From The New York Times (Michael Wines):
The once broad and blue river has in many places dwindled to a murky brown trickle. Reservoirs have shrunk to less than half their capacities, the canyon walls around them ringed with white mineral deposits where water once lapped. Seeking to stretch their allotments of the river, regional water agencies are recycling sewage effluent, offering rebates to tear up grass lawns and subsidizing less thirsty appliances from dishwashers to shower heads.
But many experts believe the current drought is only the harbinger of a new, drier era in which the Colorado’s flow will be substantially and permanently diminished.
Faced with the shortage, federal authorities this year will for the first time decrease the amount of water that flows into Lake Mead, the nation’s largest reservoir, from Lake Powell 180 miles upstream. That will reduce even more the level of Lake Mead, a crucial source of water for cities from Las Vegas to Los Angeles and for millions of acres of farmland.
Reclamation officials say there is a 50-50 chance that by 2015, Lake Mead’s water will be rationed to states downstream. That, too, has never happened before.
“If Lake Mead goes below elevation 1,000” — 1,000 feet above sea level — “we lose any capacity to pump water to serve the municipal needs of seven in 10 people in the state of Nevada,” said John Entsminger, the senior deputy general manager of the Southern Nevada Water Authority.
Since 2008, Mr. Entsminger’s agency has been drilling an $817 million tunnel under Lake Mead — a third attempt to capture more water as two higher tunnels have become threatened by the lake’s falling level. In September, faced with the prospect that one of the tunnels could run dry before the third one was completed, the authority took emergency measures: still another tunnel, this one to stretch the life of the most threatened intake until construction of the third one is finished.
These new realities are forcing a profound reassessment of how the 1,450-mile Colorado, the Southwest’s only major river, can continue to slake the thirst of one of the nation’s fastest-growing regions. Agriculture, from California’s Imperial Valley to Wyoming’s cattle herds, soaks up about three-quarters of its water, and produces 15 percent of the nation’s food. But 40 million people also depend on the river and its tributaries, and their numbers are rising rapidly…
The Colorado basin states tried in the 1920s to stave off future fights over water by splitting it, 50-50, between the upper-basin states of Utah, New Mexico, Colorado and Wyoming and the lower-basin states of Arizona, Nevada and California.
In fact, the deal underestimated how much water the fast-growing lower-basin states would need. During most of the wet 20th century, however, the river usually produced more than enough water to offset any shortage.
Now, the gap between need and supply is becoming untenable.
Lake Mead currently stands about 1,106 feet above sea level, and is expected to drop 20 feet in 2014. A continued decline would introduce a new set of problems: At 1,075 feet, rationing begins; at 1,050 feet, a more drastic rationing regime kicks in, and the uppermost water intake for Las Vegas shuts down. At 1,025 feet, rationing grows more draconian; at 1,000 feet, a second Las Vegas intake runs dry.
Lake Powell is another story. There, a 100-foot drop would shut down generators that supply enough electricity to power 350,000 homes.
The federal Bureau of Reclamation’s 24-month forecasts of water levels at Powell and Mead do not contemplate such steep declines. But neither did they foresee the current drought.
“We can’t depend on history to project the future anymore,” Carly Jerla, a geological hydrologist and the reclamation bureau’s Colorado River expert, said in an interview. The drought could end tomorrow, she said — or it could drag on for seven more years…
Should Mead continue to fall, Arizona would lose more than half of its Colorado River water before California lost so much as a drop.
That would have a cascading effect. The Central Arizona Project would lose revenue it gets from selling water, which would raise the price of water to remaining customers, leading farmers to return to pumping groundwater for irrigation — exactly what the Central Arizona Project was supposed to prevent.
“By going back to the pumps, you’ll have made the decision that agriculture will no longer be an industry in central Arizona,” David Modeer, the project’s general manager, said in an interview.
Even Californians doubt Arizona would stand for that, but no successor to the 1960s agreement is in place. And California has a vital interest in holding on to its full allotment of water. The Southern California region using Colorado water is expected to add six million people to the existing 19 million in the next 45 years, and its other water source — the Sierra Nevada to the north — is suffering the same drought and climate problems as the Colorado basin…
That leaves conservation, a tack the lower-basin states already are pursuing. Arizona farmers reduce runoff, for example, by using laser technology to ensure that their fields are table flat. The state consumes essentially as much water today as in 1955, even as its population has grown nearly twelvefold.
Working to reduce water consumption by 20 percent per person from 2010 to 2020, Southern California’s Metropolitan Water District is recycling sewage effluent, giving away high-efficiency water nozzles and subsidizing items like artificial turf and zero-water urinals.
Southern Nevada’s water-saving measures are in some ways most impressive of all: Virtually all water used indoors, from home dishwashers to the toilets and bathtubs used by the 40 million tourists who visit Las Vegas each year, is treated and returned to Lake Mead. Officials here boast that everyone could take a 20-minute shower every day without increasing the city’s water consumption by a drop.