Arizona joined the other six Colorado River Compact states Tuesday in a water-sharing agreement with Mexico that will keep the entire 1,450-mile length of the river wet for the first time since 1998.

Mexico will store some of its share of the river's annual flow in Lake Mead, which benefits the states by raising lake levels and forestalling potential shortages in times of drought.

In return, Mexico will take a share of water surpluses when available. Conservation groups will buy water rights from Mexican farmers to restore a minimum flow to the lower stretch of the river, which has been effectively dead for decades.

It means that, as early as 2014, the river could flow past Yuma all the way to its delta on the Gulf of California.

That stretch, a lush haven for birds and a place of nutrient infusion for fisheries a century ago, essentially dried up after the construction of Glen Canyon Dam in the 1960s.

"If it were in that (original) condition today, it might well be considered one of the eight wonders of the world," said Patrick Graham, Arizona director for the Nature Conservancy.

Ecological restoration is important for migratory birds, he said, but also for people living there who lost commercial and recreational fisheries.

"It provides them a source of income and a connection back to that environment that they were dislocated from," Graham said.

The Nature Conservancy will join the Sonoran Institute, the Environmental Defense Fund and the Mexican conservation group Pronatura Noroeste in raising money to buy 54,000 acre-feet of water to restore the flow to the sea during the agreement's five-year term.

An acre-foot is about what it takes to supply two Southwestern U.S. households for a year. It's not nearly what flowed historically, but it's a river.

"It's a great first step," Graham said.

The deal, inked by Interior Secretary Ken Salazar and numerous dignitaries at a ceremony in the San Diego area's Hotel del Coronado, also shores up Arizona's water supply against future droughts.

By storing in Lake Mead up to 250,000 acre-feet of its yearly 1.5 million acre-foot Colorado River allotment, Mexico will raise the reservoir a few feet. The states can use this as a hedge in dry years, to be replaced in wet years.

"With this agreement, we're in a better position to put off some of those shortages and give us more time for perhaps the next year's hydrology to improve," said Sandy Fabritz-Whitney, director of the Arizona Department of Water Resources. "It's protective of Arizona's water supply."

Arizona gets this bonus more or less for free. With the other states, it must share some of its surplus with Mexico in good years.

"I wouldn't call that giving anything up -- it's surplus water," Fabritz-Whitney said.

The Central Arizona Project, though, is paying into a fund to rebuild Mexican canals and water systems that were damaged by a 2010 earthquake. That damage crippled Mexico's ability to use its share of the Colorado River and nudged the country toward this water-sharing agreement.

CAP will cover $2.5 million of a $21 million fund from U.S. water interests and will get 23,750 acre-feet of Mexico's water over five years

"We all depend on the river, and our willingness to work together bodes well for the future," CAP General Manager David Modeer said in a news release.

Salt River Project officials also backed the deal as a potential solution to future supply threats.

Not all water users embrace the deal. California's Imperial Irrigation District deadlocked in a board vote on the agreement last week, spokeswoman Marion Champion said. Some apparently believed surpluses available in any given year should go to California farmers who can put them to use. They also questioned the Metropolitan Water District of Southern California's plan to take that state's share of excess Mexican water.

Interior Department officials, in a conference call after the signing, said they were confident Imperial would eventually sign on and that the deal is historic even without the district. Salazar called it the most important Colorado River deal between the two nations since the 1944 treaty that set water rights on both sides of the border. The agreement is an amendment to that treaty and is called "Minute 319."

During a Monday stop in Arizona to watch the start of an ecologically restorative Grand Canyon flood at Glen Canyon Dam, Salazar told The Arizona Republic that the deal with Mexico erases years of squabbling.

"We've ushered in an era of collaboration and problem-solving," he said.

In addition, the U.S. and Mexican governments will jointly contribute more than 100,000 acre-feet to a one-time "pulse" of floodwater to the delta to help restore natural conditions. Such floods were routine before the river's taming.