JACKSON - Here's the regional forecast for the 21st century:

More frequent, extended droughts in states including Wyoming, Colorado, Idaho and Montana. Less mountain water runoff throughout the Southwest, and increased flooding in California, Oregon and Washington.

Global climate change should lead to more precipitation on the planetary scale, but less water in the American West, a scientist with the National Oceanic and Atmospheric Administration said Monday.

Add expected, continued growth throughout the West, and water scarcity could prove the greatest crisis the region faces in the coming decades, said Brad Udall, director of the Western Water Assessment, a joint effort of the University of Colorado and NOAA.

Udall urged the Western Governors' Association to move as quickly as possible toward developing large-scale, regionwide water conservation plans, as the most viable way to avoid a serious water shortage crisis. Udall's address kicked of the morning's discussions at Teton Village here, on the second day of the annual governors' conference.

"We now know and have known for quite a while that climate change will fundamentally change the water supply," Udall said. "If we want protect the values of the West that we all love, we have got to get serious about water conservation."

Water conservation has a two-fold efficiency benefit, Udall told the gathering, because the production, purification, pumping, delivery and home heating of water uses enormous amounts of energy. If states and municipalities can reduce their water consumption levels, they'll also significantly reduce overall energy consumption, he said.

A couple of emerging technologies could help create new sources of fresh water - including desalinization and purification systems that allow water to be reused locally - but the best, most achievable and effective way people can increase water supplies is to stop wasting so much, Udall told the governors.

Even though people who aren't growing crops need only about a gallon of water a day, per individual, to survive, non-farming citizens in the West use, on average, 150 gallons of water per person per day, he said.

One of the primary reasons for this level of consumption, Udall said, is that water is simply too cheap, and the price is not in line with the value of the resource.

While a significant portion of the per-capita water consumption occurs inside homes, a larger portion is used outdoors, for such things as watering the lawn and washing cars.

Duane Smith, executive director of the Oklahoma Water Resources Board, told the governors that fundamental changes need to me made to the mission statements of several federal agencies, including the U.S. Army Corps of Engineers and the U.S. Bureau of Reclamation, in order to make it a priority for these federal agencies to work with states on their water plans.

Currently all federal involvement and planning is done on a project-by-project basis, with no thought to the overall water picture, he said.

Smith urged the governors to push for Congress to make the necessary changes on the federal level.

"We believe this is critically important to the Western states," Smith said. "We're going to change the way the federal government interacts with the states."

Smith helped write the report, which the governors unanimously adopted, titled "Water Needs and Strategies for a Sustainable Future." The report calls for improved collaboration among the states and the federal government on water policy, and offers strategies for regionwide planning.

In a discussion following presentations on the report, Idaho Gov. C.L. "Butch" Otter said the challenges of the West's scarce water supply have been ignored for "far too long."

The region needs, among other things, a better understanding of the total water inventory available, and scientists need to get a better handle on the relationship between streams, runoff and groundwater, Otter said.

"We've got to know what we have in order to know if we can sustain that growth," Otter said.

Nebraska Gov. Dave Heineman said water is "the issue of the decade" in his state, as it, like other states, has faced "historic drought."

Otter agreed with the panelists that the "lowest-hanging fruit" in the water shortage crisis is conservation, but also called for an expanded infrastructure for water development, including increasing the heights of dams wherever possible.

"It fell to all of us as we became governors to be in the position to decide how to divide up scarcity," he said.

Wyoming Gov. Dave Freudenthal noted that water conservation makes a lot of sense, but implementing conservation plans on the state and local level can be a struggle, because water policy is based on a historical premise of utilization, rather than conservation.

The challenge, both Freudenthal and Udall noted, is that in order to shift toward water conservation throughout the West, there will have to be a fundamental shift in perceptions about water.

The historical legal framework for water use in states such as Idaho and Wyoming required farmers to use all of the water they were allotted or lose some of that allotment in the future.