California's Central Valley

Science Center Objects

Competition for water resources is growing throughout California, particularly in the Central Valley. Statewide population growth, anticipated reductions in Colorado River water deliveries, drought, and the ecological crisis in the Sacramento-San Joaquin Delta have created an intense demand for water. USGS Tools and information can be used to help manage the Central Valley aquifer system, an important State and national resource.

The USGS California Water Science Center (CAWSC) is providing the tools and information needed to help manage water resources in the Central Valley of California.

The Central Valley of California, which stretches from Redding to below Bakersfield, is predominantly used for agriculture, providing one quarter of the Nation's food as well as accounting for 20% of the Nation's groundwater demand.  Fifty percent of the water used in the Central Valley comes from groundwater. As California enters it's 5th straight year of sever drought, groundwater resources throughout the Central Valley are being withdrawn faster than they are being replenished. When groundwater levels continue to drop, land surface can begin to subside, or sink. 

Post-development hydrogeology of the Sacramento Valley
Post-development hydrogeology of the Sacramento Valley.

The CAWSC is studying both water use and availability as well as land subsidence throughout the Central Valley. An over view of the Valley and CAWSC research is available on the CAWSC Central Valley web site.

Central Valley Hydrologic Model

One key tool being used to assist water managers in the Central Valley is the Central Valley Hydrologic Model (CVHM). The CVHM is an extensive, detailed three-dimensional (3D) computer model of the hydrologic system of the Central Valley. The Central Valley Hydrologic Model (CVHM) simultaneously accounts for changing water supply and demand across the landscape, and simulates surface water and groundwater flow across the entire Central Valley. 

A complete description of the model and datasets used in the model are available on the CAWSC CVHM web site.

Land Subsidence

Over time, overpumping in the San Joaquin Valley has caused groundwater-level declines and associated aquifer-system compaction and land subsidence that has resulted in permanent aquifer-system storage loss. By 1970, significant land subsidence (more than one foot) had occurred in about half of the San Joaquin Valley and locally, some areas had subsided by as much as 28 feet. Reduced surface-water availability during 1976-77, 1986-92, 2007-09, and 2012-2015 caused groundwater-pumping increases in the San Joaquin Valley, declines in water-levels to near or beyond historic lows, and renewed aquifer compaction. The resulting land subsidence has reduced the freeboard and flow capacity of the Delta-Mendota Canal—as well as the California Aqueduct and other canals that transport floodwater and deliver irrigation water—requiring expensive repairs.

Screenshot of the drought indicators map
Screenshot of the CAWSC Drought Indicators interactive map.

The USGS CAWSC is monitoring land subsidence in the Central Valley and throughout California through an extensive land subsidence monitoring network.

Drought 

The CAWSC has produced an interactive map combining water levels, CVHM regions, and subsidence data. The map is a great visualization of the effects of the ongoing severe drought in California. CAWSC also has a complete web site dedicated to information and data about the severe drought in California including the CAWSC role in science-based decision making.