Click image for enlargement. Graphic by Mike Johnson. Fern Harbecke mows grass on Aug. 11 at the Harbecke Ranch in Spring Valley. The Southern Nevada Water Authority recently bought the ranch and farm, including water rights. Photo by John Locher.

Rural ranchers, big-city mayors and water experts will descend on Carson City next week for what could go down as one of the most important state hearings in Nevada history.

Starting Monday, the state's chief water regulator will hear testimony on the Southern Nevada Water Authority's plans to pipe billions of gallons of groundwater to Las Vegas from Spring Valley, a 1 million-acre watershed that includes portions of White Pine and Lincoln counties.

Based on evidence presented during the three-week hearing, State Engineer Tracy Taylor will decide how much water, if any, the water authority should be allowed to remove from Spring Valley, whose center lies about 250 miles north of Las Vegas.

To supporters and opponents of the pipeline project, the hearing represents nothing less than a battle for Nevada's soul.

Without water from Spring Valley, water authority General Manager Pat Mulroy said, Southern Nevada could exhaust its water supply within a decade, prompting the state's growth-based economy to shrivel on the vine.

But attorney Matt Kenna, who represents those opposed to the pipeline project, said large-scale groundwater pumping in White Pine County could wipe out springs, rare wildlife and the livelihoods of rural residents, including some of Nevada's pioneering families.

Spring Valley lies at the northern end of the $2 billion pipeline network the Southern Nevada Water Authority hopes to build across Eastern Nevada.

Of the roughly 200,000 acre-feet of water that one day could be pumped to Las Vegas, as much as 91,000 acre-feet would come from Spring Valley.

If Taylor were to reject all 19 of the authority's groundwater applications in Spring Valley, Mulroy said the entire pipeline would be scrapped.

"Because it's our largest filing in any single basin, this is kind of like the anchor tenant for the entire project," she said. "In terms of water supply, it's critical on all kinds of levels."

In a statement issued earlier this week, Taylor promised to uphold his statutory responsibility to "remain neutral and consider all the information presented based on sound science and applicable laws."

He wouldn't comment further "due to the quasi-judicial nature of these proceedings."

His ruling on Spring Valley is not expected before the end of the year, and whatever he decides is likely to be challenged in court by one side or the other.

To win state approval for its applications, the authority will be required to show:

• That unappropriated water exists in Spring Valley.

• That it can be withdrawn without harming current water rights or the environment.

• And that doing so is in the best interests of the public.

For the first two items, water authority Deputy General Manager Kay Brothers said the agency has amassed stacks of studies, computer models and experts, including former State Engineer Michael Turnipseed, once Taylor's boss.

Opponents of the pipeline will counter with their own data analysis and a panel of experts on water, wildlife, agriculture and economic development.

To address the issue of public interest, the authority has called a panel of political heavyweights including Las Vegas Mayor Oscar Goodman and Nevada Gaming Association President Bill Bible to testify about the link between water and Southern Nevada's economic future.

"They're basically trying to say, 'We're more important in Las Vegas because we have more people,' but that's not how the public interest test works," said Kenna, who is staff attorney for the Western Environmental Law Center.

If developed as planned, the pipeline project is expected to deliver enough rural groundwater to Las Vegas to supply as many as 425,000 homes.

With state approval, the authority hopes to reach Spring Valley and neighboring Snake Valley with its pipeline network by 2015.

Some groundwater from rural areas could be put to use in the Las Vegas Valley before then, but "the basins that have the most water are the farthest away," Brothers said.

Mulroy said much of the hearing will be intensely technical, with a great deal of testimony from hydrologists, biologists and geologists.

But she also expects a fair share of drama.

"It's going to be difficult. I think there's going to be a lot of emotion," she said. "But the more we can let the science speak, the more we can cut through some of that emotion."

The hearing is scheduled to last through Sept. 29, though it could wrap up early if the water authority reaches an 11th-hour agreement with officials from the U.S. Department of Interior.

Department officials want assurances that groundwater pumping won't harm protected resources at Great Basin National Park, which borders Spring Valley to the east, or on any other federally managed land in the area.

Mulroy said that with the proper mix of monitoring programs and other protections, federal officials could be persuaded to forgo their four days of testimony at the hearing.

"I think we're very, very close," she said Friday.

Kenna said it would be a shame if Interior Department officials decide not to testify, because "the federal government's evidence agrees with ours." But, he said, "We'd be presenting the same case whether the government is in or out."

An agreement that won't be in place in time for the hearing is one water authority officials tried to hammer out with White Pine County.

The two sides began meeting in March, but the talks eventually stalled when county officials refused to drop state-level protests of the authority's groundwater applications.

County officials also demanded control of the pipeline's "on/off" switch should damage from groundwater pumping begin to appear.

Mulroy said the water authority's negotiating team was under tremendous political pressure from those who don't want to see even a drop of water piped south from White Pine County.

"It was very disappointing," she said. "I've always understood their fears and ... their concerns. But their unwillingness to work through those things, that's the frustrating part."

Asked whether she ever expects to earn the trust of rural residents, Mulroy said, "We didn't ask them to trust us. We asked them to sit on a joint basin-management committee. We asked them to take a seat at the table."

But Kenna said his clients will always have reason to be doubtful.

"We don't think any agreement would be sufficient once that pipeline is built," Kenna said. "It's very hard to turn off that water once a population has become dependent on it."