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 boundaries and describes the hydrologic characteristics of California’s groundwater basins. California’s Groundwater also provides information on groundwater management and recommendations for the future.
With the passage of the Sustainable Groundwater Management Act in 2014, California’s Groundwater now serves an additional role by providing Groundwater Sustainability Agencies with three critical pieces of information regarding groundwater basins: Critical Conditions of Overdraft, Basin Boundaries, and Basin Priority.
Updates to California’s Groundwater will be released every five years starting in 2020.


Timeline of California’s Groundwater (Bulletin 118)
1956
California Department of Water Resources (DWR) established.
1975
The 93rd United States Congress passed the Safe Drinking Water Act.
1978
California Senate Bill 1505 passed. Required DWR to work with public agencies to conduct an investigation of the state’s groundwater basins and to look at patterns of groundwater pumping recharge to identify basins subject to critical conditions of overdraft.
1992
Assembly Bill 3030, the Groundwater Management Act, passed. Required formal, but voluntary groundwater management planning for the first time in California.
1999
California Legislature Budget Act of 1999 authorized funding for B-118 Update 2003 and directed DWR to complete several tasks including developing criteria for evaluation of groundwater management plans and developing a model groundwater management ordinance.
2002
Senate Bill 1938 passed. Expanded groundwater management plan requirements beyond those of Assembly Bill 3030.
2009
Senate Bill x7-6 passed: California Statewide Groundwater Elevation Monitoring (CASGEM) Program
2011
Assembly Bill 359 passed. Required that groundwater management plans map and report groundwater recharge areas.
2014
Governor Jerry Brown released initial California Water Action Plan. Set forth 10 priority actions that guide the state’s effort to create more resilient, reliable water systems and to restore critical ecosystems.
2014
The Sustainable Groundwater Management Act (SGMA) signed into law. Provided framework for required groundwater management in medium- and high-priority basins.
2016
Governor Jerry Brown released final California Water Action Plan.
Timeline of California’s Groundwater (Bulletin 118)
1952
- Identified 286 alluvium-filled valleys believed to be basins with usable groundwater.
- Created a statewide numbering system based on the boundaries of the nine Regional Water Quality Control Boards.
1966
Bulletin 118-2 published: Evaluation of Ground Water Resources: Livermore and Sunol Valleys Appendix A: Geology
1967
Bulletin 118-1 published: Evaluation of Groundwater Resources: South San Francisco Bay Appendix A. Geology
1968
Bulletin 118-1 published: Evaluation of Groundwater Resources: South San Francisco Bay Volume 1. Fremont Study Area
1973
Bulletin 118-1 published: Evaluation of Groundwater Resources: South San Francisco Bay Volume 2. Additional Fremont Study Area
1974
Bulletin 118-2 published: Evaluation of Ground Water Resources: Livermore and Sunol Valleys
1974
Bulletin 118-3 published: Evaluation of Ground Water Resources: Sacramento County
1975
- Identified 459 groundwater basins and subbasins in California and provided summary information on basin and aquifer characteristics, groundwater use, and water quality concerns.
- Summarized technical information for 248 groundwater basins, and mapped their locations.
- Included water-bearing material, well yields in the basin, depth of water bearing zones, storage capacity, usable capacity, extent of basin development, degree of knowledge of the basin, and local groundwater-related problems.
1975
Bulletin 118-4 published: Evaluation of Ground Water Resources: Sonoma County Volume 1. Geologic and Hydrologic Data
1975
Bulletin 118-1 published: Evaluation of Groundwater Resources: South San Francisco Bay Volume 3. Northern Santa Clara County
1978
Bulletin 118-6 published: Evaluation of Ground Water Resources: Sacramento Valley
1980
- Identified 471 groundwater basins/subbasins.
- Summarized information on basin characteristics, groundwater use, and included maps of areal extent.
- Included descriptions of basin settings and boundaries for selected basins.
- Identified 11 critically overdrafted groundwater basins and four basins with "special problems."
1981
Bulletin 118-1 published: Evaluation of Groundwater Resources: South San Francisco Bay Volume 4. South Santa Clara County
1982
Bulletin 118-4 published: Evaluation of Ground Water Resources: Sonoma County Volume 2. Santa Rosa Plain
1982
Bulletin 118-4 published: Evaluation of Ground Water Resources: Sonoma County Volume 3. Petaluma Valley
1982
Bulletin 118-4 published: Evaluation of Ground Water Resources: Sonoma County Volume 4. Sonoma Valley
1983
Bulletin 118-4 published: Evaluation of Ground Water Resources: Sonoma County Volume 5. Alexander Valley and Healdsburg Area
2003
- Contained a status report on groundwater management in California and an inventory of California’s groundwater information.
- Identified 515 basins/subbasins, and listed and mapped them by hydrologic region.
- Included a map of the region groundwater development, general groundwater quality information, and changes in any basins from earlier B-118 reports. The list of critically overdrafted groundwater basins, published in the 1980 update of Bulletin 118, was not reevaluated for Update 2003.
- Included groundwater data tables for each hydrologic region, the basins/subbasins, each basin’s area, a groundwater budget based on the level of basin knowledge, maximum and average well yields (if known), types of groundwater monitoring in the basin, and average and range of total dissolved solids concentrations (if known).
- Created an online supplement to the Bulletin-118 Update 2003 text, including a GIS data file containing the basin boundaries of all 515 basins.
- Included separate text descriptions of the basins, and additional information compiled by DWR staff, such as a physical basin boundary description, hydrologic setting and hydrogeology of the basin, the degree of groundwater development in the basin, specific yields of aquifers (if known), groundwater management occurring in the basin, water quality and known issues, and references.
2013
- While not a formal Bulletin-118 document, the 2013 Groundwater Update contained the most detailed information on California's groundwater resources and additional chapters for each of the 10 hydrologic regions of California.
2016
- SGMA established the basin boundary modification process which allowed local groundwater sustainability agencies to request modifications to their basin boundaries for either scientific or jurisdictional reasons. Finalized basin boundary modifications became official when published in the 2016 Interim Bulletin-118 Update. A total of 517 basins/subbasins were identified in the 2016 Interim Update.
- DWR updated the methodology of analysis for conditions of critical overdraft and identified 21 critically overdrafted groundwater basins (up from 11 in 1980). The methodology and findings became official once the 2016 Interim Update was published. SGMA required critically overdrafted basins to submit groundwater sustainability plans two years earlier than high- and medium-priority basins.
2020
DWR publishes California's Groundwater Update 2020, the first Bulletin 118 five year update as required by SGMA.
Bulletin 118 statewide reports provide information about the nature and occurrence of groundwater in California with a focus on the state's groundwater basins.

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.














B118 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 full 2003 Basin Descriptions have not been updated for B118 Interim Update 2016; however, we developed a new procedure for basin boundary descriptions as part of the 2016 Basin Boundary Modification process. As a result, all basins that had boundary modifications in 2016 have revised basin boundary descriptions. We will update basin description information as GSAs implement their GSPs and new and additional information becomes available.
View 2016 Basin Boundary Descriptions
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. The compressed downloaded file contains both a shapefile of the basin boundary data, and a geodatabase containing a basin boundary feature class. Metadata is included with each version of the basin boundary data set.
Bulletin 118 Basin Boundary GIS Data
The Bulletin 118 Basin Boundary GIS data can also be accessed through the California Natural Resources Agency’s Open Data Portal. There you will find additional formats, including GeoJSON and KML, available for download. 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
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
530-529-7337
Roy.Hull@water.ca.gov
North Central Region
Bill Brewster
Senior Engineering Geologist
3500 Industrial Blvd
West Sacramento, CA 95691
916-376-9657
Bill.Brewster@water.ca.gov
South Central Region
Mike McKenzie
Senior Engineering Geologist
3374 East Shields Avenue
Fresno, CA 93726
559-230-3308
Charles.McKenzie@water.ca.gov
Southern Region
Jack Tung
Engineering Geologist
770 Fairmont Ave, Suite 200
Glendale, CA 91203
818-549-2341
Jack.Tung@water.ca.gov
DWR Headquarters
Brett Wyckoff
Senior Engineering Geologist
901 P Street
P.O. Box 942836
Sacramento, CA 94236
916-651-9283
Brett.Wyckoff@water.ca.gov