One of America’s largest reservoirs just hit a record low

By summer, the effects of the weak 2025-2026 mountain snowpack in the Upper Colorado Basin had reached Lake Powell. With far less snowmelt than usual feeding the Colorado River, inflows dwindled, and the second-largest reservoir in the United States fell to record-low levels in late August and early September.

Lake Powell Falls Below Its Previous Record

Satellite images captured the dramatic change in Lake Powell near Glen Canyon Dam. The images were collected by the OLI (Operational Land Imager) aboard the NASA-USGS Landsat 8 satellite on September 1, 2017 (left), and September 10, 2026 (right).

In the 2026 image, Lake Powell’s water surface stood at 3,517.24 feet. Roughly a month earlier, the reservoir had already fallen below its previous record low of 3,519.92 feet, which was set on April 13, 2023. Water levels continued declining into early September.

The 2017 image provides a striking contrast, showing Lake Powell during one of its highest water levels of the past decade.

Lake Mead Also Reaches Record Lows

The Colorado River first flows into Lake Powell before continuing downstream toward Lake Mead. In August 2026, Lake Mead also reached record-low levels.

The river system, managed by the U.S. Bureau of Reclamation (USBR) and other agencies, is a critical source of both water and electricity across the Southwest. More than 40 million people depend on it, including residents of Las Vegas, Phoenix, Los Angeles, and San Diego. The river also supplies water to roughly 5 million acres of farmland.

Why Snow Matters So Much to the Colorado River

Much of the Colorado Basin is arid or semi-arid, which makes mountain snow especially important. A substantial share of the Colorado River’s annual flow begins as snow that accumulates at high elevations during winter and melts during spring and early summer.

The Upper Colorado Basin, along with many mountainous regions across the U.S. West, received unusually little snow during winter 2025-2026. The shortage amounted to a snow drought.

Periods of record warmth made conditions worse by further reducing the snowpack. As a result, the spring snowmelt delivered far less water to reservoirs than it normally would, providing little relief for already depleted lake levels.

Emergency Steps to Protect Lake Powell

In April 2026, the USBR began taking measures to stabilize Lake Powell and prevent the reservoir from dropping below the elevation required for hydropower generation.

Without intervention, the agency considered that possibility realistic by August 2026.

To help support Lake Powell, USBR began releasing additional water from Flaming Gorge Reservoir in northern Utah and southern Wyoming. At the same time, officials reduced the amount of water being released from Lake Powell into Lake Mead.

The agency also canceled a “controlled flood” planned for April that was intended to rebuild sandbars used as fish habitat. In August, officials also skipped a “cool mix” release designed to help protect native species.

A Megadrought Continues to Strain the Southwest

Drought in the U.S. Southwest has persisted since around the beginning of the 21st century. Experts have described the prolonged dry period as a megadrought, and it continues to place intense pressure on the region’s limited water supplies.

NASA-supported projects and monitoring systems are giving water managers and other decision-makers across the Colorado Basin more detailed information about drought conditions and how they are changing.

At the Colorado River’s headwaters, for example, a dashboard built around the Western Land Data Assimilation System (WLDAS) provides real-time visualizations of soil moisture, snow water equivalent, and evapotranspiration. The information helps support Colorado’s drought task force and contributes to weekly U.S. Drought Monitor maps.

Satellite Data Helps Track Drought Across the Basin

Closer to Lake Powell, the Drought Severity Evaluation Tool, co-developed with the Navajo Nation, allows leaders to track localized drought indicators, precipitation patterns, and vegetation health across tribal lands. (With funding from NOAA’s National Integrated Drought Information System, its adoption expanded to Oklahoma’s Chickasaw and Choctaw Nations in 2025.)

Another resource, the Colorado River Integrated Assessment tool, was developed by Arizona State University researchers in partnership with the Central Arizona Project. It brings together improved modeling with NASA-satellite-validated measurements of snowpack, surface and groundwater storage, soil moisture, and other conditions throughout the Colorado River Basin in a single interactive system.