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The Department of Water Resources (DWR) released the Draft California’s Groundwater: Bulletin 118 – Update 2025 (CalGW Update 2025) on October 20, 2025, opening a 45-day public comment period.
Public Webinar Meeting
On November 4, DWR presented an overview and accepted questions on the Draft CalGW Update 2025 at a public virtual webinar meeting. See the list of webinar wrap-up materials and information below:
Webinar recording (with English and Spanish captions): https://www.youtube.com/watch?v=oY7xmjpLbcA
- Select your preferred language for captions: in the menu bar of the video, select the ‘Settings’ wheel icon, click ‘Subtitles/CC’, and then select between ‘Off’, ‘English’ or ‘Spanish’.
Presentation slides (PDF): https://water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/Groundwater-Management/Bulletin-118/Files/CalGW-Update-2025/FINAL-B-118-Public-Webinar_ADA-Nov-4-2025_2.pdf
Questions asked during webinar and questions answered by DWR:
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Question #1: How does the report deal with multiple overlying aquifers in a particular place?
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Answer #1: California’s Groundwater: Bulletin 118 describes groundwater conditions at the hydrologic basin scale, which typically contains multiple overlying aquifers. The shallow aquifers are discussed in contents related to recharge, aquifer recharge potential mapping, and basin characterization using airborne electromagnetic (AEM) data. The well depth distribution also provides information on various aquifers that are tapped for production and monitoring. Chapter 3 of CalGW Update 2025 describes California's natural groundwater infrastructure and the location of groundwater resources, highlighting the role of natural and built infrastructure, including aquifers, in maintaining the state’s water security. Specifically, Section 3.4 discusses the identification and description of the physical properties of groundwater basins, including aquifers and conditions that local agencies are continually refining, in part with assistance from DWR’s Basin Characterization Program. Groundwater Sustainability Plan (GSP) annual data on water budget summarized in Chapter 4 are based on numerical models that incorporate multiple aquifer layers in a particular location. In addition, DWR plans to update its Basin Reports, originally developed in 2003 for each of the 515 groundwater basins and subbasins, although they are not part of Update 2025. These updated reports will incorporate new data from SGMA implementation and other groundwater programs, providing more detailed information on basin boundaries, geology, hydrology, water budgets, and aquifers—including areas with multiple overlying aquifers. Once complete, the reports will be available on the CalGW webpage.
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Question #2: The question asked during the webinar: “I understand that DWR was the source of the countable wells. Was the criteria for a well the same for all basins? Not all usable wells were counted.” required clarification to provide a helpful answer. At this time, we have not received clarification, but instead are answering the following question that we think captures the intent of the one asked: “How did DWR determine what well data were used in the CalGW Update 2025 and were these criteria applied uniformly in all basins?”
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Answer #2: The well data DWR used in the CalGW Update 2025 are from publicly available datasets (groundwater levels, water quality, land subsidence, etc.) collected by DWR Region Offices and data submitted by local agencies. Data came from well types including monitoring, irrigation, production, and domestic wells. Well types and locations that were not included in the CalGW Update 2025 were excluded due to a variety of factors, including insufficient data for the reporting period, the well was reported to run dry, monitoring was discontinued due to well removal, etc. More information about datasets used can be seen in the following question.
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Question #3: Will the datasets/GIS files be made available by DWR for use in other analysis/reports?
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Answer #3: Datasets used to develop CalGW Update 2025 are available on California Natural Resource Agency’s Open Data site and also on DWR’s SGMA Portal (SGMA-required data submitted by groundwater sustainability agencies [GSAs]). The final version of CalGW Update 2025 is expected to be released in spring 2026, which will include Appendix C. “Methods and Assumptions”. Datasets used in the report that are a snapshot or queried will be available for download as part of the final release. Other datasets used in their original form will be identified as part of Appendix C. This appendix will provide details on methods and assumptions that were used to create the figures and tables in CalGW Update 2025. These methods and assumptions focus only on new data and analysis. Figures and tables are briefly discussed along with the datasets used to create them, where applicable.
Public Comment Period
A 45-day public comment period is now open on the Draft CalGW Update 2025. All comments will be reviewed and will provide valuable feedback to DWR to improve the analysis, reporting, and access to California’s groundwater information.
Public comments can be emailed to CalGW@water.ca.gov and will be accepted through Friday, December 5, 2025.
The final version of CalGW Update 2025 is expected to be released in spring 2026.
Draft CalGW Update 2025
CalGW Update 2025 provides a comprehensive inventory and assessment of available information on the occurrence and nature of groundwater and informs decisions on the protection, use, monitoring and management of the resource. This five-year update builds on the CalGW Update 2020 by integrating data submitted to DWR by local agencies under the Sustainable Groundwater Management Act (SGMA), including information reported in Groundwater Sustainability Plans (GSP), Alternatives to GSPs, annual reports, and other groundwater initiatives. CalGW Update 2025 is part of a comprehensive suite of resources designed to support groundwater understanding and management across the state, including the Semi-Annual Updates, CalGW Live, and the Basin Characterization program.
The draft publication contains a Highlights overview section in English and Spanish and a detailed Statewide Report (Chapters 1 – 6), which features current knowledge of groundwater resources including information on the location, characteristics, use, management status, and conditions of the state’s groundwater. Also included in this draft release is an info-graphic summary of the ten hydrologic regions, showing regional groundwater at a glance (Chapter 7) and some appendices such as findings and recommendations that support the future management and protection of groundwater, a glossary of terms, reference materials, and an update on land subsidence in California. This information can help communities and local water managers work together to find unique ways to manage their groundwater basins for long-term reliability and support actions being implemented as part of Governor Gavin Newsom’s 2020 California Water Resilience Portfolio.
The draft release of CalGW Update 2025 consists of files listed below. A fact sheet on the CalGW Update 2025 and the public review process is available in English and Spanish.
Draft CalGW Update 2025
For general inquiries, please contact: sgmps@water.ca.gov and for more information on all of these releases and updates, visit the California’s Groundwater webpage or contact: CalGW@water.ca.gov.
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