SEATTLE -- UPDATE (Dec. 21): At 7 a.m., USACE, Seattle District's Reservoir Control Center (RCC) returned control of Ross Dam to Seattle City Light.
UPDATE (Dec.19): Ross Dam is scheduled to return to Seattle City Light around Dec. 21, unless conditions change.
UPDTE (Dec. 18): At 1:00 a.m., USACE, Seattle District's Reservoir Control Center (RCC) returned control of Upper Baker Dam to Puget Sound Energy.
UPDATE (Dec. 17): At 8:30 a.m., Dec. 15, USACE, Seattle District's Reservoir Control Center (RCC) assumed control of Ross Dam and Upper Baker Dam operations, due to a natural flow forecast of the Skagit River at Concrete, Washington, showing over 90,000 cfs within eight hours. This action is meant to reduce flood risk on the Skagit River as forecasts predict high flows and additional atmospheric river impacts Dec. 17-18 in coordination with Skagit County.
USACE reservoir regulators are providing reservoir release instructions to Puget Sound Energy for Upper Baker Dam and Seattle City Light for Ross Dam, to minimize flood impacts at Concrete and the downstream communities on the Skagit River. The current flow at Concrete is approximately 56,000 cfs. USACE is coordinating with Skagit County Emergency Management in accordance with flood operations protocol. No major concerns or impacts are expected at the current flows.
The RCC retains control of Ross Dam and Upper Baker Dam releases until flows recede and it is able to release the water stored during this flood operation. Because of the water stored during last week’s flood event, it may take longer than usual to draft the reservoirs below our flood control pools and to hand back control to the utilities.
High flows are anticipated across Western Washington throughout the week, and all USACE projects in western Washington are in flood operations. USACE will continue to monitor conditions and adjust regulation as needed for flood risk management.
The U.S. Army Corps of Engineers (USACE), Seattle District, is regulating water flow in the Skagit River Basin in response to ongoing atmospheric rivers.
On Dec. 8, USACE Reservoir Control Center’s (RCC) assumed control of operations at Ross Dam, which is owned by Seattle City Light, and Upper Baker Dam, owned by Puget Sound Energy. The team began regulating water flow to manage the impacts of heavy rainfall and mitigate potential flooding.
On Dec. 12, the peak pool at Ross Dam reached 1,594.53 feet at 4 a.m. Once flows at Concrete, Washington, dropped below major flood stage, USACE began drafting water from the reservoir to create flood control space and prepare for additional rainfall. Regulating water flow from both dams helped to reduce the peak river stage in Concrete, Washington.
“We are using available storage space in these reservoirs to reduce the peak flow level downstream as much as much as possible to lessen the impact on downstream communities,” said Kyle Comanor, senior water manager for Seattle District’s Western Washington division. “However, residents should be prepared for high river levels to return as the next atmospheric river hits our region Sunday night into Monday."
On Dec. 11, inflows into Ross Dam peaked at approximately 50,000 cubic feet per second (cfs). In response, outflows from Ross Dam were reduced to the minimum flow of 450 cfs, marking a reduction of more than 100 times the peak flow rate. Without this strategic reduction, peak stages in Concrete and Mount Vernon, Washington, could have been much higher, leading to more severe flooding.
Despite using Ross and Upper Baker Dams to their fullest extent possible to reduce downstream flood stages, Mount Vernon, Washington, still endured a record flood stage of over 37.7 feet. Uncontrolled rivers and streams in the basin, such as the Sauk River, contributed to this unprecedented flooding.
“This is not a typical weather event,” said Mark Stoelinga, a USACE meteorologist with Seattle District. “We are managing unprecedented rainfall and runoff to minimize risks to local communities.”
The RCC water management team continues to monitor water levels and regulate flows to mitigate flooding impacts. By storing excess water during peak inflow events and releasing it at a controlled, slower rate, USACE helps to "blunt" the peak flow, spreading the volume of water over time and reducing the severity of flooding downstream.
This approach significantly reduces the risk of infrastructure damage and potential loss of life.
For more information, residents are encouraged to visit Skagit County’s Emergency Management website at https://www.skagitcounty.net/Departments/emergencymanagement/main.htm
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