Seven U.S. States Touched by the Colorado River

The Colorado River and its tributaries drain 246,000 sq mi (637,000 km²) across the Southwest. The mainstem directly borders or flows through seven U.S. states before crossing into Mexico (where it historically reached the Gulf of California).

States in Downstream Order

1. Colorado – Headwaters in Rocky Mountain NP (La Poudre Pass, 10,184 ft).
2. Utah – Enters via Canyonlands NP; major tributary: Green River.
3. Arizona – Grand Canyon, Lake Mead, forms AZ–NV & AZ–CA borders.
4. Nevada – Lake Mead shoreline; Las Vegas draws 90 % of water from here.
5. California – Imperial Valley agriculture (All-American Canal), Salton Sea inflow.
6. New Mexico – Only via tributary (San Juan River); small northwestern corner.
7. Wyoming – Only via tributary (Green River headwaters in Wind River Range).

Key Infrastructure

• Glen Canyon Dam / Lake Powell (AZ/UT) – 24.3 MAF storage.
• Hoover Dam / Lake Mead (AZ/NV) – 26.1 MAF; largest U.S. reservoir.
• Imperial Dam & All-American Canal – diverts 3.1 MAF to CA/AZ agriculture.

Compact & Crisis

The 1922 Colorado River Compact allocated 15 MAF/yr (7.5 each to Upper & Lower Basins) plus 1.5 MAF to Mexico (1944 Treaty). Structural deficit (demand ~16.5 MAF vs. 21st-century avg. flow ~12.5 MAF) has triggered Tier 1/2 shortages (2022–24), mandatory cuts to AZ, NV, Mexico. Renegotiation of post-2026 guidelines underway.