Temporary water management for Walla Walla River and Mill Creek

WALLA WALLA – This week, community members in Walla Walla noticed lower-than-normal flows in Yellowhawk Creek. The reduced flows are part of a larger effort to protect water supplies in the greater Walla Walla River Basin and allow fish to migrate to Mill Creek’s upper reaches safely.

As the demand for water increases and supplies dwindle in the Walla Walla River Basin, the Washington Department of Ecology is working with the State of Oregon, the Confederated Tribes of the Umatilla Indian Reservation, and stakeholders on both sides of the state border to find solutions. One of those projects involves temporarily using water rights from Oregon in a new program to protect fish.

According to the agreement, water rights from Oregon have been put into a temporary trust, protecting the water from being diverted for other uses as it flows through Mill Creek and to the Walla Walla River. The temporary trust began Aug. 1 and will continue through Sept. 30. 

The goal is to maintain a minimum of eight cubic feet per second of water in Mill Creek before it enters the Walla Walla River. To achieve this, Ecology uses control points to manage water resulting in some tributaries having less water than typical this time of year.

The temporary changes in water management mean less water is being diverted into Yellowhawk Creek. Ecology is committed to maintaining streamflow in the creek, and fisheries managers are available to respond if conditions change. Ecology’s watermaster for the basin closely monitors water levels and will move as much water as possible down Yellowhawk Creek once the increased flow in Mill Creek is satisfied.

“Fisheries managers from Oregon, Washington, and the Confederated Tribes of the Umatilla Indian Reservation determined that running protected water down the mainstem Mill Creek would be preferable to running it down Yellowhawk, which was the historic practice,” said Jaime Short, water resources section manager for Ecology’s Eastern Region. “Increased flows in Mill Creek will allow fish to migrate to the upper portions of the basin and provide better habitat.”

This temporary water trust is only one of the many efforts underway to increase water supplies and improve habitat in Mill Creek. For example, the U.S. Army Corps of Engineers is working on a weir notching project to make it easier for fish to get upstream. By increasing the summer flows in Mill Creek, Ecology can help this effort.

Ecology was given authority in 2023 to enroll water rights, including rights from Oregon, into Washington’s Water Right Trust program. This effort is part of the overall Walla Walla Watershed Strategy, an effort to improve streamflow and water supplies in the Walla Walla River basin over the next 30 years.

Together with the Confederated Tribes of the Umatilla Indian Reservation, the state of Oregon, and stakeholders on both sides of the state border, the initiative answers the decades-long challenge of meeting the basin’s growing water needs.

As the strategy evolves, the goal remains to improve streamflow and water supplies in the Walla Walla watershed. It will do this by focusing on:

Floodplains, critical species, habitat, and water quality 

Water supply, streamflows, and groundwater 

Land use and flood control

Quality of life 

Monitoring and metering

For questions about the temporary water trust and changes in water management in the Walla Walla basin, contact Ecology Water Resources section manager Jaime Short at 509-990-7636 or Ecology Watermaster Eric Hartwig, at 509-540-7680.