The drought has returned with a vengeance to Rim Country, draining reservoirs and raising fears of a fierce, early fire season.
Blame La Niña — below-normal sea surface temperatures in the eastern Pacific that often produce dry winters in the Southwestern United States as a counterpoint to wetter than normal winters in the Pacific Northwest.
Normally, the watershed of the Tonto National Forest gets about 4 inches of rain in January and February. This year, we’ve received well under one inch —and most of that fell in January.
The figures look even worse for Payson so far this year. Normally, between January and the end of March Payson gets 6.28 inches. So far, we’ve had just .29 of an inch.
The Blue Ridge Reservoir now holds about half its capacity, with the spring runoff period already under way. The Salt River Project probably won’t start releasing water into the East Verde River until early April, said SRP spokesman Jeff Lane.
Precious little snow fell on the Mogollon Rim this year to replenish those reservoirs. In February, the snowpack stood at just 21 percent of normal, capping a dismally dry year.
“There’s just not much snow up there,” said Lane.
Most of southern Arizona — including the southwestern half of Gila County — has slipped into “severe” drought, according to the U.S. Weather Service’s drought monitor. The northeastern portion of the county is suffering from “moderate” drought.
Payson hopes to this spring start construction on a $34 million pipeline to deliver water from where SRP’s existing Blue Ridge pipeline empties into the East Verde at Washington Park. Starting in about three years, the pipeline should deliver about 3,000 acre-feet annually, cushioning the region’s reliance on groundwater wells that fall with the rainfall totals.
That will double the town’s sustained water supply — providing Blue Ridge doesn’t go dry. The watershed above Blue Ridge remains one of the most productive watersheds in the state, however — catching both winter and summer storms that break on the topographical barrier of the Mogollon Rim. Payson hopes to use extra Blue Ridge water in wet years to top off its now-depleted underground water table, which should provide reserves to get the area through the dry years.
However, a second dry winter that has shriveled even Blue Ridge now has underscored the challenges Arizona residents will face as the region slips back into a deep drought, despite the relief of a pair of nearly normal winters two years ago.
SRP’s entire reservoir system has dropped alarmingly, after a few big winter storms filled it to the brim two years ago.
Tonto Creek has all but dried up at its junction with Roosevelt Lake. Normally, the creek carries 144 cubic feet of water per second (cfs). Now, it has just 22 cfs. The Salt River at Roosevelt has dropped from its normal 1,230 cfs to just 511 cfs. The Verde River has suffered a less drastic decline, but still carries only 228 cfs instead of its normal 756 cfs.
As a result, Roosevelt Lake now has just 1.1 million-acre feet — about 67 percent of its capacity. Down on the Verde River, Horseshoe Lake had gone dry and Bartlett has just 38 percent of its capacity.
A second dry year means that the region has slipped back into the drought that bedeviled it for a decade, before the respite of the winters of 2009 and 2010. Fortunately, that brief period of normal rainfall refilled the reservoirs on which the Valley depends for its drinking water.
That drought caused widespread tree deaths in Arizona forests as a result of bark beetle infestations, fires and dehydration. Forest managers worry that the possible failure of the spring rains due to the effects of La Niña and an underlying warming trend will produce another disastrous fire season. Reportedly, the Tonto National Forest is debating an early shutdown of the forest to recreation, a potentially heavy blow to Rim Country’s tourist dependent economy.
One recent study found a link between La Niña ocean surface cooling and rainfall patterns in the Southwest stretching back 1,100 years. The study showed that tree ring growth rates of trees on mountain slopes in the Southwest and corals in the Central Pacific echo the ebb and flow of La Niña. However, that study also showed dramatic and still poorly understood variations in the duration and the intensity of La Niña conditions. The study found that the La Niña conditions were weakest during the Medieval Warm Period between about 960 and 1100 A.D. That period recorded the highest average temperatures in the Northern Hemisphere in the 2,000 years before a sharp rise in global temperatures starting in the last half of the 20th century.
The La Niña conditions were the strongest in the 1800s, including during the period referred to as the “Little Ice Age,” with Northern Hemisphere temperatures much lower than the long-term average.
Many climate scientists said that a gradual rise in global temperatures may be causing a more rapid cycling between surface-cooling La Niña phases and surface-warming El Niño phases, but increasing instability of the atmosphere with the rise in energy stored as heat.
However, most of the computer models have trouble predicting the localized effects of the slow, overall warming, especially when it comes to predicting rainfall in an already unstable area like the American Southwest. Most models predict an increase in the number and severity of droughts — but also more violent storms. Several recently published projections predict an early onset of the hot, dry pre-monsoon weather when Arizona has suffered its most devastating wildfires. Those projections suggest that the fire season will take hold in April or May instead of May or June. The most worrisome projections suggest the crucial summer monsoons might prove unreliable if the warming trend passes a still speculative threshold.
Most climate scientists agree that the planet has been gradually warming up in the past five years, in part as a result of the greenhouse, heat-trapping effect of carbon dioxide and other pollutants released by cars, factories and power plants. One survey published in Nature Climate Change found near-unanimous agreement on the trend among climate scientists, but much more skepticism among members of the general public. About 45 percent of members of the general public said they believed there is a lot of disagreement among scientists about global warming, while 5 percent said they believe most scientists say the planet is not warming and 16 percent said they weren’t sure.
People who were aware of the overwhelming agreement among climate scientists on the warming trend and the likely influence of human beings were much more likely to support climate policy, according to the survey.