最近获悉鄱阳湖遭遇百年未遇的干旱，作为长江水系的水银行，其干旱影响重大。

May 2, 2004
The New York Times
Drought Settles In, Lake Shrinks and West's Worries Grow
By Kirk Johnson and Dean E. Murphy
PAGE, Ariz. - At five years and counting, the drought that has parched much of the West is getting much harder to shrug off as a blip.
Those who worry most about the future of the West - politicians, scientists, business leaders, city planners and environmentalists - are increasingly realizing that a world of eternally blue skies and meager mountain snowpacks may not be a passing phenomenon but rather the return of a harsh climatic norm.
Continuing research into drought cycles over the last 800 years bears this out, strongly suggesting that the relatively wet weather across much of the West during the 20th century was a fluke. In other words, scientists who study tree rings and ocean temperatures say, the development of the modern urbanized West - one of the biggest growth spurts in the nation's history - may have been based on a colossal miscalculation.
That shift is shaking many assumptions about how the West is run. Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming, the states that depend on the Colorado River, are preparing for the possibility of water shortages for the first time since the Hoover Dam was built in the 1930's to control the river's flow. The top water official of the Bush administration, Bennett W. Raley, said recently that the federal government might step in if the states could not decide among themselves how to cope with dwindling supplies, a threat that riled local officials but underscored the growing urgency.
"Before this drought, we had 20 years of a wet cycle and 20 years of the most growth ever," said John R. D'Antonio, the New Mexico State engineer, who is scrambling to find new water supplies for the suburbs of Albuquerque that did not exist a generation ago.
The latest blow was paltry snowfall during March in the Rocky Mountains, pushing down runoff projections for the Colorado River this year to 55 percent of average. Snowmelt is the lifeblood of the river, which provides municipal water from Denver to Los Angeles and irrigates millions of acres of farmland. The period since 1999 is now officially the driest in the 98 years of recorded history of the Colorado River, according to the United States Geological Survey.
"March was a huge wake-up call as to the need to move at an accelerated pace," said Mr. Raley, assistant secretary of the interior for water and science.
Losing Water at Lake Powell
Some of the biggest water worries are focused here on Lake Powell, the vast blue diamond of deep water that government engineers created in one of the driest and most remote areas of the country beginning in the 1950's. From its inception, Lake Powell, the nation's second-largest artificial lake, after Lake Mead in Nevada, was a powerful symbol across the West. Some saw it as a statement of human will and know-how, others of arrogance.
Powell, part of the Glen Canyon National Recreation Area, has lost nearly 60 percent of its water and is now about the size it was during the Watergate hearings in 1973, when it was still filling up. White cliffs 10 stories high, bleached by salts from the lake and stranded above the water, line its side canyons. Elsewhere, retreating waters have exposed mountains of sediment.
The tourist economy here in Page has been battered. The National Park Service, which operates the recreation area, has spent millions of dollars in recent years just to lay concrete for boat-launch ramps that must be extended every year, a process that one marina operator here called "chasing water."
Daniel C. McCool, a professor of political science at the University of Utah and director of the American West Center, says Powell is the barometer of the drought because what has happened here is as much about politics, economics and the interlocking system of rules and rights called the law of the river as it is about meteorology.
Part of the lake's problem, for example, dates to a miscalculation in 1922, when hydrologists overestimated the average flow of the Colorado River and locked the number into a multistate agreement called the Colorado River Compact. The compact, along with a subsequent treaty with Mexico, requires Lake Powell to release 8.23 million acre-feet of water each year below the river's dam, Glen Canyon, no matter how much comes in.
Because the river's real average flow was less than the 1922 compact envisioned, Powell very often released more than half of the water the Colorado River delivered. But it did not really matter because the upper basin states were not using their share. Now, communities from Denver to Salt Lake City and Indian tribes with old water rights in their portfolios are stepping forward to stake their claims. Lake Powell, which has been called the aquatic piggy bank of the upper West, is overdrawn.
If water levels continue to fall, Powell will be unable to generate electricity as early as 2007 or sooner, some hydrologists say. And it would be reduced more or less to the old riverbed channel of the Colorado River not long after that. Even now, the lake's managers say, it would take a decade of historically normal rainfall to refill it.
"If we're only in the middle of this drought, then Lake Powell might be very close to some very dramatic problems," said Dr. John C.
Dohrenwend, a retired geologist for the Geological Survey who lives near the lake.
Insufficient water for the Glen Canyon Dam turbines would be only the beginning. At that point, much of the lake bottom would be exposed, creating a vast environment for noxious weeds like tamarisk and thistle. The next step in the spiral would come at what is called "dead pool," here decades' worth of agricultural chemicals at the lake bottom would begin mixing more actively with the reactivated river. The question then, environmentalists say, is what would happen to the Grand Canyon, just south of the dam.
An Issue That May Go to Congress
"Americans won't stand for the Grand Canyon being endangered," said John Weisheit, the conservation director for Living Rivers, an environmental group in Moab, Utah, that advocates removing the dam at Glen Canyon and allowing the river to return to its natural course. "In another year, they're going to be talking more seriously about Powell in Congress."
But the fact is, no one knows: the weather could change tomorrow. Many past Western droughts have ended suddenly, with a bang of precipitation. But some dry spells persisted for generations. From about 900 to 1300, scientists say, periodic drought in the West was the norm. Only a few times during that period, according to tree-growth measurements, was precipitation anywhere near the relatively high levels of the 20th century.
"What is unusual is not the drought periods, but the above-average wet periods," said Dr. Robert Webb, a hydrologist with the Geological Survey who specializes in the Colorado River.
The uncertainty has local, state and federal officials along the 1,450-mile river scurrying to secure water allotments while also preparing for the worst.
Already in Las Vegas, the regional water agency is removing the equivalent of a football field of grass every day from front lawns, playgrounds and golf courses to save on outdoor watering. Farther downriver, Arizona officials are pumping billions of gallons of water into aquifers to save for an even less rainy day.
Electricity has become a concern. The Western Area Power Administration, the federal agency that distributes power from hydroelectric projects in the Rocky Mountain West, plans to reduce by about 25 percent the amount of electricity it can promise in future years.
Conserving on a Large Scale
In Los Angeles, a representative from the West's largest urban water agency, the Metropolitan Water District of Southern California, is among a group of Western water officials dusting off plans to help limit evaporation from reservoirs, which could save billions of gallons. One idea is to pour a nontoxic substance over the reservoirs to form a water-trapping barrier.
The group, which has been holding meetings, is even looking at far-off solutions like raising the height of Hoover Dam so that more water could be collected and saved during wet times.
"We understand we have a problem and we are working on it," said the Los Angeles representative, Dennis Underwood, a former head of the federal Bureau of Reclamation, which oversees dams and reservoirs in the West.
There are also worries downstream from Powell at Lake Mead, which serves Nevada, Arizona and California. It could drop low enough as early as next year to force officials to declare a drought emergency. That would hurt the booming southern Nevada economy through significantly higher water rates and outright bans on things like new swimming pools, said Patricia Mulroy, general manager of the Southern Nevada Water Authority.
Mr. Raley of the Interior Department said he wanted the states to consider a water bank, in which unused water could be leased or sold across state lines. Some previous efforts to create banks, with federal oversight, have been contentious because they were seen by smaller states as a means to funnel more of the river to water-guzzling California.
But the notion of cutting private water deals on the Colorado is gaining broader acceptance, in large part because of the drought. The most celebrated example was a deal last year to sell irrigation water in the Imperial Valley of Southern California to the urban water district in San Diego.
Some advocates for agriculture fear that water-to-the-highest-bidder could ravage ranches and farms if owners were induced to sell their irrigation rights. But private-market supporters say the truth, like it or not, is that farmers own most of the West's water, and ultimately there will be fewer of them.
There is some concern that if the Colorado River goes into crisis, the ensuing tangle of litigation over water rights, endangered species and border disputes could undo the system of Western water law that has evolved over the last 100 years.
Some say that would be a good thing.
"The law of the river is hopelessly, irretrievably obsolete, designed on a hydrological fallacy, around an agrarian West that no longer exists," Professor McCool at the University of Utah said. "After six years of drought, somebody will have to say the emperor has no clothes."
Water officials in Arizona and Nevada say they would also like to rethink the law of the river to put their states on a more equal footing in sharing the Colorado River. But Mr. Raley said such talk invites disaster and chaos, especially during a drought.
"This isn't the time to plunge into chaos," he said.
Other people who live here on the fringe of Lake Powell say that the West's great reservoirs have, in their very decline, proved their value in stretching out limited water resources and underlined the difference between past civilizations here that anthropologists say were wiped out or displaced by drought.
"Those people back then had nothing to catch and save their water - now we do," said Ronald W. Thompson, district manager of the Washington County Water Conservancy District in southwestern Utah.
"I'm a believer that history repeats itself - long-term drought could return," Mr. Thompson said. "But I suspect our civilization can weather this."
Kirk Johnson reported from Page, Ariz., for this article and Dean E. Murphy from Grand Canyon National Park.