The San Carlos Reservoir, a crucial water source in Arizona, has hit record low water levels in 2026 due to drought. The reservoir, which is formed by the Coolidge Dam, is one of the largest bodies of water in Arizona and plays a vital role in delivering water to people, farms, and wildlife.
The Gila River, which flows into the reservoir, is among the Southwest’s most important rivers, linking the snow-fed mountains of southwestern New Mexico to the desert lowlands of southwestern Arizona. However, in 2026, lackluster snowfall left the mountain snowpack in the Gila River watershed at just 2 percent of the 1991-2020 March median.
San Carlos Reservoir Water Levels
The limited snowpack pushed April streamflow to 39 percent of normal, and by June, after mandatory water releases for downstream agriculture, the reservoir held less than 400 acre-feet of water. This is less than 1 percent of the reservoir’s capacity, prompting officials to close the reservoir indefinitely on June 5, 2026.
The declining water levels contributed to low oxygen levels, or hypoxia, which killed virtually all of the fish in the reservoir. 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.
Impact of Drought on San Carlos Reservoir
The decomposing fish may pose health risks to people attempting to boat or fish, the San Carlos Recreation and Wildlife Department warned. The reservoir has hit similarly low water levels in the past, running out of water at least 20 times since it was filled in 1930.
Other years with major fish kills include 1976 and 2018. After more than 5 million fish died during a similar event in 1976, the Gila Herald reported that it took five years for the lake’s ecosystem to rebound. The region is currently in the midst of a multi-year dry period that has left much of the Gila River’s headwaters in New Mexico in a state of severe drought.
Causes of the Drought
The causes of the drought are complex and multifaceted. Climate change is playing a significant role, with rising temperatures and changing precipitation patterns contributing to the drought. The region’s geography, with its snow-fed mountains and desert lowlands, also makes it prone to drought.
- Lack of snowfall in the Gila River watershed
- Low streamflow in the Gila River
- Mandatory water releases for downstream agriculture
- Climate change and rising temperatures
- Changing precipitation patterns
Conclusion and Future Outlook
The future outlook for the San Carlos Reservoir is uncertain, with the region’s drought showing no signs of abating. However, heavy rains during the coming wet season could help the reservoir recover. A seasonal monsoon outlook released by NOAA in May 2026 projected a 33 to 50 percent chance that an above-average amount of rain would fall in the region that summer. El Niño in the central and eastern equatorial Pacific, which was strengthening in late spring 2026, can make heavy rains in the U.S. Southwest more likely.
Source: science.nasa.gov.
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