The Willamette Valley Project had an exciting spring this year, with a significant snow and rainfall event. The U.S. Army Corps of Engineers, Portland District has since worked to refill the Willamette Valley’s 13 reservoirs to their maximum extent possible to prepare for the summer recreation season, while preparing the reservoirs for winter precipitation events.
In the span of two months, the Willamette Valley witnessed a snow storm and a high water event that increased inflows into the system. All that precipitation at once is great for the summer recreation season, right?
The short answer: no. The Willamette Valley is a rain-driven system, and uses snowpack to supplement water inflows throughout the summer. While the Valley’s snowpack continued to build into March, the April rain event melted a significant portion of that snowpack, which left little to be used for the late summer months.
Inflows from the April rain event required the Corps to release water from the Willamette Valley Project’s 13 dams to draft back down to meet our rule curve, or the authorized maximum water elevation on a given day. This rule curve sets guidelines for flood risk management and balancing project benefits.
Right now, the Willamette Valley Project’s 13 reservoirs are 72% full. Detroit and Fern Ridge reservoirs are 96% full. Cougar reservoir is currently at the lowest elevation, at 33% full, to augment for mainstem flows as well as low summer flows for U.S. Forest Service in-stream habitat restoration.
The Corps manages the Willamette Valley dams and reservoirs to work as a system to provide flood risk management, recreation, water quality and supply, and more to the region.
Weather and numerous other factors impact water levels in the Willamette Valley's lakes and reservoirs throughout the summer and fall, including the Willamette Biological Opinion – which focuses on meeting target flows for fish downstream.
The Corps encourages the public to check reservoir levels before heading out the door. Visit the teacup chart for up-to-date reservoir levels: http://www.nwd-wc.usace.army.mil/nwp/teacup/willamette/.
For additional information or questions regarding water levels, call the Willamette Valley Project ranger staff at 541-942-5631.