"It's hypocritical for us to tell Nevada not to develop a water project. Ultimately they will figure out how to do it," Thompson said. He is concerned Nevada, which has its own interest in the Colorado River, will be less inclined to support Utah's campaign to secure water rights, regulatory approvals and rights of way needed for the Lake Powell Pipeline.
Thompson raised these concerns last week at a meeting of the State Water Development Commission. Most of the commissioners, including Thompson, voted to formally ask Herbert to reconsider his decision.
Nevada officials likewise hope an accord is still within reach, although they declined to discuss their state's leverage on Utah water projects.
"Gov. Herbert has committed to continue to work with Nevada to identify options for addressing this issue. That said, we believe this agreement is good for both states and we would welcome reconsideration from Gov. Herbert with regard to signing it," said Leo Drozdoff, director of the Nevada Department of Natural Resources and Conservation. The Southern Nevada Water Authority, the agency proposing to pump and pipe Snake Valley water to Las Vegas, declined to comment for this story.
Meanwhile, conservationists ridiculed Thompson's position as a self-serving gesture to protect the controversial Lake Powell Pipeline proposal, calling this project both costly and unnecessary.
"It has nothing to do with need. They are doing it so other states won't be able to use the river," said Utah Rivers Council Executive Director Zach Frankel. "Ron Thompson is not an objective source on this. He is looking out for his agency's interests."
Frankel, as well as local officials and business owners, contend the proposed agreement with Nevada would not truly protect Snake Valley from Las Vegas' thirst once it begins pumping. Groundwater depletion could turn the valley into a "dust bowl," yet the agreement fails to anticipate air quality impacts, critics say.
"Pieces of paper are worthless and most often in these circumstances, are written to placate the opponents at the time only to be broken in the future," Terry Mascaro, a Baker, Nev., business owner, wrote in an open letter castigating the commission's recent vote. "A 39-page paper document will never stop the stated destruction to us out here."
Millard County's elected leaders oppose the agreement, reached without an opportunity for public comment, because it would promise groundwater to Nevada that they believe is not there. Once impacts from pumping become apparent it could be too late or too costly to fix the damage, they say.
But many on the water development commission question whether Utah could secure a better agreement than the one Herbert has rejected. That pact would have safeguarded the valley's existing water users in a tiered water-sharing arrangement and featured several provisions to protect the landscape and monitor environmental changes, backers say.
"We had long indicated we would sign, then backed out at the last minute. It looks like our word is not that good. It was a strong agreement in Utah's favor," Thompson said. "It's a false premise that if Utah doesn't come to an agreement, Nevada won't be able to develop its water interest [in the Snake Valley]."
Thompson believes Nevada's water troubles are an accident of history that began in the 1920s when the Colorado River Compact was established, allocating the Silver State a relative trickle of the mighty river's flow. Back then, no one envisioned subdivisions, much less water-guzzling tourist amenities, blooming in the Las Vegas Valley.
Nevada's 300,000-acre-foot annual apportionment hardly lines up with its territory's contribution to the Colorado's flow or its current needs, while nearly one-third of Utah's 1.4 million-acre-foot share has gone undeveloped. (About 326,000 gallons, an acre foot of water supplies two to four households annually.)
For years, Utah and other basin states have opposed renegotiating the compact and encouraged Nevada to tap sources inside its borders.
"Utah has a long history working with all the basin states and Nevada. We have a long border and history of comity. Those [border] communities have been interrelated since they were developed," Thompson said, noting St. George's own extensive ties to the Nevada economy.
The states are the nation's two driest, as well as among the fastest growing, suggesting the competition for water may only get more intense. But what if Utah leased its unused share of the Colorado River to Nevada?
Conservationists say such an arrangement would make Utah money and help solve Las Vegas' water woes without developing a destructive groundwater pumping scheme. In the mid-1990s, Utah's then-Gov. Mike Leavitt proposed as much, but the idea did not get much traction among policy makers.
"That's narrow-mindedness. That's myopia," Frankel said.