Partnered with the National Center for Atmospheric Research

Southwest North America

Fifteen years (and counting) of hot drought has left reservoirs low and forests parched.

Since 1999, this region has experienced nearly continuous and ongoing drought. Although centered in New Mexico and Arizona, dry conditions have extended into Texas and California, with substantial impacts on agriculture. Reservoirs along the Colorado River lie at half capacity. Rangelands, irrigation districts, ecosystems and urban water supplies are at risk. Winter moisture is strongly influenced by the Pacific ENSO system and decadal variability, whereas summer moisture (especially in Mexico) is driven by the North American monsoon. A rich history of hydroclimate from tree-rings in the SW US is complemented by cave and sediment-based data, and by a growing set of sites in Mexico; evidence of recurrent prolonged droughts is clear and compelling over the past two millennia. The devastating social and ecological impacts of these droughts are found in the archaeological and historical record.