The Colorado River is running low because of a collision between two forces: a megadrought that has shrunk the river’s natural supply and decades of water use that consistently exceed what the river can provide. The region’s 22-year drought is the driest period the American Southwest has experienced in at least 1,200 years, and rising temperatures are making it worse by pulling more moisture out of the landscape before it ever reaches the river.
A 1,200-Year Drought
The current drought across the Southwest isn’t an ordinary dry spell. It began around the year 2000 and has persisted for more than two decades, qualifying it as a megadrought. A 2022 study led by UCLA researchers confirmed it is the most severe drought the region has seen in at least 1,200 years. Prior to this one, the last megadrought of comparable length ended over 400 years ago.
What separates this drought from historical ones is the role of human-caused warming. Earlier megadroughts were driven entirely by natural climate variability. This one has a compounding factor: higher temperatures accelerate water loss across the entire Colorado River Basin, making even modest reductions in rainfall far more damaging to river flow.
How Warming Shrinks the River
Less rain and snow is only part of the problem. Even in years with decent snowfall, the river receives less water than it used to. A study published in Science estimated that the Colorado River loses about 9.3% of its annual flow for every degree Celsius of warming. The mechanism is straightforward: as temperatures rise, snow melts earlier and exposes darker ground and vegetation, which absorbs more sunlight and drives more evaporation. Water that would have flowed into the river instead evaporates back into the atmosphere.
The damage is concentrated in the mountains. Roughly 30% of the Colorado River Basin is high-elevation snowpack territory, the zone where snow accumulates in winter and melts into streams each spring. That zone is responsible for most of the river’s water. But warming has caused these snowpack regions to dry out at double the rate of lower-elevation areas. Research in Water Resources Research found that 86% of the basin’s runoff losses are coming from these critical high-altitude areas alone. In practical terms, even a good snow year no longer translates into a full river the way it once did.
More Water Promised Than the River Has
The legal framework governing the Colorado River was built on a flawed assumption. The 1922 Colorado River Compact divided the river between the Upper Basin states (Colorado, Wyoming, Utah, New Mexico) and the Lower Basin states (Arizona, California, Nevada), giving each group 7.5 million acre-feet per year. A later treaty added 1.5 million acre-feet for Mexico, bringing total commitments to 16.5 million acre-feet annually.
The problem is that 16.5 million acre-feet was based on flow measurements taken during an unusually wet period in the early 20th century. The river’s long-term average is lower, and in recent drought years, actual flows have fallen well below the amounts promised on paper. For decades, the gap was covered by drawing down reservoir storage. That strategy worked until the reservoirs themselves started running dangerously low.
Where the Water Goes
About 40 million people across seven states and parts of Mexico depend on the Colorado River, but the vast majority of the water doesn’t flow to cities. Irrigated agriculture accounts for 74% of all direct human water use from the river and 52% of total consumption (including evaporation and other losses). The single largest crop category is cattle feed. Alfalfa and other grass hays grown to feed livestock consume 46% of all water directly used from the river.
This means nearly half the river’s usable water goes to growing animal feed, much of it in desert regions that require heavy irrigation. Urban areas like Las Vegas, Phoenix, and Los Angeles use a significant but comparatively smaller share. Any serious plan to balance the river’s budget has to address agricultural consumption, which is why water rights negotiations have become so politically charged.
Reservoir Levels Tell the Story
Lake Mead and Lake Powell, the two largest reservoirs in the United States, serve as the river’s savings accounts. Both have dropped dramatically since 2000. As of early 2026, Lake Mead’s water surface sat at roughly 1,066 feet elevation. Its full pool level is 1,221 feet, meaning the reservoir remains far below capacity. When Lake Mead dropped below 1,075 feet in previous years, it triggered the first-ever federal water shortage declarations, forcing mandatory cuts to Arizona, Nevada, and Mexico.
Lake Powell, upstream at Glen Canyon Dam, was measured at about 3,534 feet elevation in early 2026. Its full pool is 3,700 feet. Below 3,490 feet, the dam can no longer generate hydroelectric power, a threshold that came uncomfortably close in 2022 and 2023. Losing hydropower at Glen Canyon would affect electricity for millions of customers and remove a critical tool for managing downstream water releases.
What’s Being Done
In 2023, Arizona, California, and Nevada reached an agreement to conserve at least 3 million acre-feet of Colorado River water by the end of 2026, with at least half of that total saved by the end of 2024. This Lower Basin Plan combines voluntary conservation, compensated water reductions, and operational changes to keep reservoir levels from hitting critical thresholds.
These measures have provided some breathing room. A few wet winters, including a strong 2023 snowpack season, helped push reservoir levels up modestly. But conservation agreements and lucky weather haven’t closed the fundamental gap between how much water the river produces and how much is allocated. Negotiations over permanent, post-2026 rules for the river are ongoing, and they will likely require deeper cuts to agricultural and municipal water use across every basin state.
Ecological Damage Along the River
The river’s decline is reshaping ecosystems that evolved over millions of years. Four fish species found nowhere else on Earth, the Colorado pikeminnow, razorback sucker, bonytail, and humpback chub, depend on the river’s historically warm, silty, turbulent waters. Dams already transformed the river’s character decades ago by releasing cold, clear water from the bottom of reservoirs. Low water levels compound the problem by altering water temperatures, flow patterns, and habitat availability even further.
The Colorado River famously no longer reaches the sea in most years. Its delta at the Gulf of California, once a vast wetland, has largely dried up. The combination of upstream diversions and drought has left almost nothing for the river’s final stretch, turning what was once a rich estuary into cracked mudflats.