Court injunction delays refilling of Willamette Basin reservoirs

Though not ordered to delay and still early in the season, Dorena (above) and Cottage Grove lakes are off to a slow start refilling.

Some reservoirs in the Willamette Basin will delay refilling this year due to a court injunction aimed at improving water quality and passage for threatened fish species. 

Neither Dorena nor Cottage Grove reservoirs are named in the injunction; the refilling period for the local reservoirs began on Feb. 1 this year. 

However, U.S. Army Corps of Engineers (Corps) water managers will delay refilling Cougar and Fall Creek reservoirs and conduct spill operations at Foster Dam as required by the injunction. 

The delay at Cougar and Fall Creek will impact the Corps’ ability to refill the reservoirs to their normal summer levels, which in turn is expected to impact boating and recreation activities at those locations. 

The court order came last fall, granting in part a motion for injunctive relief to plaintiffs Northwest Environmental Defense Center, WildEarth Guardians and Native Fish Society’s regarding concerns over endangered salmonid species. 

On Sept. 1, 2021, the U.S. District Court for the District of Oregon issued an interim injunction that requires the Corps to undertake specific actions to improve fish passage and water quality at several Willamette Valley Project dams for the benefit of Upper Willamette River (UWR) spring Chinook salmon and UWR winter steelhead salmon, both of which are listed as threatened under the Endangered Species Act. 

The Corps is working in coordination with the National Marine Fisheries Service, U.S. Fish and Wildlife Service, Bonneville Power Administration, and U.S. Bureau of Reclamation to implement the injunction measures, some of which began in fall 2021. 

Though the injunction is not impacting Cottage Grove or Dorena reservoirs, the lakes are still off to a slow start meeting ideal levels as February has seen very little precipitation. 

“Every year, we strive to meet the public’s expectations surrounding water availability within the Willamette Valley System of reservoirs during the summer,” said Erik Petersen, operations project manager, in a press release. “There are and will always be constraints on how we manage water. People can look to last year’s drought and several challenging water years over the last couple of decades to see some of the difficulties we face. However, we must find ways to protect threatened fish species if we want to continue enjoying the other benefits these dams provide and will absolutely align with the intent and direction of the court.” 

The Corps’ thirteen Willamette Valley reservoirs support a variety of purposes, most notably flood risk management, fish and wildlife, water quality, hydropower generation and recreation. 

The reservoirs are kept at a lower level in the winter to reduce downstream flooding and are refilled in the spring in preparation for the conservation season, where water upstream is used for recreation and downstream is used to maintain adequate summertime flows in the rivers for fish, water quality and irrigation. 

The Army Corps of Engineer’s “water control diagram” sets the ideal water levels throughout the year. 

From mid-May to the beginning of September, water is to be maintained at the lakes’ highest conservation levels. In the autumn, there is a gradual drop and, through the winter, water levels are maintained at their lowest point. 

On Feb. 1, lake levels begin a steady climb back along a curve up to the maximum pool. 

Congressional edict sets the water management requirements of dammed lakes. 

“And that’s why when sometimes people say, ‘Well, why don’t you fill it earlier?’ or, ‘Let it be full later,’ we will say, ‘Well, this literally would take an act of Congress to change the way we operate the dam, because that’s how they were authorized to be operated,’” U.S. Army Corps of Engineers Park Ranger Christie Johnson told The Sentinel during last year’s drought. 

The Willamette Basin relies heavily on rainfall to refill its reservoirs, meaning Dorena and Cottage Grove lakes cannot depend on snow melt to meet desired levels. Because of the drought, both lake levels hit record lows last year and failed to reach the recommended levels by a wide margin. 

With the refill period only having started a couple weeks ago, however, it is too early to tell if the lakes are in danger of a repeat from last year. 

Also, because annual water year forecasts have high variability, it will be difficult to predict with certainty all potential impacts until later in the spring. 

Corps officials have stated they are aware of the potential affects to recreation visitors and will work to share information as limitations to access and use of reservoirs becomes clearer. 

For those visiting other reservoirs in the Willamette Valley Basin, the Corps has released information about the delays: 

Fall Creek: The Corps will hold Fall Creek Reservoir, 22 miles southeast of Eugene, to 700 ft. above sea level until mid-March and then refill and hold at 728 ft. through May. This may eliminate use of two boat ramps for use: Cascara and Winberry. However, North Shore may be available. Corps staff is unsure of how that will impact camping opportunities. 

Cougar: Corps water managers will not substantially refill Cougar, 50 miles east of Eugene, until May 1, attempting to reach 1,571 ft. by July 1. However, no boat ramps will be available at that reservoir elevation, and typically, precipitation available to refill after that date is minimal. 

Foster: The Corps will use spillways to release water for fish passage and maintain a reservoir elevation of 613 ft. until early April at Foster Dam in Sweet Home, Ore., which is below the elevation of two boat ramps: Calkins Park and Gedney. By May 11, the Corps plans to have lake levels up to 637 ft. by using water from Green Peter Reservoir, a few miles northeast of Sweet Home. 

While this is a consistent operation as in years past, Foster refill will be a little later than normal, and that could impact water levels at Green Peter, depending on the rest of the refill season. 

Low water levels may make boating more hazardous, so boaters should take extra precaution and always wear a life jacket. 

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