The Gila River is among the Southwest’s most important rivers, delivering water for people, farms, and wildlife while linking the snow-fed mountains of southwestern New Mexico to the desert lowlands of southwestern Arizona.
In wetter years, seasonal snowfall on the Mogollon Mountains and Black Range provides much of the river’s spring flow and helps refill San Carlos Reservoir, which is formed by the Coolidge Dam. When filled to capacity, the reservoir is one of Arizona’s largest bodies of water.
However, in 2026, lackluster snowfall left the mountain snowpack in the Gila River watershed at 2 percent of the 1991-2020 March median. The limited snowpack pushed April streamflow to 39 percent of normal. By June, after mandatory water releases for downstream agriculture, the reservoir held less than 400 acre-feet of water.
The Landsat image above (right) shows the near-empty reservoir on May 22, 2026, when it stored 389 acre-feet of water—less than 1 percent full; the other image (left) shows the same area in June 2023, when it was about 60 percent full. The green vegetation growing along the river channel and reservoir edge includes a mixture of tamarisk, willow, cottonwood, sedges, and grasses.
Officials closed the reservoir indefinitely on June 5, 2026, after the declining water levels contributed to low oxygen levels—hypoxia—that killed virtually all of its fish. Species living in the reservoir included largemouth bass, black crappie, bluegill, channel catfish, flathead catfish, and several stocked species, including brown trout and rainbow trout. The decomposing fish may pose health risks to people attempting to boat or fish, the S …