PHOENIX - The water level on Eastern Arizona's San Carlos Lake is so low the irrigation district that takes water from the lake for deliveries to Pinal County farmers has turned off the spigot.
As the lake empties because of persistent drought, authorities worry that thousands of fish could die.
The water level now sits at less than 5 percent of what it was a year ago and is nearing its lowest point in nearly 20 years.
In 1976 and 1977, the reservoir dried up entirely, resulting in millions of dead fish. But the water isn't likely to completely disappear this winter unless the weather turns abruptly warm and dry.
Fishing is still permitted, but farmers were cut off Monday when the San Carlos Irrigation Project, the federal overseer of operations at the reservoir, stopped releasing water.
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The move will force farmers and other users to turn to other sources, including wells and water from the Central Arizona Project canal. Both alternatives are more expensive.
The irrigation district is hoping for a good, soaking winter storm to help replenish the lake, about 25 miles east of Globe, but without extra runoff from mountain snowpack, the water will be scarce this year for farmers in Pinal County and the Gila River Reservation, the areas served by San Carlos.
"It just depends on how much water comes in," said Doug Mason, general manager of the San Carlos Irrigation and Drainage District, which manages water for about 600 agricultural users. "Our allotments for next year, how much water everyone gets, will be based on how much water we get in storage," Mason said.
As of Tuesday, the reservoir held about 9,200 acre-feet of water. As recently as Sept. 1, storage stood at nearly 37,000 acre-feet. In December 2008, the lake held more than 217,000 acre-feet. (An acre-foot equals 325,851 gallons, the amount needed to cover 1 acre with 1 foot of water.)
The reservoir's original capacity was 1.2 million acre-feet, although it has rarely neared that level.
As the lake level drops, the threat to fish grows.
Less water means less food and oxygen available for the largemouth bass, black crappie and other species.
"It's like having too many fish in an aquarium," said Kirk Young, fisheries chief for the Arizona Game and Fish Department. "After a while, there's just not enough oxygen in the water to sustain life."
The tribe worked with state and federal officials several years ago to create a minimum level of water, known as the minimum pool, to protect the fish. But that pool shrinks with the reservoir, mostly because of evaporation.
The minimum pool is now about 2,500 acre-feet.
Clarence Begay, irrigation manager for the San Carlos Irrigation Project, said the decision to halt water deliveries was an attempt to protect the minimum pool.
"We'll be monitoring inflows in hopes that we'll receive more water," he said.
Sweeping up the fish and moving them to another reservoir is not an option, said Young, the state fisheries chief.
Disease and other pathogens, as well as concerns about invasive species, make relocation too risky.
"The number of fish we could move wouldn't contribute enough to make it worth the effort," he said. "It would risk the healthy waters."
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