Evaluation of PCB Concentrations, Masses, and Movement from Dredged Areas in San Francisco Bay

San Francisco Estuary Institute (SFEI) | March 28th, 2019

This report is a product of a Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) project funded to analyze sediment PCB data in the Dredged Materia

This report is a product of a Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) project funded to analyze sediment PCB data in the Dredged Materials Management Office (DMMO) database to address priority management questions for PCBs. 

Evaluation of Salinity Patterns and Effects of Tidal Flows and Temporary Barriers in South Delta Channels

California Department of Water Resources (DWR) | September 15th, 2016

There are several important water issues in the south Delta related to the San Joaquin River (SJR) inflow, Central Valley Project (CVP) and State Water Project (SWP) expo

There are several important water issues in the south Delta related to the San Joaquin River (SJR) inflow, Central Valley Project (CVP) and State Water Project (SWP) export pumping, reverse flows in Old and Middle Rivers, tidal water elevations and corresponding tidal flows in south Delta channels, effects of the temporary rock barriers that are installed seasonally by DWR in various south Delta channels, as well as the sources and longitudinal patterns of salinity caused by the net inflows, outflows, and tidal movement of water in south Delta channels. This study investigated the likely inflow locations of higher salinity water (i.e., sources) measured in Old River between the head of Old River and the Delta-Mendota Canal (DMC); the electrical conductivity (EC) at the Old River at Tracy Boulevard EC monitoring station was often the highest EC measured in the south Delta channels and has frequently exceeded the D-1641 EC objectives.

Evolution of global snow drought characteristics from 1850 to 2100

Environmental Research Letters (IOP) | June 6th, 2023

Examining the causes and consequences of hybridization during Chinook salmon reintroductions: using the San Joaquin River as a restoration case study of management options

University of California, Davis (UC Davis) | June 15th, 2014

Successful salmonid restoration efforts depend upon an understanding of the evolutionary processes that historically shaped population diversity, as well as the realities

Successful salmonid restoration efforts depend upon an understanding of the evolutionary processes that historically shaped population diversity, as well as the realities of currently available, altered river systems. Habitat alterations over the past century have dramatically changed the ecological forces that shaped salmonid speciation and evolution, bringing formerly separate and distinct populations into contact and in some cases leading to hybridization. Hybridization can threaten the genetic diversity within salmonid species and may affect the outcomes of restoration efforts. Here we use the San Joaquin River Restoration as a case study to discuss some of the genetic challenges of Chinook salmon restoration in a newly reopened habitat. We discuss a range of genetic management strategies—from passive reintroduction to tightly managed, active reintroduction—and the strengths and weaknesses of each approach.

Expert review of the sediment screening guidelines for the beneficial reuse of dredged material in San Francisco Bay, Workshop Summary Report

Publisher not available | March 17th, 2020

Exploring scientific and management implications of upper trophic level food webs in the Delta

Delta Stewardship Council (Delta Council) | April 17th, 2024

The Sacramento-San Joaquin Delta (the Delta) has complex and evolving ecosystems characterized by multiple food webs that vary in time and space. Here, food webs are defi

The Sacramento-San Joaquin Delta (the Delta) has complex and evolving ecosystems characterized by multiple food webs that vary in time and space. Here, food webs are defined as the network of species interactions (competition, predation) and interactions with their environment that are related through the flow of energy through the ecosystem (e.g., Paine 1980). Physical modifications, in addition to the introduction of non-native species and the changing climate, have significantly altered the structure and energetic pathways of the food webs for decades. The science clearly suggests that predicting the impacts of habitat restoration, fisheries, changes in environmental drivers (e.g., climate, changes in nutrient loading, invasive species) on the ecological carrying capacity and productivity of the Delta, as well as the bioaccumulation of contaminants on species or the ecosystem, requires an understanding of food web processes.

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. 

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 Affecting the Composition and Salinity of Exports from the South Sacramento-San Joaquin Delta

California Department of Water Resources (DWR) | February 24th, 2004

The goal of this report is to identify factors affecting the composition and salinity of exports from the south Sacramento-San Joaquin Delta.  Composition is defined her

The goal of this report is to identify factors affecting the composition and salinity of exports from the south Sacramento-San Joaquin Delta.  Composition is defined here as sources of salt such as rivers and seawater. The individual objectives are to Review south Delta export composition studies; Describe the salinity trends in cross-Delta flow and the San Joaquin River - the two immediate sources of water flowing to the SWP and CVP export sites in the south Delta; Identify factors determining the export of cross-Delta flow versus the San Joaquin River; and Describe long-term salinity trends in SWP exports from the south Delta and factors affecting them.  

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.