On its 1,450-mile journey from the mountains of Colorado and Wyoming, through Arizona and into Mexico, the Colorado River supplies water to nearly 40 million people in seven states and Mexico.

The river irrigates millions of acres of farmland, generates significant hydroelectric power and nourishes riparian habitats throughout the Southwest. Its famed rapids and canyons offer whitewater rafting, and the lakes created by its dams provide open water for boating and recreation.

Because of these essential and wide-ranging benefits, the river has spawned numerous debates about its future. A new chapter in these discussions is emerging with the release last week of the U.S. Bureau of Reclamation's most comprehensive study of the Colorado River to date.

The Colorado River Basin Water Supply and Demand Study was completed in cooperation with the seven Colorado River Basin states (Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming), Native American tribes, multiple water users in the basin and other entities.

The basin study is the first to quantify the anticipated imbalances between the amount of river water that will be available in the future and the demands on the river system, including water needs for recreation, the environment and power generation in the seven states.

Using multiple scenarios and the latest information on the potential impact of climate change, the study concludes that a basinwide deficit of 3.2 million acre-feet could be expected by 2060. Because a portion of Arizona's Colorado River entitlement has the lowest priority in times of shortage, the study confirms that Arizona must continue to do what it has successfully done throughout its history -- plan and invest in its water resources.

It is fitting that the basin study has been released in the year of Arizona's centennial. Arizona has a legacy of leadership in water management. From the Native Americans who built canals and irrigation systems, to early settlers who expanded these canal systems, to the construction of the Salt River Project, including Roosevelt and other dams, to the completion of the Central Arizona Project, Arizona has always enhanced its supplies while working diligently to conserve and manage all water supplies.

The landmark 1980 Arizona Groundwater Management Act, the nation's most visionary water-management law, requires that we prevent the overuse of groundwater in the state's most heavily populated areas. Since its bipartisan implementation, Arizona has mandated conservation programs, ensured that new residential developments have a 100-year water supply, and encouraged the underground storage of nearly 8million acre-feet of water for use in times of drought.

With our arid state awareness and common-sense programs, Arizonans are leading the country in water conservation and reuse efforts. We have done all this without sacrificing our quality of life or economic prosperity.

In the late 1950s, Arizona's population was about 1.1 million, our statewide income was about $12 billion and our total water use was about 7 million acre-feet (one acre-foot is equal to 325,851 gallons or the amount of water used by two families of four in a year). Today, our population has grown to 5.1 million and our income has increased to $153 billion, but through significant investments in conservation, reuse and infrastructure, our water use is about the same as it was more than a half-century ago.

Although the conclusions of the basin study are not unexpected, they are certainly a call to action. The study shows that we must enhance our current water conservation, reuse, and infrastructure projects. We must also invest in new ways to augment, protect and sustain the Colorado River so that it can reliably meet current and future water needs while preserving a healthy river system.

The basin study identifies multiple projects and programs, ranging from individual conservation activities to large-scale regional augmentation programs designed to bring new water supplies into the basin that must be explored because no single solution will suffice to address the projected imbalances. The planning horizons and funding strategies for these types of projects require that we start our efforts today, before projected imbalances impact Arizonans.

Arizona has long been on the cutting edge of water-supply augmentation and water management. The key to our ongoing prosperity is to continue to work together to plan for and invest in sustainable water supplies for future generations.

Sandra Fabritz-Whitney is director of the Arizona Department of Water Resources. John Sullivan is associate general manager of Salt River Project. David Modeer is general manager of the Central Arizona Project. Kathleen Ferris is executive director of the Arizona Municipal Water Users Association. Warren Tenney is a board member of the Southern Arizona Water Users Association.