Arizona No. 1 in population rise

But resource limits – especially water – may curb the state's expected surge in people after 2045.

Two desert states continue to grow more rapidly than all others. But Arizona can now lay claim to the title of the country's fastest growing state, outpacing Nevada for the first time in nearly two decades.

According to figures released Friday by the Census Bureau, Arizona's population grew by 3.6 percent between July 2005 and July 2006. Nevada's grew 3.5 percent in the same period.

But it's not always easy being big – and getting bigger at a rapid clip – in the middle of a desert. The growth that Arizona – and greater Phoenix, in particular – are experiencing has placed a great strain on the use of public land, roadways, and precious natural resources – especially water.

"Historically, water has been the resource that's driven population growth in the state," says Patricia Gober, a geography professor at Arizona State University in Tempe. But whether the supply of "water can keep abreast of the population growth is the issue that will challenge us in the future."

To be sure, Arizona has been booming for decades. Just prior to World War II, the state hosted 499,000 people. Today, 12 times that many people – nearly 6.2 million – call the Grand Canyon state home. In Maricopa County, which includes Phoenix and is the state's most densely populated area, the population grew in the same period from about 400,000 to nearly 4 million.

Planners project that by 2010, the greater Phoenix and Tucson areas will merge. And forecasters predict that the population in that swath of land, dubbed the Arizona Sun Corridor, will top 10 million by 2040.

That's when water limitations could begin to kick in. According to the Central Arizona Project (CAP), which supplies roughly a quarter of the state's water, current water supplies can support central Arizona's population through 2030, when the population is expected to reach 8.5 million people. Add on likely water supplies and the region can make it to around 2045, when the population is projected to reach 10.2 million.

After that, growth will have to depend on "possibly available supplies" of water and, eventually, "uncertain supplies," according to a presentation this summer by Terri Sue Rossi, a CAP planning analyst.

In the past, Arizona has planned for growth, particularly in the area of water. It was behind the building of the Roosevelt Dam and the diversion of water from the Colorado, Salt, and Verde rivers to supply the ever-growing thirst in the populous areas of the arid state.

"It's been the general understanding that we grow by increasing our water supply from other places," says Professor Gober, co-author of "Metropolitan Phoenix: Place Making and Community Building in the Desert." "But in the future our growth is dependent on the more judicious use of the water we have."

The state's water use peaked in 1980, then fell because of federal conservation mandates, leveling off through 2000, according to the US Geological Survey. But the population surge is pushing researchers and government officials to consider managing growth more closely. Gov. Janet Napolitano, for example, has already formed an interagency task force made up of officials from eight state agencies.

"The governor is talking about enhancing capacity for planning," says Jeanine L'Ecuyer, spokeswoman for the governor. "We tend to think of growth as new houses and roads. But housing, transportation, water, schools, sufficient teachers, and on and on – it's all interrelated."

The governor and her task force are focusing on several areas, which she will lay out in her state of the state address next month, including water supply and roadway construction.