Climate Action Plan, Phase 3: Climate Change Vulnerability Assessment

California Department of Water Resources (DWR) | February 14th, 2019

Climate change impacts have been widely documented globally, across the nation, and within the state. Loss of snowpack; longer, more frequent heat waves; and longer, more

Climate change impacts have been widely documented globally, across the nation, and within the state. Loss of snowpack; longer, more frequent heat waves; and longer, more intense wildfire seasons are already being experienced in California. While uncertainties remain about the exact timing and extent of projected impacts, numerous climate-driven hazards represent a clear threat to Department of Water Resources (DWR) facilities, managed lands, operations, and staff activities. By conducting this department-wide vulnerability assessment, DWR seeks to better prepare its decision-making for an uncertain future.  This climate change vulnerability assessment (VA) provides the first evaluation of its kind for facilities owned and operated by DWR and the activities that DWR performs. This analysis draws from the extensive body of knowledge about climate change and attempts to evaluate, describe, and quantify — where possible — DWR’s vulnerabilities to expected increases in wildfire, extreme heat, and sea-level rise, as well as to changes in hydrology and ecosystems that will impact DWR’s facilities, operations, and other activities. Table ES-1 presents examples of vulnerabilities identified in this assessment and summarizes quantitative indicators of climate change risk.  Using a mid-century time horizon, climate-change-driven hazards assessed in this VA are presented under six categories: wildfire, extreme heat, sea-level rise, long-term persistent hydrologic changes, short-term extreme hydrologic events, and habitat and ecosystem services degradation. This assessment applies a common framework to examine vulnerability through three components of how DWR’s assets and operations could be exposed to future climate hazards, how these assets and operations are sensitive (or susceptible) to impacts of this exposure, and the capacity of these assets and operations to cope with or adapt to changing conditions or events. 

Climate Adaptation Master Plan for Water (CAMP4W)

Metropolitan Water District of Southern California (MWD) | March 26th, 2025

To ensure the continued reliability of water supplies for the communities we serve, Metropolitan embarked on the development of a comprehensive Climate Adaptati

To ensure the continued reliability of water supplies for the communities we serve, Metropolitan embarked on the development of a comprehensive Climate Adaptation Master Plan for Water (CAMP4W), a comprehensive set of policy directives and decision-making tools that ensure the Board of Directors is equipped to consider climate risks to water supplies, water quality, infrastructure, operations, workforce, public health, and financial sustainability to its deliberations and investment decisions. It provides a roadmap to guide future investments and decision-making as we confront our new climate reality in the years and decades ahead.

Climate and choice in the Colorado River Basin

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

Climate and land change impacts on future managed wetland habitat: a case study from California’s Central Valley

Landscape Ecology (Springer) | January 7th, 2022

Concept California’s Central Valley provides critical habitat for migratory waterbirds, yet only 10% of naturally occurring wetlands remain. Competition for limited wa

Concept California’s Central Valley provides critical habitat for migratory waterbirds, yet only 10% of naturally occurring wetlands remain. Competition for limited water supplies and climate change will impact the long-term viability of these intensively managed habitats. Objectives Forecast the distribution, abundance, and connectivity of surface water and managed wetland habitats, using 5 spatially explicit (270 m2) climate/land use/water prioritization scenarios. Mapping potential future dynamic flooded habitat used by waterbirds and other wetland-dependent wildlife to inform management decisions. Methods We integrated a climate-driven hydrologic water use model with a spatially explicit land change model, to examine stakeholder-driven scenarios of future land change, climate, and water use and their impacts on future habitat availability. Results Declining water availability is the dominant driver of habitat loss across scenarios. The hot/dry scenarios showed the greatest declines in January flooded area by 2101—an important month for overwintering waterbirds. In contrast, higher water supplies in wet climates drive perennial cropland conversion and loss of potential habitat. Potential flooded cropland declined (25 and 33%) under warmer/wetter climate conditions due to this conversion to perennial crops, exposing habitat vulnerability. Conclusion Climate-driven loss of water availability had a greater impact on flooded habitat availability than land-use change. When combined, climate change and the conversion of potentially flooded cropland to perennial cropland will threaten future waterbird habitat particularly in January, the peak of the migratory bird season, even when habitat restoration goals are met. Stakeholder-informed scenario analysis can identify target areas for potential habitat change, vulnerability, and conservation.

Climate and landscape drive the pace and pattern of conifer encroachment into subalpine meadows

Ecological Society of America (Wiley) | May 8th, 2018

Mountain meadows have high biodiversity and help regulate stream water release following the snowmelt pulse. However, many meadows are experiencing woody plant encr

Mountain meadows have high biodiversity and help regulate stream water release following the snowmelt pulse. However, many meadows are experiencing woody plant encroachment, threatening these ecosystem services. While there have been field surveys of individual meadows and remote sensing‐based landscape‐scale studies of encroachment, what is missing is a broad‐scale, ground‐based study to understand common regional drivers, especially at high elevations, where land management has often played a less direct role. With this study, we ask: What are the climate and landscape conditions conducive to woody plant encroachment at the landscape scale, and how has historical climate variation affected tree recruitment in subalpine meadows over time? We measured density of encroaching trees across 340 subalpine meadows in the central Sierra Nevada, California, USA, and used generalized additive models (GAMs) to determine the relationship between landscape‐scale patterns of encroachment and meadow environmental properties. We determined ages of trees in 30 survey meadows, used observed climate and GAMs to model the relationship between timing of recruitment and climate since the early 1900s, and extrapolated recruitment patterns into the future using downscaled climate scenarios. Encroachment was high among meadows with lodgepole pine (Pinus contorta Douglas ex Loudon var. murrayana (Balf.) Engelm.) in the immediate vicinity, at lower elevations, with physical conditions favoring strong soil drying, and with maximum temperatures above or below average. Climatic conditions during the year of germination were unimportant, with tree recruitment instead depending on a 3‐yr seed production period prior to germination and a 6‐yr seedling establishment period following germination. Recruitment was high when the seed production period had high snowpack, and when the seedling establishment period had warm summer maximum temperatures, high summer precipitation, and high snowpack. Applying our temporal model to downscaled output from four global climate models indicated that the average meadow will shift to forest by the end of the 21st century. Sierra Nevada meadow encroachment by conifers is ubiquitous and associated with climate conditions increasingly favorable for tree recruitment, which will lead to substantial changes in subalpine meadows and the ecosystem services they provide.

Climate and Water: Knowledge of Impacts to Action on Adaptation

Annual Review of Environment and Resources (Annual Reviews) | November 30th, 2012

As adaptation becomes more tightly integrated into the range of responses to climate change, understanding how knowledge of climate change impacts and vulnerabilities can

As adaptation becomes more tightly integrated into the range of responses to climate change, understanding how knowledge of climate change impacts and vulnerabilities can be effectively used is essential both to direct research and to support action. This article reviews literature along an intellectual transect from knowledge of climate impacts on water systems to the influence of that knowledge on adaptation responses. We discuss scientific evidence for changing hydroclimatic regimes, methods for translating climatic information into results relevant to adaptation, uncertainties in these results, methods for addressing uncertainty via adaptation processes, challenges and opportunities for knowledge development and transfer, and sociopolitical factors that enable or hinder the use of knowledge. Challenges remain in developing and applying methods for identifying and reducing underlying vulnerabilities and reliably connecting technical knowledge of climate impacts with local needs remains an unsolved problem. But new decision-making methods and the potential to learn from analogous water management situations provide hope for near-term progress.

Climate benefits from establishing marine protected areas targeted at blue carbon solutions

National Academy of Sciences (NAS) | April 13th, 2022

Marine protected areas (MPAs) are recognized as highly effective tools for marine conservation. They may also play an important role in mitigating climate change. A vari

Marine protected areas (MPAs) are recognized as highly effective tools for marine conservation. They may also play an important role in mitigating climate change. A variety of climate change solutions are rooted in the ocean, centered primarily around “blue carbon” and the capacity of marine life to sequester carbon dioxide (CO2) with some potential to reduce emissions. However, the global potential of these solutions remains misunderstood and untapped. Here, we analyze the potential impact on carbon removal and emissions reduction of adopting six ocean-based solutions in MPAs: coastal wetlands protection, coastal wetlands restoration, macroalgae protection, macroalgae restoration, seafloor protection, and seaweed farming. The carbon removal and avoided emissions achieved by implementing these solutions globally through 2060 were estimated using meta-analysis of existing studies. Applying all six ocean solutions under global implementation scenarios yields total emissions reduction by 2060 of 16.2 ± 1.82 gigatonnes of carbon dioxide equivalent (GtCO2-eq) for the plausible scenario and 24.8 ± 2.46 GtCO2-eq for the ambitious scenario. That equates to around 2% of the total carbon mitigation needed to meet the Paris Agreement goals of limiting global warming to 2 °C by 2050. Around 70% of this reduction is attributable to carbon removal and 30% to avoided emissions. Enhancing MPAs’ blue carbon potential could be a key contributor to drawing down carbon and could provide many additional benefits to the marine environment and human society, such as rebuilding biodiversity and sustaining food production. However, more regional-scale studies are needed to inform the best strategies for preserving and enhancing carbon removal in ocean sinks.

Climate Change 2022 Impacts, Adaptation and Vulnerability

Intergovernmental Panel on Climate Change (IPCC) | February 28th, 2022

This Summary for Policymakers (SPM) presents key findings of the Working Group II (WGII) contribution to the Sixth Assessment Report (AR6) of the IPCC. The report builds

This Summary for Policymakers (SPM) presents key findings of the Working Group II (WGII) contribution to the Sixth Assessment Report (AR6) of the IPCC. The report builds on the WGII contribution to the Fifth Assessment Report (AR5) of the IPCC, three Special Reports, and the Working Group I (WGI) contribution to the AR6 cycle. This report recognizes the interdependence of climate, ecosystems and biodiversity, and human societies (Figure SPM.1) and integrates knowledge more strongly across the natural, ecological, social and economic sciences than earlier IPCC assessments. The assessment of climate change impacts and risks as well as adaptation is set against concurrently unfolding non-climatic global trends e.g., biodiversity loss, overall unsustainable consumption of natural resources, land and ecosystem degradation, rapid urbanisation, human demographic shifts, social and economic inequalities and a pandemic. The scientific evidence for each key finding is found in the 18 chapters of the underlying report and in the 7 cross-chapter papers as well as the integrated synthesis presented in the Technical Summary (hereafter TS) and referred to in curly brackets {}. Based on scientific understanding, key findings can be formulated as statements of fact or associated with an assessed level of confidence using the IPCC calibrated language. The WGII Global to Regional Atlas (Annex I) facilitates exploration of key synthesis findings across the WGII regions. The concept of risk is central to all three AR6 Working Groups. A risk framing and the concepts of adaptation, vulnerability, exposure, resilience, equity and justice, and transformation provide alternative, overlapping, complementary, and widely used entry points to the literature assessed in this WGII report. Across all three AR6 working groups, risk provides a framework for understanding the increasingly severe, interconnected and often irreversible impacts of climate change on ecosystems, biodiversity, and human systems; differing impacts across regions, sectors and communities; and how to best reduce adverse consequences for current and future generations. In the context of climate change, risk can arise from the dynamic interactions among climate-related hazards (see Working Group I), the exposure and vulnerability of affected human and ecological systems. The risk that can be introduced by human responses to climate change is a new aspect considered in the risk concept. This report identifies 127 key risks9. {1.3, 16.5} The vulnerability of exposed human and natural systems is a component of risk, but also, independently, an important focus in the literature. Approaches to analysing and assessing vulnerability have evolved since previous IPCC assessments. Vulnerability is widely understood to differ within communities and across societies, regions and countries, also changing through time.

Climate Change Adaptations for Local Water Management in the San Francisco Bay Area

California Energy Commission (CEC) | July 1st, 2012

Climate change will affect both sea level and the temporal and spatial distribution of runoff in California. These climate change impacts will affect the reliability of w

Climate change will affect both sea level and the temporal and spatial distribution of runoff in California. These climate change impacts will affect the reliability of water supplies and operations of California’s water supply system. To meet future urban water demands in the San Francisco Bay Area, local water managers can adapt by changing water supply portfolios and operations. An engineering economic model, CALVIN, which optimizes water supply operations and allocations for the State of California, was used to explore the effects on water supply of a severely warm dry climate and substantial sea level rise, and to identify economically promising long-term adaptations for San Francisco Bay Area water systems. This reconnaissance level modeling suggests that even under fairly severe forms of climate change, Bay Area urban water demands can be largely met, but at a cost. Costs are from purchasing water from agricultural users (with agricultural opportunity costs), more expensive water supply alternatives such as water recycling and desalination, and some increases in water scarcity (costs of water use reduction). The modeling also demonstrates the importance of water transfer and intertie infrastructure to facilitate flexible water management among Bay Area water agencies. The intertie capacity developed by Bay Area agencies for emergencies, such as earthquakes, becomes even more valuable for responding to severe changes in climate.

Climate Change Analysis for the Santa Ana River Watershed

U.S. Bureau of Reclamation (USBR) | September 24th, 2013

The Santa Ana Watershed Basin Study (Basin Study) is a collaborative effort by the Santa Ana Watershed Project Authority (SAWPA) and the Bureau of Reclamation (Reclamatio

The Santa Ana Watershed Basin Study (Basin Study) is a collaborative effort by the Santa Ana Watershed Project Authority (SAWPA) and the Bureau of Reclamation (Reclamation), authorized under the Sustain and Manage America's Resources for Tomorrow SECURE Water Act (Title IX, Subtitle F of Public Law 111-11). The study began in 2011 and was completed in the spring of 2013. The Basin Study complements SAWPA’s Integrated Regional Water Management (IRWM) planning process, also known as the “One Water One Watershed” (OWOW) Plan, and refines the watershed’s water projections, and identifies potential adaptation strategies, in light of projected effects of climate change. This climate change analysis for the Santa Ana River Watershed (SARW) is a contributing section to the Basin Study. This report explains the methods used to develop an analysis of potential implications of the changing climate, and how those implications might affect issues of importance to the Santa Ana River Watershed. Chapter 1 provides an introduction to the project and the study area, along with a summary of relevant previous studies. The development of climate projections and hydrology models used can be found in Chapter 2. Chapter 3 provides projections for water supply and demand in the SARW. An impact analysis was conducted focusing on key areas of importance to the SARW, the results of which can be found in Chapter 4. A tool to evaluate demand management is presented in Chapter 5, along with a case study of potential adaptation strategies. Chapter 6 addresses uncertainties in climate change analysis. In light of climate change, prolonged drought conditions, growth, and population projections, a strong concern exists to ensure there will be adequate water supplies to meet future water demand. The findings of this Basin Study will be used to update the OWOW Plan, evaluate the implications of climate change, assess increased energy demand, and ensure that future water quality and supply needs are met. Goals of the study include: incorporating existing regional and local planning studies within the watershed; sustaining the innovative “bottom up” approach to regional water resources management planning; ensuring an integrated, collaborative approach; using science and technology to assess climate change and greenhouse emissions effects; facilitating watershed adaptation planning; and expanding outreach to all major water uses and stakeholders. Future water supply was analyzed for the Santa Ana River Watershed using the Variable Infiltration Capacity (VIC) hydrologic model (Liang et al., 1994; Liang et al., 1996; Nijssen et al., 1997) to project streamflow using 112 different projections of future climate. Projected climate variables, including daily precipitation, minimum temperature, maximum temperature, and wind speed, came from the Bias Corrected and Spatially Downscaled Coupled Model Intercomparison Project Phase 3 (BCSD-CMIP3) archive. Historical VIC model simulations over the period 1950-1999 were conducted using historical meteorological forcings (factors affecting the climate of the earth that drive or “force” the climate to change) developed by Maurer et al., (2002), and subsequent extensions. The VIC hydrologic model solves the water balance for each of a series of 1/8° by 1/8° (~12km x 12 km) grid cells, which represent the watershed. Daily climate projections span the time period January 1, 1950 to December 31, 2099 and exist for each grid cell. Grid based outputs of daily runoff and baseflow generated by the VIC hydrologic model are routed to select sites throughout the watershed to produce daily streamflow projections. Through coordination with SAWPA and local water agencies, 36 key locations in the basin were determined, so that sub-basins could be delineated. Change factors were developed by calculating decade mean (reference decade – 1990s; three future decades – 2020s, 2050s, and 2070s) total precipitation and temperature, then calculating percent change, and finally calculating the median change for all the 112 projections. Final products include data sets at key locations for precipitation, temperature, evapotranspiration, April 1st Snow Water Equivalent (SWE), and streamflow. These data sets were used to answer frequently asked questions regarding impacts of climate change on the Santa Ana River Watershed.