Review of CDFW Recommendations for the 2022 Readoption of Drought Emergency Regulations on the Scott River and Recommendations for Future Management During Extreme Drought Conditions

Siskiyou Farm Bureau | August 31st, 2022

Review of North Delta Salmon Out-Migration Study

CALFED | January 23rd, 2008

This document is a review of the North Delta Salmon Out-Migration Study (NDSOS) proposed to the California Department of Water Resources (DWR) by a group of PIs l

This document is a review of the North Delta Salmon Out-Migration Study (NDSOS) proposed to the California Department of Water Resources (DWR) by a group of PIs lead by Jon Burau of the USGS. To carry out this review, the CALFED Science program, acting at the request of DWR and the PIs, convened a panel that was given a substantial written proposal describing the study. In addition to the written proposal, the PIs gave a series of presentations to a majority of the panel members at a public workshop held on January 10, 2008. The presentations provided many details about the proposed study that were not included in the written proposal. The panel was charged by CALFED to: “.... make recommendations concerning, and oversee incorporation of modifications to, the proposed study to ensure that, when funded, executed, and analyzed, the proposed investigation will provide the best-available science when characterizing the hydrodynamics and movement of out-migrating salmon smolts in the north Delta region in response to several alternate regional configurations.” This report is the panel’s response to that charge. In the sections that follow, we start by describing those aspects of the proposal that the panel found would work well or were strong positives. We follow this with a critique of perceived shortcomings of the proposal and a set of recommendations for possible changes to the proposed work that would improve the proposed study. These recommendations were based on the information in the written proposal provided to the panel and on the presentations made at the public workshop.

Review of the Long-Term Operations of the Central Valley Project and the State Water Project

National Academy of Sciences (NAS) | November 10th, 2025

The CVP and SWP (referred to collectively as “the Projects”) rarely deliver their full contracted  amount of water. Some of this is inherent in the operation of larg

The CVP and SWP (referred to collectively as “the Projects”) rarely deliver their full contracted  amount of water. Some of this is inherent in the operation of large water projects with diverse demands in a dry and highly variable climate. A growing, complex regulatory environment of state and federal laws, some of which were created to protect fish species endemic to the Delta, has further restricted CVP and SWP operations.  These fish include the southern distinct population segment of North American green sturgeon, California Central Valley steelhead, Central Valley spring-run Chinook salmon, Sacramento River winter-run Chinook salmon, longfin smelt, and Delta smelt. Operating the Projects while trying to prevent species extinction can be a source of conflict if the actions to prevent extinction reduce the amount of water that can be exported. Project operation into the future will likely become more challenging as changes in various climatic factors push the listed species closer to their thresholds of survivability. Hence, in late 2023 USBR contracted with the National Academies of Sciences, Engineering, and Medicine (NASEM) to form an expert committee that could serve as an independent review for the CVP and SWP as they operate into the future. The Committee’s statement of task appears in Box S-1. The three actions chosen for the study—the Shasta Coldwater Pool Management Action, the Old and Middle River Flow Management Action, and the Summer-Fall Habitat Action for Delta Smelt— are perceived as consequential for species survival and controversial for their effects on water deliveries to contractors.

Revised Incidental Take Methodology for the Coordinated Long-Term Operation of the CVP and SWP

U.S. Fish and Wildlife Service (FWS) | January 30th, 2019

Revisiting chlorophyll a thresholds for San Francisco Bay: Insights from observations of phytoplankton molecular abundance

Elsevier | February 14th, 2026

Harmful Algal Blooms (HABs) are a hazard for coastal environments worldwide; identifying screening thresholds of chlorophyll-a (chl-a) associated with inc

Harmful Algal Blooms (HABs) are a hazard for coastal environments worldwide; identifying screening thresholds of chlorophyll-a (chl-a) associated with increased risk of HABs is a management priority. Molecular surveillance of coastal phytoplankton and bivalve biotoxins could be used to link chl-a with HAB risk, but requires an understanding of whether the HAB risks increase uniformly as chl-a rises, or whether some taxa are disproportionately favored, and if these relationships vary by season. In this study, we present a novel use of molecular abundance data to investigate the scientific bases for estuarine chl-a thresholds protective against HABs. In San Francisco Bay (SFB), California, the relationship between molecular relative abundance (as measured by 18S metabarcoding) of nine different HAB taxa, absolute quantitative polymerase chain reaction (qPCR) abundance, and mussel toxin concentrations of a subset of the taxa were investigated for thresholds as a function of increasing chl-a. Our results show most HAB taxa did not increase in absolute or relative abundance during SFB’s spring bloom interval, when chl-a levels were highest (>10 µg/L) but the assemblage was dominated by non-harmful diatoms. However, several flagellated, mixotrophic taxa did increase above their molecular baseline in fall, and the combined probability of any HAB occurring above baseline was elevated when chl-a reached ∼4.6 µg/L in the fall. This work demonstrates the promise of molecular approaches in disentangling the seasonally complex interplay between stressors and phytoplankton/HAB community responses and has the potential to provide clearer, more cost-effective monitoring and mitigation strategies for managers.

RipZET: Documentation of Tool Demonstration in Marin County

San Francisco Estuary Institute (SFEI) | March 31st, 2015

The San Francisco Estuary Institute and Aquatic Science Center (SFEI‐ASC) has developed the Riparian Zone Estimation Tool (RipZET) to help the California community of

The San Francisco Estuary Institute and Aquatic Science Center (SFEI‐ASC) has developed the Riparian Zone Estimation Tool (RipZET) to help the California community of riparian interests visualize and characterize riparian areas as habitat unto themselves as well as their capacity to function as buffers for protecting the ecosystem services of the state’s streams, lakes and wetlands. RipZET is a tool used with Geographic Information System (GIS) and spreadsheet software to estimate “functional riparian width,” or the width associated with different riparian functions (e.g., large woody debris input, shading, floodwater storage), which varies with channel type and watershed location. The concept of functional riparian width is central to the riparian definition recommended by the National Research Council (NRC 2002) and is integral in many recently developed riparian design and management guidelines around the country.

Risks and Options to Reduce Risks to Fishery and Water Supply Uses of the Sacramento/San Joaquin Delta

California Department of Water Resources (DWR) | January 1st, 2008

Assembly Bill (AB) 1200 (Laird, Chapter 573, Statutes of 2005) highlighted the complex Delta water issues, and directed the Department of Water Resources (DWR) and the De

Assembly Bill (AB) 1200 (Laird, Chapter 573, Statutes of 2005) highlighted the complex Delta water issues, and directed the Department of Water Resources (DWR) and the Department of Fish and Game (DFG) to report to the Legislature and Governor on the following: • Potential impacts of levee failures on water supplies derived from the Sacramento-San Joaquin Delta due to future subsidence, earthquakes, floods, and effects of climate change • Options to reduce the impacts of these factors • Options to restore salmon and other fisheries that use the Delta estuary The State is currently involved in four major planning efforts to evaluate ecosystem and water supply issues and consider options for improvements: 1. The Delta Risk Management Strategy (DRMS) is evaluating Delta issues primarily from the perspective of the risks from levee failures and ways to reduce those risks 2. The CALFED Ecosystem Restoration Program (ERP) Conservation Strategy is identifying restoration opportunities within the Delta and Suisun Marsh ecological restoration zones based on existing elevations, soil types, habitats and natural process requirements of pelagic organisms and other native fish species 3. The Delta Vision will develop a durable vision for sustainable management of the Delta with the goal of managing the Delta over the long term to restore and maintain identified functions and values that are determined to be important to the environmental quality of the Delta and the economic and social well being of the people of the state 4. The Bay Delta Conservation Plan (BDCP) is evaluating Delta issues primarily for the goal of obtaining permits for water supply operations through a comprehensive conservation plan for the Delta designed to protect and restore at-risk species. Since each process has only prepared initial findings at this point in time, this document reports on progress made to define the risks and options to reduce risks for the Delta as requested by the Legislature.

River-Aquifer Interactions, Geologic Heterogeneity, and Low-Flow Management

U.S. Geological Survey (USGS) | ?

Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard mater

Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard materials beneath the river. Low flows are often important ecologically. Numerical simulations were used to assess how textural heterogeneity of an alluvial system influences river seepage and low flows. The Cosumnes River in California was used as a test case. Declining fall flows in the Cosumnes River have threatened Chinook salmon runs. A ground water–surface water model for the lower river basin was developed, which incorporates detailed geostatistical simulations of aquifer heterogeneity. Six different realizations of heterogeneity and a homogenous model were run for a 3-year period. Net annual seepage from the river was found to be similar among the models. However, spatial distribution of seepage along the channel, water table configuration and the level of local connection, and disconnection between the river and aquifer showed strong variations among the different heterogeneous models. Most importantly, the heterogeneous models suggest that river seepage losses can be reduced by local reconnections, even when the regional water table remains well below the riverbed. The percentage of river channel responsible for 50% of total river seepage ranged from 10% to 26% in the heterogeneous models as opposed to 23% in the homogeneous model. Differences in seepage between the models resulted in up to 13 d difference in the number of days the river was open for salmon migration during the critical fall months in one given year.

Ruling on Plaintiffs’ Motion for Preliminary Injunction, Case No. Bcv-22-103220-Gap, Bring Back the Kern et al v. City of Bakersfield et al

Superior Court of California, County of Kern | October 30th, 2023

SacPAS Fish Model: A model for emergence, migration and survival of Sacramento River salmon

Delta Stewardship Council (Delta Council) | November 1st, 2017