Map Shows 6 US Reservoirs at Their Lowest May Levels in 30 Years

Six major U.S. reservoirs have fallen to their lowest levels in at least three decades for this time of year, according to federal data, highlighting mounting pressure on water supplies as drought conditions persist across parts of the country.

The dams were flagged by the Bureau of Reclamation's reservoir storage dashboard, which tracks water levels at more than 50 major sites and compares them with historical data dating back to 1990. As of late May, six reservoirs were at their lowest recorded level for that date in the past 30 years, with one expert telling Newsweek the levels are concerning.

Reservoirs With Low Water Levels

The six reservoirs span multiple states and show sharply uneven conditions. In the Colorado River Basin, the country's two largest reservoirs-Lake Mead and Lake Powell-are both under significant strain. Lake Mead, home of the Hoover Dam, held about 7.8 million acre-feet of water, or 49.2 percent of its typical level for this time of year, while Lake Powell was even lower at 5.7 million acre-feet, just 38.5 percent of average.

This week, a large-scale red, white and blue light display installed for Memorial Day celebrations has illuminated the Hoover Dam even as Lake Mead drops to critically low levels, highlighting the contrast between national celebration and the growing strain on vital infrastructure. The reservoir, which supplies water and power across the Southwest, is not only a key storage site but also central to hydropower generation-meaning continued declines could affect both electricity output and water availability for millions who depend on the Colorado River system.

Elsewhere, storage levels vary widely. American Falls Reservoir in Idaho was at 65.9 percent of typical levels, and Green Mountain Reservoir in Colorado stood at 58.9 percent. Lake Havasu, which also sits on the Colorado River system, remained closer to normal at 91.7 percent.

The most extreme shortfall was recorded at Choke Canyon Reservoir in Texas, where storage had dropped to just 49,551 acre-feet-11.9 percent of its typical level-illustrating how severe conditions have become in some regions even outside the core Western drought zone.

Each of the six reservoirs were recorded at the lowest level for the corresponding late-May date in three decades of data, based on a rolling 30-year baseline that highlights unusually low seasonal conditions even when all-time records are not broken.

Brian Fuchs is a climatologist at the National Drought Mitigation Center, he explained that these reservoir levels are not shocking, but concerning.

"The West had a very low snowpack season," Fuchs told Newsweek. "Many areas had well below normal snow which means that the typical flush of water during the melt out of this snow is not taking place. Many water managers are preparing for less water to deliver and some may have trouble meeting all their needs."

What It Means During Drought

The latest snapshot fits into a broader pattern of intensifying drought across the United States, with large portions of the West, Plains, South and Southeast now facing moderate to exceptional dryness. The combination of persistently warm temperatures, reduced snowpack and uneven rainfall is limiting how much water flows into rivers and reservoirs, particularly at a time of year when systems typically replenish. As a result, some regions are entering the summer with already depleted supplies, increasing the risk of water shortages, agricultural strain and higher energy demand as conditions worsen.

“Currently, 20.19 percent of the continental United States is in extreme drought on the U.S. Drought Monitor with a new update coming out tomorrow,” Fuchs said. “Conservation and smart water usage is key, but some customers will see reduced deliveries and that will impact many, including those in agriculture.”

Pressure is particularly acute in the Colorado River Basin, where Lake Mead and Lake Powell form the backbone of water storage for the Southwest. Together, they supply water to more than 40 million people and underpin a vast hydropower network-meaning sustained declines can have consequences not only for water access, but also energy production and costs.

Drought has repeatedly caused costly damage across the United States, underscoring the broader stakes behind falling reservoir levels.

Over the past four decades, extreme drought events have resulted in tens of billions of dollars in losses, from widespread crop failures to strained water supplies and rising energy costs.

More recently, severe drought and heat in parts of the South and Midwest caused billions of dollars in damages in 2023 alone, alongside hundreds of deaths.

While the current data reflects seasonal lows rather than all-time records, federal projections have warned both reservoirs could again approach or fall below their historical minimum levels if dry conditions persist.

Lower reservoir levels can limit drinking water supplies, reduce irrigation for agriculture and cut hydropower output if water drops below key operating thresholds. With demand set to rise over the summer, current levels offer an early warning of how quickly pressure can build when dry conditions persist.

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This story was originally published May 27, 2026 at 9:48 AM.