OULDER CITY, Nev., Oct. 16 — Secretary of the Interior Gale A. Norton signed a contentious agreement here on Thursday that signals an epic shift in the struggle over water in the arid West from farmland to the swimming pools, showers and green lawns of cities.
The agreement ends one of the West's longest-running water wars by requiring California, the nation's thirstiest state, to gradually reduce its dependence on the Colorado River, which acts as a huge spigot for snow melt from the Rocky Mountains for more than 25 million people from Denver to Los Angeles.
At its core, the agreement affirms a tough lesson for the bone-dry region: Because of finite supplies and a population boom, water reserved over the past century for irrigating crops must be diverted more and more to urban areas.
The deal calls for the largest movement of farm water to municipal users in the nation and will be in effect for at least 35 years. As compensation, farmers, some of whom might need to plant less, will be paid handsomely for water they get for a very small cost from the federal government.
"With this agreement, conflict on the river is stilled," Ms. Norton said from a concrete perch overlooking the Hoover Dam, where a formal signing ceremony was attended by federal officials, representatives of the seven states that draw from the Colorado and four water districts in California that had been feuding over that state's share of the river.
The last time a water deal of this significance was reached on the Colorado, the federal government was represented by Herbert Hoover, who was then secretary of commerce under President Warren G. Harding. That deal, the Colorado River Compact, was signed on Nov. 24, 1922, and led to the construction of the Hoover Dam and California's commitment to limit its Colorado River water use to 4.4 million acre-feet.
In recent years, the state has been taking closer to 5.2 million acre-feet. An acre-foot is 326,000 gallons, or enough on average to provide for two households for a year.
"This is a huge breakthrough," Ms. Norton said in an interview. "Even the agreement that allowed the construction of the Hoover Dam left some issues unresolved. This resolves issues that have been unresolved for over 70 years."
The deal comes at a time when the Colorado is enduring a fifth consecutive year of drought and California and its neighbors, experiencing unbridled population growth, are at loggerheads over how to meet everyone's water needs.
Ms. Norton and state and local water officials said the drought was a driving force behind the negotiations, as water districts across the West got a sobering view of how tight supplies could become.
"This deal has a huge economic impact by stabilizing the water supply not only for California, but for Nevada, Arizona and the upper basin states," said Pat Mulroy, director of the Southern Nevada Water Authority, referring to Colorado, Wyoming, Utah and New Mexico. "As all of these states develop, finding a point of water stability is essential."
Under the agreement, farmers in the Imperial Valley, a fertile basin in Southern California that would be a wasteland without water from the Colorado, must eventually sell hundreds of thousands of acre-feet of water a year to San Diego County, a sprawling coastal metropolis of more than three million people with virtually no local water supplies.
The San Diego district will pay market prices for the water, or about $258 per acre-foot at the outset. The farmers typically pay only delivery fees for their water, which amount to $15 or $20 per acre-foot.
An earlier version of the deal collapsed in December when many Imperial Valley farmers balked at the notion of selling their water, but as water experts predicted then, it was only a matter of time before agricultural interests relented to the unstoppable march of the urbanized West.
"About every 100 years, we have something like this we can agree upon," said Maureen Stapleton, general manager of the San Diego County Water Authority. "It is a day of historic celebration."
Noticeably absent from the festivities on Thursday, which included a reception at Hoover Dam and a banquet in Las Vegas, were many Imperial Valley farmers, who for the first time in a century will be giving up large volumes of their water.
"There is very little interest in celebrating," said Michael B. Cox, president of the Imperial County Farm Bureau, who skipped Thursday's ceremony. "A lot of us understand we needed to do a transfer, but man, so many of those provisions are just hard to accept."
The Imperial Irrigation District, which provides water to the farmers, remains deeply divided on the issue, approving the agreement by a 3-to-2 vote two weeks ago. Many farmers fear that the agreement has opened the way for more demands on their supplies and that ultimately they will be driven out business by the unquenchable thirst of California's growing cities.
Already, the state's largest water district, the Metropolitan Water District of Southern California, receives nearly 9 percent of its supplies from agricultural sources, including some from the Imperial Valley.
"The farmers are split down the middle on this," said Bruce R. Kuhn, a district board member who was the swing vote. "This is a first. This is like the pioneers coming West."
But Lloyd Allen, an Imperial farmer who is president of the irrigation district, showed up on Thursday in his cowboy hat and heaped praise on Ms. Norton and Gov. Gray Davis of California, who pushed the negotiations forward after December's impasse and helped break a deadlock by agreeing to state assistance for the Salton Sea, a salty body of water brimming with bird life in the Imperial Valley that relies on agricultural runoff to keep from drying up.
"I am going to go out there in the middle of that bridge and I am going to get on my hands and knees and I am going to kiss that dam," Mr. Allen told the gathering.
He continued, "This thing has made where I live a beautiful, beautiful valley. Now I find out it is going to make a lot more beauty over there on that coastal plain because you are going to get a lot of water from this."
California had promised to limit its use of Colorado River water in the 1920's. It was a pledge that Congress had insisted upon before approving construction of the dam, which created Lake Mead, a huge reservoir about 30 miles southeast of Las Vegas. .
But even with California's promises, the growing state continued to draw more than its share from the Colorado for the better part of a century, leading to protracted legal battles. Three years ago, the six other Colorado River basin states, along with the Department of the Interior, gave California an ultimatum: Get your house in order by Dec. 31, 2002 — namely work out a deal where water from California's farms is shared with its cities — or all supplies of river water above 4.4 million acre-feet will be cut off.
When the deadline passed, Ms. Norton turned off the flows to the Imperial farmers and the Metropolitan Water District, an unprecedented punishment.
That jolt led to a new round of negotiations, which were completed only last Friday and were approved the same day by Ms. Norton. With the deal now signed, Ms. Norton said on Thursday that she would turn the water flows back on, and that California would be given 14 years to wean itself from its overdependence on the river.