The Six Major Rivers of the Columbia River System

The **Columbia River Basin** (668,000 km² / 258,000 sq mi) is drained by six principal rivers that form the Columbia River System:

1. Columbia River (Mainstem): 2,000 km (1,243 mi). Source: Columbia Lake, BC. Mouth: Astoria, OR/WA.
2. Snake River: **Largest tributary** (1,735 km / 1,078 mi). Source: Yellowstone, WY. Joins Columbia at Tri-Cities, WA. Hells Canyon (deepest gorge in NA).
3. Kootenay (Kootenai) River: 780 km. BC → Montana/Idaho → BC → Columbia. Libby Dam (Lake Koocanusa).
4. Pend Oreille River: 209 km (lower). Outlet of Lake Pend Oreille (ID). Joins Columbia in BC. Includes Clark Fork (source in MT).
5. Spokane River: 179 km. Lake Coeur d'Alene (ID) → Columbia (WA). Spokane Falls, hydro dams.
6. Yakima River: 344 km. Entirely in WA. Cascade headwaters → Columbia (Richland). Heavily irrigated (Yakima Valley).

Other Significant Tributaries

• Willamette (OR), Deschutes (OR), John Day (OR), Wenatchee, Methow, Okanagan (BC/WA), Clearwater (ID), Salmon (ID).

System Significance

• **Hydropower:** 60% of PNW electricity (Grand Coulee, Chief Joseph, Bonneville, etc.).
• **Salmon/Steelhead:** Iconic anadromous runs (endangered).
• **Irrigation:** 3M+ hectares.
• **Navigation:** 750 km inland to Lewiston, ID (barges).
• **Treaty:** Columbia River Treaty (1964, US/Canada) — flood control, power sharing.

Six major rivers, one interconnected lifeline for the Pacific Northwest.