Umatilla and Walla Walla (Major Population Group)
The Umatilla/Walla Walla MPG includes three extant steelhead populations in the Umatilla, Walla Walla, and Touchet rivers and one extirpated population from Willow Creek. The Umatilla River is in Oregon, the Touchet River in Washington, and the Walla Walla River is in both states. The Umatilla River originates in the Blue Mountains of northeastern Oregon and flows north and west to enter the Columbia River at river kilometer (rkm) 465. Land use is mostly dryland and irrigated agriculture. The Walla Walla River also originates in Oregon and flows northwest into Washington to join the Columbia, while the Touchet originates in the Blue Mountains on the Washington side and flows south and west into the Walla Walla. The Walla Walla River basin is extensively and intensively irrigated, with timber harvest in the high and mid elevations. All three populations in this MPG are summer run. The Umatilla River and Walla Walla River populations are monitored with dam counts, PIT tag arrays, and spawning ground surveys.