South Coast

Clean Water, Clean Beaches Water Quality Funding Measure*

Los Angeles County Department of Public Works (LACDPW) | September 21st, 2012

The Problem: Stormwater and runoff rushes down the street, picking up trash and toxic pollutants. On a rainy day, over 10 billion gallons of contaminated stormw

The Problem: Stormwater and runoff rushes down the street, picking up trash and toxic pollutants. On a rainy day, over 10 billion gallons of contaminated stormwater flows directly — untreated — into rivers, creeks, lakes and our bay and coastal waters. Polluted stormwater and urban runoff include toxins and pathogens that can affect our health, drinking water supplies, and the health of marine life. Contaminants include: Industrial solvents, paints and chemicals; heavy metals like lead, mercury, chromium and arsenic; infection-causing bacteria; pesticides and fertilizers; and trash like plastics, cigarette butts, candy wrappers and syringes. *The proposed solution, a parcel tax to fund stormwater remediation and capture projects, failed before the Los Angeles County Board of Supervisors in 2013.

Climate Action Plan

Metropolitan Water District of Southern California (MWD) | May 31st, 2022

The Metropolitan Water District of Southern California’s (Metropolitan) core mission is to provide a clean, reliable water supply to Southern California. Changing clim

The Metropolitan Water District of Southern California’s (Metropolitan) core mission is to provide a clean, reliable water supply to Southern California. Changing climatic conditions, variable precipitation patterns, availability of water supplies, changes in consumer demands, and sea level rise will change the way Metropolitan provides its services and how it operates its regional water system. Metropolitan recognizes the potential impact of climate change to water availability and is committed to environmental stewardship to protect this valuable resource. Reducing greenhouse gas (G H G) emissions is an important step in protecting California and the region from the effects of climate change. Reducing G H G emissions from Metropolitan’s operations supports California’s overall G H G reduction goals. This Climate Action Plan (CAP) sets targets for reducing G H G emissions from Metropolitan’s operations, including conveyance, storage, treatment, and delivery of water to its 26 member water agencies. Additionally, this CAP complements Metropolitan’s existing long-range planning efforts, including the Integrated Water Resources Plan, Energy Sustainability Plan, and Capital Investment Plan. Through the implementation of this CAP, Metropolitan will strengthen its commitment to environmental sustainability, increase the resiliency of its operations, and strategically achieve G H G reduction goals. For additional details on the purpose of this CAP and Metropolitan’s history and existing operations, refer to Section 1.0, Purpose, Overview, and Environmental History and Leadership.

Climate Action Plan Phase 1 Greenhouse Gas Emissions Reduction Plan Update 2023

California Department of Water Resources (DWR) | March 22nd, 2024

DWR developed the Greenhouse Gas Emissions Reduction Plan Update 2023 (Update 2023) to review its GHG reductions since Update 2020 and to update strategies for further re

DWR developed the Greenhouse Gas Emissions Reduction Plan Update 2023 (Update 2023) to review its GHG reductions since Update 2020 and to update strategies for further reduction consistent with legislative changes, including the GHG emissions reduction targets established in SB 1020 (2022) and SB 1203 (2022). It also includes DWR’s new role in emergency energy generation. Since the 2012 Plan was adopted, California’s wholesale electricity market has also seen a significant increase in renewable resources. To reflect this change and to align with industry practice in emission reporting, Update 2023 incorporates updated emission factors to determine emissions from unspecified market resources.

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 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 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.

Climate change increased the likelihood of wildfire disaster in highly exposed Los Angeles area

American Geophysical Union (AGU) | January 28th, 2025

 To determine the role of climate change in this observed trend we combine the observation-based estimates with climate models. Eight of the eleven models examined also

 To determine the role of climate change in this observed trend we combine the observation-based estimates with climate models. Eight of the eleven models examined also show an increase in extreme January FWI, increasing our confidence that climate change is driving this trend. Combining models and observations, we find that human-induced warming from burning fossil fuels made the peak January FWI more intense, with an estimated 6% increase in intensity, and 35% more probable. 

Climate change is increasing the likelihood of extreme autumn wildfire conditions across California

Environmental Research Letters (IOP) | August 20th, 2020

California has experienced devastating autumn wildfires in recent years. These autumn wildfires have coincided with extreme fire weather conditions during periods of stro

California has experienced devastating autumn wildfires in recent years. These autumn wildfires have coincided with extreme fire weather conditions during periods of strong offshore winds coincident with unusually dry vegetation enabled by anomalously warm conditions and late onset of autumn precipitation. In this study, we quantify observed changes in the occurrence and magnitude of meteorological factors that enable extreme autumn wildfires in California, and use climate model simulations to ascertain whether these changes are attributable to human-caused climate change. We show that state-wide increases in autumn temperature (~1 °C) and decreases in autumn precipitation (~30%) over the past four decades have contributed to increases in aggregate fire weather indices (+20%). As a result, the observed frequency of autumn days with extreme (95th percentile) fire weather—which we show are preferentially associated with extreme autumn wildfires—has more than doubled in California since the early 1980s. We further find an increase in the climate model-estimated probability of these extreme autumn conditions since ~1950, including a long-term trend toward increased same-season co-occurrence of extreme fire weather conditions in northern and southern California. Our climate model analyses suggest that continued climate change will further amplify the number of days with extreme fire weather by the end of this century, though a pathway consistent with the UN Paris commitments would substantially curb that increase. Given the acute societal impacts of extreme autumn wildfires in recent years, our findings have critical relevance for ongoing efforts to manage wildfire risks in California and other regions.

Climate change is increasing the risk of a California megaflood

American Association for the Advancement of Science (AAAS) | August 12th, 2022

Despite the recent prevalence of severe drought, California faces a broadly underappreciated risk of severe floods. Here, we investigate the physical characteristics of

Despite the recent prevalence of severe drought, California faces a broadly underappreciated risk of severe floods. Here, we investigate the physical characteristics of “plausible worst case scenario” extreme storm sequences capable of giving rise to “megaflood” conditions using a combination of climate model data and high-resolution weather modeling. Using the data from the Community Earth System Model Large Ensemble, we find that climate change has already doubled the likelihood of an event capable of producing catastrophic flooding, but larger future increases are likely due to continued warming. We further find that runoff in the future extreme storm scenario is 200 to 400% greater than historical values in the Sierra Nevada because of increased precipitation rates and decreased snow fraction. These findings have direct implications for flood and emergency management, as well as broader implications for hazard mitigation and climate adaptation activities.

Climate change is narrowing and shifting prescribed fire windows in western United States

Nature Portfolio (Springer Nature) | October 3rd, 2023