The Yakima Basin in Washington State is undergoing a seasonal shift that affects how water moves through the river system.
Each year when this happens, the U.S. Bureau of Reclamation and local irrigation districts perform an operation called the “flip-flop”.
The name comes from the way reservoir releases are adjusted across the basin. Some releases are reduced while others are increased.
One of the objectives of the operation is to create favorable conditions for Chinook salmon spawning. Another goal of the operation is to build up reservoirs to hold water for future months.
River flow patterns are expected to change over the coming weeks.
Water managers are advising people who work or recreate near area rivers to use caution as conditions change.
River operations begin shifting across the basin
The Bureau of Reclamation began conducting its annual flip-flop operation in the Yakima Basin recently.
As part of this operation, releases from Rimrock Reservoir have already started to increase and are expected to peak around September 15. Additional adjustments to releases will begin immediately after Labor Day.
Water will be diverted through Spillway 1146, operated by the Kittitas Reclamation District, into the Yakima River at Thorp.
Buoys and warning signs will be placed by Reclamation at river crossings by September 8.
These buoys and signs are expected to remain in place until October 15, or until spillway releases stop. Recreationists and employees working near the river should take precautions because of the turbulence associated with the spillway releases.
River users should steer away from areas of rapid current caused by spillway discharges and be mindful of warning buoys.
River conditions can appear quite different from just a few weeks ago.
Flow adjustments create conditions for spawning
Although the flows may seem dramatic, the primary focus of the flip-flop is to provide suitable fish habitats.
The overall goal of the flip-flop is to create instream conditions that are favorable for Chinook salmon spawning in the upper Yakima, Cle Elum, and Bumping Rivers. The operation also aims to create better conditions for egg incubation after spawning.
The flip-flop achieves this by altering how water is released from reservoirs throughout parts of the basin.
Releases from upper reservoirs are lowered, while releases from lower reservoirs are increased.
That shift is why it is called a “flip-flop”.
Stabilizing river flows during a key period for salmon is an objective of the flip-flop strategy, according to the Bureau of Reclamation. The annual operation is part of broader basin management efforts.
After mid-September, river operations gradually transition back to normal conditions, completing the annual cycle.
Reservoir storage remains part of the strategy
The flip-flop is not limited to only the current river conditions.
Additionally, it provides improved reservoir storage headed into winter and prepares the system for next spring’s irrigation season.
The operation provides benefits for several water users across the basin.
Among those that will be impacted by the seasonal changes caused by the operation are farmers and irrigators.
Coordination helps guide the seasonal transition
Coordination among local districts, municipalities, and stakeholders is necessary for this effort. Chad Stuart, manager of Reclamation’s Yakima Field Office, said that cooperation is essential.
The Bureau of Reclamation states that annually flipping flows helps meet basin-wide needs regarding water, fish, and public safety. It supports both ecological and agricultural demands as the basin transitions into the next water year.
River flows will continue to be monitored while the operation is underway. Streamflow data continues to be monitored using Reclamation’s real-time monitoring systems.
Currently, the seasonal shift is an intentional change in how water moves through part of the basin.
For the next few weeks, one set of releases will go down while another goes up.
After mid-September, operations will gradually return to their normal pattern. Until then, water managers will continue balancing river conditions and reservoir storage.
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