When Mulroy announced her plan in 1989, the proposal drew a round of more than 4,000 legal protests from ranchers, as well as from the federal government. Since then, the Water Authority has adroitly moved to head off many of those challenges. Mulroy has spent $79 million in eastern Nevada buying up ranches and related water rights. (The Water Authority acquired several thousand cows and sheep as a result of those deals, and now has a sideline called Great Basin Ranch, and its own cattle brand.)

In 2006, Mulroy neutralized the most significant source of opposition when she struck a deal with the U.S. Department of the Interior, which was worried that the project could harm springs in three national wildlife refuges and Great Basin National Park. The government agreed to drop its protests in exchange for a promise from the Water Authority to fund a program that is now monitoring groundwater levels and the project's potential effects on wildlife.

In Snake Valley, another potential source of opposition came from the state of Utah, which shares the aquifer there with Nevada. But the Lincoln County Conservation, Recreation and Development Act, introduced by Sen. Harry Reid, D-Nev., and approved by Congress in 2004, required Nevada and Utah to negotiate a division of the water in Snake Valley.

That's the agreement released this August. "The purpose of the agreement is to build some kind of cooperative management of Snake Valley so we don't have a pumping war in the West Desert," says Boyd Clayton, Utah's deputy state engineer.

The deal is also an important part of a bigger bargain between Utah and Nevada. In the past, Mulroy has said that if Utah doesn't support her quest for groundwater from the Great Basin, she would respond by monkey-wrenching Utah's plans to build a pipeline from Lake Powell to St. George, the fastest-growing part of the state. Boyd Clayton, the deputy Utah state engineer, says that the recent Snake Valley water-sharing agreement reduces the risk of interference. "Clearly, if Nevada perceives that we're not trying to deal with them equitably on this issue," he says, "they're less likely to be helpful and equitable as Utah tries to develop the Lake Powell pipeline."

That has left Millard County in a delicate position. "Sen. (Bob) Bennett's (R-Utah) office has contacted us a few times, saying we need to be a little careful," says Walker, the Millard County chairman. "We're sort of stuck in the middle." 

But with its potential hurdles out of the way, the Water Authority has received approval from the Nevada state engineer, the state's top water regulator, for 114,755 acre-feet of water from Delamar, Dry Lake, Cave, Spring and Snake valleys -- enough for more than 1.5 million people in Las Vegas.

Tim Durbin is a former United States Geological Survey hydrologist who for about a decade did contract work for the Water Authority. In 2001, he began designing a model that the Authority could use to predict the effects of pumping on the Great Basin aquifers. The computer model was a crucial piece of evidence presented to the state engineer during hearings about whether to grant water rights for the project. Yet when Durbin ran the model, he says, it became clear that any amount of pumping would have an effect.

"Southern Nevada Water Authority, for years, has been claiming that somehow they can Pipeline develop this with no impacts, and that is just absolute total nonsense," he says. "There is absolutely no way of developing groundwater in these valleys without having impacts."

But when Durbin testified before the state engineer in 2006, "A lot of pressure was put on me to, in some ways, disown my own work," he says. "The report I prepared was, in effect, taken away from me and rewritten by (the Water Authority) to remove anything that suggested impacts."

Durbin no longer works with the Water Authority; he now has a contract with the National Park Service to help analyze the project's potential impacts. The only way that the project's impacts can be reduced, he says, is to pursue targeted pumping that avoids the most sensitive springs. "The extractions can be designed to focus the impacts on certain parts of the hydrologic system and away from others," he says.

For her part, Mulroy says that Durbin's model was less sophisticated than another one that the Water Authority is now developing. And, she says, her agency will finesse its pumping to minimize impacts on the desert springs. "If you follow Durbin's line of thinking, no groundwater can be touched, period," says Mulroy. But a more flexible approach can prove more sustainable. "You change your pumping strategies, year to year. You move pumping around. You let basins rest. And you artificially recharge."

Under an artificial recharge program, annual snowmelt from the mountains can be channeled into infiltration basins in the desert valleys to "recharge" the aquifer with water. "That's why we bought the ranches," says Mulroy. "If you put infiltration basins at the base of those mountains, you can get that runoff into the ground rather than have it run off and evaporate on the playa."

The one thing that could derail the project now is money. Four years ago, the price tag was pegged at $2 billion. Today, that number stands at $3.5 billion. And when it comes to how the Water Authority will finance the project, Mulroy is keeping her cards close to her vest. "At this point, we're spending only the money that we absolutely have to spend," Mulroy says. "The combination of a very effective conservation plan" -- with correspondingly reduced water sales -- "and a crashed economy with no connection charges" -- the hookup fees for new homes through which the Authority generates most of its revenue -- "have left revenues pretty stressed."

Even if the Water Authority is in a thrifty bent of mind right now, Mulroy says her agency is prepared to reach for the underground water when the moment is right. Much depends on the now-more-than-decade-long drought on Colorado River, and on yet another agreement. Three years ago, the seven states that draw water from the river negotiated a set of ground rules for how to share shortages if Lake Mead and Lake Powell, the river's two main reservoirs, continue to shrink. 

Thanks to those rules, 1,075 is now the most important number in Vegas. The water level in Lake Mead -- one of the key indicators of the state of the system -- is now at 1,093 feet. When it drops below 1,075 feet, the first round of shared shortages will kick in on the renewed series of negotiations between the seven states -- and, Mulroy says, the Water Authority will launch construction of the groundwater project. 

"We need to start," she says, "the minute we hit 1,075."

For more on the plan:

Silenced Springs

Suck this, Vegas!