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 Water: The Colorado River

Public Policy Institute of California (PPIC) | October 1st, 2016

The Colorado River—a major water source for Southern California’s cities and farms—is shared among seven states and Mexico. Water use now outstrips supply. The

The Colorado River—a major water source for Southern California’s cities and farms—is shared among seven states and Mexico. Water use now outstrips supply. The environmental impacts of water use in this basin pose special challenges. This brief describes adaptation strategies so that the river can continue to provide essential benefits to the region. This publication is part of a briefing kit that summarizes a dozen of the state’s most pressing water management issues.

California’s Water: Water for Farms

Public Policy Institute of California (PPIC) | October 1st, 2016

California is the nation’s largest farm state and a global market leader. Farms have steadily improved productivity per unit of water used, but the latest drought h

California is the nation’s largest farm state and a global market leader. Farms have steadily improved productivity per unit of water used, but the latest drought has exposed agriculture’s growing vulnerability to water shortages. This brief describes a number of opportunities to strengthen agricultural water management for the long term. This publication is part of a briefing kit that summarizes a dozen of the state’s most pressing water management issues.

Can water reuse save the Colorado?

University of California, Los Angeles (UCLA) | April 2nd, 2025

To assess the current state of water recycling across the Colorado River Basin and its affected states, UCLA Institute of the Environment and Sustainability, in partnersh

To assess the current state of water recycling across the Colorado River Basin and its affected states, UCLA Institute of the Environment and Sustainability, in partnership with Natural Resources Defense Council, has investigated water recycling progress and policy development across the seven states in the basin.

Central Valley Project: Water Supply and Yield Study

U.S. Bureau of Reclamation (USBR) | March 12th, 2008

Hydrologic conditions in California vary greatly from year to year, season to  season, and place to place.  Wet years bring the threat of floods, and drought years put

Hydrologic conditions in California vary greatly from year to year, season to  season, and place to place.  Wet years bring the threat of floods, and drought years put pressure on available water supplies. The majority of the state’s precipitation occurs in the northern third of the state during the winter, while much of the water is used in the central and southern portions  of the state during the spring and summer. Because of this, meeting California’s water demands is complicated by the logistics of moving water from its source to its place of use, which may be over hundreds of miles. The availability of storage and conveyance facilities may limit California’s ability to deliver water to the right place at the right time. The purpose of this Water Supply and Yield (WSAY) Study is to identify the following: 1. Opportunities for new firm yield and water supply improvements for CVP water service contractors (entities with contracts for the delivery of CVP water) 2. Water management actions or projects that would improve firm yield for the CVP while balancing the available supplies with existing demands 3. The financial costs of the water management actions or projects 4. Beneficiaries and beneficiaries’ willingness to pay for identified improvements

Climate and choice in the Colorado River Basin

Agricultural & Applied Economics Association (AAEA) | October 31st, 2024

Climate Change and Future Water Availability in the United States, Chapter E of U.S. Geological Survey Integrated Water Availability Assessment—2010–20

U.S. Geological Survey (USGS) | January 15th, 2025

The following are the key points of this chapter:  The steady rise in global temperature as a result of human activity is causing changes in Earth’s water cycle.

The following are the key points of this chapter:  The steady rise in global temperature as a result of human activity is causing changes in Earth’s water cycle. The amount of water stored within and moving between vapor, liquid and frozen components of the water cycle is shifting, with significant consequences for water availability. Climatic drivers underlie regional or local changes in water supply and their socioeconomic impacts. Threats to the quantity and quality of water available for humans and ecosystems in North America include increases in drought, aridification, and fire weather; heavy precipitation and flooding; cryosphere decline; rising surface-water temperatures; and saltwater intrusion in coastal areas. An understanding of how changes in the major climatic drivers impact the water cycle and the accurate simulation of impacts in hydrological models are crucial to predicting future water availability and developing adaptation strategies to ensure human and ecosystem water supplies. Companion chapters: U.S. Geological Survey Integrated Water Availability Assessment—2010–20, Chapter A Water Supply in the Conterminous United States, Alaska, Hawaii, and Puerto Rico, Water Years 2010–20, Chapter B Status of Water-Quality Conditions in the United States, 2010–20, Chapter C  Water Use Across the Conterminous United States, Water Years 2010–20, Chapter D  Integrated Water Availability in the Conterminous United States, 2010–20, Chapter F 

Climate change decisive for Asia’s snow meltwater supply

Nature Portfolio (Springer Nature) | June 24th, 2021

Streamflow in high-mountain Asia is influenced by meltwater from snow and glaciers, and determining impacts of climate change on the region’s cryosphere is essential to

Streamflow in high-mountain Asia is influenced by meltwater from snow and glaciers, and determining impacts of climate change on the region’s cryosphere is essential to understand future water supply. Past and future changes in seasonal snow are of particular interest, as specifics at the scale of the full region are largely unknown. Here we combine models with observations to show that regional snowmelt is a more important contributor to streamflow than glacier melt, that snowmelt magnitude and timing changed considerably during 1979–2019 and that future snow meltwater supply may decrease drastically. The expected changes are strongly dependent on the degree of climate change, however, and large variations exist among river basins. The projected response of snowmelt to climate change indicates that to sustain the important seasonal buffering role of the snowpacks in high-mountain Asia, it is imperative to limit future climate change.

Climate Change Impacts to Water and Sanitation for Frontline Communities in the United States Water, Sanitation, and Climate Change in the United States Series, Part 1

Pacific Institute | January 15th, 2024

Climate change is among the most urgent, wide-ranging crises we face. It poses significant challenges and is already resulting in severe impacts to drinking water and san

Climate change is among the most urgent, wide-ranging crises we face. It poses significant challenges and is already resulting in severe impacts to drinking water and sanitation access. This is true for both those currently living without access and for communities where forces like drought, flooding, sea level rise, wildfires, and intensifying storms threaten backsliding by degrading or stripping basic water and sanitation services from the people. Access to sufficient, safe, acceptable, physically accessible, and affordable water and sanitation is essential for human health and wellbeing, as well as economic prosperity—and climate change will inevitably make ensuring all have access more challenging. Without water and sanitation access, people do not have water to drink, cannot clean, shower, or wash their hands, and cannot safely dispose of human waste. They may have to travel long distances to purchase and haul water back to their homes. Without access to water, they also have less ability to cool their homes, protect themselves from wildfires, and work or go to school. An economic assessment by DigDeep found that for every household in the United States without access to water and sanitation, the domestic economy loses $15,800 annually in extra health care costs, time and money spent on bottled water, lost educational or work opportunities, and premature death (DigDeep 2022). This is part one  in the Pacific Institute's three-part Water, Sanitation, and Climate Change in the United States series. Click here for part two and here for part three.

Climate change threatens California’s future

Public Policy Institute of California (PPIC) | January 31st, 2020

California faces a twofold climate challenge: finding cost-effective ways to reduce emissions of greenhouse gases (GHGs) and preparing for the changes that are

California faces a twofold climate challenge: finding cost-effective ways to reduce emissions of greenhouse gases (GHGs) and preparing for the changes that are expected even if global emissions fall. Greenhouse gas emissions pose a serious threat. The state experienced 7 of its 10 warmest years on record from 2012 to 2018, and warming is expected to continue. Sea level is predicted to rise 2 to 7 feet on California’s coast by 2100, and the frequency of extreme events such as droughts, heat waves, wildfires, and floods is expected to increase. Higher temperatures result in more precipitation falling as rain (and less as snow), which will increase both the frequency and magnitude of flooding and diminish water reserves in the Sierra snowpack.