U.S. Department of the Interior, Bureau of Reclamation


Published date March 15, 2016

Reclamation: Managing Water in the West: Sacramento and San Joaquin Rivers Basin Study

  • ​Evaluates the effects of projected 21st century climate changes along with assumptions about potential population increases and land use changes
  • Finds that climate impacts include:
    • Temperatures are projected to increase steadily during the century, with changes generally increasing from about 1.6 degrees Fahrenheit (°F) in the early 21st century to almost 4.8°F in the Sierra Nevada Mountains by late in the 21st century
    • Precipitation may be only slightly changed especially early in the century with a trend toward increased precipitation in the Sierra Nevada in the late century; however, increased forest evapotranspiration due to warming may reduce runoff from mountain watersheds
    • Snowpack will likely decline considerably due to warming particularly in the lower elevations of the mountains surrounding the Central Valley
    • Runoff will increase during fall and winter months; peak runoff may shift by more than a month earlier in some watersheds; spring runoff will decrease due to reduced winter snowpack
    • Sea levels are expected to increase; however, there is considerable uncertainty about the magnitude of increase—which may range from as little as 20 inches to as much as 55 inches in the Sacramento-San Joaquin Delta (Delta) by the end of century