During the next century, the Southwestern United States is anticipated to warm at a rate second only to Alaska, driving up evaporation rates, driving down soil moisture, and resulting in reduced stream flow, increased erosion/sedimentation, and increased wildfire severity and forest loss. These changes are likely to radically transform the region's watersheds, altering flood hydrology, further disrupting riparian ecosystems, and decreasing surface water supplies by 20 to 25 percent. With drought conditions anticipated to occur in 80 percent of the years between now and 2100, water is anticipated to be the defining issue of this century.