Originally Published: September 25, 2011 10:12 p.m.
PHOENIX - Arizona has been in drought conditions since 1999. Experts say a dry winter and a weak monsoon this year could make matters worse.
The La Nina weather pattern - the ocean force responsible for the scant snowfall in Arizona's high country last year - has returned and could set the stage for even drier conditions next year, forecasters say.
The latest weekly survey by the Nebraska-based National Drought Mitigation Center shows all of Arizona in some degree of drought, from abnormally dry conditions in the state's western third to pockets of extreme drought on the Navajo Reservation and extreme and exceptional drought in the southeastern corner of the state.
Meanwhile, a winter forecast by the Climate Prediction Center suggests little will change on the survey's drought map in the coming months. The odds favor drier, warmer weather over most of Arizona through December.
The Arizona Republic reports that dry conditions have forced some ranchers to continue reducing livestock herds already decimated by more than a decade of poor range conditions.
Brittle forests contributed to a record wildfire season this year that has charred more than 1 million acres and lingered into September. San Carlos Lake near Coolidge is nearly empty, leaving less water for farmers in Pinal and Gila counties.
In the Phoenix metropolitan area, the lack of cooling rain pushed August temperatures to record levels and fed an unusual number of dust storms.
As winter approaches, forecasters say the declining water temperatures in the Pacific Ocean could steer storms away from Arizona for a second year in a row, leaving below-average runoff next year.
Such a "double dip" La Nina - a weather maker that typically brings warmer, drier winters to the Southwest every three to six years - would raise new concerns about fire danger, rangeland health and water supplies for towns that rely on wells.
Many climate experts say Arizona never emerged from a drought that began in the late 1990s, even though depleted in-state reservoirs refilled during occasional wet winters. Now, some climatologists suggest there could be a link between this dry cycle and other extreme weather events.
"We're seeing drought from Arizona to Georgia, unprecedented drought, but the thing that's made it the worst ever in places like Texas, New Mexico and Oklahoma hasn't been the rainfall deficit," said Jonathan Overpeck, founding co-director of the University of Arizona's Institute for the Environment. "It's been the heat. We just haven't had the clouds or the rain to cool the heat."
Arizona gets most of its precipitation during two wet seasons. Winter, when snow accumulates in the mountains before melting into rivers and streams, is by far the most important contributor to water resources and range health. The summer monsoon can help refill aquifers and green up the rangelands until winter returns.
This year, both seasons underperformed. After an encouraging start, winter snow runoff was below average in Arizona's high country, muted by La Nina, and the monsoon has been spotty at best.
"It's bad enough when you lose two seasons, but we're looking to the winter and it looks like there's going to be a La Nina, so we could be losing three wet seasons," said Michael Crimmins, who monitors drought and climate for the University of Arizona's Cooperative Extension. "That doesn't happen all that often in Arizona, so we're concerned."
The dry conditions have taken their steepest toll this year on ranchers and farmers who depend on rain or rain-fed creeks or aquifers. Many still feel the effects of the longer drought, which forced ranchers to sell livestock and, in some cases, produce fewer crops. For them, the drought never really ended.
Conditions are bleakest in the state's southeastern corner, where range conditions have declined steadily. The monsoon has left only spotty moisture, and it often arrives in short, intense bursts. That means more water runs off than sinks into the ground.
Poor winter snowfall left forests tinder-dry by early summer, setting the stage for the state's worst wildfire on record, the Wallow fire in eastern Arizona, and the worst overall year for fires. Lightning-caused fires continued to smolder into September, and the toll on the landscape is nearing 1.1 million acres burned.
Scientists coined the term "megadrought" to describe dry periods that could be measured in decades rather than years, and some say the Southwest could experience such a long drought if temperatures keep rising.
"Arizona is on the front end of climate change," Overpeck said. "In no other part of the country outside of Alaska are we seeing it more clearly. It's going to get hotter, and we're going to get less moisture."