Abstract
Early settlement of the American West was predicated on settlers’ ability to access water. As populations grew and demand increased, infrastructure to support water delivery kept pace, but we have reached a turning point. Water delivery is no longer limited by conveyance, but rather the reliability of its supply. The Colorado River, the primary water source for nearly 40 million people, embodies the challenges facing water managers in the West. This paper considers the historical climate in the Southwestern United States as well as climate forecasts through the end of the century and what these tell us about Colorado River flow. It outlines research methods used for reconstructing paleoclimate and provides an explanation for the uncertainty in forecasting flows based on past and future models. The paper concludes with examples of successful adaptation to water shortage and policy suggestions for decision-makers based on existing research.