News Release
| Release Number: | 06-009 |
| Dated: | 1/19/2006 |
| Contact: | Heidi Y. Helwig, 503-808-4510 |
Portland, Ore—Just one foot of water can mean the difference between a wet sidewalk and a wet welcome mat. The U.S. Army Corps of Engineers continues to store as much water as possible in its Willamette Basin dams to keep those welcome mats dry, though as the reservoirs continue to fill—Fern Ridge Dam was about less than 1 foot from full at 4 a.m. Jan. 19—water must be released downstream.
“With two to three times the normal amount of precipitation over the last 30-40 days, and larger than expected inflow into the reservoir, our operating strategy is to increase releases from Fern Ridge Reservoir,” said Julie Ammann of the Corps’ Reservoir Control Center. Releases will be increased to about 4,200 cubic feet per second by the end of today. Even at this rate, flows at Monroe should remain below flood stage, she said, though she noted low-lying agricultural lands or homes built in lower areas may experience minor flooding. “The increased release of water will help to regain valuable storage space in the reservoir now to prepare for any future rain events,” Ammann said.
Expect local rivers to flow high, as the Corps will continue releasing water from its reservoirs between storms to provide more flood damage reduction space in the reservoirs. When the next storm arrives, the Corps will reduce releases, if possible, and store water to reduce downstream impacts. With storms occurring in rapid succession in the last four to six weeks, without adequate time in between to diminish the reservoir storage effectively, the already complex job of managing water in the reservoirs becomes even more complicated, said Erik Petersen, operations manager for the Willamette Valley Projects. The Corps will evaluate and adjust releases hourly.
Without the Corps dams in place, however, it would be a miracle to find a dry welcome mat anywhere on the Long Tom River downstream of Fern Ridge Dam and in many locations across the Willamette Valley, low-lying land or not, Amman said.
Corps Calculations show that after the New Years Eve rain event, reservoirs were managed to reduce river levels on the Middle Fork of the Willamette River near Jasper, Fall Creek, Hills Creek and Lookout Point by 8.8 feet—the unregulated peak reached 6.1 feet—and reduced flows by 56,000 cfs.
On the Coast Fork of the Willamette near Goshen, water regulators stored flood waters and made controlled releases through Cottage Grove and Dorena dams to keep river levels 5.4 feet lower than would have been possible without the dams. On the Long Tom River at Monroe, Fern Ridge Reservoir was managed to reduce downstream river levels by 3.8 feet and reduced flows by 12,000 cfs. The regulated peak stage and flows reached 8.7 feet and 6,200 cfs, respectively.
On the McKenzie River at Vida, Blue River and Cougar reservoirs reduced river levels by 5 feet and reduced flows by 23,000 cfs. Downstream river levels on the South Santiam River at Jefferson were reduced by 5 feet with careful regulation of Green Peter and Foster dams. Detroit Reservoir storage and release schedules reduced North Santiam River levels by 4 feet and reduced flows by 27,000 cfs.
On the Willamette River at Eugene, Salem and Oregon City, river levels would have been 12.8 feet, 7 feet and 3 feet higher, respectively.
The Corps works closely with the National Weather Service to run daily operational models. Based on these models, the Corps makes operational decisions about how much water to release and sends these schedules directly to the projects. On-site project operators physically make the operational changes.
The 13 dams in the Willamette Valley control runoff from 27 percent of the total Willamette Basin. Since the dams were built, they have cumulatively prevented more than $18.6 billion in flood damages.
In addition to minimizing flood damages, Corps reservoirs also are operated for hydropower, irrigation, fisheries, water supply, water quality and recreation. The Corps’ goal is to effectively balance these competing needs to serve the region and its people.