The southwestern United States is expected to have declining surface-water availability in the next 10-30 years. A study published this week in Nature Climate Change reports that these decreases are sufficiently large to place additional stress on regional water resources needed to meet the demands of agriculture and a growing population.

Richard Seager and co-workers use simulations from the Coupled Model Intercomparison Project Phase 5 to examine changes in precipitation, evapotranspiration, runoff and soil moisture across seasons for three water resource regions: California and Nevada, Colorado River headwaters and Texas. A steady drop in net water coming into these regions is projected, and the authors suggest that the declining water availability will translate into reduced soil moisture and runoff over the next few decades.