PORTLAND, OR - The U.S. Army Corps of Engineers, Northwestern Division, in coordination with its Portland, Seattle, and Walla Walla Districts as well as B.C. Hydro, Bonneville Power Administration, U.S. Bureau of Reclamation, the National Weather Service’s, Northwest River Forecast Center, and others are continuing to monitor river conditions across the Columbia River Basin.
The flow levels in many tributaries are receding with the lighter precipitation forecast through the week, but flooding continues in the Spokane Basin and in the Snake River and tributaries above Weiser, Idaho, with isolated locations scattered elsewhere in the basin including Vancouver, Washington. Flows are expected to recede to levels below flood stage at several of the tributary locations over the next week.
While flows are receding, the U.S. Army Corps of Engineers must release additional water from storage reservoirs to create adequate space to manage the high flows expected during the spring runoff. “The dams in the reservoir system are operating as designed,” said Steve Barton, Chief of the U.S Army Corps of Engineers Columbia Basin Water Management Division. “To meet flood risk management requirements for the spring runoff, about 3 million acre-feet of water must be released from the storage dams by April 30. This is enough water to cover the state of Massachusetts in about 6 inches of water.” How these releases impact river stages will largely depend upon weather and snowmelt.
Snowmelt is already affecting the current runoff and contributing to reservoir levels. “While we have seen some low and mid-elevation snowmelt, there is still a lot of snow in the mountains waiting to come off,” stated Barton. With more precipitation in the forecast, those living near the Columbia River or tributaries affected by the snowmelt runoff are reminded to be safe around high, fast moving water.
Bonneville Dam on the Columbia River is currently releasing water at a rate of 450,000 cubic feet per second; enough water to fill a football field 8 feet deep in one second. The Columbia River at Vancouver is currently above its flood stage of 16 feet and is expected to rise to just over 17 feet by mid-week.
When levels are above 16 feet some islands and low areas will experience flooding with minor impacts to parks and trails along the river. When levels are above 17 feet, some lowland access roads, parking areas, and trails on Sauvie Island, around Vancouver Lake, and near downtown Vancouver will be flooded. Additionally, access to some house-boat communities will be impaired. Recreation and camping areas at Cottonwood Beach near Washougal and on Government Island will be impacted. When levels are above 18 feet, unleveed lowland, pasture, and farmland will begin to flood. The main impacted areas have historically been from Sauvie Island downstream to Woodland, WA. There will also be some inundation of parks and trails along the Columbia in and near Vancouver and Portland. To track and understand direct impacts please visit the National Weather Service’s Advanced Hydrologic Prediction Service.
Flows are forecast to remain high into April as upstream storage projects increase releases to create reservoir space to store spring snowmelt. The Willamette and Columbia rivers join together near Portland and Vancouver. As Willamette River flows recede, flows through dams on the Columbia River can increase, likely holding the gage at Vancouver within 1-foot of flood stage.
Public safety is a priority and the public is urged to follow local emergency management officials for guidance if necessary.
For maps of hydrology on the Columbia River visit the Northwest River Forecast Center:
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