Priorities for California Water (2017)

Public Policy Institute of California (PPIC) | October 13th, 2017

This past year was a prime example of California’s highly variable climate—and a precursor of the types of extremes that are expected to become more common. After fiv

This past year was a prime example of California’s highly variable climate—and a precursor of the types of extremes that are expected to become more common. After five years of drought exacerbated by record heat, 2017’s record rain and snow brought more challenges—stressing dams and levees, causing landslides, and adding fuel to fire-prone landscapes. Across California, leaders have responded with a number of policy and management reforms, including some that will help the state adapt to droughts and floods of the future. But there’s more work to be done. In this policy brief we outline issues that are front and center for managing California’s water supply and natural environment. We also suggest priorities for actions that would improve California’s water systems and better support the state’s residents, businesses, and ecosystems.

Priorities for California's Water: Responding to the Changing Climate

Public Policy Institute of California (PPIC) | November 18th, 2021

Water is central to how California adapts to a changing climate. To those of us steeped in the complexities of managing the state’s water resources, the current fast-mo

Water is central to how California adapts to a changing climate. To those of us steeped in the complexities of managing the state’s water resources, the current fast-moving drought—coming on the heels of the record-breaking 2012–16 drought—is a stark reminder that we must accelerate preparation for the disruptive changes underway. Californians have taken steps to address major threats to our water resources. But a recent IPCC report underscored that the climate is changing faster than anticipated, and that many of these changes are already locked in. Rising temperatures are making our winters shorter and our droughts more intense, outpacing our ability to manage water supplies and the natural environment. We need to act with urgency to adapt to these changes. And we need to rethink how we store water. This brief examines how the current drought and a changing climate are affecting California’s ability to manage water and lays out priority actions to address major challenges—including some urgent short-term actions should the drought continue into next year.

Priorities for California’s Water

Public Policy Institute of California (PPIC) | November 14th, 2022

This report considers the state of water in California: What changes are we seeing now, and what should we expect in the near future? Then it examines how these climate s

This report considers the state of water in California: What changes are we seeing now, and what should we expect in the near future? Then it examines how these climate shifts will impact urban and rural communities, agriculture, and the environment. Finally, it explores wet-year strategies that will help Californians get through the dry years.

Priorities for California’s Water -- Stewarding the Wet Years

Public Policy Institute of California (PPIC) | November 2nd, 2023

The 2023 water year provided a case study of California’s increasingly volatile climate, with large swings between wet and dry conditions both within and between years.

The 2023 water year provided a case study of California’s increasingly volatile climate, with large swings between wet and dry conditions both within and between years. It highlighted our need to better navigate multiple imperatives: storing more water during intense wet periods to build water supply reliability, protecting communities and infrastructure against the threat of increasingly damaging floods, and taking better advantage of wet years to improve the health of freshwater ecosystems and native fish and wildlife.

Priorities for California’s Water: Advancing Research During Uncertain Times

Public Policy Institute of California (PPIC) | November 12th, 2025

In California, research underpins all water-related activity. It is vital for coping with too much water, too little water, and rapid changes in hydrology. Whether you ar

In California, research underpins all water-related activity. It is vital for coping with too much water, too little water, and rapid changes in hydrology. Whether you are a farmer managing the precise application of water to your crops, a utility providing clean drinking water supplies to your community, or a restorationist trying to heal a damaged wetland, your actions rely upon decades of applied research that guides your actions and measures your success.  The same reliance on research applies if you are developing policies to reduce the price of water, increase its reliability, regulate its usage, and reduce hazards from floods. None of this works without a vast research enterprise that is regularly updating the science and technology we use to manage water, prepare for the future, inform the public, and address new problems as they arise. 

Probabilistic Subsidence Forecast Model for the California Aqueduct Subsidence Program, San Joaquin Valley, California: Revision 1 Design Report

California Department of Water Resources (DWR) | October 4th, 2024

This report documents the development of a probabilistic subsidence forecast model for simulating a plausible range of future land-surface altitude conditions along the C

This report documents the development of a probabilistic subsidence forecast model for simulating a plausible range of future land-surface altitude conditions along the California Aqueduct (Aqueduct) and San Luis Canal in the San Joaquin Valley (SJV), with an emphasis on areas of localized subsidence (i.e., “subsidence bowls”). The model forecasts will be used to inform long-term planning and on-going analyses of potential investments needed to provide a suitable level of performance for the Aqueduct. The forecast model is primarily based on an empirical relationship between historical subsidence rates and annual water deliveries from the Central Valley Project (CVP) and State Water Project (SWP). A key assumption of the model is that the rate of groundwater overdraft, which contributes to loss of aquifer storage and permanent land subsidence, is correlated with CVP and SWP deliveries, and specifically with higher groundwater storage loss during severe drought years. Another key assumption is that the same rates of subsidence will continue even after groundwater levels decline and extraction may be coming from deeper parts of the aquifer system. If the geology and/or aquifer properties change dramatically in response, then these new conditions may have an unmodeled impact on future rates. 

Procedures to evaluate sea-level change: impacts, responses, and adaptation

U.S. Army Corps of Engineers (USACE) | June 30th, 2014

Productive wetlands restored for carbon sequestration quickly become net CO2 sinks with site-level factors driving uptake variability

PLOS | March 25th, 2021

Inundated wetlands can potentially sequester substantial amounts of soil carbon (C) over the long-term because of slow decomposition and high primary productivity, partic

Inundated wetlands can potentially sequester substantial amounts of soil carbon (C) over the long-term because of slow decomposition and high primary productivity, particularly in climates with long growing seasons. Restoring such wetlands may provide one of several effective negative emission technologies to remove atmospheric CO2 and mitigate climate change. However, there remains considerable uncertainty whether these heterogeneous ecotones are consistent net C sinks and to what degree restoration and management methods affect C sequestration. Since wetland C dynamics are largely driven by climate, it is difficult to draw comparisons across regions. With many restored wetlands having different functional outcomes, we need to better understand the importance of site-specific conditions and how they change over time. We report on 21 site-years of C fluxes using eddy covariance measurements from five restored fresh to brackish wetlands in a Mediterranean climate. The wetlands ranged from 3 to 23 years after restoration and showed that several factors related to restoration methods and site conditions altered the magnitude of C sequestration by affecting vegetation cover and structure. Vegetation established within two years of re-flooding but followed different trajectories depending on design aspects, such as bathymetry-determined water levels, planting methods, and soil nutrients. A minimum of 55% vegetation cover was needed to become a net C sink, which most wetlands achieved once vegetation was established. Established wetlands had a high C sequestration efficiency (i.e. the ratio of net to gross ecosystem productivity) comparable to upland ecosystems but varied between years undergoing boom-bust growth cycles and C uptake strength was susceptible to disturbance events. We highlight the large C sequestration potential of productive inundated marshes, aided by restoration design and management targeted to maximise vegetation extent and minimise disturbance. These findings have important implications for wetland restoration, policy, and management practitioners.

Progress on Incorporating Climate Change into Planning and Management of California’s Water Resources

California Department of Water Resources (DWR) | July 9th, 2006

On June 1, 2005, Governor Arnold Schwarzenegger issued Executive Order S-3-05 establishing greenhouse gas emissions targets for California and requiring biennial reports

On June 1, 2005, Governor Arnold Schwarzenegger issued Executive Order S-3-05 establishing greenhouse gas emissions targets for California and requiring biennial reports on potential climate change effects on several areas, including water resources. The Governor established a Climate Action Team (CAT) to guide the reporting efforts. The CAT selected four climate change scenarios that reflect two greenhouse gas emissions scenarios represented by two Global Climate Models (GCMs). The CAT requested that those four climate change scenarios be used whenever possible in the climate change reporting efforts. This report is the Department of Water Resources response to the Executive Order. This report describes progress made incorporating climate change into existing water resources planning and management tools and methodologies.

Projected 21st Century Coastal Flooding in the Southern California Bight. Part 1: Development of the Third Generation CoSMoSModel

Journal of Marine Science and Engineering (MDPI) | May 24th, 2018

Due to the effects of climate change over the course of the next century, the combination of rising sea levels, severe storms, and coastal change will threaten the susta

Due to the effects of climate change over the course of the next century, the combination of rising sea levels, severe storms, and coastal change will threaten the sustainability of coastal communities, development, and ecosystems as we know them today. To clearly identify coastal vulnerabilities and develop appropriate adaptation strategies due to projected increased levels of coastal flooding and erosion, coastal managers need local-scale hazards projections using the best available climate and coastal science. In collaboration with leading scientists world-wide, the USGS designed the Coastal Storm Modeling System (CoSMoS) to assess the coastal impacts of climate change for the California coast, including the combination of sea-level rise, storms, and coastal change. In this project, we directly address the needs of coastal resource managers in Southern California by integrating a vast range of global climate change projections in a thorough and comprehensive numerical modeling framework. In Part 1 of a two-part submission on CoSMoS, methods and the latest improvements are discussed, and an example of hazard projections is presented. Click here for Part 2.