About the river

Overview

The Colorado River is a vital source of water, hydropower, recreation, ecosystem services, and other amenities for people in the seven basin states (Colorado, Wyoming, Utah, New Mexico, Arizona, Nevada, and California), over two dozen federally recognized tribes, and the Republic of Mexico. Over 40 million people rely on the Colorado River and its tributaries in part or in full for their municipal water supply, while 5.5 million acres of irrigated crops and pasture depend on this water too. Many of these water uses occur outside of the physical basin, supplied through transbasin diversions. The hydropower facilities at major dams collectively generate over 10,000 megawatt-hours annually when reservoirs are full. A 2014 study estimated the total economic activity across the seven basin states supported by Colorado River water to be $1.4 trillion annually.

The extensive human uses of the river are predicated on an equally extensive system of dams, reservoirs, diversion structures, canals, pump stations, and tunnels that was largely built between the 1930s and 1980s; the linchpins of the system are the enormous mainstem reservoirs Lake Powell and Lake Mead. The Bureau of Reclamation operates the major reservoirs, with many state and local entities helping to operate the system. In total, the reservoirs can store close to 60 million acre-feet, equivalent to about four years of average flow. The vast physical infrastructure controlling the river has developed in parallel with the complex legal and policy framework governing water allocation and operation of the system, known as the Law of the River. All of the major elements of the Law of the River, starting with the 1922 Colorado River Compact, have necessitated new infrastructure, funded it, and/or governed its operation.

In its natural state, the river was a muddy lifeline through a mainly arid region, distributing water, nutrients, and millions of tons of sediment downstream and ultimately to the Gulf of California, creating an extensive and rich delta ecosystem. Dozens of endemic fish species were adapted to the relatively warm and turbid waters of the mainstem and large tributaries. Riparian vegetation and associated species depended on periodic flood flows and flushes of sediment. By heavily regulating streamflows from the mountain headwaters to the mouth, the combined edifice of infrastructure and policy has massively changed the geomorphic and ecological functioning of the Colorado River. The imperilment of federally listed species by these changes has prompted costly and continuing multi-agency management programs to conserve those species.

The current situation

The system’s reservoirs, as designed, have buffered most water users from the vagaries of the large seasonal and annual variability in the river's natural flow even as overall basin water use increased by over 50% between 1960 and 2000. But starting in 2000, an extended dry period along with warming temperatures led to average annual streamflows about 20% lower than the long-term average. During this period of low inflows, full water deliveries to the Lower Basin states (California, Arizona, Nevada) and Mexico continued under the Law of the River, while Upper Basin water use stayed relatively constant as well.

As a result of this chronic imbalance between supply and demand, system storage has declined to levels never seen before, except in modeled future scenarios. Lake Powell, as of October 2022, is at 25% of capacity and is uncomfortably close to the minimum level for producing hydropower--and possibly for reliably delivering any water downstream. Lake Mead is at 28% of capacity, also close to its minimum power pool, and closer to dead pool (i.e., unable to deliver any water downstream) than to half-full.

Under agreements made in 2007 and 2019 to forestall severe system impacts, mandatory ("Tier 1") curtailments of Lower Basin and Mexico water use were first triggered in August 2021, with larger "Tier 2" curtailments, totaling 0.7 million acre-feet per year, triggered in August 2022. Even so, the increasingly tenuous state of the system led the Commissioner of Reclamation to demand, in June 2022, that the seven basin states collectively reduce their annual water uses by an additional 2 to 4 million acre-feet in 2023 to ensure there would be no near-term (1-4 years) complete loss of hydropower or water releases from Powell and Mead. As of October 2022, there has been limited progress by the states in committing to specific additional reductions or taking measures that would plausibly lead to reductions.

This short-term water and power crisis has come to the forefront just as Reclamation, the basin states, tribes, Mexico, and other stakeholders started to revisit the 2007 Interim Guidelines for operating Powell and Mead and addressing basin water shortages, in preparation for developing new long-term guidelines by 2026. The new guidelines will need to incorporate lessons from the post-2000 period, and accommodate the increasing influence of climate change on basin hydrology. Other complex challenges in the basin await further amelioration efforts if not durable solutions, such as unresolved tribal water allocations and infrastructure needs, endangered fish and other species, altered streamflow and sediment regimes below dams, and the shrinking Salton Sea.

Additional resources

Reclamation Colorado River Basin homepage

Includes links to recent Reclamation news releases, 1- to 5-year projections of system conditions

CBRFC Upper Colorado Situational Awareness

Dashboard shows late-fall soil moisture (map) and current snowpack (map); current water-year and month-to-date precipitation (maps); most recent forecasts of April-July and water-year inflows to Lake Powell; observed inflows to Lake Powell.

CBRFC Lower Colorado Situational Awareness

Dashboard shows current soil moisture (map) and current snowpack (map); current water-year and month-to-date precipitation (maps).