So all may drink wisely from the Colorado

The seven thirsty states that drink from the Colorado River have learned a lot about conserving water, from desert landscaping to underground storage. But a credible new study shows that won't be enough to solve the region's water supply problem.

Tough choices lie ahead.

The study by the National Research Council used tree-ring differences to track the history of water flow in the river basin. It revealed that the years prior to a 1922 compact that set multistate sharing were exceptionally wet. That pact is still in effect.

Extended droughts, such as the one the region has been experiencing since 2000, have been common. The seven states – Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming – should be prepared for extended and possibly more severe droughts, according to the study. Right now, the basin's two big reservoirs, Lake Mead and Lake Powell, are about half full.

Global warming also has to be taken into account. While scientists aren't sure how climate change will affect precipitation, rising temperatures are already having an impact on rain and snow once they hit the ground. The creeping thermometer has resulted in earlier snowmelt and higher human, plant, and animal demand – as well as higher rates of evaporation.

The other big factor is surging population growth. Las Vegas may be using less water per capita these days, but total water consumption in Clark County, which includes the desert-sprawling city, doubled between 1985 and 2000. Since 1990, Arizona's population increased by roughly 40 percent, Colorado's by about 30 percent.

Conservation, while helpful, is not the "panacea," the report concludes. That poses some difficult choices.

Should the basin cut back on water for lettuce fields and ranches and pipe more of it to homes and offices in spreading urban areas? Agriculture accounts for about 80 percent of the basin's water use. Less water for food raises the question of food security – or not, depending on how one views America's increasing food imports.

Other tough issues: What about the price of water? Agricultural subsidies, for instance, mean farmers aren't paying for the real cost of water. And what of population growth? Should sunny Arizona pull the shades on folks who want to move there?

The challenge lies in figuring out a balance between the demands of unlimited population and a limited natural resource. That's certainly not unique to the basin, but it's exacerbated by the need to work collectively in a region that has always thrived on individualism.

Still, the seven states can take heart in this: They have already proven that they can work together on this issue. A year ago, top water officials from the seven states penned a preliminary agreement to address water shortages. What brought them together was the desire to work out a solution for themselves, rather than have one imposed by Washington.

At the same time, the string of dry years has made residents and officials alike much more attuned to the threat of drought. They may be facing a limited resource, but they shouldn't limit their efforts to lick this problem with fresh ideas.