Drought conditions in the Colorado River basin have persisted since the year 2000, and this has resulted in decreased Colorado River streamflow, challenging water management for communities, agriculture and ecosystems. According to existing tree-ring based drought reconstructions, this current drought is comparable to the most severe drought of the last 1200 years, which occurred in the twelfth century. However, there is limited evidence that suggests a more severe and sustained drought occurred in the 2nd century, which if it happened today would have severe impacts. This project will extend tree ring reconstruction of drought back to 2000 years ago and characterize the 2nd century drought. These data will be combined with other geological records of drought in order to assess how drought severity and duration has changed through time, the contributions of changes in rainfall and temperature on droughts and the streamflow of the Colorado River, and inform understanding of drought risk in the future. The project includes development of K-12 homeschool educational materials, and opportunities for a postdoc and undergraduate students to participate in the research. The goal of this project is to use existing and new tree ring samples to reconstruct drought in the Colorado River basin during the past 2000 years. The tree-ring data will be combined with other proxy records and hydrological modeling to investigate the intensity and persistence of the second century drought in t