Boulder City, Nev.—Lake Mead, the largest reservoir in the U.S., has reached its lowest water level since it was filled nearly 90 years ago, underscoring the ongoing crisis in the Colorado River system. Federal data indicate Lake Mead’s water level hit 1,040.4 feet (317.1 meters) above sea level last Friday. This is slightly below the elevation of 1,040.58 feet (317.27 meters) recorded previously on July 28, 2022. Lake Mead straddles the Arizona-Nevada border near Las Vegas.

This recent low follows a winter with the worst snowpack recorded in the Colorado River Basin. The melting snow is essential for the river that supports farmers, industries, wildlife, hydropower producers, and over 40 million people across seven U.S. states, tribal nations, and Mexico.

Federal officials announced a short-term plan last week to prevent a crisis in the waterway. States dependent on the river, including California, Colorado, Arizona, Nevada, New Mexico, Wyoming, and Utah, have struggled to agree on a long-term water-sharing strategy. The proposal involves California, Nevada, and Arizona sharing water cuts.

Chronic overuse, drought, and rising temperatures have severely depleted Lake Mead and the country’s second-largest reservoir, Lake Powell. These reservoirs are at their lowest levels in nearly 70 years. To safeguard the system’s hydropower capabilities, federal officials stated that they will avoid releasing cool Lake Powell water from Glen Canyon Dam in Arizona to protect the habitat of a threatened native fish species.

Severe drought conditions on Lake Mead in 2022 exposed human remains and led officials in Las Vegas to pump water from deeper within the reservoir to supply water to millions.

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