Half roller coaster, half water slide, the fitful winter and monsoon rains this year showed up just in time to fill nearly empty reservoirs. And that will keep the water flowing for the next 4-6 years, even if one of the worst droughts in a century returns, say water planners.
The current rainy season turned into the 19th wettest year on record for the Salt and Verde River watersheds on which Rim Country and the Valley depend, according to figures complied by the Salt River Project.
"Even if it had been a much wetter year, we wouldn't have the reservoirs any more full right now," said SRP's Manager of Water Resource Operations Charles Ester. "We went over capacity on the Verde (reservoirs)" by 150,000 acre feet, which flowed through the bypasses and on down through Phoenix.
As of this week, Lake Roosevelt remained at 95 percent capacity, as did the rest of the reservoirs on the Salt River -- Saguaro, Canyon and Apache. Roosevelt remains the most important reservoir, with its 1.6 million acre-foot capacity.
The little reservoirs on the Verde River, Bartlett and Horseshoe, by contrast stand at only about 60 percent full at the moment. That's because SRP had an agreement with the federal government to empty out the lakes to benefit endangered species.
The lower reservoir levels avoid killing the cottonwoods and willows in which endangered willow flycatchers are nesting and prevent non-native fish from spawning and moving up the Verde River.
All told, SRP's reservoirs now are 91 percent full, compared to 56 percent a year ago and much less the year before that. About 1.3 million acre feet flowed into the reservoirs during the spring runoff, about double the long-term average runoff of 683,000 acre feet.
Most of the bounty came as a result of three record-breaking wet months and a deep snow pack during the winter. The area had more than 10 inches of rain between December and February. But a bone-dry early spring spurred fears that the decade of drought had clamped down on the region again. Fortunately, a strong early monsoon period eased concerns -- for the moment.
Weather experts credited El Nino conditions in the Pacific with generating the wet storms -- although the same El Nino water temperatures in 2007 generated a paltry 211,000 acre feet during the five month runoff season -- one third of a normal year and about one-seventh of this year. That made 2007 the 17th driest year on record and the 10th drought season in the past 12 years.
The current runoff season also brought some relief from drought conditions on the Colorado River watershed, which produces water for seven states and feeds into the Central Arizona Project that brings water to Phoenix and Tucson.
The two giant reservoirs on the Colorado River have been rising rapidly as snows melt in the Rocky Mountains. Ester said the 200-mile-long Lake Powell had risen about 55 feet. The rush of water into Lake Mead now seems likely to stave off rationing of water from the Colorado for at least a couple more years, said Ester.
The runoff was well timed for SRP, which had just finished a major project to protect against flood by dramatically increasing the height of Roosevelt Dam.
The project created 62 feet of extra height on the dam, which means the water utility captured all of the extra runoff without having to let any of it through the spillways -- as it did on the Verde.
The rising water behind Roosevelt Dam did inundate the lush riparian areas along the creeks leading into the lake, killing many trees that species like the endangered willow flycatchers use for nesting during the years when Roosevelt dwindled to an alarming 17 percent of its capacity.
However, under an agreement with the federal government SRP had bought and restored about three times as much riparian habitat on the Salt, Verde and Gila Rivers, where water flows have nourished other riparian areas.
The single year of heavy runoff will virtually eliminate groundwater pumping in the Valley this year and enable SRP to continue normal water deliveries for four to six years, even if the severe drought reasserts itself.
A similar wet year about five years ago kept one of the most severe droughts on record from forcing the giant utility to impose severe water rationing.