The Mojave, Sonoran, and Chihuahuan Desert regions of the southwestern United States and northwestern Mexico are some of the hottest and driest areas in North America. The scarce availability of water has defined these desert landscapes, their history of human settlement, and our modern economy.  For example, these desert regions produce significant high-value vegetables, fruits, and nuts. But agricultural producers will face increasing challenges in adapting to drier conditions, shifts in seasonal growing seasons, and reduced groundwater availability. Tourism and recreation, generated by the winding canyons, snow-capped peaks, and scenic vistas, also provide a significant economic force that will also be increasingly affected by reduced streamflow and a shorter snow season, influencing everything from lake and river recreation to the ski industry.