California's Groundwater (Bulletin 118)

California’s Groundwater (Bulletin 118) is the State’s official publication on the occurrence and nature of groundwater in California. The publication defines the groundwater basin boundaries and summarizes groundwater information for each of the State’s 10 hydrologic regions.

California’s Groundwater features current knowledge of groundwater resources including information on the location, characteristics, use, management status, and conditions of the State’s groundwater. The publication also presents findings and recommendations that support the future management and protection of groundwater.

With the passage of the Sustainable Groundwater Management Act in 2014, California’s Groundwater now serves an additional role by providing important information on groundwater basins including Critical Conditions of Overdraft, Basin Boundaries, and Basin Priority. This information can help local communities, community-based organizations, local water managers, and public officials work together to create solutions for the long-term reliability of groundwater.

DWR has also developed California’s Groundwater Online, linked below, to improve the access and timeliness of groundwater data submitted by local agencies. California’s Groundwater Online is a web-based dashboard that utilizes many of the same data sets from the California’s Groundwater Update 2020 document and the California Natural Resources Agency Open Data Platform to improve the access and timeliness of groundwater data submitted by local agencies.

The next update to California’s Groundwater will be published in 2025.

The following video is available below in both English and Spanish closed captioning.

Draft California's Groundwater - Update 2020

The draft documents can be accessed below:

Public Comment Period

DWR held a 45-day public comment period which closed on April 26, 2021. All comments will be reviewed and will provide valuable feedback to DWR to improve the final version of the report.

Public Webinar Meeting

DWR hosted a public webinar meeting on March 30, 2021, to present an overview of California’s Groundwater Update 2020. Recordings of the webinar presentation are available below in both English and Spanish closed captioning.


Subtítulos en Español

The presentation slides from the webinar are also available below, in PDF format, in both English and Spanish:

Presentation Slides - English Presentation Slides - Español


Using California’s Groundwater Update 2020

A one-page guide on how to navigate California’s Groundwater Update 2020.

Frequently Asked Questions on California's Groundwater - Update 2020

More information is available below in Frequently Asked Questions on California's Groundwater - Update 2020 in English and Spanish.

Statewide Reports

Bulletin 118 statewide reports provide information about the nature and occurrence of groundwater in California with a focus on the state's groundwater basins.

View Report

Bulletin 118 - Interim Update 2016

Update 2016 updates portions of Bulletin 118 Update 2003 and includes time-sensitive information important to implementing the new Sustainable Groundwater Management Act (SGMA). Additionally, a new procedure for basin descriptions was developed as part of the basin boundary modification process. All basins with boundary modifications in 2016 have revised basin boundary descriptions that replace their 2003 descriptions

View Report

CWP Groundwater Update 2013

California's Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013 compiles and analyzes readily-available groundwater information to characterize California’s groundwater basins, aquifers, and well infrastructure.

B118 2003 PDF

Bulletin 118 - Update 2003

Update 2003 is the most recent comprehensive report on groundwater. It describes California’s groundwater basins and subbasins, including basin boundaries, hydrologic and hydrogeologic summaries, groundwater storage capacity and water budget, groundwater level and quality trends, well yields, basin management, and references.

B118-80 PDF

Bulletin 118-80 - Ground Water Basins in California: A Report to the Legislature in Response to Water Code Section 12924

This report, prepared under Senate Bill 1505, Chapter 601, Statutes of 1978, Section 12924 of the California Water Code, identifies the State's groundwater basins on the basis of geological and hydrological conditions and consideration of political boundary lines whenever practical. This report also contains existing general patterns of ground water pumping and ground water recharge within such basins to the extent necessary to identify basins which are subject to critical conditions of overdraft. This document is available upon request, please email

Publish Date: Jan 01, 1980

B118-75 PDF

Bulletin 118-75 - California's Ground Water

Conclusions and recommendations are presented in Chapter I. Chapter II describes groundwater as a resource. Chapter III contains tabular summaries of information for 248 of the more important ground water basins, along with maps showing their locations. It provides references to 194 of the Department of Water Resources' reports on these basins and to 185 reports of other agencies. Chapter IV discusses ground water basin protection and utilization, and Chapter V describes opportunities for basin management and desirable future studies. This document is available upon request, please email

Publish Date: Sep 01, 1975

Water Quality Investigations Report 1952 PDF

Ground Water Basins in California, Water Quality Investigations Report No. 3

This report identifies the areas of alluvial-fill in the State of California which may be areas of groundwater storage. It establishes a uniform name an numbering system for groundwater basins which can be expanded as new areas of storage are identified. A selected bibliography pertaining to groundwater resources in California is included. This document is available upon request, please email

Publish Date: Nov 01, 1952

In addition to the statewide editions of Bulletin 118, DWR has published the following limited Bulletin 118 reports that focus on specific areas of the state.

Copies of all historic publications are available by request. Email

Bulletin 118-1 - South San Francisco Bay

  • Volume 1 - Fremont Study Area (Publish Date: Aug 01, 1968)
  • Volume 2 - Additional Fremont Study Area (Publish Date: Aug 01, 1973)
  • Volume 3 - Northern Santa Clara County (Publish Date: Dec 01, 1975)
  • Volume 4 - South Santa Clara County (Publish Date: Jan 01, 2015)
  • Appendix A - Geology (Publish Date: Aug 01, 1967)

Bulletin 118-2 - Livermore and Sunol Valleys

  • Bulletin 118-2 - Livermore and Sunol Valleys (Publish Date: Jun 01, 1974)
  • Appendix A - Geology (Publish Date: Aug 01, 1966)

Bulletin 118-3 - Sacramento County

  • Bulletin 118-3 - Sacramento County (Revision Date: Apr 01, 1980) (Publish Date: Jul 01, 1974)

Bulletin 118-4 - Sonoma County

  • Volume 1 - Geologic and Hydrologic Data (Publish Date: Dec 01, 1975)
  • Volume 2 - Santa Rosa Plain (Publish Date: Sep 01, 1982)
  • Volume 3 - Petaluma Valley (Publish Date: Jun 01, 1982)
  • Volume 4 - Sonoma Valley (Publish Date: Feb 01, 1982)
  • Volume 5 - Alexander Valley and Healdsburg Area (Publish Date: Jun 01, 1983)

Bulletin 118-6 - Sacramento Valley

  • Bulletin 118-6 - Sacramento Valley (Publish Date: Aug 01, 1978)

California’s Groundwater (B-118) Update 2003 provided online descriptions of California’s groundwater basins and subbasins. The 2003 Basin Descriptions included available information on narrative descriptions of basin boundaries, summaries of the hydrologic and hydrogeologic setting, groundwater storage capacity and water budget, groundwater level and quality trends, well yields, basin management, and references. The basin descriptions will now be called “basin reports” and DWR will start updating them in 2021. They will be updated in order of priority, high to low, and it may take several years for all 515 basin reports to be updated. DWR will utilize new and additional information available as GSAs implement their GSPs to assist with the updates of basin reports.

The 2003 Basin Descriptions, available through the link below, have not been updated for California’s Groundwater Interim Update 2016 or the comprehensive 2020 Update; however, DWR developed a new procedure for basin boundary descriptions as part of the 2016 Basin Boundary Modification process. That procedure was used for both rounds of basin boundary modifications, in 2016 and 2018, and the revised basin boundary descriptions for those events are available through the links below. For basins that had boundaries modified in 2016 or 2018, one should consult their basin boundary modification reports for basin boundary information, instead of the boundary information in their 2003 basin descriptions, which are no longer accurate (only for those basins with boundary revisions). In addition, the information on the area of the basins, in the 2003 basin descriptions will no longer be accurate for basins with boundary modifications, although the area attributes in DWR’s basin boundary GIS data set are accurate. DWR expects these discrepancies to be corrected as basin reports are updated over time.


NOTE: The basin boundary descriptions contained in the 2003 basin descriptions are no longer valid for the basins with revised boundaries.


A GIS data set, containing the boundaries for each of California's groundwater basins, is available for download through the California Natural Resources Agency’s Open Data Portal. There you will be able to download the data set in many available formats, including shapefile, geodatabase containing a basin boundary feature class, GeoJSON, and KML. Metadata is included with each version of the basin boundary data set. It should be noted that the shapefile available for download on the Open Data web site is projected in WGS84 Web Mercator.


CASGEM California Statewide Groundwater Elevation Monitoring (CASGEM) Program - collaboration between local monitoring parties and DWR to collect groundwater elevations statewide and make that information publicly available.

Data & Tools

Data & Tools We have a long history of data collection, monitoring, and reporting. With the passage of the Sustainable Groundwater Management Act (SGMA), there is an increased need for local and state agencies and the public to easily access water data in order to make informed management decisions. Here you will find a curated set of data, interactive mapping tools, and reports which are important resources to inform sustainable groundwater management decision-making.

Contact Information

Northern Region
Roy Hull
Engineering Geologist
2440 Main Street
Red Bluff, CA 96080

North Central Region
Bill Brewster
Senior Engineering Geologist
3500 Industrial Blvd
West Sacramento, CA 95691

South Central Region
Mike McKenzie
Senior Engineering Geologist
3374 East Shields Avenue
Fresno, CA 93726

Southern Region
Jack Tung
Senior Engineering Geologist
770 Fairmont Ave, Suite 200
Glendale, CA 91203

DWR Headquarters
Brett Wyckoff
Senior Engineering Geologist
901 P Street
P.O. Box 942836
Sacramento, CA 94236