San Francisco Bay

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 and the Agricultural Sector in the San Francisco Bay Area: Changes in Viticulture and Rangeland Forage Production Due to Altered Temperature and Precipitation Patterns

California Energy Commission (CEC) | July 31st, 2012

Climate change has the potential to alter the San Francisco Bay Area’s agricultural production, a $2 billion industry. Two of the top sectors, wine and ranching, are ex

Climate change has the potential to alter the San Francisco Bay Area’s agricultural production, a $2 billion industry. Two of the top sectors, wine and ranching, are examined in this paper. Downscaled models suggest that forage production in Bay Area rangelands may be enhanced by future conditions in most years, at least in terms of peak standing crop. However, the timing of production is as important as its peak, and altered precipitation patterns could mean delayed germination and earlier senescence, resulting in shorter growing seasons. An increase in the frequency of extremely dry years also increases the uncertainty of forage availability. Similarly, wine grape yields are projected to increase throughout much of the Bay Area, but wine grape quality may decline substantially under future climate conditions, as the crop ripens earlier during hotter months. The implications for these shifts in wine grape and forage production are that the aspects of Bay Area agriculture most sensitive to climate change are not yields, but subtler nuances of production such as quality and timing. Adaptive measures will need to be taken to maintain the economic viability of these enterprises.

Climate Change and the Delta

University of California, Davis (UC Davis) | October 1st, 2016

Climate change amounts to a fast approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic

Climate change amounts to a fast approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic variability, complex water-management systems have been developed, even as the Delta’s natural ecosystems have been largely devastated. Climate change is projected to challenge these management and ecological systems in different ways that are characterized by different levels of uncertainty. Future precipitation changes are less certain, with as many climate models projecting wetter conditions as drier. Warmer temperatures will likely enhance evaporation and raise water temperatures. Consequently, climate change is projected to yield both more extreme flood risks and greater drought risks. Effects on the Delta ecosystem that are traceable to warming include sea level rise, reduced snowpack, earlier snowmelt and larger storm-driven streamflow, warmer and longer summers, warmer summer water temperatures, and water-quality changes. These changes and their uncertainties will challenge the operations of water projects and uses throughout the Delta’s watershed and delivery areas. Although the effects of climate change on Delta ecosystems may be profound, the end results are difficult to predict, except that native species will fare worse than invaders. Successful preparation for the coming changes will require greater integration of monitoring, modeling, and decision-making across time, variables, and space than has been historically normal.

Climate Change and the Delta: A Synthesis (Public Review Draft)

Delta Stewardship Council (Delta Council) | March 23rd, 2018

The Delta Reform Act of 2009 (Water Code Section 85066) requires that the Delta Stewardship Council adopt a Delta Plan (the Plan) to achieve the coequal goals of providin

The Delta Reform Act of 2009 (Water Code Section 85066) requires that the Delta Stewardship Council adopt a Delta Plan (the Plan) to achieve the coequal goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem (Water Code Section 85000). In the time since the Plan was adopted in 2013, a significant shift in State planning for Delta ecosystem protection, restoration, and enhancement has occurred, prompting review of the Delta Plan to  examine whether its strategies are still suited to achieve the ecological goals of the Delta Reform Act. As such, the Delta Stewardship Council (Council) is developing an amendment of the Plan’s Chapter 4, Protect, Restore, and Enhance the Delta Ecosystem. Council staff are reviewing the best-available science to inform amendment of Chapter 4 of the Delta Plan. To support this effort, Council staff have developed three science  synthesis papers. This paper focuses on the effects of climate change in the Delta and is accompanied by two other papers focused on the Delta ecosystem (terrestrial and  aquatic resources) and restoration. Climate change is of interest for the Chapter 4  amendment given recent rapid advancements in research on climate change and its  effects on the Delta ecosystem that have occurred since the Delta Plan was adopted in  2013 (Dettinger et al. 2016). Climate change has the potential to significantly affect the Delta ecosystem by raising  air and water temperatures, changing the timing and volume of flows into and through  the Delta, increasing tidal inundation with sea-level rise (SLR), and increasing salinity  intrusion into the Delta. Climate change is recognized as a global stressor in Chapter 4 of the 2013 Delta Plan, but the effects of climate change on Delta ecosystems are  discussed only briefly and with limited consideration of management strategies that address the issue. Chapter 4 of the Delta Plan identifies five key stressors to the Delta  ecosystem and core strategies for addressing each. Climate change has interrelated  effects on all five core strategy areas: Delta flows, habitat, water quality, non-native 28 species, and hatcheries and harvest management. The Delta Reform Act specifies consideration of “the future impact of climate change and sea-level rise” (Water Code Section 85066), and identifies a restoration timeline horizon of 2100 (Water Code Section 85302). More generally, Executive Order B-30-15, signed by Governor Brown in April 2015, requires that State agencies incorporate climate change into planning and investment decisions, and that they prioritize natural infrastructure and actions for climate preparedness.

Climate Change Impacts, Vulnerabilities, and Adaptation in the San Francisco Bay Area: A Synthesis of PIER Program Reports and Other Relevant Research

California Research Bureau (CRB) | July 31st, 2012

This paper synthesizes San Francisco Bay Area-focused findings from research conducted in 2010–2012 as part of the state’s Vulnerability and Adaptation study sponsore

This paper synthesizes San Francisco Bay Area-focused findings from research conducted in 2010–2012 as part of the state’s Vulnerability and Adaptation study sponsored by the California Energy Commission’s Public Interest Energy Research (PIER) Program. Historical observations of changes already evident are summarized, as well as projections of future changes in climate based on modeling studies using various plausible scenarios of how emissions of heat-trapping gases in the atmosphere may change. Studies synthesized here show how these climate changes increase risks to society and natural ecosystems in a number of ways. Sectors for which impacts, vulnerabilities, and adaptation options are presented include water, agriculture, energy supply and demand, transportation, ecosystems, public health, wildfire, and coastal resources. Results show that depending on the vulnerability of human and natural communities, and their abilities to respond to these growing risks through adaptive changes, the San Francisco Bay Area could experience either significant impacts or maintain its resilience in the face of a rapidly changing environment.

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

Climate Change Risks Faced by the California Central Valley Water Resource System

California Energy Commission (CEC) | ?

Observed climate trends and projections of accelerated future change have motivated several studies of the impacts of climate change on water resources management in Cal

Observed climate trends and projections of accelerated future change have motivated several studies of the impacts of climate change on water resources management in California. This paper presents a methodology that improves on previous approaches, revealing fundamental climate change risks to one of the State of California’s key water resource systems — the integrated California Central Valley System (CCVS). By using a bottom-up decision scaling approach, starting with a systematic climate change stress test of the performance of the system to changes in temperature and precipitation, specific vulnerabilities to the system are identified. This study also improves on previous water resource vulnerability analyses by incorporating and evaluating a much wider range of inter-annual precipitation variability than has previously been used. By drawing from the 1,100-year (reconstructed dendrochronology) record of Sacramento and San Joaquin river flows, vulnerabilities to low frequency natural climate variability are analyzed in concert with expected potential climate changes. The results of this analysis provide a comprehensive summary of the sensitivity of the system to climate change. This paper provides results and discussion of select future system performance metrics at 2050. Results indicate that declines in almost every category (e.g., supply, storage, delta outflow) of system performance are likely. The likelihood of severely degraded future performance is especially high for north-of-Delta carryover storage and Delta exports. The results of this study are expected to provide water managers and decision-makers with more actionable science because they provide probabilistic results that can be used in more traditional risk management approaches to planning of climate change adaptation investment decisions.

Climate Change Scenarios for Air and Water Temperatures in the Upper San Francisco Estuary: Implications for Thermal Regimes and Delta Smelt

University of California, Davis (UC Davis) | June 10th, 2024