Report Highlights Climate Change Implications for Western States

Projected changes in temperature and precipitation are likely to affect the timing and quantity of runoff in the Sacramento and San Joaquin river basins during the 21st century, the Bureau of Reclamation concludes in a new report on climate change released today by Interior Secretary Ken Salazar.

“Water is the lifeblood of our communities, rural and urban economies, and our environment,” Salazar said in a statement. “Small changes in water supplies or the timing of precipitation can have a big impact on all of us. This report provides the foundation for understanding the long-term impacts of climate change on Western water supplies and will help us identify and implement appropriate mitigation and adaptation strategies for sustainable water resource management.”

The report, which responds to requirements under the SECURE Water Act of 2009, shows several increased risks to western United States water resources during the 21st century. Specific projections include:

  • a temperature increase of 5-7 degrees Fahrenheit;
  • a precipitation increase over the northwestern and north-central portions of the western United States and a decrease over the southwestern and south-central areas;
  • a decrease for almost all of the April 1st snowpack, a standard benchmark measurement used to project river basin runoff; and
  • an 8% to 20% decrease in average annual stream flow in several river basins, including the Colorado, the Rio Grande, and the San Joaquin.

For the Sacramento and San Joaquin river basins, annual precipitation is expected to be highly variable over the next century, with runoff expected to decline slightly in the latter half of the century.

Climate change-related surface water decreases are likely to put significant pressure on groundwater basins, and warmer conditions could place stress on fisheries, reduce salmon habitat, increase demands for instream flows and increase the prevalence of invasive species, according to the report.

“Impacts to water are on the leading edge of global climate change, and these changes pose a significant challenge and risk to adequate water supplies, which are critical for the health, economy, and ecology of the United States," Reclamation Commissioner Mike Connor said in a statement.

The Bureau is working with stakeholders to develop a sustainable water strategy through the WaterSMART Basin Studies Program. As part of the program, the Bureau is developing and evaluating options for meeting future water demands in river basins where water supply and demand imbalances exist or are projected. 

The SECURE Water Act Report, with fact sheets highlighting climate challenges and impacts in the eight western river basins, is available here.

A fact sheet specific to the Sacramento and San Joaquin river basins can be found here.