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 most significant droughts: Comparing historical and recent conditions

California Department of Water Resources (DWR) | March 23rd, 2015

The water years of 2012-14 stand as California’s driest three consecutive years in terms of statewide precipitation, and as of this writing in February 2015 the drought

The water years of 2012-14 stand as California’s driest three consecutive years in terms of statewide precipitation, and as of this writing in February 2015 the drought is continuing on. This report was prepared to compare the hydrology and impacts experienced during 2012-2014 with those of California’s largest historical droughts, in response to questions from local water agencies and others regarding the drought’s relative severity and the changed conditions since our prior major droughts. California’s immediately prior drought of statewide scale occurred in 2007-09; it was the first drought for which a statewide proclamation of emergency was issued. The 2012-14 period now marks the second time a statewide proclamation of emergency has been issued for drought. California’s most significant historical statewide droughts were the six-year drought of 1929-34, the two-year drought of 1976-77, and the six-year event of 1987-92. These droughts stand out in the observed record due to their duration or severe hydrology. The 1929-34 event occurred within the climatic context of a decades-plus dry period in the 1920s-30s whose hydrology rivaled that of the most severe dry periods in more than a millennium of reconstructed Central Valley paleoclimate data. The drought’s impacts were small by present-day standards, however, since the state’s urban and agricultural development was far less than that of modern times. The 1976-77 drought, although brief in duration, was notable for the severity of its hydrology. The 1987-92 drought was California’s first extended dry period since the 1920s-30s, and provides the closest comparison for drought impacts under a present-day level of development. The 2012-14 event set other records in addition to that of driest three-year period of statewide precipitation. The drought occurred at a time of record warmth in California, with new climate records set in 2014 for statewide average temperatures. Records for minimum annual precipitation were set in many communities in calendar year 2013. Calendar year 2014 saw record-low water allocations for State Water Project and federal Central Valley Project contractors. Reduced surface water availability triggered increased groundwater pumping, with groundwater levels in many parts of the state dropping 50 to 100 feet below their previous historical lows. These record-setting conditions speak to the need for continued improvement of our ability to respond to dry conditions. Knowledge of the impacts historically experienced in our past large droughts and the lessons learned during those events can help us be better prepared.

California's Rivers and Streams

Public Policy Institute of California (PPIC) | January 26th, 2026

California's Volatile Hydroclimate: Lessons From the Paleoclimate Record

American Geophysical Union (AGU) | November 24th, 2021

California's Water – Energy Relationship

California Energy Commission (CEC) | November 1st, 2005

This is an urgent time of both challenge and opportunity. The primary finding of this paper is that a major portion of the solution is closer coordination between the wat

This is an urgent time of both challenge and opportunity. The primary finding of this paper is that a major portion of the solution is closer coordination between the water and energy sectors. A meaningful solution cannot be reached in the current regulatory environment where water utilities value only the cost of acquisition, conveyance, treatment, and delivery; wastewater utilities value only the cost of collection, treatment, and disposal; electric utilities value only saved electricity; and natural gas utilities value only saved natural gas. The state must both develop and expand best practices and existing programs to realize the substantial incremental benefits of joint water and energy resources and infrastructure management. While many nuances of this complex statewide problem are still unclear, staff’s analysis shows that significant energy benefits can be reaped through the twin goals of the efficient use of water by end users and the efficient use of energy by water systems. It is also clear that not nearly enough has been done to ensure that California’s water supply strategies are synchronized, hand-in-hand, with its energy strategies. Nor has enough been done to forge partnerships between the water and energy sectors so that their natural synergies, joint resources, and assets can be effectively leveraged for the benefit of all Californians. The state has the opportunity now to reap near-term energy benefits by helping California’s water and wastewater utilities become more energy self-sufficient, which will ease pressures on California’s already stressed electric system. By adjusting existing policies, programs, and resources, water and wastewater utilities could be converted from high energy users to net renewable energy producers. California’s water and energy policymakers need to commit today to the joint planning and management of these critical resources. The state’s water plan and resource strategies are being reviewed with all key stakeholders, and implementation plans are already on the drawing table. At the same time, the California Public Utilities Commission has approved substantial utility ratepayer expenditures in energy efficiency programs for the 2006-2008 program cycle. The state must waste no time in taking advantage of these rapidly evolving events. The state can meet energy and demand-reduction goals comparable to those already planned by the state’s investor-owned energy utilities for the 2006-2008 program period by simply recognizing the value of the energy saved for each unit of water saved. If allowed to invest in these cold water energy savings, energy utilities could co-invest in water use efficiency programs, which would in turn supplement water utilities’ efforts to meet as much load growth as possible through water efficiency. Remarkably, staff’s initial assessment indicates that this benefit could be realized at less than half the cost to electric ratepayers of traditional energy efficiency measures. This staff report examines how energy is used – and how it can be saved – in the water use cycle. The strategies and goals for a comprehensive statewide water-energy program would achieve incremental energy benefits for water and energy utilities. The overarching goal of establishing a comprehensive statewide water-energy program would create a dynamic, living process where key stakeholders have incentives to continuously identify and implement strategies optimizing the state’s water and energy resources and assets on an integrated, coordinated, and collaborative basis. This opportunity must not be lost since the need is so great. Because of all these factors, staff recommends that an action-oriented approach structured to achieve near-term results be developed immediately.

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 Water–Energy Relationship

California Energy Commission (CEC) | November 1st, 2005

This report examines the dynamic give-and-take relationship between California’s water and energy resources. Among many other issues, this staff report examines the s

This report examines the dynamic give-and-take relationship between California’s water and energy resources. Among many other issues, this staff report examines the state’s water sector and its energy use, along with changes likely to occur in the future.

California’s Agricultural and Urban Water Supply Reliability and the Sacramento–San Joaquin Delta

University of California, Davis (UC Davis) | October 13th, 2016

Much of the water supplied in California for agriculture and cities is taken directly from the Sacramento–San Joaquin Delta (Delta) or indirectly from surface and groun

Much of the water supplied in California for agriculture and cities is taken directly from the Sacramento–San Joaquin Delta (Delta) or indirectly from surface and groundwater diversions upstream. These water supplies have great economic and social value, and considerable ecosystem effects. Long thought of as the major source of water for economic growth in California, the reliability of water supplied from the Delta is threatened by drought, flood, climate change, earthquakes, growing water demands, and deteriorating conditions for endangered species and native ecosystems. Research in recent years has improved understanding of how management of the Delta ties together the quantity and quality of water available statewide. These ties run from the Sierra mountains and coastal streams, through the Central Valley, to the San Francisco Bay Area, and over the Tehachapi Mountains to southern California. For decades, Californians counted on reducing Delta outflows to supply water for growing water demands in its watershed and in water importing areas. With greater competition for water, concern for environmental effects, and a changing climate, the reliability of such supplies is now diminishing. This must lead to tighter accounting and modeling of water supplies in the Delta and throughout its watershed. This paper reviews issues about Delta water supplies, operations, regulations, and reliability; the economic value of supply; costs of unreliability in quantity and quality; and several directions for further scientific and technical work on water supply reliability.