From the Arizona Republic:
In 1911, a group of farmers on the lower Salt River, struggling to cope with floods and drought, built Roosevelt Dam and developed a reliable water supply that has met the needs of a growing region for 100 years.
In 2011, the challenge is no longer how to ensure enough water to develop farming in the arid Valley, but where Phoenix and other Arizona cities will find water for the next 100 years.
Demand has spread beyond the capacities of Roosevelt and the other dams on the Salt and Verde rivers. Drought has underscored the vulnerability of Colorado River water, delivered to the Valley in the last big water project built here, the Central Arizona Project Canal. Climate change has added uncertainty.
What is certain is that there will be no Roosevelt Dam for the next generation, no single piece of infrastructure that can create another 100-year supply of water.
For more, see: Arizona challenge: Finding water for the next 100 years