CARSON CITY, Nev. (AP) – Opponents of a state decision to allow 6.1 billion gallons of water a year to be pumped from three rural Nevada valleys and piped to Las Vegas went to court Aug. 8 to challenge the decision.

Representatives of the Great Basin Water Network and other groups and individuals opposed to the Southern Nevada Water Authority pumping plan said in a petition filed in district court in Ely that the pumping from Delamar, Dry Lake and Cave valleys would be excessive.

The petition says state engineer Tracy Taylor overestimated the amount of water that can be drawn from the valleys, didn’t evaluate impacts on existing water rights and the environment, and didn’t reserve enough groundwater for future economic development in the valleys.

In his July 9 ruling, Taylor reduced an initial SNWA request for more than 11 billion gallons of groundwater a year. That followed a hearing in which the Southern Nevada Water Authority argued that it’s entitled to the water and opponents warned that the pumping could have a catastrophic impact.

Taylor said use of the water in the approved amounts “will not unduly limit future growth and development” in the three valleys, all in central Lincoln County. But before any water is pumped, he wants to see more biological and hydrologic studies. He also said the pumping could be halted if it proves to be “detrimental to the public interest or is found to not be environmentally sound.”

The valleys, located between about 75 miles and 125 miles from Las Vegas, are the first to be tapped for SNWA’s massive pipeline project.

In a related case, two Utah counties filed an appeal in mid-August in the same court in Ely, challenging Taylor’s decision limiting their involvement in a late-2009 hearing on SNWA plans to tap 16 billion gallons of groundwater a year in Snake Valley, on the Nevada-Utah border.

In July, Taylor denied requests by Salt Lake and Utah counties for “interested party” status, saying the counties should have filed a formal objection in 1989 to the massive pipeline project.

In their lawsuit, the Utah counties allege that siphoning water from Snake Valley would cause vegetation to die and lead to dust storms that would reach the Wasatch Front, already struggling with particulate pollution.

Taylor also rejected the “interested party” status for the Great Basin Water Network, the Wells Band of the Te-Moak Tribe of Western Shoshone, Ely Shoshone Tribe and Confederated Tribes of the Goshute Reservation, Trout Unlimited, Water Keepers, the North Snake Valley Water Association and Central Nevada Regional Water Authority, representing six Nevada counties.

SNWA hopes to begin delivering rural groundwater to Las Vegas by 2015. Its eventual goal is to import enough water to serve more than 230,000 homes, in addition to about 400,000 households already getting its water. Cost of its 200-mile-long pipeline project has been estimated at anywhere from $2 billion to $3.5 billion.

The project is backed by casino executives, developers, union representatives and others who point to water conservation efforts in the Las Vegas area and who warn of a worsening economic downturn affecting the entire state unless the city has enough water to keep growing.