San Francisco Bay

Decoupling outmigration from marine survival indicates outsized influence of streamflow on cohort success for California’s Chinook salmon populations

Canadian Journal of Fisheries and Aquatic Sciences (Canadian Science Publishing) | October 17th, 2018

Historically, marine survival estimates for salmon have been confounded with freshwater seaward migration (outmigration) survival. Telemetry studies have revealed low and

Historically, marine survival estimates for salmon have been confounded with freshwater seaward migration (outmigration) survival. Telemetry studies have revealed low and variable survival during outmigration, suggesting marine mortality may not be the primary source of variability in cohort size as previously believed. Using a novel combination of tagging technologies, survival during these two life stages was decoupled over 5 years for Sacramento River Chinook salmon (Oncorhynchus tshawytscha). Outmigration survival ranged from 2.6% to 17%, and marine survival ranged from 4.2% to 22.8%. Influential environmental drivers in both life stages were also compared with smolt-to-adult ratios (SAR) for three Chinook salmon populations over 20 years. Streamflow during outmigration had higher correlation with SAR (r2 > 0.34) than two marine productivity indices (r2 < 0.08). The few SAR estimates that were poorly predicted by flow occurred during years with the lowest marine productivity, suggesting most interannual SAR fluctuations are explained by outmigration survival, but abnormally poor marine conditions also reduce SAR. The outsized influence of flow on SAR provides managers with a powerful mitigation tool in a watershed where flow is tightly regulated.

DEDUCE: Delta Environmental Data for the Understanding of California Estuary Factsheet

San Francisco Estuary Institute (SFEI) | July 3rd, 2017

Delta Adapts: Creating a Climate Resilient Future

Delta Stewardship Council (Delta Council) | June 25th, 2021

The time to act is now. Climate change is already altering the physical environment of the Sacramento–San Joaquin Delta and Suisun Marsh (Delta), and we will continue t

The time to act is now. Climate change is already altering the physical environment of the Sacramento–San Joaquin Delta and Suisun Marsh (Delta), and we will continue to experience its effects through hotter temperatures, more severe wildfires, and prolonged droughts. Over the long term, climate change in the Delta is expected to harm human health and safety, disrupt the economy, diminish water supply availability and usability, shift ecosystem function, compromise sensitive habitats, and increase the challenges of providing basic services. Many of these impacts will disproportionately affect vulnerable communities. Although the exact extent and timing of these impacts is uncertain, this climate change vulnerability assessment phase of Delta Adapts will help the Delta Stewardship Council (Council) understand specific regional climate risks and vulnerabilities. Regional, collaborative adaptation strategies rooted in science are more critical than ever. The next phase of Delta Adapts, preparing an adaptation strategy, will identify ways to address the risks and vulnerabilities.

Delta Adapts: Creating a Climate Resilient Future

Delta Stewardship Council (DSC) | June 25th, 2025

The Delta Stewardship Council (Council) was established, in part, to provide sustainable management for the Delta ecosystem, and climate adaptation is a critical consider

The Delta Stewardship Council (Council) was established, in part, to provide sustainable management for the Delta ecosystem, and climate adaptation is a critical consideration to achieve that mission in future decades. To respond to the challenge of climate adaptation,the Council developed this initiative, Delta Adapts: Creating a Climate Resilient Future (Delta Adapts). Climate change must be considered to attain the state’s coequal goals, as established by the 2009 Delta Reform Act: securing a reliable water supply for California, protecting and restoring the ecosystem and wildlife it supports, and enhancing the Delta as a unique place, with its community, tribal, and agricultural heritage. The Council adopted the Delta Plan, which has regulatory policies that protect land for restoration and agriculture, help manage flood risk, and improve water supply reliability. The Delta Plan directs the Council to guide and regulate actions of the 200+ state and local agencies in the Delta to ensure they support statewide water supply reliability and Delta ecosystem restoration.

Delta Adapts: Creating a Climate Resilient Future Sacramento-San Joaquin Delta Climate Change Adaptation Plan (Draft)

Delta Stewardship Council (Delta Council) | November 1st, 2024

Initiated in 2018 by the Council, Delta Adapts began with a Climate Change Vulnerability Assessment (CCVA) to understand how regional climate impacts will affect the Delt

Initiated in 2018 by the Council, Delta Adapts began with a Climate Change Vulnerability Assessment (CCVA) to understand how regional climate impacts will affect the Delta’s ecosystems, water supply, infrastructure, agriculture, and communities, including socially vulnerable communities (defined in Chapter 1). Now, this Adaptation Plan builds upon the CCVA and proposes strategies to address how Delta communities, infrastructure, and ecosystems can adapt to climate change in a manner consistent with the Council’s resilience goals.

Delta Aquatic Resources Inventory Factsheet

San Francisco Estuary Institute (SFEI) | July 1st, 2019

 DARI is the Delta Aquatic Resources Inventory of surface waters, wetlands and other aquatic resources in the Sacramento-San Joaquin Delta (Delta). The goal of the DARI

 DARI is the Delta Aquatic Resources Inventory of surface waters, wetlands and other aquatic resources in the Sacramento-San Joaquin Delta (Delta). The goal of the DARI project is to develop a geospatial inventory of aquatic resources that will be used as a common base map for the Delta. A similar mapping approach used to create the California Aquatic Resource Inventory (CARI; www. sfei.org/cari) will be applied to provide a map of the aquatic resources and their associated attributes. The final map will be incorporated into CARI and made publicly available through EcoAtlas (ecoatlas.org) and similar platforms. 

Delta Conservation Adaptive Management Action Strategy

Delta Stewardship Council (Delta Council) | April 11th, 2019

Various efforts are ongoing to restore and enhance ecosystems in the Sacramento-San Joaquin Delta, Yolo Bypass, and Suisun Marsh (hereafter the Delta) that require suppor

Various efforts are ongoing to restore and enhance ecosystems in the Sacramento-San Joaquin Delta, Yolo Bypass, and Suisun Marsh (hereafter the Delta) that require support for adaptive management. Adaptive management is a science-based, structured approach to environmental decision making under uncertain conditions. Adaptive management emphasizes acquisition and use of new knowledge in natural resource management, leading to continuous iterative improvements in project planning, implementation, monitoring, and follow-up. Adaptive management is required for compliance with multiple regulatory processes, such as consistency with the Delta Plan and the Suisun Marsh Plan, but recent reviews have found that a full adaptive management cycle is rarely completed at either the project- or system-level in the Delta (Delta Independent Science Board 2016; Nagarkar and Raulund-Rasmussen 2016). To address this issue, the Delta Science Program initiated an effort to work with agency and stakeholder partners in the Delta to develop a comprehensive, science-based adaptive management approach to support achievement of Delta conservation goals. Conservation, as defined in the Delta Conservation Framework (Sloop et al. 2018), consists of efforts to protect, restore, and enhance ecosystems in the Delta. The Delta Conservation Adaptive Management Action Strategy is based on the Adaptive Management Framework outlined in the Delta Plan (Figure 1, Delta Stewardship Council 2013). 

Delta Conveyance Environmental Review Notice of Preparation Overview

California Department of Water Resources (DWR) | January 15th, 2020

The Department of Water Resources (DWR) is pursuing an environmental review process to evaluate a single tunnel option to modernize Delta conveyance under the California

The Department of Water Resources (DWR) is pursuing an environmental review process to evaluate a single tunnel option to modernize Delta conveyance under the California Environmental Quality Act (CEQA). The first step in this process is release of a Notice of Preparation (NOP). The NOP informs agencies and the public about the preparation of the Environmental Impact Report (EIR) and solicits input on the scope and content of the EIR, including information needs, potential project effects and mitigation measures, and possible alternatives to the proposed project. Modernizing Delta conveyance is part of the state’s Water Resilience Portfolio, which describes the framework to address California’s water challenges and support long-term water resilience and ecosystem health.

Delta Conveyance Project Draft Environmental Impact Report Explained

California Department of Water Resources (DWR) | July 27th, 2022

The Delta Conveyance Project Draft Environmental Impact Report Explained is a companion to the Delta Conveyance Project’s Draft Environmental Impact Report (EIR) to hel

The Delta Conveyance Project Draft Environmental Impact Report Explained is a companion to the Delta Conveyance Project’s Draft Environmental Impact Report (EIR) to help members of the public better understand the proposed Delta Conveyance Project and the requirements for the Department of Water Resources (DWR) in preparing an EIR under the California Environmental Quality Act (CEQA). Although not required by CEQA, this document is intended to acquaint readers with the proposed Delta Conveyance Project and alternatives analyzed in the Draft EIR and provide a short summary of impacts to key resource areas. This document is separate from and not intended to be a substitute or surrogate for the comprehensive summary of the Draft EIR that is being circulated with the Draft EIR. Readers are encouraged to review the Draft EIR Executive Summary and full Draft EIR and provide comments during the public review period.

Delta Conveyance Project Draft Environmental Impact Statement

U.S. Army Corps of Engineers (USACE) | December 16th, 2022

The California Department of Water Resources (DWR or the applicant) is proposing to construct new conveyance facilities in the Sacramento–San Joaquin Delta (Delta). As

The California Department of Water Resources (DWR or the applicant) is proposing to construct new conveyance facilities in the Sacramento–San Joaquin Delta (Delta). As the lead agency for the Delta Conveyance Project (project or proposed action), the U.S. Army Corps of Engineers (USACE) Sacramento District has prepared an environmental impact statement (EIS) for construction of the action alternatives. This Draft EIS analyzes the applicant’s proposed action and alternatives, which include intake facilities on the Sacramento River, tunnel reaches and tunnel shafts, a southern forebay and pumping plant, and south Delta conveyance facilities that would connect to the existing State Water Project (SWP) infrastructure. Because construction of the proposed action and action alternatives would alter federal levees, permission from USACE is required under Section 14 of the Rivers and Harbors Act (RHA) (33 United States Code [USC] § 408) (Section 408). Construction of the proposed action and action alternatives would cross under the Stockton Deep Water Ship Channel (a federal navigation project); therefore, a real estate outgrant1 from USACE would be required. In addition, the proposed work in navigable waters of the United States requires authorization from USACE under Section 10 of the RHA (33 USC § 403), and discharge of dredged or fill material into waters of the United States requires authorization from USACE under Section 404 of the Clean Water Act (CWA) (33 USC § 20 1344). DWR is the requester under Section 408 and the applicant under Section 10, Section 404, and the real estate outgrant. Once constructed, the new facilities that comprise the proposed action would become part of the SWP. Operation of the SWP, including the facilities proposed in this project, is outside USACE authority under Section 408, Section 10, and Section 404. Therefore, the Draft EIS focuses only on 25 those actions requiring USACE authorization or approval. Operations are discussed briefly and qualitatively throughout the Draft EIS. Readers should refer to the Delta Conveyance Project Draft Environmental Impact Report (Delta Conveyance Project Draft EIR) (California Department of Water Resources 2022) for a more in-depth analysis of operations and associated effects on the environment. Where noted, this Draft EIS incorporates by reference portions of the Delta Conveyance Project Draft EIR (California Department of Water Resources 2022).