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.

Thumbnail image of B118 fact sheet document
Bulletin 118 Fact Sheet ( PDF)
Two-page description of the upcoming comprehensive Bulletin 118 Update 2020, including a link to a Bulletin 118 user questionnaire.
Tags: Groundwater-Management, Bulletin-118
Thumbnail image of B118 fact sheet document
Hoja Informativa del Boletín 118 (Español PDF)
Descripción de dos páginas de la próxima actualización comprensivo del Boletín 118 de 2020, incluyendo un enlace a un cuestionario de usario del Boletín 118.
Tags: Groundwater-Management, Bulletin-118
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California's Groundwater FAQ ( PDF)
Frequently asked questions, and corresponding answers, related to California’s Groundwater
Tags: Groundwater-Management, Bulletin-118
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Preguntas Frecuentes sobre el Agua Subterránea de California (Español PDF)
Preguntas frecuentes y respuestas correspondientes relacionadas con el agua subterránea de California
Tags: Groundwater-Management, Bulletin-118

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

Cover of Update 2018
Bulletin 118 - Interim Update 2016 ( PDF) | (Publish Date: Version:
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.
Tags: Groundwater-Management, Sustainable-Groundwater-Management-ActBulletin-118, Groundwater-Basin-Boundaries, Sustainable-Groundwater-Management-Act
Cover of B118 update in 2003
Bulletin 118 - Update 2003 ( ) | (Publish Date:
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 ( ) | (Publish Date:
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.
B118-75 PDF
Bulletin 118-75 - California's Ground Water ( ) | (Publish Date:
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.
Water Quality Investigations Report 1952 PDF
Ground Water Basins in California, Water Quality Investigations Report No. 3 ( ) | (Publish Date:
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.

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

View 2003 Basin Descriptions

NOTE: The basin boundary descriptions contained in the 2003 basin descriptions are no longer valid for the basins with revised boundaries.



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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.

Bulletin 118 Groundwater Basins - Open Data


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
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