The U.S. Geological Survey offered a sneak preview Monday of the agency's upcoming study of groundwater resources in the Great Basin.

Ranchers, conservationists and local government officials have been eagerly awaiting the report because of what it may portend for the proposal by southern Nevada water officials to tap aquifers in the state's eastern valleys and pump it to Las Vegas via a pipeline network.

The preliminary findings: There is more groundwater in the Snake Valley - which straddles Utah and Nevada - than originally thought. But there is also apparently more water flowing between Great Basin aquifers than has been historically assumed, meaning Snake Valley could eventually be impacted by groundwater pumping in neighboring Spring Valley, and perhaps elsewhere.

"There's no water in Snake Valley to go. That's pretty evident," said Millard County Commissioner John Cooper. "The aquifers are even more connected than we thought they were. You take water out of Spring Valley, Steptoe Valley or Hamelin Valley, and it's going to come out of Snake Valley."

Kimball Goddard, director of the USGS's Nevada Water Science Center, told a gathering of water officials, geologists and local and state government leaders in Salt Lake City that a draft of the Basin and Range Carbonate Aquifer System Study is essentially finished and now undergoing peer review. It is scheduled to be released around June 1.

Based upon the preliminary results, Goddard said that Snake Valley probably holds just over 130,000 acre-feet of groundwater underneath - an acre-foot being the amount of water it takes to cover an acre of land with one foot of water, or the amount a family of four typically consumes in a year.

That is more than the 100,000 acre-feet that previous studies estimated was under Snake Valley. But Goddard also said that groundwater flows, which move north into Snake Valley from Spring, Steptoe and Hamelin valleys may account for as much as half of that supply.

"That's more than we previously thought," he said, emphasizing that the uncertainty ranges in estimating such trans-basin flows "is pretty high."

But Goddard did say that the development of water resources in Spring Valley, and perhaps elsewhere, will likely impact Snake Valley's water table, though such effects might not be felt for decades.

Mark Ward, an attorney for the Utah Association of Counties, says that such information should compel Utah to widen the scope of its discussions with Nevada as it negotiates a water-sharing agreement with its neighbor.

But Mike Styler, director of the Department of Natural Resources, says such discussions are already taking place.

"We've known there is a connection. And it's more complicated by the fact that we may not see the real effects for decades," he said. "That's why we need something in the agreement that allows us to, after 20 years, go back and take another look at it."

jbaird@sltrib.com