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.

Climate change and California drought in the 21st century

National Academy of Sciences (NAS) | March 31st, 2015

Climate science has advanced over decades from an initial focus on the development and use of numerical models of Earth’s climate and compilation of rich netw

Climate science has advanced over decades from an initial focus on the development and use of numerical models of Earth’s climate and compilation of rich networks of obser- vational data, to now being in a position to“detect” and “attribute” specific impacts and events to anthropogenic climate change. Recent analyses have thus established the“fingerprint” of anthropogenic climate change in an increasingly diverse array of meteorological and hydrological phenomena around the world, from heat waves to coastal damages during extreme tides and storms, flooding from more intense precipitation events, and severe drought. In a new study published in PNAS, Diffenbaugh et al. now add weight to the accumulating evidence that anthropogenic climatic changes are already influencing the frequency, magnitude, and duration of drought in California. The authors show that the increasing co-occurrence of dry years with warm years raises the risk of drought despite limited evidence of a trend in precipitation itself, highlighting the critical role of elevated temperatures in altering water availability and increasing overall drought intensity and impact.

Climate Change and Flooding in Central Appalachia

Pacific Institute | November 30th, 2023

Climate Change and Integrated Regional Water Management in California: A Preliminary Assessment of Regional Approaches

California Department of Water Resources (DWR) | June 6th, 2012

This report examines the initial steps that IRWM regions are taking in response to new requirements to address climate change vulnerabilities and consider greenhouse gas

This report examines the initial steps that IRWM regions are taking in response to new requirements to address climate change vulnerabilities and consider greenhouse gas emissions in IRWM plans. Given our evolving understanding of climate change impacts and appropriate adaptation strategies, effectively integrating climate change into planning is a challenging task. This report seeks to learn from initial steps by IRWM regions in order to inform future guidance and support. It also identifies key considerations for DWR and IRWM regions in analyzing and adapting to climate change risks within an adaptive management framework. Specifically, this report seeks to: 1. Assess the manner and degree to which the climate change requirements in the 2010 IRWM Guidelines are met in Round 1 Proposition 84 Planning and Implementation grant proposals, and in recently approved IRWM plans 2. Assess current IRWM regional approaches to analyzing and adapting to climate change risks, in light of the overall goal to promote an adaptive management approach 3. Provide recommendations on key steps for DWR and IRWM regions to support the development of informative climate change analyses and mechanisms for adaptive management at regional and state levels This assessment is based on a review of the current IRWM climate change requirements, existing IRWM plans, and Planning and Implementation grant proposals funded in 2011. It is also informed by interviews conducted by DWR regional climate change specialists with representatives of IRWM regions regarding their plans to address climate change.

Climate Change and Rural Water for Frontline Communities in the Southwest United States

Pacific Institute | March 26th, 2024

Climate change is threatening rural water supply and quality in the Southwest United States and will intensify water challenges in the coming years. Climate impacts such

Climate change is threatening rural water supply and quality in the Southwest United States and will intensify water challenges in the coming years. Climate impacts such as prolonged drought conditions and extreme high temperatures paired with groundwater depletion and reduced mountain snowpack are increasing the risk of water supply shortages in the region. Climate change models project an increase in temperature and an overall decline in average annual precipitation in the Southwest, though punctuated with extreme precipitation and more damaging flooding events.

Climate Change and Sea Level Rise Scenarios for California Vulnerability and Adaptation Assessment

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

This white paper provides an evaluation of physical elements of climate change and sea level rise that are contained in the California Climate Change Vulnerability and Ad

This white paper provides an evaluation of physical elements of climate change and sea level rise that are contained in the California Climate Change Vulnerability and Adaptation Assessment. The analyses use six global climate models, each run under the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios B1 and A2 scenarios. From the global climate models and associated downscaled output, these scenarios contain a range of warming, continued interannual and decadal variation of precipitation with incremental changes by the middle and end of twenty-first century, substantial loss of mountain snow pack, and a range of sea level rise along the California coast.

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 aridification of North America

National Academy of Sciences (NAS) | May 19th, 2020

Discussions of droughts and their impacts often center on the lack of precipitation, just as assessments of hydrologic impacts under a changing climate most ofte

Discussions of droughts and their impacts often center on the lack of precipitation, just as assessments of hydrologic impacts under a changing climate most often focus on how average precipitation in a given locale is likely to change in the future. Within climate science, however, focus has begun to include the growing role warming temperatures are playing as a potent driver of greater aridity: hotter climate extremes; drier soil conditions; more severe drought; and the impacts of hydrologic stress on rivers, forests, agriculture, and other systems. This shift in the hydrologic paradigm is most clear in the American Southwest, where declining flows in the region’s two most important rivers, the Colorado and Rio Grande, have been attributed in part to increasing temperatures caused by human activities, most notably the burning of fossil fuels. Warmer summers are also likely to reduce flows in the Columbia River, as well as in rivers along the Sierra Nevada in California. Now, an important study [Increased drought severity tracks warming in the United States’ largest river basin, J.T. Martin et al] documents how warming is also causing flow declines in the northern Rocky Mountains and in the largest river basin in the United States, the Missouri. This work further highlights the mechanisms behind the temperature-driven river flow declines and places more focus on how anthropogenic climate warming is progressively increasing the risk of hot drought and more arid conditions across an expanding swath of the United States.

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.