San Joaquin River

Exploring the Potential for Water-Limited Agriculture in the San Joaquin Valley

Public Policy Institute of California (PPIC) | July 21st, 2022

The rollout of California’s Sustainable Groundwater Management Act (SGMA) is altering the state’s agricultural landscape. As groundwater sustainability measures are

The rollout of California’s Sustainable Groundwater Management Act (SGMA) is altering the state’s agricultural landscape. As groundwater sustainability measures are implemented and water scarcity increases, at least half a million acres are projected to come out of irrigated production in the San Joaquin Valley, the state’s agricultural heartland. Rather than widespread land idling—which comes with unintended consequences such as dust, weeds, pests, and soil degradation — a switch from summer irrigated crops to winter crops produced with limited water (including winter cereals and forage crops, among others) might keep some of this land in production. Although water-limited agriculture faces large hurdles, some promising aspects warrant further exploration.

Exploring Water System Vulnerabilities in California's Central Valley Under the Late Renaissance Megadrought and Climate Change

American Geophysical Union (AGU) | April 24th, 2025

Extreme hydrological changes in the southwestern US drive reductions in water supply to Southern California by mid century

Environmental Research Letters (IOP) | September 21st, 2016

The Southwestern United States has a greater vulnerability to climate change impacts on water security due to a reliance on snowmelt driven imported water. The State of C

The Southwestern United States has a greater vulnerability to climate change impacts on water security due to a reliance on snowmelt driven imported water. The State of California, which is the most populous and agriculturally productive in the United States, depends on an extensive arti cial water storage and conveyance system primarily for irrigated agriculture, municipal and industrial supply and hydropower generation. Here we take an integrative high-resolution ensemble modeling approach to examine near term climate change impacts on all imported and local sources of water supply to Southern California. While annual precipitation is projected to remain the same or slightly increase, rising temperatures result in a shift towards more rainfall, reduced cold season snowpack and earlier snowmelt. Associated with these hydrological changes are substantial increases in the frequency and the intensity of both drier conditions and ooding events. The 50 year extreme daily maximum precipitation and runoff events are 1.5–6 times more likely to occur depending on the water supply basin. Simultaneously, a clear de cit in total annual runoff over mountainous snow generating regions like the Sierra Nevada is projected. On one hand, the greater probability of drought decreases imported water supply availability. On the other hand, earlier snowmelt and signicantly stronger winter precipitation events pose increased flood risk requiring water releases from control reservoirs, which may potentially decrease water availability outside of the wet season. Lack of timely local water resource expansion coupled with projected climate changes and population increases may leave the area in extended periods of shortages.

Extreme Precipitation-Temperature Scaling in California: The Role of Atmospheric Rivers

American Geophysical Union (AGU) | July 25th, 2023

Facilitating Adaptive Management in California’s Sacramento–San Joaquin Delta

University of California, Davis (UC Davis) | July 1st, 2017

Uncertainties in understanding ecosystems increase the risk that management will fail to achieve desired results. Adaptive management is a structured, iterative applicati

Uncertainties in understanding ecosystems increase the risk that management will fail to achieve desired results. Adaptive management is a structured, iterative application of science-based knowledge to reduce uncertainties and build flexibility into decision-making. However, adaptive management is more easily planned than implemented, and it is only beginning to be applied in the California’s Sacramento–San Joaquin Delta. We draw from two assessments of adaptive management in the Delta and examples of its use elsewhere to suggest how the process can be facilitated. Although a highly structured adaptive-management process may not always be needed, several elements are essential. Adaptive management should begin by clearly identifying the problem, goals, and objectives; recognizing uncertainties; identifying decision points and alternative approaches; recognizing when adjustments are needed and having the flexibility to make them; and considering societal and political constraints. Model complexity should be matched to that of the system and management needs; experiments can help unravel causal relationships. Monitoring, analyses, and syntheses require comprehensive data-management systems. More frequent and organized communications among scientists, managers, stakeholders, and decision-makers are necessary. We propose the establishment of an “Adaptive Management Team” to coordinate efforts across the management spectrum of the Delta and to provide guidance and link individual projects to shared approaches and experiences. Reliable long-term support will be needed to assess results of management actions, adjust approaches where improvement is likely, and strive toward the legislated goals of enhancing the Delta ecosystem while also providing reliable water supplies to much of California, and doing both these things in a manner that protects values of the Delta as a place where people live and work. 

Facing the Climate Gap: How Environmental Justice Communities are Leading the Way to a More Sustainable and Equitable California

University of Southern California (USC) | October 31st, 2012

California has traditionally led the nation in protecting and preserving the environment – and we have proudly continued the trend with the 2006 passage and ong

California has traditionally led the nation in protecting and preserving the environment – and we have proudly continued the trend with the 2006 passage and ongoing implementation of the California Global Warming Solutions Act (AB 32). Aimed at reducing greenhouse gas emissions (GHGs) and slowing climate change, AB 32 came under political attack in 2010 when an initiative, funded largely by oil refiners, sought to delay application of the legislation’s rules. Fortunately, voters soundly rejected that effort, but many observers have worried that California’s concerns about climate could wane, particularly since the actual impacts of climate change can seem abstract and far-off. Against this backdrop, a wide range of community-based organizations have been working to “make it real” by connecting the dots between global warming and human impacts, and by helping residents adapt now and not later. In what might be a surprise to some observers, many of these organizations are working with low-income communities of color – those often stereotyped as the least concerned about climate change.

Factors Affecting Marsh Vegetation at the Liberty Island Conservation Bank in the Cache Slough Region of the Sacramento–San Joaquin Delta, California

U.S. Geological Survey (USGS) | July 5th, 2017

The Liberty Island Conservation Bank (LICB) is a tidal freshwater marsh restored for the purpose of mitigating adverse effects on sensitive fish populations elsewhere in

The Liberty Island Conservation Bank (LICB) is a tidal freshwater marsh restored for the purpose of mitigating adverse effects on sensitive fish populations elsewhere in the region. The LICB was completed in 2012 and is in the northern Cache Slough region of the Sacramento–San Joaquin Delta. The wetland vegetation at the LICB is stunted and yellow-green in color (chlorotic) compared to nearby wetlands. A study was done to investigate three potential causes of the stunted and chlorotic vegetation: (1) improper grading of the marsh plain, (2) pesticide contamination from agricultural and urban inputs upstream from the site, (3) nitrogen-deficient soil, or some combination of these. Water samples were collected from channels at five sites, and soil samples were collected from four wetlands, including the LICB, during the summer of 2015. Real-time kinematic global positioning system (RTK-GPS) elevation surveys were completed at the LICB and north Little Holland Tract, a closely situated natural marsh that has similar hydrodynamics as the LICB, but contains healthy marsh vegetation. The results showed no significant differences in carbon or nitrogen content in the surface soils or in pesticides in water among the sites. The elevation survey indicated that the mean elevation of the LICB was about 26 centimeters higher than that of the north Little Holland Tract marsh. Because marsh plain elevation largely determines the hydroperiod of a marsh, these results indicated that the LICB has a hydroperiod that differs from that of neighboring north Little Holland Tract marsh. This difference in hydroperiod contributed to the lower stature and decreased vigor of wetland vegetation at the LICB. Although the LICB cannot be regraded without great expense, it could be possible to reduce the sharp angle of the marsh edge to facilitate deeper and more frequent tidal flooding along the marsh periphery. Establishing optimal elevations for restored wetlands is necessary for obtaining the full suite of ecosystem services provided by tidal wetlands. A better system of tidal benchmarks throughout the delta is needed to help restoration practitioners correctly grade the elevation of newly restored wetlands.

Factors and Processes Affecting Delta Levee System Vulnerability

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

The authors appraised factors and processes related to human activities and high water, subsidence, and seismicity. Farming and drainage of peat soils over time has cause

The authors appraised factors and processes related to human activities and high water, subsidence, and seismicity. Farming and drainage of peat soils over time has caused a gradual sinking which contributed to internal levee failures. Although these subsidence rates have decreased with time, they still contribute to levee instability. Additional data is needed to assess spatial and temporal effects of subsidence caused by peat thinning and deformation. Since the mid-1970s large-scale, State investments in levee upgrades have increased conformance, however accounts continue to conflict on how these investments correspond to the numbers of failures. Both modeling and history suggest that the projected increases of high-flow frequency associated with climate change will increase levee-failures rates. Quantification of this increased threat requires further research. A reappraisal of seismic threats resulted in updated ground motion estimates for multiple faults and earthquake occurrence frequencies. The immediate seismic threat, liquefaction, is the sudden loss of strength due to an increase in the pressure of the pore fluid and corresponding loss of contact forces. However, levees damaged during an earthquake that do not immediately fail, may eventually breach. Consequences for future levee failure are estimated to cost up to billions of dollars. The analysis of future risks will benefit from more detailed descriptions of levee strength and upgrades, consideration of subsidence, climate change, and earthquake threats. Ecosystem benefits of levee habitats in this highly altered system are thin. Better recognition and coordination is needed among the creation of high value habitats, levee needs, costs, benefits of levee improvements, and breaches.  

Facts on the Water Rights Question in the Central Valley Project

California Farm Bureau (CFB) | March 11th, 1948

Fallowed agricultural lands dominate anthropogenic dust sources in California

Nature Portfolio (Springer Nature) | April 26th, 2025