California's Fourth Climate Change Assessment Statewide Summary Report

Governor's Office of Planning and Research (OPR) | August 27th, 2018

California’s Fourth Climate Change Assessment (Fourth Assessment) advances actionable science that serves the growing needs of state and local-level decision-

California’s Fourth Climate Change Assessment (Fourth Assessment) advances actionable science that serves the growing needs of state and local-level decision-makers from a variety of sectors. This cutting-edge research initiative is comprised of a wide-ranging body of technical reports, including rigorous, comprehensive climate change scenarios at a scale suitable for illuminating regional vulnerabilities and localized adaptation strategies in California; datasets and tools that improve integration of observed and projected knowledge about climate change into decision- making; and recommendations and information to directly inform vulnerability assessments and adaptation strategies for California’s energy sector, water resources and management, oceans and coasts, forests, wildfires, agriculture, biodiversity and habitat, and public health. In addition, these technical reports have been distilled into summary reports and a brochure, allowing the public and decision-makers to easily access relevant findings from the Fourth Assessment. Click here for key findings brochure

California's Groundwater Conditions: Semi-Annual Update May 2025

California Department of Water Resources (DWR) | June 24th, 2025

This semi-annual report presents data received by DWR as of April 2025 and reflects the impacts of a few wet years after a drought period. However, it should be noted tha

This semi-annual report presents data received by DWR as of April 2025 and reflects the impacts of a few wet years after a drought period. However, it should be noted that groundwater response is a slow process and may take months to years to fully respond to changes in surface water conditions. This report is the latest in a series of Semi-Annual Groundwater Conditions Updates, last published in October 2024. These updates are part of the informational resources associated with DWR’s California’s Groundwater (Bulletin 118). The most recent groundwater data is available on the California’s Groundwater Live website, which is updated daily as data is received by DWR. Additional data and information are available in the CNRA Open Data and Water Data Library websites.

California's Groundwater Update 2025 (Bulletin 118)

California Department of Water Resources (DWR) | October 20th, 2025

California’s Groundwater: Bulletin 118 — Update 2025 (CalGW Update 2025) is a compendium of statewide data and information on the occurrence, nature, use, and conditi

California’s Groundwater: Bulletin 118 — Update 2025 (CalGW Update 2025) is a compendium of statewide data and information on the occurrence, nature, use, and conditions of California’s groundwater resources and management. Chapters 1-6 Chapter 7 Appendix A: Findings and Recommendations Appendix B: Glossary Appendix D: Citations, Reference Materials, and Links Appendix I: Land Subsidence  

California's Water Supply Strategy: Adapting to a Hotter, Drier Future

California Department of Water Resources (DWR) | August 16th, 2022

California's Water Supply Strategy: Adapting to a Hotter, Drier Future

Office of Governor Gavin Newsom | August 11th, 2022

California’s Climate Adaptation Water Strategy: An Analysis of Implications for Individual and Community Rights and Responsibilities

California Department of Water Resources (DWR) | July 31st, 2009

The inevitable consequences of climate change will put some of California's people and communities more at risk than others. Because of location and a limited capacity to

The inevitable consequences of climate change will put some of California's people and communities more at risk than others. Because of location and a limited capacity to adapt, vulnerable populations may face profound and disproportionate harm. California's Climate Adaptation Strategy planners are seeking ways to address this potential harm. The California Adaptation Strategy (CAS) Working Groups are seeking to address the impact of climate change on the state’s vulnerable populations. This analysis therefore asks how California can create a policy environment for equitable adaptation processes and outcomes. This analysis begins with a literature review on equity issues in adaptation planning, then examines the Water Working Group’s draft climate adaptation strategies, and then presents the results of twenty-six expert interviews. Two key concerns in the development of adaptation policy that arise in this analysis are feedback loops between vulnerable communities and policymakers and direct access to resources to enable greater adaptive capacity. While this analysis looks closest at the Water Working Group’s strategies, it is anticipated that many of the findings will apply to the overall strategy.

California’s Flood Future: Recommendations for Managing the State’s Flood Risk

California Department of Water Resources (DWR) | November 1st, 2013

California is at risk for catastrophic flooding that could have wide-ranging impacts due to the size of its economy and the number of people residing in the state. The St

California is at risk for catastrophic flooding that could have wide-ranging impacts due to the size of its economy and the number of people residing in the state. The State’s economy ranks ninth globally; therefore, the consequences associated with its potential exposure to property damage, economic harm, and loss of life are great. California is the nation’s most populous state, ranks third largest in land size, and has widely varying climates and topographies, all of which make developing one-size-fits-all solutions to flood risk management impracticable. In California, 20 percent of the almost 38 million residents live within 500-year floodplains (i.e., have a 0.2 percent chance of flooding in a given year). Four of the nation’s 15 largest cities are in California (Los Angeles, San Diego, San Jose, and San Francisco), and all are at risk for some type of flooding. These factors make decisions regarding California’s flood risk management policies and financial investments vital to the State and the nation. This report, California’s Flood Future: Recommendations for Managing the State’s Flood Risk (Flood Future Report) presents an overview of the flood threats facing the state, approaches for reducing flood risk, and recommendations for managing California’s flood risk. The Flood Future Report is the first statewide report to be developed through collaboration between the California Department of Water Resources (DWR) and the United States Army Corps of Engineers (USACE). As a joint report by the State and Federal governments, the document represents an unprecedented level of intergovernmental cooperation, including tribal entities.1 Additionally, this report would not have been possible without the participation of and information shared by more than 140 local flood management agencies. The Flood Future Report represents the first characterization of flood management activities and exposure to flood hazard throughout each county and hydrologic region of the state. This statewide assessment is intended to provide valuable information for local, State, and Federal decision makers as they chart California’s complex flood management future.

California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013

California Department of Water Resources (DWR) | April 1st, 2015

The primary goal of California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013 (California’s Groundwater Update 201

The primary goal of California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013 (California’s Groundwater Update 2013) is to provide foundational information to improve the statewide and regional understanding of groundwater conditions and management programs. The set of data, information, and analyses developed by the California Department of Water Resources (DWR) will help set the stage for future Bulletin 118 and California Water Plan updates, and help local and regional agencies plan for sustainable groundwater management by providing an on-going reporting of essential groundwater data, information, and analyses. A second goal is to identify data gaps and groundwater management challenges that are meant to serve as a guidepost for prioritizing future groundwater data collection and funding opportunities. The final goal is to develop a set of recommendations to improve groundwater management in California. Findings, data gaps, and recommendations were developed for the state as a whole and for each of the 10 hydrologic regions. Statewide findings, data gaps, and recommendations presented herein serve as a summary of those commonly identified at the regional level.

California’s Groundwater: Bulletin 118 — Update 2025 Highlights

California Department of Water Resources (DWR) | October 20th, 2025

California’s Groundwater: Bulletin 118 — Update 2025 (CalGW Update 2025) serves as the most up-to-date and comprehensive compendium of statewide data and information

California’s Groundwater: Bulletin 118 — Update 2025 (CalGW Update 2025) serves as the most up-to-date and comprehensive compendium of statewide data and information on the occurrence, nature, uses, management, climate change vulnerability, monitoring, and conditions of California’s groundwater resources. Building on the legacy of Bulletin 118 and past California Water Plans, CalGW Update 2025 synthesizes recent data — available up to December 2023 — and closes key knowledge gaps to inform more effective statewide groundwater planning and decision-making.  CalGW Update 2025 consists of this Highlights document and a detailed statewide report, supported by a series of appendices. 

California’s Most Significant Droughts: Comparing Historical and Recent Conditions

California Department of Water Resources (DWR) | February 2nd, 2015

This report was prepared in response to the dry conditions of 2012-14 (Figure 1.1) and particularly in response to the very dry hydrology of water year 2014. Water year 2

This report was prepared in response to the dry conditions of 2012-14 (Figure 1.1) and particularly in response to the very dry hydrology of water year 2014. Water year 2014 ranked as the third driest on record in terms of statewide precipitation, with the three-year period of water years 2012-14 ranking as the driest consecutive three-year period on record in terms of statewide precipitation. Continuing dry hydrology in 2015 raises questions about the similarity of present conditions to those of prior droughts and changes in observed impacts as California’s population increases and new institutional requirements are put in place. The purpose of this report is to compare present conditions with California’s most significant droughts of statewide scope, to help answer questions about the comparative severity of drought hydrology and drought impacts. The report also summarizes lessons learned and commonalities seen in the state’s most severe historical droughts.