"The major findings of the report are that Las Vegas is nowhere near as efficient as it could be and nowhere near as efficient as it should be," said Dr. Peter Gleick, president of the Pacific Institute, an Oakland, Calif.-based environmental think tank.

The report, titled "Hidden Oasis: Water Conservation and Efficiency in Las Vegas," was released earlier this month by the Pacific Institute and the Boulder, Colo.-based environmental group Western Resource Advocates.

Taryn Hutchins-Cabibi, water policy analyst for Western Resource Advocates, said a lot of time and money has been spent to convince people to tear up their lawns, but a significant amount of water-guzzling turf remains -- some 15,000 acres by some estimates.

By replacing all that grass with desert plants and switching to more efficient landscape irrigation systems, the community could reduce its outdoor water use by 40 percent, she said.

Indoor use also could be slashed by 40 percent at residences and by 30 percent at hotel-casinos through the use of high-efficiency washing machines and low-flow toilets and shower heads, Hutchins-Cabibi said.

Such conservation opportunities must be explored before billions of dollars are spent on a pipeline to tap rural aquifers across eastern Nevada, said Bob Fulkerson, executive director of the Progressive Leadership Alliance of Nevada.

But Southern Nevada Water Authority officials dismissed the report's findings as overstated and misleading.

"Is conservation important? Absolutely. Is it a substitute for an independent water source? Not even close," said J.C. Davis, spokesman for the water authority.

That's because the valley gets 90 percent of its water supply from the Colorado River and uses most of it to irrigate landscaping outdoors, Davis said. Water used indoors for things such as showers, toilets and washing machines doesn't count against the valley's share of the Colorado because it is captured, treated and returned to Lake Mead.

Doug Bennett, conservation manager for the authority, said some of what the report recommends has been tried before or is already being done. Other measures represent what he called "kick-in-the-door retrofit programs" that might do more harm than good.

Bennett said the authority has made great strides in recent years by working cooperatively with builders, residents and business owners to reduce water use. "If you cram conservation down everybody's throats, I think you'll get exactly the opposite reaction."

But Gleick defended the report, calling it a blueprint for "doing what we want to do with less water."

"These are proven solutions that are cost effective and can reduce the wasteful use of water in Las Vegas," he said.

The debate comes as Nevada's largest water utility, the Las Vegas Valley Water District, considers an increase in its rates to drive home what officials call the "price signal" for conservation.

Davis said water district customers can probably expect some sort of rate increase -- one aimed mostly at high-volume water users -- to take effect in the spring.

In coming weeks, the Clark County Commission, in its role as the water district board, will discuss how large that rate increase should be.

Contact reporter Henry Brean at hbrean@reviewjournal.com or (702) 383-0350.