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Mill Creek

Project Type: Flow Restoration
Location: Walla Walla Watershed

WWT has worked with the Confederated Tribes of the Umatilla Indian Reservation, the City of Walla Walla and landowners to help rewater 31 miles of Mill Creek that would get almost entirely diverted in late summer, and support passage for threatened summer steelhead and bull trout to quality upstream habitat.

Our Approach
  • Helping Rivers Flow
  • Restoring Landscapes for Water
  • Planning for Future Water Uses
  • Finding Alternative Water Sources

Mill Creek, a tributary of the Walla Walla River, was identified under the national water quality list as having insufficient stream flow and high water temperatures, which severely limit access for both summer steelhead and bull trout upstream habitat.

Because the Maxson family was committed to habitat restoration on their property, they enrolled in the Conservation Reserve Enhancement Program (CREP), which helped them return several acres of their lands to natural habitat that would support deer and upland bird populations. WWT worked with the Maxons to place their water rights associated with CREP riparian buffers into the Trust Water Program where they are protected for instream flows. As a result, the family combines flow restoration with riparian habitat restoration through CREP, while continuing to support a horse boarding/training facility and a variety of crops on their property.

With collaborative efforts, this project created multiple benefits in the Walla Walla Basin. Summer steelhead and bull trout in the basin are listed as threatened under the Endangered Species Act. High stream temperatures and insufficient stream flows in Mill Creek have severely limited the accessibility of both of these species to quality habitat upstream, and their ability to use the lower reaches of Mill Creek for spawning and rearing. Mill Creek is used primarily as a migration corridor for both adult and juvenile steelhead, but supports spawning and rearing as well. Bull trout use the creek for migration, but winter over when stream flows are sufficient. Spring Chinook, extinct since the 1950s are being introduced by the Confederated Tribes of the Umatilla Indian Reservation and may eventually use Mill Creek as a passage corridor or for winter rearing.

At a Glance

Working Partners
  • Confederated Tribes of the Umatilla Indian Reservation
  • City of Walla Walla
  • WA Dept. of Ecology
  • Bonneville Power Administration
  • National Fish & Wildlife Foundation
  • Walla Walla County Conservation District
  • Local water rights holders
ESA-listed Fish Species
Summer Steelhead
Bull Trout
Non-ESA-listed Fish Species
Spring Chinook
Total Projects In This River/Tributary
Level of Climate Threat
The projected impact of climate change on summer streamflows by 2040 (via Washington Department of Ecology).
Streamflow restored
River Miles Benefitting