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Posted Mar 17, 2010, 11:58 PM
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The Man
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Join Date: Apr 2009
Location: Tempe, AZ
Posts: 1,536
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http://www.azcentral.com/news/articl...inter0317.html
Quote:
For parched state, wet winter means quenched thirst
by Shaun McKinnon - Mar. 17, 2010 12:00 AM
The Arizona Republic
Winter storms plastered Arizona's high country with snow and soaked the lower deserts with rain until the ground was almost sloshing, but that was just the first half of an increasingly wet story.
As temperatures rise this week, the snow will start to melt, gushing down streams and rivers into reservoirs that, in many cases, are already full. The overflow on the Salt and Verde rivers alone could exceed a year's supply of water for Valley residents.
The runoff will ease drought conditions across much of the state, rejuvenating parched forests and rangelands and replenishing groundwater aquifers. Whether the winter has ended the drought, now more than a decade old, probably won't be known for another year or more. It's already clear that drought conditions will persist on the Colorado River.
The bringer of the bounty was almost certainly El Niño, an ocean-warming phenomenon that typically steers wet weather across Arizona and New Mexico. Storms have delivered nearly record rain and snow in some areas, with precipitation totals as high as three and four times the seasonal average.
The results are visible in the mountains, where authorities are cautioning visitors about muddy roads and trails; at dams, where excess water is pouring through spillways; and in the normally dry lower Salt River, now a real river as it cuts across Phoenix.
The water in the Salt is almost all overflow from the six upstream reservoirs, two on the Verde and four on the upper Salt. The reservoirs filled even before snow started to melt. Roosevelt Lake, the largest of the six, reached an all-time high level on Friday.
That means there's no room to store whatever remains in the high country, a projected 1 million acre-feet, or about 326 billion gallons.
"It's over a year's worth of water we aren't able to capture," said Charlie Ester, water-operations chief for Salt River Project, the Tempe-based utility that delivers about 1 million acre-feet to cities and farmers annually. An acre-foot is 325,851 gallons, enough to serve two average households for one year.
"It's a shame we can't put it in the bank until next year," Ester said, "but a lot of it will go into the ground, and it'll be there for the next terrible drought, which you know is on its way."
Water that doesn't percolate into the ground along the river channel will accumulate behind Painted Rock Dam on the Gila River near Gila Bend.
The Army Corps of Engineers, which operates the dam for flood control, has already started to release water into the lower Gila. Some of it could reach the Colorado River near Yuma in the coming weeks, offsetting what the United States owes Mexico, which holds the rights to 1.5 million acre-feet a year from the Colorado.
That would be good news for states that rely on the Colorado, which is not sharing in El Niño's spoils. Snowpack is below average in the mountains of Colorado and Wyoming, and the runoff is expected to produce less than 70 percent of the normal springtime flow into the Colorado River.
At one point, federal officials warned that the poor runoff season could push water levels at Lake Mead, one of two huge reservoirs on the Colorado, to within 2 feet of the depth that would trigger cutbacks to Arizona and Nevada.
Those forecasts have been revised, in part because the storms in Arizona and California reduced demand on the river, allowing more water to remain in storage at Mead. Since Jan. 1, the amount of water delivered to farmers has been 575,000 acre-feet less than expected, according to the U.S. Bureau of Reclamation.
The Central Arizona Project, which delivers Colorado River water to Phoenix and Tucson, has also taken less water from the river this year because its primary storage reservoir, Lake Pleasant, has filled quickly with runoff from the Agua Fria River.
The Agua Fria produced about four times its average flow this winter, CAP officials estimate. Its peak came in January, during a storm that destroyed a number of homes near Black Canyon City.
CAP officials say even with the added Agua Fria runoff, they plan to take their full share of Colorado River water this year.
While water managers have focused on the robust supply side of the winter, scientists and wildlife biologists are watching how rivers and wetlands react. Even an occasional surge of water through a desert river can revive plants and wildlife habitat.
On the Bill Williams River in western Arizona, the runoff is allowing scientists and resource managers to conduct another series of controlled releases from Alamo Dam. The scientists want to see how the pulses of water affect vegetation, wildlife and water quality.
"This is a good learning opportunity for us," said Andrew Hautzinger, a hydrologist and chairman of a project aimed at preserving the Bill Williams. "We have an array of committed scientists, and we think we can work on ways to do restoration on a river."
River ecologists wince when they hear people talk about the water flowing past the dams as wasted simply because it can't be stored for people to use later.
"The idea that it's not being used by people and therefore is a waste is a sad way to look at the natural world," said Michelle Harrington, director of the advocacy group Arizona Rivers. "Everything needs water to live. We should be happy that at times there is enough for more than just us."
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