A proposed water-sharing agreement between Utah and Nevada could help deliver water to Las Vegas, but critics maintain any water piped south from Snake Valley in the west desert would set up the valley for devastation and the Wasatch Front for harmful dust storms.

The agreement, made public Thursday after four years of negotiations, would divide equally the water in the valley that hasn't already been allocated.

The deal would hold off a final decision on a 285-mile, $3.5 billion pipeline to Las Vegas until 2019. The point is to avoid a water war that would have to be decided by the U.S. Supreme Court, Mike Styler, executive director of the Utah Department of Natural Resources, said Thursday.

"The goal," Styler said, "is to protect the way of life of the water users in Snake Valley."

But critics, including Snake Valley residents, Millard County, the Great Basin Water Network and the National Park Service, say any drawdown of the aquifer would be harmful because the desert valley's water equilibrium already is fragile.

"Any drawdown will result in unacceptable consequences, including the drying up of meadows and the potential for dust storms," said Steve Erickson, a Salt Lake City resident speaking for the Great Basin Water Network.

A huge problem, Erickson said, is that when the U.S. Geological Survey estimated how much water the aquifer holds, it included all the water the valley's vegetation needs to survive. If there is no water left for the shallow-rooted plants, they will die and the soil they hold in place will blow away -- and Utah's urban Wasatch Front is directly downwind.

Snake Valley rancher Dean Baker, who lives on the Nevada side of Snake Valley but has been a water-sharing negotiator on Utah's behalf, said he still opposes the pipeline but supports the proposed agreement.

The Nevada state engineer has scheduled a fall 2011 hearing to decide whether to grant the Southern Nevada pipeline request. Delaying that hearing until 2019, Baker said, could allow the two states to alter their views on how water rights in general should be managed.

"This agreement, with the 10 years and gathering of knowledge, gives a potential change, both in laws and tradition," Baker said.

Baker and Erickson are troubled by the $3 million mitigation fund the agreement would allow, saying it's too little and doesn't apply to environmental havoc. "Mitigation equals compensation. You can't drink dollar bills," Erickson said. "Once the water's gone, it's gone."

But Allen Biaggi, director of the Nevada Department of Conservation and Natural Resources, said the proposal for dividing the water "is equitable."

Las Vegas now relies on the Colorado River for 90 percent of its water, an unstable situation, Biaggi said. Nevada is under orders to fully develop all of its own water resources before it can request more from the Colorado, whose allocation was set up in 1922.

At that time, Vegas was just a meadow where ranchers watered their sheep, which is why Nevada was granted a mere 300,000 acre-feet from the river per year, Biaggi said. An acre-foot is enough to cover an acre of ground with a foot of water or supply up to two households for a year.

Though Snake Valley lies mostly in Utah, the water flows from the mountains around Great Basin National Park in Nevada. Officials there and at the Fish Springs National Wildlife Refuge have said taking water from Snake Valley would harm both parks.

The agreement would not automatically grant water rights but says each state ultimately would have rights to 66,000 acre-feet from the Snake Valley aquifer, a figure that includes what both states already get.

Nevada would get 36,000 of 41,000 unallocated acre-feet. A reserve of 24,000 acre-feet -- available only if the Nevada and Utah's state engineers agree its drawdown wouldn't "unreasonably" affect supplies of water already allocated -- would be divided 18,000 acre-feet for Nevada and 6,000 acre-feet for Utah.

The agreement also would require studies to set a baseline against which any potential environmental harm could be measured. No water rights could be granted before scientists complete the hydrologic and biologic studies.

The Utah Association of Counties and the Millard County Commission strongly oppose the agreement. A letter to Styler from Millard County, which officially protested the Las Vegas water authority's water application when it was made in 1989, tore apart the proposal almost line by line.

They maintain that the Southern Nevada Water Authority should not be a party to the agreement because that would elevate what essentially is a utility to the level of the commission. They view the agreement as forcing Utah to give up its sovereignty and rights to administrative and legal dispute resolution.

The agreement would mean Millard County -- the only Utah entity that filed a protest 20 years ago, when Styler was on the County Commission -- has lost its right to be heard, said Mark Ward, an attorney for the Utah Association of Counties.