Principal aquifers of California

"[1] The state of California recognizes 515 groundwater basins and subbasins within these aquifers.

The California state hydrologic regions and drainage areas are quite similar but not identical to the federal hydrologic unit system's California water resource region surface-water drainage basins.

The California Department of Water Resources has detailed descriptions (online in PDF format, etc.)

[2] The principal aquifers of the United States are organized by national principal aquifer codes and names assigned by the National Water Information System (NWIS) of the United States Geological Survey.

Aquifers are identified by a geohydrologic unit code (a three-digit number related to the age of the formation) followed by a four- or five-character abbreviation for the geologic unit or aquifer name.

California aquifers, excerpted from map in Ground Water Atlas of the United States (USGS, 2000): Lavender is "other" for "rocks that generally yield less than 10 gal/min to wells"; dark green-blue (3) are the California coastal basin aquifers , bright-turquoise blue (7) is the Central Valley aquifer system , flat cobalt-blue (1) down south is Basin and Range aquifers