Introduction

Over the past several decades, research and development has played an important role in water management on the Colorado River Basin (CRB). In the early 1970s, a federal study called into question the ability of the Colorado River system to meet demand within the basin (USDOI, 1974). In 1976, evidence that the Colorado River may have been over-allocated was provided in the form of a tree-ring reconstruction of Colorado River streamflow (Stockton and Jacoby, 1976). Researchers identified the early 1920s, when the river was apportioned, as a particularly wet period within the 450-year reconstructed record. The paleo-record also revealed historical periods of low flow with longer duration and greater magnitude than those seen in the gauged record. As a result of these observations, the extensive ‘Severe and Sustained Drought Study’ was undertaken by a consortium of universities and consultants in the early 1990s. It was funded by the Department of the Interior and other federal, regional, and state agencies. The final report and numerous papers published in 1995 assessed the hydrological, social, economic and environmental impacts of a severe and sustained drought, as well as policy options for mitigating these impacts. High river flows in the 1990s delayed further discussion and action, but drought in the early 2000s, with 2010 marking the lowest 11-year period in almost a century, served as a ‘focusing event’ (Pulwarty and Melis, 2001) and revived efforts to plan for and adapt to drought.