Projections of declining surface-water availability for the southwestern United States

• Published in: Nature climate change Vol. 3; no. 5; pp. 482 - 486
• Main Authors: Seager, Richard, Ting, Mingfang, Li, Cuihua, Naik, Naomi, Cook, Ben, Nakamura, Jennifer, Liu, Haibo
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2013; Nature Publishing Group
• Subjects: 704/106/242; 704/106/35; 704/106/694; Climate Change; Climate Change/Climate Change Impacts; Climatology. Bioclimatology. Climate change; Earth sciences; Earth, ocean, space; Ecological effects; Environment; Environmental assessment; Environmental Law/Policy/Ecojustice; Evapotranspiration; Exact sciences and technology; External geophysics; Freshwater; Global warming; Headwaters; Hydrology. Hydrogeology; Intergovernmental Panel on Climate Change; letter; Meteorology; River flow; Rivers; Runoff; Soil moisture; Surface water; Tropical environments; Water availability; Water in the atmosphere (humidity, clouds, evaporation, precipitation); Water resources; Southwestern U.S; United States; USA, Colorado R; USA, Texas; USA, Nevada; USA, California; Multimodel; Century 21st; soil moisture; General circulation models; atmospheric precipitation; climate warming; water balance; Climate models; evapotranspiration; North America; Climate prediction; Runoff; global change; water resource management; climate change
• ISSN: 1758-678X; 1758-6798
• DOI: 10.1038/nclimate1787

Under global warming, arid subtropical regions are expected to get drier and expand polewards. This study uses model simulations to examine changes in hydrological parameters for the southwestern United States. The predictions for 2021–2040 show declines in surface-water availability, resulting in reduced soil moisture and runoff. Global warming driven by rising greenhouse-gas concentrations is expected to cause wet regions of the tropics and mid to high latitudes to get wetter and subtropical dry regions to get drier and expand polewards 1 , 2 , 3 , 4 . Over southwest North America, models project a steady drop in precipitation minus evapotranspiration, P − E , the net flux of water at the land surface 5 , 6 , 7 , leading to, for example, a decline in Colorado River flow 8 , 9 , 10 , 11 . This would cause widespread and important social and ecological consequences 12 , 13 , 14 . Here, using new simulations from the Coupled Model Intercomparison Project Five, to be assessed in Intergovernmental Panel on Climate Change Assessment Report Five, we extend previous work by examining changes in P , E , runoff and soil moisture by season and for three different water resource regions. Focusing on the near future, 2021–2040, the new simulations project declines in surface-water availability across the southwest that translate into reduced soil moisture and runoff in California and Nevada, the Colorado River headwaters and Texas.