After an exceptionally poor snow season, one of Arizona’s largest reservoirs shrank to lower than 1% full, wiping out almost all its fish and leaving its restoration depending on future rains.
The Gila River is an important waterway within the American Southwest, supplying water for communities, agriculture, and wildlife because it flows from the snow-covered mountains of southwestern New Mexico into the desert landscapes of southwestern Arizona.
During years with wholesome winter snowfall, the Mogollon Mountains and Black Range present a lot of the river’s spring runoff. That snowmelt replenishes San Carlos Reservoir, which was created by the Coolidge Dam and, when full, ranks amongst Arizona’s largest reservoirs.
Historic Snowpack Shortfall Leaves Reservoir Nearly Empty
Conditions have been dramatically totally different in 2026. A really dry winter left the snowpack throughout the Gila River watershed at simply 2 % of the 1991-2020 March median. With so little snow accessible to soften, April streamflow dropped to solely 39 % of regular.
After required water releases for downstream farms, the scenario grew to become much more extreme. By June, San Carlos Reservoir contained fewer than 400 acre-feet of water.
Satellite photographs captured the dramatic transformation. A Landsat picture taken on May 22, 2026 (above), reveals the reservoir holding simply 389 acre-feet of water, leaving it lower than 1 % full. By comparability, imagery from June 2023 (beneath) reveals the identical reservoir at roughly 60 % capability. Along the remaining water, vegetation together with tamarisk, willow, cottonwood, sedges, and grasses strains the river channel and uncovered shoreline.
Low Water Triggers Massive Fish Die-Off
As water ranges continued to fall, officers indefinitely closed San Carlos Reservoir on June 5, 2026. The shrinking reservoir brought about oxygen ranges to fall to dangerously low ranges, a situation generally known as hypoxia, killing just about all of the fish.
The reservoir supported species such as largemouth bass, black crappie, bluegill, channel catfish, flathead catfish, and stocked fish including brown trout and rainbow trout.
The San Carlos Recreation and Wildlife Department also warned that decomposing fish could create health hazards for anyone attempting to boat or fish in the reservoir.
A History of Dry Reservoir Conditions
Although the current situation is severe, it is not without precedent. News reports indicate that San Carlos Reservoir has completely run dry at least 20 times since it first filled in 1930.
Even during the reservoir’s dedication, conditions were so dry that grass covered parts of the exposed lakebed. Humorist Will Rogers famously joked to President Calvin Coolidge, “If that was my lake, I’d mow it.”
Major fish kills have also occurred before, including in 1976 and 2018. Following the 1976 event, when more than 5 million fish died, the Gila Herald reported that the reservoir’s ecosystem needed five years to recover.
Monsoon Rains Could Bring Relief
Much of the Gila River’s headwaters in New Mexico remains in severe drought as part of an ongoing multi-year dry period, according to the U.S. Drought Monitor.
Still, the river’s flow naturally varies from year to year, leaving open the possibility of a recovery. Heavy rainfall during the summer wet season could quickly improve water levels.
A NOAA seasonal outlook issued in May 2026 projected a 33 to 50 percent chance of above-average rainfall across the region during the summer monsoon. At the same time, El Niño conditions strengthening across the central and eastern equatorial Pacific could further increase the likelihood of heavy rain in the U.S. Southwest.
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