From Climate-Change Spaghetti to Climate-Change Distributions for 21st Century California

University of California, Davis (UC Davis) | March 1st, 2005

The uncertainties associated with climate-change projections for California are unlikely to disappear anytime soon, and yet important long-term decisions will be needed t

The uncertainties associated with climate-change projections for California are unlikely to disappear anytime soon, and yet important long-term decisions will be needed to accommodate those potential changes. Projection uncertainties have typically been addressedby analysis of a few scenarios, chosen based on availability or to capture the extreme cases among available projections. However, by focusing on more com-mon projections rather than the most extreme projections (using a new resampling method), new insights into current projections emerge: (1) uncertainties associated with future greenhouse-gas emissions are comparable with the differences among climate models, so that neither source of uncertainties should be neglected or underrepresented; (2) twenty-first century temperature projections spread more, overall, than do precipitation scenarios; (3) projections of extremely wet futures for California are true outliers among current projections; and (4) current projections that are warmest tend, overall, to yield a moderately drier California, while the cooler projections yield a some-what wetter future. The resampling approach appliedin this paper also provides a natural opportunity to objectively incorporate measures of model skill and the likelihoods of various emission scenarios into future assessments.

Funding Opportunity for Voluntary Participation in the Lower Colorado Conservation and Efficiency Program

U.S. Bureau of Reclamation (USBR) | October 12th, 2022

Funding Water in Times of Financial Uncertainty: The Case for a Public Goods Charge in California

Stanford University | January 15th, 2015

Funding for water-related public purpose projects has become increasingly scarce in California. Utilities are facing new challenges that require additional capital while

Funding for water-related public purpose projects has become increasingly scarce in California. Utilities are facing new challenges that require additional capital while the state’s legal system has restricted the ability of local governments to raise funds. This fiscal landscape requires the water sector to find new ways to finance water-related public interest projects, including conservation and efficiency programs, monitoring and evaluation, and infrastructure maintenance and modernization. California must also generate supplementary funds for new water technology research, development, and dissemination if the state is to continue to grow despite dwindling water supplies. In recent decades, California has relied heavily on general obligation (GO) bonds to finance a variety of water-related projects. GO bonds, however, are unreliable funding mechanisms as they require voter approval if they survive the legislative process, and they can be costly in the long run as they are repaid with interest. Additionally, GO bonds violate the beneficiary-pays principle as the entire state repays a debt that benefits taxpayers in certain regions more than others. This research paper looks at a supplemental funding mechanism, a Public Goods Charge (PGC), as an additional way for California to provide for water investment in the future. In a PGC scheme, ratepayers are charged a small, usage-related fee, and the funds are subsequently allocated to public interest projects at the local, utility, state, and broader scales. This method was used to fund electricity public purpose programs in California from 1998-2011, resulting in over $5.8 billion collected by the state’s three main Investor Owned Utilities (IOUs), with additional funds collected by local Publicly Owned Utilities (POUs), for energy innovation over 14 years. Utilities and the state as a whole benefitted economically and environmentally from the increased funding for energy efficiency, renewables, and research and development. The electricity PGC helped to transform California’s energy landscape into one that includes more modern and sustainable infrastructure systems. Significant energy savings were also achieved during the PGC era.

Future Changes in Global Atmospheric Rivers Projected by CMIP6 Models

American Geophysical Union (AGU) | January 31st, 2024

Future dryness in the southwest US and the hydrology of the early 21st century drought

National Academy of Sciences (NAS) | December 14th, 2010

Recently the Southwest has experienced a spate of dryness, which presents a challenge to the sustainability of current water use by human and natural systems in

Recently the Southwest has experienced a spate of dryness, which presents a challenge to the sustainability of current water use by human and natural systems in the region. In the Colorado River Basin, the early 21st century drought has been the most extreme in over a century of Colorado River flows, and might occur in any given century with probability of only 60%. However, hydrological model runs from downscaled Intergovernmental Panel on Climate Change Fourth Assessment climate change simulations suggest that the region is likely to become drier and experience more severe droughts than this. In the latter half of the 21st century the models produced considerably greater drought activity, parti- cularly in the Colorado River Basin, as judged from soil moisture anomalies and other hydrological measures. As in the historical record, most of the simulated extreme droughts build up and per- sist over many years. Durations of depleted soil moisture over the historical record ranged from 4 to 10 years, but in the 21st century simulations, some of the dry events persisted for 12 years or more. Summers during the observed early 21st century drought were re- markably warm, a feature also evident in many simulated droughts of the 21st century. These severe future droughts are aggravated by enhanced, globally warmed temperatures that reduce spring snowpack and late spring and summer soil moisture. As the climate continues to warm and soil moisture deficits accumulate beyond historical levels, the model simulations suggest that sustaining water supplies in parts of the Southwest will be a challenge.

Future loss of Arctic sea-ice cover could drive a substantial decrease in California’s rainfall

Nature Portfolio (Springer Nature) | December 5th, 2017

From 2012 to 2016, California experienced one of the worst droughts since the start of observational records. As in previous dry periods, precipitation-inducing winter st

From 2012 to 2016, California experienced one of the worst droughts since the start of observational records. As in previous dry periods, precipitation-inducing winter storms were steered away from California by a persistent atmospheric ridging system in the North Pacific. Here we identify a new link between Arctic sea-ice loss and the North Pacific geopotential ridge development. In a two-step teleconnection, sea-ice changes lead to reorganization of tropical convection that in turn triggers an anticyclonic response over the North Pacific, resulting in significant drying over California. These findings suggest that the ability of climate models to accurately estimate future precipitation changes over California is also linked to the fidelity with which future sea-ice changes are simulated. We conclude that sea-ice loss of the magnitude expected in the next decades could substantially impact California’s precipitation, thus highlighting another mechanism by which human-caused climate change could exacerbate future California droughts.

Future precipitation increase from very high resolution ensemble downscaling of extreme atmospheric river storms in California

American Association for the Advancement of Science (AAAS) | July 15th, 2020

Precipitation extremes will likely intensify under climate change. However, much uncertainty surrounds intensification of high-magnitude events that are often i

Precipitation extremes will likely intensify under climate change. However, much uncertainty surrounds intensification of high-magnitude events that are often inadequately resolved by global climate models. In this analysis, we develop a framework involving targeted dynamical downscaling of historical and future extreme precipitation events produced by a large ensemble of a global climate model. This framework is applied to extreme “atmospheric river” storms in California. We find a substantial (10 to 40%) increase in total accumulated precipitation, with the largest relative increases in valleys and mountain lee-side areas. We also report even higher and more spatially uniform increases in hourly maximum precipitation intensity, which exceed Clausius- Clapeyron expectations. Up to 85% of this increase arises from thermodynamically driven increases in water vapor, with a smaller contribution by increased zonal wind strength. These findings imply substantial challenges for water and flood management in California, given future increases in intense atmospheric river-induced precipitation extremes.

Generalized Streamflow Relations of the San Bernardino and Eastern San Gabriel Mountains, California

U.S. Geological Survey (USGS) | October 19th, 1972

Geohydrology and Evapotranspiration at Franklin Lake Playa, Inyo County, California

U.S. Geological Survey (USGS) | July 1st, 1997

Geohydrology and Water Chemistry of the Alexander Valley, Sonoma County, California

U.S. Geological Survey (USGS) | January 12th, 2006

This study of the geohydrology and water chemistry of the Alexander Valley, California, was done to provide an improved scientific basis for addressing emerging wate

This study of the geohydrology and water chemistry of the Alexander Valley, California, was done to provide an improved scientific basis for addressing emerging water-management issues, including potential increases in water demand and changes in flows in the Russian River. The study tasks included (1) evaluation of existing geohydrological, geophysi- cal, and geochemical data; (2) collection and analysis of new geohydrologic data, including subsurface lithologic data, ground-water levels, and streamflow records; and (3) collection and analysis of new water-chemistry data. The estimated total water use for the Alexander Valley for 1999 was approximately 15,800 acre-feet. About 13,500 acre-feet of this amount was for agricultural use, primarily vineyards, and about 2,300 acre-feet was for municipal/industrial use. Ground water is the main source of water supply for this area. The main sources of ground water in the Alexander Valley are the Quaternary alluvial deposits, the Glen Ellen Formation, and the Sonoma Volcanics. The alluvial units, where sufficiently thick and saturated, comprise the best aquifer in the study area. Average recharge to the Alexander Valley is estimated from a simple, basinwide water budget. On the basis of an estimated annual average of 298,000 acre-feet of precipitation, 160,000 acre-feet of runoff, and 113,000 to 133,000 acre-feet of evapotranspiration, about 5,000 to 25,000 acre-feet per year is available for ground-water recharge. Because this estimate is based on differences between large numbers, there is significant uncertainty in this recharge estimate. Long-term changes in ground-water levels are evident in parts of the study area, but because of the sparse network and lack of data on well construction and lithology, it is uncertain if any significant changes have occurred in the northern part of the study area since 1980. In the southern half of the study area, ground-water levels generally were lower at the end of the 2002 irrigation season than at the end of the 1980 season, which suggests that a greater amount of ground water is being pumped in the southern half of the study area in recent years compared with that pumped in the early 1980s. Water-chemistry data for samples collected from 11 wells during 2002–04 indicate that water quality in the study area generally is acceptable for potable use. Two wells, however, each contained one constituent (241 μg/L of manganese and 1,350 μg/L of boron) in excess of the recommended standards for drinking water (50 μg/L and 1,000 μg/L, respectively). The chemical composition of water from most of the wells sampled for major ions plot as a mixed cation-bicarbon- ate, magnesium-bicarbonate, or calcium-bicarbonate type water. The ionic composition of the historical and recent samples from wells in the Alexander Valley is similar to that of the historical surface-water samples collected from the Russian River near Healdsburg. This suggests a similar source of water, particularly for wells that are less than 200 feet total depth and perforated in Quaternary alluvial deposits. Water from deeper, non-alluvial wells may contain slightly higher concentrations of sodium as a result of cation exchange. Water samples collected from several wells over an approximately 30–year period suggest a progressive change in water chemistry over time. Samples from the southern part of the valley show a trend towards higher ionic concentrations and increasing concentrations of particular constituents such as sulfate.