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Columbia River Basin
The most notable basin within the region is the Columbia River. The Columbia River is
the largest river in the Pacific Northwest and the fourth largest river in terms of average
discharge in the U.S. The Columbia River drains over 258,000 square miles, and is the
sixth largest in terms of drainage area. Major tributaries include the Snake, Willamette,
Salmon, Flathead, and Yakima rivers. Smaller rivers include the Owyhee, Grande
Ronde, Clearwater, Spokane, Methow, Cowlitz, and the John Day Rivers (see Table 38
for a description of select Columbia River tributaries). The Snake River is the largest
tributary at more than 1,000 miles long. The headwaters of the Snake River originate in
Yellowstone National Park, Wyoming. The second largest tributary is the Willamette
River in Oregon (Kammerer 1990; Hinck, Schmitt et al. 2004). The Willamette River is
also the 19 th largest river in the nation in terms of average annual discharge (Kammerer
1990). The basins drain portions of the Rocky Mountains, Bitteroot Range, and the
Cascade Range.
Table 38. Select tributaries of the Columbia River (Carter and Resh 2005)
Watershed
Snake/Salmon
rivers
Approx
Length
(mi)
Basin
Size (mi 2 )
870 108,495
Physiographic
Provinces*
CU, NR, MR,
B/R
229
Mean
Annual
Precipitation
(in)
Mean
Discharge
(cfs)
No.
Fish
Species
(native)
14 55,267 39 (19)
No. Endangered
Species
5 fish (4 T, 1 E), 6
(1 T, 5 E) snails,
1 plant (T)
Yakima River 214 6,139 CS, CU 7 3,602 50 2 fish (T)
Willamette River 143 11,478 CS, PB 60 32,384
61
(~31)
5 fish (4 T, 1 E),
* Physiographic Provinces: CU = Columbia-Snake River Plateaus, NR = Northern Rocky
Mountains, MR = Middle Rocky Mountains, B/R = Basin & Range, CS = Cascade-Sierra
Mountains, PB = Pacific Border
The Columbia river and estuary were once home to more than 200 distinct runs of Pacific
salmon and steelhead with unique adaptations to local environments within a tributary
(Stanford, Hauer et al. 2005). Salmonids within the basin include Chinook salmon, chum
salmon, coho salmon, sockeye salmon, steelhead, redband trout, bull trout, and cutthroat
trout.