2022–2026 Science Action Agenda: A Vision for Integrating Delta Science

Delta Stewardship Council (Delta Council) | April 5th, 2022

2024 5-Year Review: Summary & Evaluation of Northern California Steelhead

National Oceanic and Atmospheric Administration (NOAA) | July 9th, 2024

Many West Coast salmon and steelhead (Oncorhynchus spp.) stocks have declined substantially from their historic numbers and now are at a fraction of their historical abun

Many West Coast salmon and steelhead (Oncorhynchus spp.) stocks have declined substantially from their historic numbers and now are at a fraction of their historical abundance. Several factors contribute to these declines, including: overfishing, loss of freshwater and estuarine habitat, hydropower development, poor ocean conditions, and hatchery practices. These factors collectively led to the National Marine Fisheries Service’s (NMFS) listing of 28 salmon and steelhead stocks in California, Idaho, Oregon, and Washington under the Federal Endangered Species Act (ESA). The ESA, under section 4(c)(2), directs the Secretary of Commerce to review the listing classification of threatened and endangered species at least once every 5 years. A 5-year review is a periodic analysis of a species’ status conducted to ensure that the listing classification of a species as threatened or endangered on the List of Endangered and Threatened Wildlife and Plants (List) (50 CFR 17.11 – 17.12; 50 CFR 223.102, 224.101) is accurate (USFWS and NMFS 2006; NMFS 2020). After completing this review, the Secretary must determine if any species should: (1) be removed from the list; (2) have its status changed from endangered to threatened; or (3) have its status changed from threatened to endangered. If, in the 5-year review, a change in classification is recommended, the recommended change will be further considered in a separate rule-making process. The most recent 5-year review analysis for West Coast salmon and steelhead occurred in 2016. This document describes the results of the 2024 review of ESA-listed Northern California steelhead (NC steelhead). A 5-year review is: • A summary and analysis of available information on a given species; • The tracking of a species’ progress toward recovery; • The recording of the deliberative process used to make a recommendation on whether or not to reclassify a species; • A recommendation on whether reclassification of the species is indicated.

A Comparative Study for Estimating Crop Evapotranspiration in the Sacramento-San Joaquin Delta

University of California, Davis (UC Davis) | April 23rd, 2018

Consumptive water use by crops, often referred to as evapotranspiration (ET), is frequently the largest component of an agricultural region’s water balance. This study

Consumptive water use by crops, often referred to as evapotranspiration (ET), is frequently the largest component of an agricultural region’s water balance. This study investigates crop consumptive use in the Sacramento-San Joaquin Delta (“Delta”) of California using a comparative approach with several prominent methods for estimating crop ET, including estimates based on crop coefficients, water balances, energy balance using remote sensing, and field measurements. Click here to download full report and links to appendices

A conceptual model for floodplains in the Sacramento-San Joaquin Delta

University of California, Davis (UC Davis) | October 3rd, 2012

Floodplains are among the most biologically productive and diverse ecosystems on Earth and they provide significant benefits to society such as attenuation of floodwaters

Floodplains are among the most biologically productive and diverse ecosystems on Earth and they provide significant benefits to society such as attenuation of floodwaters, groundwater recharge, filtration of nutrients and sediments, carbon sequestration, fisheries productivity and recreation.  However, floodplains are also among the most converted and threatened ecosystems.  Floodplain habitats in the Sacramento-San Joaquin Delta, and throughout California’s Central Valley, have been greatly reduced from their historic extent and key processes that create and maintain floodplains, such as flood flows and meander migration, have been greatly altered.  These widespread alterations to habitats and processes have lead to declines in many species’ populations in California’s Central Valley and Delta, creating challenges for both environmental and water management. To address these challenges numerous entities and programs are now focused on restoring floodplains and other Delta habitats.  This paper provides a conceptual model for floodplains that characterizes the key features and identifies the critical processes, drivers, and linkages that allow floodplains to produce a variety of functional outputs of management importance.  These outputs include: (1) the floodplain habitat mosaic, including riparian vegetation and its associated wildlife; (2) spawning and rearing habitat for native fish; and (3) food-web productivity that can support native fish on the floodplain as well as be exported to downstream ecosystems.  The model emphasizes that the production of these outputs from floodplains requires vertical and lateral hydrological connectivity across a broad range of flow conditions.  For example, long-duration flooding in the spring promotes native fish spawning and food-web productivity that benefits native species.

A Delta Renewed: A Guide to Science-Based Ecological Restoration in the Sacramento-San Joaquin Delta

San Francisco Estuary Institute (SFEI) | November 1st, 2016

This report offers guidance for creating and maintaining landscapes in the Sacramento-San Joaquin Delta that support desired ecological functions, while retaining the ove

This report offers guidance for creating and maintaining landscapes in the Sacramento-San Joaquin Delta that support desired ecological functions, while retaining the overall agricultural character and water-supply service of the region. Based on extensive research into how the Delta functioned historically, how it has changed, and how it is likely to evolve, we discuss where and how to re-establish the dynamic natural processes that can sustain native Delta habitats and wildlife into the future. The approach, building on work others have piloted and championed, is to restore or emulate natural processes where possible, establish an appropriate mosaic of habitat types at the landscape scale, use multi-benefit management strategies to increase support for native species in agricultural and urban areas, and allow the Delta to adapt to future uncertainties of climate change, levee failure, and human population growth. With this approach, it will be critical to integrate ecological improvements with the human landscape: a robust agricultural economy, water infrastructure and diversions, and urbanized areas. Strategic restoration that builds on the history and ecology of the region can contribute to the strong sense of place and recreational value of the Delta.

A Delta Renewed: A Guide to Science-Based Ecological Restoration in the Sacramento-San Joaquin Delta

San Francisco Estuary Institute (SFEI) | November 1st, 2016

A Delta Renewed and the larger Delta Landscapes project are part of an ongoing effort to address these critically important challenges. They provide guidance for restora

A Delta Renewed and the larger Delta Landscapes project are part of an ongoing effort to address these critically important challenges. They provide guidance for restoration that renews critical functions over time without having major negative impacts on the current human enterprise in the Delta area and on other areas dependent on its services. The idea is to determine the most efficient ways to recover Delta functioning so that human benefits are maintained, while investing in process-based recovery of landscape functions. The scientists working on this project assume that this goal is best achieved if we can understand how the Delta functioned before major European modification. We can then use that knowledge as a guide to developing a diverse portfolio of habitats and connections that might sustain native species, and the attributes of a healthy Delta into the future. The effort to reconstruct the Delta of the early 1800s has been challenging, but is now completed. The next step is to devise management scenarios that will recover important functions and native species where possible. There is no intent to try to recreate the Delta of the past. That is impossible without sacrificing our objective of maintaining and even improving the human enterprises now present. What is essential now is to obtain general agreement among all of the stakeholders, which includes all citizens of California, that the Delta should be managed for the benefit of people and wildlife in a sustainable way. Given the uncertainties inherent in any large-scale reconciliation effort, there is a real need to appreciate the complex interactions and inter-dependencies that characterize the various components of the Delta landscape. There is also a need to understand the uncertainties of future climate change and to recognize the diversity of needs among our fellow citizens. Our hopes for success will ultimately depend on generating a spirit of cooperation for the common good. It won’t be easy, but the stakes are high. The Delta Landscapes project is dedicated to that goal.

A Delta Renewed: A Guide to Science-Based Ecological Restoration in the Sacramento-San Joaquin Delta

San Francisco Estuary Institute (SFEI) | November 15th, 2016

This final report of the Delta Landscapes Project, A Delta Renewed, offers guidance for creating and maintaining landscapes that can provide desired ecological functi

This final report of the Delta Landscapes Project, A Delta Renewed, offers guidance for creating and maintaining landscapes that can provide desired ecological functions for decades to come. Based on extensive research into how the Sacramento-San Joaquin Delta used to function, how it has changed, and how it is likely to evolve, we make recommendations for how to re-establish the dynamic natural processes that can sustain native Delta wildlife as healthy populations into the future. The approach, building on work others have piloted and championed, is to restore or emulate natural processes where possible, establish an appropriate configuration of habitat types at the landscape scale, and use multi-benefit management strategies to create a more viable Delta ecosystem that can adapt and continue to provide valued functions as the climate changes. This approach is designed to integrate with the human landscape: ecosystem improvements as a part of a robust agricultural economy, water infrastructure and diversions, and urbanized areas. Strategic restoration which builds on the history and ecology of the region can contribute to the strong sense of place and recreational value of the Delta in the future. See more at: http://www.sfei.org/projects/delta-landscapes-project#sthash.RryQdaII.dpuf

A Delta Transformed: Ecological Functions, Spatial Metrics, and Landscape Change in the Sacramento-San Joaquin Delta

San Francisco Estuary Institute (SFEI) | October 1st, 2014

In A Delta Transformed, completed in 2014, SFEI researchers used the spatial data generated in the Delta Historical Ecology Investigation, as well as updated modern veget

In A Delta Transformed, completed in 2014, SFEI researchers used the spatial data generated in the Delta Historical Ecology Investigation, as well as updated modern vegetation and land cover datasets, to carry out detailed analyses of how the Delta landscape has been altered since the early-1800s. By quantifying changes in metrics relevant to native wildlife (such as the extent and timing of inundation, habitat patch sizes, length of channel networks), the report provides a foundation for defining, designing, and evaluating landscapes that support desirable ecological functions in the future. See more at: http://www.sfei.org/projects/delta-landscapes-project#sthash.RryQdaII.dpuf

A Framework for Research Addressing the Role of Ammonia/Ammonium in the Sacramento-San Joaquin Delta and the San Francisco Bay Estuary Ecosystem

CALFED | April 13th, 2009

The Sacramento-San Joaquin Delta and the San Francisco Bay Estuary ecosystem has been drastically altered by human activity since at least the mid-1800s, leading to numer

The Sacramento-San Joaquin Delta and the San Francisco Bay Estuary ecosystem has been drastically altered by human activity since at least the mid-1800s, leading to numerous physical, chemical and biological changes [e.g., see Healey (2008) and Healey et al. (2008) for overviews]. Recent concerns include (1) the precipitous decline of four fish species that inhabit the Delta (collectively referred to as the pelagic organism decline, or POD) and (2) apparent major shifts in community composition of algae and higher trophic levels in the Delta and downstream in Suisun Bay. The four POD species of concern are delta smelt (longfin smelt), threadfin shad and striped bass. One of the potential causes of the POD and the community changes is the discharge of increasing concentrations of a combination of ammonia (NH3) and ammonium (NH4+) into the Delta ecosystem and eventually into Suisun Bay. For brevity, we hereafter abbreviate the ammonia/ammonium combination as ammonia/um. To address the potential for adverse effects of ammonia/um on the Bay-Delta ecosystem, a ammonia/um workshop was convened by the CALFED Science Program on 10 and 11 March 2009 in Sacramento, California. We participated as an expert panel and were charged with preparing a framework for research that will address the role of ammonia/um in the Bay-Delta ecosystem. In this report, we present our perception and interpretation of the major concerns related to ammonia/um in the Bay-Delta ecosystem; a conceptual framework of the major physical, chemical and biological drivers controlling the ecosystem (including POD populations); our assessment of the major research needs; and concluding remarks. For some research needs, we recommend specific types of research and provide literature citations; however, for other research needs we recommend general approaches for which targeted research will be determined later. In many ways, Bay-Delta research is breaking new ground by tackling a large-scale, complex freshwater-estuarine ecosystem affected by multiple, interactive stressors. Consequently, the Bay-Delta research program will establish a template for future research and management decisions in other hydrologically, biogeochemically, and trophically-similar systems, rather than relying on paths trodden by others.

A Machine Learning Tool for Design of Behavioral Fish Barriers in the Sacramento-San Joaquin River Delta

U.S. Geological Survey (USGS) | January 16th, 2024

Survival of out-migrating juvenile salmonids (Oncorhynchus spp.) through the Sacramento-San Joaquin River Delta averages less than 33 percent, depending on water flow thr

Survival of out-migrating juvenile salmonids (Oncorhynchus spp.) through the Sacramento-San Joaquin River Delta averages less than 33 percent, depending on water flow through the delta, and is partially governed by the distribution of fish among three Sacramento River distributaries: Sutter, Steamboat, and Georgiana sloughs. Behavioral altering structures in the junctions of the distributaries can effectively increase entrainment into favorable routes, thereby increasing through-delta (Verona to Chips Island, California) survival. The effectiveness of these structures, hence forth called “behavioral barriers,” are dependent on shape, length, location, barrier type, and water velocity, which is governed by Sacramento River discharge (hereinafter referred to as “flow”).