In 2008, the Las Vegas Valley's water supply could be augmented for the first time with groundwater piped from rural Clark and Lincoln counties.
And not a moment too soon.
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On Thursday, the Southern Nevada Water Authority board adopted a water budget for 2006 that predicts the valley could outgrow its share of the Colorado River by 2007, forcing the use of "bridge resources" such as water that has been banked here and in Arizona.
Those resources have never been significantly tapped.
Water authority officials downplayed the significance of the water budget, calling the 2007 prediction a worst-case scenario that probably will not occur that soon.
Deputy General Manager Kay Brothers said the annual budgets are based on separate, high-end demand projections from each of the authority's member agencies.
"They tend to be conservative," she said.
Brothers and others admit the Las Vegas Valley will one day outgrow its Colorado River water allotment. That is inevitable.
"We've always known we had a finite resource," said water authority spokesman J.C. Davis. "That's kind of the whole point of having those other tools in your belt."
Those tools are outlined in the 2006 water resource plan also approved Thursday by the water authority board. They include about 290,000 acre-feet of groundwater stored beneath the Las Vegas Valley, 30,000 acre-feet banked with California, and an agreement with Arizona that guarantees Nevada 1.25 million acre-feet over the next 30 years.
To reduce dependence on the Colorado and meet growing demand during the next 50 years, the water authority plans to build a $2 billion pipeline network to tap groundwater in rural basins as far north as Ely. Officials also hope to use water from the Virgin and Muddy rivers.
The first of the rural groundwater is slated to arrive in 2008 from watersheds near Indian Springs.
Brothers described the water banked here and with California and Arizona as temporary bridge resources. The in-state pipeline and river diversions are permanent resources, she said.
About 90 percent of the valley's drinking water supply now comes from the Colorado River by way of Lake Mead.
Nevada gets 300,000 acre-feet of water from the river each year, though that amount is stretched to about 460,000 acre-feet through return-flow credits the state receives for returning its treated wastewater to Lake Mead.
There are 325,851 gallons in an acre-foot, which is nearly enough water to supply two Las Vegas households for one year.
"Nevada receives a very small percentage of the Colorado River's average flow. Changing that allocation would be extremely difficult," Davis said.
A 1922 compact and several later agreements divvied up the river among seven Western states. Efforts to change the so-called law of the river have triggered bitter fights in the nation's highest courts.
The water authority might have been forced to dip into its banked reserves in 2002 had it not been for the availability of surplus Colorado River water. That year, the valley consumed about 325,000 acre-feet from the river, its highest total ever.
Since then, valleywide conservation efforts, most of them targeting landscape watering, have significantly reduced the valley's consumptive water use, despite continued population growth.
In 2004, consumptive use, the total amount of water pulled from Lake Mead, minus the amount of treated wastewater returned to the lake, fell to about 265,000 acre-feet. The valley is on pace to use a similar amount of water this year.
That's why Brothers said she questions the prediction for when water use will exceed the state's Colorado River allocation. "We still have a long way to go," she said.
Through continued conservation and careful planning, Brothers believes the state's meager share of the river could be stretched beyond 2007.
So does Tom Piechota, associate professor of civil and environmental engineering at the University of Nevada, Las Vegas.
"I don't think anyone wants to say that we shouldn't grow anymore. That's kind of extreme," said Piechota, who helped organize a symposium last year in Las Vegas on water and growth. "What people are talking about is smart growth, how we should grow in a way that is sustainable.
