San Joaquin Basin Flood‑MAR Watershed Studies Tuolumne Watershed Study Area Report

California Department of Water Resources (DWR) | December 3rd, 2025

The San Joaquin Basin Flood‑MAR Watershed Studies (Watershed Studies) — comprising five watershed reports for Calaveras, Stanislaus, Tuolumne, Merced and Upper San Jo

The San Joaquin Basin Flood‑MAR Watershed Studies (Watershed Studies) — comprising five watershed reports for Calaveras, Stanislaus, Tuolumne, Merced and Upper San Joaquin watersheds and a Basin-wide Summary — deliver data‑driven assessments of climate change vulnerabilities and adaptation that reveal risks and consequences and call for bold, coordinated solutions. In the San Joaquin Basin, the effects of climate change will exacerbate long-standing water management challenges. As these reports quantify, every water management sector — flood, water supply (surface and groundwater), and ecosystems — is vulnerable. Without bold action, the basin and its watersheds face mounting threats to communities, economies, and ecosystems. Although each watershed has unique characteristics, all confront a future climate that is hotter and characterized by more extreme weather. For flood management, the 2022 Central Valley Flood Protection Plan states clearly: Catastrophic flooding in the San Joaquin Basin is not a question of if, but when. Meanwhile, the reliability of water supplies is expected to worsen, and ecosystems face degradation. Click here for the California Department of Water Resources Watershed Studies home page

San Joaquin Basin Flood‑MAR Watershed Studies Upper San Joaquin Watershed Study Area Report

California Department of Water Resources (DWR) | December 3rd, 2025

The San Joaquin Basin Flood‑MAR Watershed Studies (Watershed Studies) — comprising five watershed reports for Calaveras, Stanislaus, Tuolumne, Merced and Upper San Jo

The San Joaquin Basin Flood‑MAR Watershed Studies (Watershed Studies) — comprising five watershed reports for Calaveras, Stanislaus, Tuolumne, Merced and Upper San Joaquin watersheds and a Basinwide Summary — deliver data‑driven assessments of climate change vulnerabilities and adaptation that reveal risks and consequences and call for bold, coordinated solutions. In the San Joaquin Basin, the effects of climate change will exacerbate long-standing water management challenges. As these reports quantify, every water management sector — flood, water supply (surface and groundwater), and ecosystems — is vulnerable. Without bold action, the basin and its watersheds face mounting threats to communities, economies, and ecosystems. Although each watershed has unique characteristics, all confront a future climate that is hotter and characterized by more extreme weather. For flood management, the 2022 Central Valley Flood Protection Plan states clearly: Catastrophic flooding in the San Joaquin Basin is not a question of if, but when. Meanwhile, the reliability of water supplies is expected to worsen, and ecosystems face degradation. Click here to be taken to California Department of Water Resources Watershed Studies homepage

Santa Ana Watershed Basin Study

U.S. Bureau of Reclamation (USBR) | September 1st, 2013

The U.S. Department of the Interior’s WaterSMART (Sustain and Manage America’s Resources for Tomorrow) program allows all bureaus of the Department to collaboratively

The U.S. Department of the Interior’s WaterSMART (Sustain and Manage America’s Resources for Tomorrow) program allows all bureaus of the Department to collaboratively work with States, Tribes, local governments, and non-governmental organizations to pursue a sustainable water supply for the Nation. This is done through a framework that provides federal leadership and assistance on the efficient use of water, and by integrating water and energy policies to support the sustainable use of all natural resources. Basin Studies, one of the tools of this program, are basin-wide efforts to evaluate and address the impacts of climate change, and define options for meeting future water demands in river basins in the western United States where imbalances in water supply and demand exist or are projected. The Bureau of Reclamation (Reclamation) and the Santa Ana Watershed Project Authority (SAWPA) partnered in the WaterSMART Santa Ana Watershed Basin Study (Study). The work done under the Study was used to help SAWPA update its One Water One Watershed (OWOW) Plan. OWOW is an Integrated Regional Water Management Plan (IRWMP) for the Santa Ana River Watershed (SARW) that serves as the blueprint for SAWPA, its member agencies and key stakeholders to effectively manage water resources over the next 30 years. The Santa Ana Watershed Basin Study illustrates how effective collaboration can improve water management. This Study takes a crest-to-coast and corner-to-corner approach throughout a 2,400-square-mile watershed, which encompasses everything from beach to mountain communities, to address the area’s unique water resource challenges. The SARW is home to more than 6 million people, and tens of millions more people visit the area each year. The region also has a large manufacturing, industrial, and agricultural base. More than 350 water, wastewater, and groundwater management, flood control, environmental and other non-governmental organizations, are working together as partners with SAWPA on the OWOW Plan. Through the Basin Study Program, Reclamation is partnering with SAWPA and its stakeholders to update key components of the Plan, now known as OWOW 2.0.  

Santa Ana Winds of Southern California: Their climatology, extremes, and behavior spanning six and a half decades

American Geophysical Union (AGU) | March 24th, 2016

Santa Ana Winds (SAWs) are an integral feature of the regional climate of Southern California/Northern Baja California region, but their climate-scale behavior is poorly

Santa Ana Winds (SAWs) are an integral feature of the regional climate of Southern California/Northern Baja California region, but their climate-scale behavior is poorly understood. In the present work,we identify SAWs in mesoscale dynamical downscaling of a global reanalysis from 1948 to 2012. Model windsare validated with anemometer observations. SAWs exhibit an organized pattern with strongest easterlywinds on westward facing downwind slopes and muted magnitudes at sea and over desert lowlands. Weconstruct hourly local and regional SAW indices and analyze elements of their behavior on daily, annual, andmultidecadal timescales. SAWs occurrences peak in winter, but some of the strongest winds have occurred infall. Finally, we observe that SAW intensity is influenced by prominent large-scale low-frequency modes ofclimate variability rooted in the tropical and north Pacific ocean-atmosphere system.

Satellite observations indicate that chia uses less water than other crops in warm climates

Nature Portfolio (Springer Nature) | September 30th, 2024

Scattered tree death contributes to substantial forest loss in California

Nature Portfolio (Springer Nature) | January 20th, 2024

In recent years, large-scale tree mortality events linked to global change have occurred around the world. Current forest monitoring methods are crucial for identifying m

In recent years, large-scale tree mortality events linked to global change have occurred around the world. Current forest monitoring methods are crucial for identifying mortality hotspots, but systematic assessments of isolated or scattered dead trees over large areas are needed to reduce uncertainty on the actual extent of tree mortality. Here, we mapped individual dead trees in California using sub-meter resolution aerial photographs from 2020 and deep learning-based dead tree detection. We identified 91.4 million dead trees over 27.8 million hectares of vegetated areas (16.7-24.7% underestimation bias when compared to field data). Among these, a total of 19.5 million dead trees appeared isolated, and 60% of all dead trees occurred in small groups ( ≤ 3 dead trees within a 30 × 30 m grid), which is largely undetected by other state-level monitoring methods. The widespread mortality of individual trees impacts the carbon budget and sequestration capacity of California forests and can be considered a threat to forest health and a fuel source for future wildfires.

Scenarios of climate adaptation potential on protected working lands from management of soils

Environmental Research Letters (IOP) | September 30th, 2019

Management of protected lands may enhance ecosystem services that conservation programs were designed to protect. Practices that build soil organic matter on agri

Management of protected lands may enhance ecosystem services that conservation programs were designed to protect. Practices that build soil organic matter on agricultural lands also increase soil water holding capacity, potentially reducing climatic water deficit (CWD), increasing actual evapotranspiration (AET) and increasing groundwater recharge (RCH). We developed nine spatially-explicit land use and conservation scenarios (2001–2100) in the LUCAS land use change model to address two questions for California working lands (cropland and rangeland): How does land use change limit opportunities to manage soils for hydrologic climate adaptation benefits? To what extent and where can soil management practices increase climate adaptation on protected working lands? Hydrologic benefits [Σ(ΔCWD, ΔAET, ΔRCH)] due to soil management were simulated in the Basin Characterization Model (a state-wide water balance model) for two Representative Concentration Pathway 8.5 climate models. LUCAS simulated land conversion and new conservation easements with potential for maximum hydrologic benefits. Climate drove differences in lost potential for water benefits due to urbanization (33.9–87.6 m3 × 106) in 2050. Conflict between development pressure and potential hydrologic benefits occurred most in Santa Clara County in the San Francisco Bay Area and Shasta County in Northern Sacramento Valley. Hydrologic benefits on easements were similar in magnitude to losses from development. Water savings from management of California Land Conservation (a.k.a. Williamson) Act contract lands were an order of magnitude greater, totaling over 460 m3 × 106 annually in a drier climate by 2050. Few counties provide most benefits because of soil properties, climate and land area protected. The increase in hydrologic benefits varies by agricultural practice and adoption rate, land use type and configuration, and terms of conservation agreements. The effectiveness of programs designed to improve climate adaptation at county to state scales will likely increase by taking this variability into consideration.

Scenarios of Future California Water Demand Through 2050

California Department of Water Resources (DWR) | August 14th, 2014

This paper describes the application of future scenarios for Water Plan Update 2013 (DWR 2013) to quantify future water demand for California and our 10 hydrologic region

This paper describes the application of future scenarios for Water Plan Update 2013 (DWR 2013) to quantify future water demand for California and our 10 hydrologic regions out to the year 2050. Starting with the publication of California Water Plan Update 2005 (DWR 2005), DWR has applied the concept of scenarios to describe future water management conditions. Scenarios are used to capture a broad range of uncertain factors that affect water management that are considered to be beyond the control of water managers. For Update 2013 scenarios were organized around narrative themes of growth and climate change, which were then quantified using factors about future population growth, housing densities, land use patterns, and climate.  For Updates 2005 and 2009, DWR attempted only to quantify future water demand management strategies at the hydrologic region scale. The hydrologic regions are large areas of tens of thousands square miles, too large to compute meaningful information on regional water management actions. But in parallel to the hydrologic region scale analysis as in current Update 2013, DWR has been pursuing a longer term project, to perform a more complete hydrologic analysis at the finer planning area scale. Results and analysis of planning area water management strategies is given in a separate report.  In addition to this paper, background information on the application of scenarios can be found in Chapter 5 and 6 of Update 2013. Chapter 5 provides information how scenarios are used to quantify water management uncertainty. Chapter 6 describes DWR’s efforts to effect long term improvements in data and analytical tools to support the Water Plan. 

Science and Decision Making: Water Management and Tree‐Ring Data in the Western United States

American Water Resources Association (AWRA) | October 5th, 2009

Growing populations, limited resources, and sustained drought are placing increased pressure on already over‐allocated water supplies in the western United States, prom

Growing populations, limited resources, and sustained drought are placing increased pressure on already over‐allocated water supplies in the western United States, prompting some water managers to seek out and utilize new forms of climate data in their planning efforts. One source of information that is now being considered by water resource management is extended hydrologic records from tree‐ring data. Scientists with the Western Water Assessment (WWA) have been providing reconstructions of streamflow (i.e., paleoclimate data) to water managers in Colorado and other western states (Arizona, New Mexico, and Wyoming), and presenting technical workshops explaining the applications of tree‐ring data for water management for the past eight years. Little is known, however, about what has resulted from these engagements between scientists and water managers. Using in‐depth interviews and a survey questionnaire, we attempt to address this lack of information by examining the outcomes of the interactions between WWA scientists and western water managers to better understand how paleoclimate data has been translated to water resource management. This assessment includes an analysis of what prompts water managers to seek out tree‐ring data, how paleoclimate data are utilized by water managers in both quantitative and qualitative ways, and how tree‐ring data are interpreted in the context of organization mandates and histories. We situate this study within a framework that examines the coproduction of science and policy, where scientists and resource managers collectively define and examine research and planning needs, the activities of which are embedded within wider social and political contexts. These findings have broader applications for understanding science‐policy interactions related to climate and climate change in resource management, and point to the potential benefits of reflexive interactions of scientists and decision makers.

Sea level rise and flooding of hazardous sites in marginalized communities across the United States

Nature Portfolio (Springer Nature) | November 20th, 2025

Sea level rise (SLR) increases the risk of flooding at coastal sites that use and produce hazardous substances. We assess whether socially marginalized populations in the

Sea level rise (SLR) increases the risk of flooding at coastal sites that use and produce hazardous substances. We assess whether socially marginalized populations in the United States are more likely to be impacted by projected SLR-related flooding of hazardous sites that could result in contaminant releases. We identify 5500 facilities at risk of a 1-in-100-year flood event by 2100 under a scenario of continued high greenhouse gas emissions, including coastal power plants, sewage treatment facilities, fossil fuel infrastructure, industrial facilities, and formerly used defense sites. Seven states (Louisiana, Florida, New Jersey, Texas, California, New York, and Massachusetts) account for nearly 80% of projected at-risk facilities. Controlling for population density and county, a one standard deviation increase in the proportion of linguistically isolated households, neighborhood residents identifying as Hispanic, households with incomes below twice the federal poverty line, households without a vehicle, non-voters, and renters is associated with 19-41% higher likelihood of having a site at risk of SLR-related flooding within 1 kilometer (odds ratios [95% confidence intervals]: 1.19 [1.09, 1.31], 1.22 [1.08, 1.37], 1.27 [1.16, 1.39], 1.35 [1.21-1.51], 1.36 [1.21, 1.53], and 1.41 [1.32, 1.52], respectively). Results elucidate the need for disaster planning, land-use decision-making, as well as mitigation strategies that address the inequitable hazards and potential health threats posed by SLR.