Sacramento River

Predicting Sediment Bulk Density for San Francisco Estuary

University of California, Davis (UC Davis) | December 19th, 2025

Sediment bulk density (ρ-dry) and particle size are two important parameters for predicting sediment bed erosion. ρ-dry, however, is difficult to measure accurately. Th

Sediment bulk density (ρ-dry) and particle size are two important parameters for predicting sediment bed erosion. ρ-dry, however, is difficult to measure accurately. The units of ρdry have not been consistently reported in the literature, leading to confusion, particularly in the calculation of sediment budgets that typically require integrating mass-based and volumetric components. Relationships between ρdry and sediment composition have been developed for multiple regions and differ between systems. Developing a system-specific predictive model for ρdry can help fill data gaps and improve sediment budgets, model accuracy, and estimates of quantities of sediment needed for restoration. In this study, we investigate whether ρdry in San Francisco Estuary can be predicted from organic carbon content or percent of fines, which are more easily or frequently measured than ρdry. We compiled sediment properties from samples collected over the past decade throughout the intertidal and subtidal regions of San Francisco Bay and the Sacramento–San Joaquin Delta to examine this relationship. Sample composition ranged from 2.18 to 99.97% fines (particles < 0.0625 mm), ρ-dry ranged from 0.22 to 1.60 g cm-3, and organic carbon ranged from 0.06 to 7.98%. Regression analysis indicates that the percent of fines explains 93% of the variation of ρ-dry (p-value < 0.05, N = 81). The coefficient of determination decreased by ~1% when organic carbon was incorporated in the regression analysis. Comparison of this predictive ρ-dry model to four published models based on samples from other regions supports previous findings that the relationship between ρdry and grain size may vary by system. We also examined additional factors that may affect sediment erodibility, such as hydrographic and oceanographic conditions. Classification of sample sites as intertidal vs. subtidal or wavy vs. non-wavy each significantly explained the residuals from the ρdry model, and both intertidal and wavy conditions were associated with higher ρ-dry values.

Preface to the Environmental Assessment for 2019 Ocean Salmon Fisheries Management Measures

National Marine Fisheries Service (NMFS) | April 1st, 2019

Preparing Scientists, Policy-Makers, and Managers for a Fast-Forward Future

University of California, Davis (UC Davis) | June 15th, 2021

Preseason Report I Stock Abundance Analysis and Environmental Assessment Part 1 for 2019 Ocean Salmon Fishery Regulations (PRE I)

Pacific Fishery Management Council | March 1st, 2019

Preseason Report II Proposed Alternatives and Environmental Assessment Part 2 for 2019 Ocean Salmon Fishery Regulations (PRE II)

Pacific Fishery Management Council | March 21st, 2019

Preseason Report III Council Adopted Management Measures and Environmental Assessment Part 3 for 2019 Ocean Salmon Fishery Regulations (PRE III)

Pacific Fishery Management Council | April 30th, 2019

Primary Production in the Delta: Then and Now

University of California, Davis (UC Davis) | October 3rd, 2016

To evaluate the role of restoration in the recovery of the Delta ecosystem, we need to have clear targets and performance measures that directly assess ecosystem function

To evaluate the role of restoration in the recovery of the Delta ecosystem, we need to have clear targets and performance measures that directly assess ecosystem function. Primary production is a crucial ecosystem process, which directly limits the quality and quantity of food available for secondary consumers such as invertebrates and fish. The Delta has a low rate of primary production, but it is unclear whether this was always the case. Recent analyses from the Historical Ecology Team and Delta Landscapes Project provide quantitative comparisons of the areal extent of 14 habitat types in the modern Delta versus the historical Delta (pre-1850). Here we describe an approach for using these metrics of land use change to: (1) produce the first quantitative estimates of how Delta primary production and the relative contributions from five different producer groups have been altered by large-scale drainage and conversion to agriculture; (2) convert these production estimates into a common currency so the contributions of each producer group reflect their food quality and efficiency of transfer to consumers; and (3) use simple models to discover how tidal exchange between marshes and open water influences primary production and its consumption. Application of this approach could inform Delta management in two ways. First, it would provide a quantitative estimate of how large-scale conversion to agriculture has altered the Delta's capacity to produce food for native biota. Second, it would provide restoration practitioners with a new approach—based on ecosystem function—to evaluate the success of restoration projects and gauge the trajectory of ecological recovery in the Delta region.

Primary Production in the Sacramento-San Joaquin Delta: A Science Strategy to Quantify Change and Identify Future Potential

San Francisco Estuary Institute (SFEI) | May 20th, 2019

Today’s Sacramento-San Joaquin Delta is an unusually low-productivity estuary. The constraints on primary production and the relative importance of different production

Today’s Sacramento-San Joaquin Delta is an unusually low-productivity estuary. The constraints on primary production and the relative importance of different production sources to the food web are major ecological uncertainties in the Delta system. Understanding how the extensive historical changes in the Delta landscape have altered primary production has the potential to inform restoration planning and management across the region.  The Delta Landscapes Project (SFEI-ASC 2014) has recently produced information that allows us, for the first time, to answer questions about historical primary production and carrying capacity from quantified changes in the areal extent and spatial configuration of habitat types in the Delta since the mid-19th century. Our focus is on estimating primary production because the potential capacity of ecosystems to support fish, bird and other wildlife populations is set by primary production – the supply of food required to produce animal biomass. 

Principles for Agreement on Bay-Delta Standards Between the State of California and the Federal Government

California State Water Resources Control Board (SWRCB) | December 15th, 1994

In order to provide ecosystem protection for the Bay-Delta Estuary, representatives of the State and Federal governments and urban, agricultural and environmental interes

In order to provide ecosystem protection for the Bay-Delta Estuary, representatives of the State and Federal governments and urban, agricultural and environmental interests agree to the implementation of a Bay-Delta protection plan through the California State Water Resources Control Board (SWRCB) consistent with the following principles.These Principles describe changes to the California Urban Water Agency/-Agricultural Water Users (CUWAIAG) proposal as the base case for Bay-Delta protections, which are intended to be in force for three years, at which time they may be revised.

Priorities for California's Water: Responding to the Changing Climate

Public Policy Institute of California (PPIC) | November 18th, 2021

Water is central to how California adapts to a changing climate. To those of us steeped in the complexities of managing the state’s water resources, the current fast-mo

Water is central to how California adapts to a changing climate. To those of us steeped in the complexities of managing the state’s water resources, the current fast-moving drought—coming on the heels of the record-breaking 2012–16 drought—is a stark reminder that we must accelerate preparation for the disruptive changes underway. Californians have taken steps to address major threats to our water resources. But a recent IPCC report underscored that the climate is changing faster than anticipated, and that many of these changes are already locked in. Rising temperatures are making our winters shorter and our droughts more intense, outpacing our ability to manage water supplies and the natural environment. We need to act with urgency to adapt to these changes. And we need to rethink how we store water. This brief examines how the current drought and a changing climate are affecting California’s ability to manage water and lays out priority actions to address major challenges—including some urgent short-term actions should the drought continue into next year.