With Lake Mead falling and the drought showing no sign of abating, it's time for the Southwest to start doing more of less: Do more to cut water use instead of simply chasing new supplies for thirsty cities and farms.

That's the conclusion of several researchers in a special presentation in a national journal on this area's problems and future concerns with water supplies, growth, drought and climate change.

The researchers wrote that the Southwest needs to consider everything from limiting swimming pools to building more rainwater- harvesting and gray-water systems to installing low-flow toilets, shower heads and washing machines.

Several authors said it's time to look more closely at limiting and managing population growth. That includes the building of more high-density subdivisions instead of current Sun Belt-style developments with large lots containing lots of grass.

One reason the changes are needed is that regardless of whether global warming makes our drought worse, it is unlikely that this region will ever return to the moist climate of the two decades ending in about 1998, one of the papers said. Another paper, reporting on Phoenix, said that if the region grows as expected by 2030 without water-use limits, there's no way to prevent major groundwater depletion no matter what happens with the weather.

The articles were published this week in the Proceedings of the National Academy of Sciences.

"I don't know what will be needed to push water managers and policymakers to take more aggressive and sustainable actions to solve our water problems in the Southwest, but something must be done to avoid the coming crisis," said one of the authors, think-tank director Peter Gleick, in an interview. Gleick is president of the Pacific Institute for Studies in Development, Environment, and Security in Oakland.

"We're in a car heading for a brick wall, and there is little indication that we've even taken our foot off the gas, much less applied the brakes."

At a very immediate level, anyone who stands on Hoover Dam and looks out at Lake Mead, which is now drained of over 60% of its water, "can see we have a water problem right here and now," the special issue's lead author, geography professor Glen MacDonald, who directs UCLA's Institute of the Environment, told the Star. "This does not take models, graphs or anything else to demonstrate."

MacDonald said he hopes the issue will help water officials to make informed decisions about water.

"It is going to require that kind of broad cooperation to keep our region vibrant. It is also going to require new approaches beyond more dams and canals. It is also going to require us to consider what is the real value of water as it becomes a even more stretched commodity."

Two articles in the issue strongly agree that this region is very likely to get drier this century, although they disagreed on whether the Southwest's current drought is caused by climate change.

A paper written by a federal researcher and a Columbia University researcher reported that the drier air is due to La Niña, a condition caused by natural sea-surface temperature variations.

A second paper argued that the region's changes in hydrologic conditions over the past 50 years can't be fully explained by national variability, and instead show signs of impacts by climate change. It was written by researchers at Scripps Institute for Oceanography and the U.S. Geological Survey.

The usual Western attitude for dealing with water problems - finding new supplies - has run its course and is no longer sustainable environmentally, Gleick and MacDonald wrote.

The push for new supplies goes back centuries to the days when the Hopi, Zuni, Rio Grande Pueblo, Hohokam and other tribes built irrigation canals and irrigated crops along the Santa Cruz, the Rio Grande and other rivers, MacDonald wrote. In the 20th century, the instruments of Western development were dams, canals, pipelines and other projects, Gleick wrote.

Now, however, ecosystems around the West are collapsing from the effects of the dams and water-diversion projects, Gleick wrote.

"Unconstrained and unmanaged growth" can no longer be accommodated with water supplies, and new thinking and management approaches are needed, he wrote.

Looking at Phoenix as an example, two Arizona State University researchers concluded after running a series of computer models that without limits on growth or water use it's not possible to stop the area's overdrafting of groundwater no matter what happens with the weather.

The water table's drop would become severe under the most pessimistic possible climate-change scenarios, the researchers said.

But if Phoenix cut its future growth rate in half and eliminated all irrigated outdoor landscaping and backyard pools, a sustainable water system can be achieved "for all but the most severe climate futures," ASU researchers Patricia Gober and Craig Kirkwood wrote.

"Designing a system to supply enough water for business as usual in the most pessimistic climate-change scenarios would be very expensive and perhaps physically impossible," they wrote. "Ignoring those scenarios and designing for a best-guess case could leave Phoenix vulnerable to a water shortage with little time to adapt."

Contact reporter Tony Davis at tdavis@azstarnet.com or 806-7746. Follow Davis on Twitter at tony davis987 and Blogging the Desert.