservoirs, which are seeing improvement given the April rainfall and some snowmelt, are expected to fill, although later than typical. Reservoir refill levels for the Willamette Valley can be found at https://www.nwd-wc.usace.army.mil/nwp/teacup/willamette/

The Corps invites the public to attend the session to learn more about current operations, future forecasts, and potential impacts to the Willamette Valley System.