Water rights and supply will be pivotal to the burgeoning growth in Dayton Valley.
The water available for use now, about 9,820 acre-feet, could accommodate an additional 12,000 homes beyond current development plans - if all the rights are used for municipal purposes.
Those rights are owned jointly by the county and development community or by other interests, including ranchers, said Dennis Smith, owner of Western Engineering in Carson City.
"Residential subdivisions can be approved (by county officials,) but they won't be built until the water rights are obtained," he said. "If you look at Carson City or the Truckee Meadows, ranching decreases as the residents increase and water is moved from irrigation to municipal use."
Chuck Swanson, public works director for Lyon County, said officials are trying to determine exactly who owns the water rights, but it's a difficult question.
"Trying to resurrect who owns what water rights is like dealing with titles on properties," he said. "They've changed hands so many times, it's difficult to determine who owns what."
Most developers understand water rights issues and know they must often wait until a rancher is willing to sell his or her rights to acquire the necessary water for development.
"Many of the larger developments won't be completed for another 10 years, giving the developer time to find those water rights," he said. "But their final size will be limited to water availability."
The basin is fully appropriated, meaning rights to all the available water is owned by someone. In Nevada, that's status quo, Smith said.
"Every basin in Nevada is fully appropriated," he said. "That means if a person owns property and wants to irrigate, they would have to purchase their water rights from another user."
Landmark developer Jim Bawden acquired water rights with the 2,400 acres he owns in Dayton Valley and is purchasing more as they become available. The valley has abundant water, much more than 9,820 acre-feet, he said.
"According to the engineers I use, the basin is very healthy. Our figures differ greatly, and I'm pretty comfortable with what's going on there," he said.
Swanson said Lyon County officials are using information from the U.S. Geological Survey and others to determine the amount of water available. He said 9,820 acre feet is a valid figure.
"We're using every source that's available, including figures from the state engineer's analysis," he said. "We don't want growth to exceed the availability of water. We don't want any surprises."
Each basin in Nevada is measured to determine its recharge rate. Using that figure, the state water engineer determines the number of water rights available for consumption. The Geological Survey, in cooperation with the Department of Natural Resources, determines the sustainable yield, Smith said.
The most recent report for the Dayton Valley basin was a cooperative effort with the Carson City Subconservancy District in 1997, said Hugh Ricci, state engineer for the Nevada Division of Water Resources.
"Many of these studies were done years ago, but as more interest develops in a particular area, new studies may be commissioned," he said.
Chuck Zimmerman, a hydrogeologist and consultant with the Carson City firm Brown and Caldwell, is working with Lyon County officials to create a water master plan and find answers as to how much water will be available for development.
"We're at the beginning of the process, in terms of quantifying the amount of water available. The issue is complicated, and right now we don't have all the answers," he said.
"It may be possible to move beyond our current supplies, something this evaluation process might help identify."
The master plan will address all issues for groundwater management, conjunctive use of surface-water resources and associated monitoring, Zimmerman said.
"There will be other planning and monitoring efforts, and it may take a number of years before we get a good perspective on how much water can be used in the Dayton Valley basin," he said. "This is just the first step."