A dispute between the Southern Nevada Water Authority and residents of the desert region Utah and Nevada share became more heated Thursday.

Residents of the region and Salt Lake City environmentalists demanded a new water study, saying a federal report indicating that much water is available may be in error. Nevada's official request for water from the Snake Valley that straddles the two states is 50,679 acre-feet per year.

The activists are concerned that withdrawing water from the Nevada side of the Snake Valley aquifer and piping it toward Las Vegas could deprive the region of water, causing damage to ranching operations and natural areas.

In August 2005, the authority's general manager, Pat Mulroy, told the Deseret Morning News that Snake Valley has a "safe yield" of 100,000 acre-feet of water per year. Of that, she said, about 20,000 acre-feet are in use, and the authority wanted 25,000 acre-feet more.

"So, even with our 25,000 additional acre-feet, that barely comes close to half of the perennial use," Mulroy said.

Since then, the issue has been framed by state and water-authority officials in terms of the authority seeking 25,000 acre-feet from the Snake Valley aquifer. But in a "Draft Conceptual Plan of Development" that was prepared by the water authority for the Bureau of Land Management and issued in July, the amount sought is listed as 50,679 acre-feet per year from Snake Valley.

Scott Huntley, spokesman for the authority, said Thursday that an environmental analysis being prepared "is taking into account the full amount of our water application estimates."

About 20 years ago, the authority filed water-right applications seeking 50,679 acre-feet per year from Snake Valley. This remains the amount the water authority wants, Huntley said.

However, he said, a few years ago, when the authority began working with the BLM regarding water rights and rights-of-way applications, the agency asked the authority for a reasonable estimate of what it thought would be conveyed from Snake Valley.

"At that time, we told BLM, giving them a reasonable estimate, that we thought about 25,000 acre-feet," Huntley said. That was "just kind of an educated guess" of the amount of water that actually would be piped out of the valley.

But when the BLM began writing an environmental impact statement, the agency asked the water authority to work on the environmental impact statement "on the basis of the full amount of water that could possibly be convened in the pipeline," which is 50,679 acre-feet, Huntley said. The amount granted would depend on decisions by the Nevada state engineer and negotiations between the two states.