01
Basin Water System
The Colorado runs about 1,450 miles from its headwaters near Grand Lake to Mexico, gathering the Green, San Juan, Gunnison, Yampa and Gila. It is a snowmelt river: high rim areas covering 15% of the basin generate most of its flow. The 1922 Compact divides it at Lees Ferry, Arizona, into an Upper and a Lower Basin. The river supplies Los Angeles, San Diego, Phoenix, Tucson, Las Vegas, Salt Lake City, Denver and Albuquerque, two Mexican states and 5.5 million irrigated acres. Twenty-two Basin Tribes hold recognised rights to about 3.2 MAF a year, 22–26% of average supply. Warming of about 1.4°C has already reduced flow; each further 1°C cuts it by roughly 9%.
02
Resources & Demand
Use now exceeds supply. Consumptive use averaged 13.1 MAF a year in 2020–2024, while natural inflows averaged 12.9 MAF in 2000–2024. The Lower Basin accounts for 49% of use, the Upper Basin 29%, Mexico 11% and reservoir evaporation the remaining 11%. Agriculture dominates, and the basin grows about 90% of US winter vegetables. Conservation is starting to show: Lower Basin use fell to 5.75 MAF in 2025, the lowest since 1983, and Southern Nevada returns 99% of its indoor water to Lake Mead for credit. Groundwater offers less relief downstream, where recharge is projected below the historical 25th percentile in 77% of future decades.
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03
Infrastructure & Governance
Storage of about 60 MAF, roughly four years of average flow, is concentrated in Lake Powell and Lake Mead, which together hold 85% of it. Their condition sets the system's limits: below 3,490 feet Glen Canyon Dam can no longer generate power, and Hoover Dam loses 70% of its capacity below 1,035 feet. The 1922 Compact apportions 7.5 MAF a year to each basin, and the 1944 Treaty guarantees Mexico 1.5 MAF, administered through binational minutes. The 2007 Interim Guidelines and 2019 Drought Contingency Plans expire on 31 December 2026. After the states missed the February 2026 deadline, Reclamation's July 2026 Final EIS set an adaptive framework for 2027–2036, with Lake Powell releases of 5.0–12.0 MAF.
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04
Investment & Resilience
Federal funding has carried the drought response. The Inflation Reduction Act has funded over USD 2 billion of Lower Basin conservation contracts toward up to 3.0 MAF of savings through 2026, and Mexico committed a further 400,000 acre-feet under Minute 330. Longer-term supply is shifting toward reuse. Pure Water Southern California is planned to purify up to 150 million gallons a day; its environmental review was certified in February 2026, and it has received a USD 80 million state grant and a USD 125 million federal grant. Tribal settlements carry the largest sums: one pending act proposes over USD 5 billion for the Navajo Nation, Hopi Tribe and San Juan Southern Paiute Tribe.
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05
Key Challenges
- Keeping Lake Powell above its 3,490-foot minimum power pool after the water year 2026 release cut from 7.48 to 6.00 MAF.
- Sharing Lower Basin shortages of up to 3.6 MAF in critically dry years, with junior Arizona users exposed first.
- Agreeing a binational successor to Minute 323 for Mexico's post-2026 contributions.
- Integrating 3.2 MAF of recognised Tribal water rights and pending settlements into the new operating framework.