Tucson businesses, apartment complexes and industries may face water-use restrictions by 2010 because of the relentless drought, the city's water chief said Tuesday.

Tucson Water Director David Modeer's prediction came after a warning from federal officials that this spring's runoff into Lake Powell — which stores Colorado River water — will be barely 50 percent of normal.

Because spring runoff into Powell has been below normal for nine of the past 11 years, a state water official said Tuesday that the Central Arizona Project could have its first shortage as early as three years from now.

That would trigger restrictions for many Tucson Water customers, although not homeowners.

Other drought-related predictions Tuesday included:

● The forest fire season is likely to start earlier than normal and has produced several small fires in the Huachuca Mountains and on Kitt Peak, said Coronado National Forest officials. More outside firefighting help than usual will be needed this year in Southeast Arizona, a forest spokeswoman said.

● Statewide, farmers and ranchers will be able to divert only half to two-thirds as much water as normal from creeks. They'll also have less water to supply their cattle stock ponds.

● Rivers across Arizona will have far lower stream flow this spring because snowpack is about 20 percent of normal and has melted a month earlier than usual, according to figures released by the U.S. Natural Resources Conservation Service.

The Gila River is expected to run 71 percent of normal at the head of the Safford Valley. The Verde, Little Colorado and Salt Rivers are expected to run at 46, 31 and 26 percent of normal.

The extended period of low flows in the Colorado River may be partially due to human-induced climate change and global warming, several scientists said this week, although tree ring studies have shown that droughts of this magnitude have occurred before, in some cases as long as 500 years ago.

"We are getting to the point where that is certainly a viable question," said Connie Woodhouse, a University of Arizona associate professor of dendrochronology and geography. "We're at the point where it could be one and could be the other — natural drought cycles or climate change. It could be a mixture of both."

If a CAP shortage happens, Tucson would not lose water at first. Users targeted for the first wave of cuts include non-Indian farmers in Central Arizona and along the Colorado, other river users in Bullhead City and Lake Havasu City, and state programs that buy and place CAP water into the ground in wet years to save for drought years.

Tucson and Phoenix would likely not face shortages until 2015 to 2020, said state water official Tom Carr, and Tucson homeowners wouldn't face restrictions until such a shortage were declared.

But even a CAP cutback for farmers would bring restrictions on Tucson businesses and industries, according to the city's new Drought Response Plan. Approved by the City Council March 20, the plan requires the city to start conducting water audits of businesses and apartment complexes in July of this year. In a CAP shortage, those businesses must start reducing use.

There are currently no official forecasts of a shortage for the CAP, which supplies water to Tucson, Phoenix and Central Arizona farmers via a giant aqueduct from the Colorado River. But Carr said the shortages loom partly because Lake Mead dropped every year since 1999.

To avoid shortages, precipitation must hit normal or above normal in Rocky Mountain states in the next few years to raise Lake Powell, said Carr, an Arizona Department of Water Resources deputy director. Powell, at the Arizona-Utah border, is 48 percent full; Lake Mead, at the Arizona-Nevada border, is 53 percent full.

But a quick turnaround in the West's decade-long drought isn't on the horizon, according to the National Weather Service.

The drought news isn't all bad, however, says the U.S. Bureau of Reclamation, which operates Colorado River reservoirs and the CAP.

"Right now we are 10 feet higher in Powell than a year ago," because last summer's rains sent good flows from Colorado, Utah and Wyoming, said Tom Ryan, a bureau hydrologist.

But this summer the lake's peak will be 51 to 52 percent full, less than last summer's peak of 53 percent, Ryan said.

Ryan didn't disagree with Carr's warning of a possible shortage by 2010.

"I would let Arizona officials speak for themselves," he said. "They understand the situation very well."

● Contact reporter Tony Davis at 806-7746 or tdavis@azstarnet.com.

For more Arizona news, visit www.azstarnet.com or www.azfamily.com.

©The Arizona Daily Star, 2006