Sacramento River

Atmospheric River Precipitation Enhanced by Climate Change: A Case Study of the Storm That Contributed to California's Oroville Dam Crisis

American Geophysical Union (AGU) | February 9th, 2022

California's reliance on precipitation from atmospheric rivers is expected to increase as our climate warms. Understanding how climate change is impacting this increasing

California's reliance on precipitation from atmospheric rivers is expected to increase as our climate warms. Understanding how climate change is impacting this increasingly dominant mode of precipitation is vitally important for water-resource management throughout the state, across the North American West Coast, and for other similarly impacted regions. Our case study of an impactful atmospheric river from early February 2017 that contributed to the Oroville Dam crisis in Northern California, modeled under preindustrial, present-day, mid-, and late-21st century unabatedly warming environments, demonstrates an overwhelming increase in precipitation throughout the event. This particular storm was comprised of two distinct pulses, and while both pulses of the storm are enhanced in the warmer future epochs, the estimated precipitation increases are disproportionately higher for the second pulse due to larger increases in temperature and moisture. Our results therefore suggest that not all atmospheric rivers are similarly affected by climate change and point to specific directions for relevant future research.

Atmospheric Rivers Impacting Northern California Exhibit a Quasi-Decadal Frequency

American Geophysical Union (AGU) | July 26th, 2021

In Northern California, much of the precipitation and surface water comes from atmospheric rivers–corridors of moisture transport from the tropics. The frequency of atm

In Northern California, much of the precipitation and surface water comes from atmospheric rivers–corridors of moisture transport from the tropics. The frequency of atmospheric rivers is cyclical, with periods of water surplus and deficit in the region that repeat every 10–17 years. While many social and political factors influence water resource distribution, understanding the climate factors that regulate water availability is important for managing water in the future. Using data from observations and modeling experiments, the pronounced wet/dry cycle in this area of the Western United States is mainly attributed to regular fluctuations in sea surface temperatures in the tropical Pacific Ocean. This analysis provides a potential source of predictability for atmospheric river frequency, and thus water availability, years before a winter season.

Authority and Effectiveness of the State Water Resources Control Board

Delta Vision Blue Ribbon Task Force (Delta Vision) | July 1st, 2008

This report addresses issues related to the effectiveness of the California State Water Resources Control Board (“State Board” or “Board”) in carrying out its rol

This report addresses issues related to the effectiveness of the California State Water Resources Control Board (“State Board” or “Board”) in carrying out its roles and responsibilities, with particular reference to the Sacramento-San Joaquin San Francisco Bay-Delta (“Delta”). Section 1 presents an overview and evaluation of the authority and responsibility of the State Board. Section 2 describes actions of the State Board over many years in connection with the Delta, and in summary form, the Mono Lake basin and the Yuba River. Based on the preceding sections, Section 3 evaluates the effectiveness of the Board with particular reference to the Delta and sets forth some observations related to the Board’s authority and effectiveness.

Availability of high-magnitude streamflow for groundwater banking in the Central Valley, California

Environmental Research Letters (IOP) | July 31st, 2017

California’s climate is characterized by the largest precipitation and streamflow variability observed within the conterminous US This, combined with chronic gr

California’s climate is characterized by the largest precipitation and streamflow variability observed within the conterminous US This, combined with chronic groundwater overdraft of 0.6–3.5 km3 yr 1, creates the need to identify additional surface water sources available for groundwater recharge using methods such as agricultural groundwater banking, aquifer storage and recovery, and spreading basins. High-magnitude streamflow, i.e. flow above the 90th percentile, that exceeds environmental flow requirements and current surface water allocations under California water rights, could be a viable source of surface water for groundwater banking. Here, we present a comprehensive analysis of the magnitude, frequency, duration and timing of high-magnitude streamflow (HMF) for 93 stream gauges covering the Sacramento, San Joaquin and Tulare basins in California. The results show that in an average year with HMF approximately 3.2 km3 of high-magnitude flow is exported from the entire Central Valley to the Sacramento-San Joaquin Delta often at times when environmental flow requirements of the Delta and major rivers are exceeded. High-magnitude flow occurs, on average, during 7 and 4.7 out of 10 years in the Sacramento River and the San Joaquin-Tulare Basins, respectively, from just a few storm events (5–7 1-day peak events) lasting for 25–30 days between November and April. The results suggest that there is sufficient unmanaged surface water physically available to mitigate long-term groundwater overdraft in the Central Valley.

Background and Recent History of Water Transfers in California

California Department of Water Resources (DWR) | July 1st, 2015

The purpose of this paper is to provide a basic understanding of water transfers in California with an emphasis on transfers that move water through the Sacramento-

The purpose of this paper is to provide a basic understanding of water transfers in California with an emphasis on transfers that move water through the Sacramento-San Joaquin Delta (Delta). This paper provides an overview of various types of water transfers, their recent history, and the regulatory setting that governs transfers. In its 1976 report, the Governor’s Commission on Water Rights recognized the importance of water transfers to the future of California’s water supply and made recommendations regarding the need for specific changes to the Water Code to facilitate the transfer of water. Many of these changes were accomplished in the following years and are reflected in the discussions below. Water transfers involve a change in the place of water use, from the water’s historic point of diversion and use, to a new location either within or outside the watershed of origin. Water may be transferred from one user to another for a variety of purposes, including agricultural, municipal and industrial uses. It may also be transferred for environmental purposes such as in-stream flow augmentation and wildlife refuges. Water transfers and exchanges can be temporary (up to one year) or long-term (more than one year, but not permanent) or permanent. Water transfers can be an effective water management tool providing much-needed flexibility in the allocation and use of water in California. Transfers in California are primarily executed to meet dry-year demands rather than to obtain a primary water supply for either agricultural or municipal development. Transfers are particularly useful for meeting critical needs during drought periods. Transfers, however, must be carried out in a responsible manner in order to assure that they do not result in adverse impacts to other water users or unreasonable effects to the environment.

Balancing Flood Risk and Water Supply in California: Policy Search Integrating Short-Term Forecast Ensembles With Conjunctive Use

American Geophysical Union (AGU) | September 24th, 2018

Short-term weather forecasts have the potential to improve reservoir operations for both flood control and water supply objectives, especially in regions currently relyin

Short-term weather forecasts have the potential to improve reservoir operations for both flood control and water supply objectives, especially in regions currently relying on fixed seasonal flood pools to mitigate risk. The successful development of forecast-based policies should integrate uncertainty from modern forecast products to create unambiguous rules that can be tested on out-of-sample periods. This study investigates the potential for such operating policies to improve water supply efficiency while maintaining flood protection, combining state-of-the-art weather hindcasts with downstream conjunctive use to transfer surplus flood releases to groundwater storage. Because available weather hindcasts are relatively short (10–20 years), we propose a novel statistical framework to develop synthetic forecasts over longer periods of the historical record. Operating rules are trained with a recently developed policy search framework in which decision rules are structured as binary trees. Policies are developed for a range of scenarios with varying forecast skill and conjunctive use capacity, using Folsom Reservoir, California, as a case study. Results suggest that the combination of conjunctive use and short-term weather forecasts can substantially improve both water supply and flood control objectives by allowing storage to remain high until forecasts trigger a release. Further, increased conjunctive use capacity reduces the importance of forecast skill, since surface storage can be moved to groundwater during the flood season without losing water supply. This analysis serves the development of forecast-based operating policies for large, multipurpose reservoirs in California and other regions with similar flood hydroclimatology.

Base of fresh ground water (approximately 3,000 micromhos) in the San Joaquin Valley, California

U.S. Geological Survey (USGS) | June 30th, 1971

Widespread pumping of groundwater in the San Joaquin Valley began about 1900, and since 1940 pumpage has increased at an accelerated rate. In response to the heavy withdr

Widespread pumping of groundwater in the San Joaquin Valley began about 1900, and since 1940 pumpage has increased at an accelerated rate. In response to the heavy withdrawal of groundwater, water levels have declined rapidly beneath extensive areas of the valley. Consequently, it becomes necessary to delineate the base of fresh groundwater so that changes in thickness of the fresh-water zone can be monitored, and limited depths of water wells can be determined. In turn, those data will be useful in determining favorable areas for groundwater storage, and areas and depths for waste-water disposal wells. Because other agencies and the U.S. Geological Survey have collected a vast amount of well log and other data, most of the information in this report was assembled from existing files. However, for areas where data were scanty, a few hundred additional electrical logs were collected to supplement the available information.

Basic & Urgent: Realizing the Human Right to Water & Sanitation for Californians Experiencing Homelessness

University of California, Berkeley (UC Berkeley) | August 15th, 2018

The report’s three main sections follow this executive summary. The Problem Overview examines: what is driving what one source called an “explosion” in the numbe

The report’s three main sections follow this executive summary. The Problem Overview examines: what is driving what one source called an “explosion” in the number of Californians who are unsheltered; the stark reality of a severe shortfall between the number of affordable housing units needed and the number that will be available for the foreseeable future; the many problems associated with failing to ensure access to water and sanitation for homeless Californians, and how access to these basic needs compares with international minimum standards; and key barriers to progress. The Case Studies on Berkeley, Oakland, and Sacramento offer: an inventory of publicly available potable water, toilets, and showers in the three cities; discussion of how unsheltered residents struggle to meet their basic water-related needs; and an examination of municipal, non-profit, and resident-driven efforts to connect people experiencing homelessness to water and sanitation. Finally, based on the research conducted for this report, the Recommendations section offers six policies, programs, and actions that advocates can bring to State or municipal leaders responsible for upholding the human rights to water and sanitation for all Californians, particularly the State’s most vulnerable unsheltered residents.

Battling the Inland Sea

University of California Press | July 1st, 1998

Bay Area Green Infrastructure Water Quality Synthesis

San Francisco Estuary Institute (SFEI) | June 1st, 2018

San Francisco Bay is impacted by the numerous urban pollutants that flow from the surrounding landscape during storm events. In San Francisco Bay, total maximum daily lo

San Francisco Bay is impacted by the numerous urban pollutants that flow from the surrounding landscape during storm events. In San Francisco Bay, total maximum daily load (TMDL) clean-up plans are in place for polychlorinated biphenyls (PCBs) and mercury (Hg) (Davis et al., 2007; Davis et al., 2012). As municipalities strive to reach regulatory targets, green infrastructure (GI) presents a promising solution for managing stormwater pollutants while achieving additional environmental and social benefits. However, remaining data gaps including the best design layout, media composition, and vegetation and submerged zone effects on performance can prevent local managers from accurately assessing water quality benefits provided by green infrastructure as well as the maintenance needs to sustain adequate performance.