Sacramento River

Flood-MAR Research and Data Development Plan

California Department of Water Resources (DWR) | October 31st, 2019

The Research Advisory Committee (RAC) is pleased to make this plan available to the growing network of farmers, researchers, planners, and water and land managers who wan

The Research Advisory Committee (RAC) is pleased to make this plan available to the growing network of farmers, researchers, planners, and water and land managers who want to expand our collective knowledge about using floodwaters for managed aquifer recharge (Flood-MAR). This plan outlines the priority information needed by those making management decisions about the where, when, and how of capturing available flood water to replenish California’s depleted aquifers.

Flooded Wetland Availability for Breeding Waterfowl in a Mediterranean Climate: Mapping 38 Years of Historical Data in Suisun Marsh, California

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

Most managed wetlands in California are ephemeral and are purposefully flooded during the fall and winter for over-wintering waterfowl and are dry during the spring and s

Most managed wetlands in California are ephemeral and are purposefully flooded during the fall and winter for over-wintering waterfowl and are dry during the spring and summer waterfowl breeding season. Only semi-permanent and permanent wetlands remain flooded through the critical summer brood-rearing period for ducklings. We examined flooded wetland availability for breeding waterfowl in the brackish Suisun Marsh (California, USA) annually during the spring (April 27–May 17, during peak nesting) and summer (June 17–July 7, during peak duckling brood rearing), for a 38-year period using Landsat satellite imagery and spectral mixture analysis. Flooded wetland area increased 43% in spring and 48% in summer from 1984 to 2021 but varied among years (spring: 37.6–88.6 km2; summer: 17.7–57.5 km2). This increase in flooded wetland area over the past four decades was due to just a few sites, with only 24% (spring) and 15% (summer) of the 198 land-owner parcels increasing in flooded area. Flooded wetland area in the spring was unrelated to annual precipitation between October and April (range: 25–104 cm) or spring precipitation between January and April (range: 8-65 cm), whereas flooded wetland area in the summer was weakly correlated to both annual and spring precipitation. Flooded wetland area in spring and summer was also weakly correlated with the median daily outflow from the Sacramento-San Joaquin River Delta between March 15 and June 15, which corresponds to a critical period of wetland water management for breeding waterfowl. Our results indicate that spring and summer flooded wetland habitat for breeding waterfowl has slightly increased over the past four decades, varies annually, and is mostly dependent on local wetland management practices rather than on precipitation or Delta outflows. Managing habitats as semi-permanent wetlands would increase flooded wetland habitat in the spring and summer and provide habitat for nesting hens and ducklings.

Floods in California

Public Policy Institute of California (PPIC) | February 29th, 2024

Flow Augmentations Modify an Estuarine Prey Field

University of California, Davis (UC Davis) | June 15th, 2023

Flows and Fishes in the Sacramento-San Joaquin Delta

Delta Stewardship Council (Delta Council) | August 1st, 2015

Record-low counts of Delta smelt at a time of persistent drought underscore the importance and challenges of managing freshwater flows for the benefit of fishes in the Sa

Record-low counts of Delta smelt at a time of persistent drought underscore the importance and challenges of managing freshwater flows for the benefit of fishes in the Sacramento-San Joaquin Delta while also meeting human demands for water. Understanding the effects of water flows on fishes is central to understanding how the Delta ecosystem functions and is key to achieving the state’s coequal goals of “providing a more reliable water supply for California and protecting, restoring and enhancing the Delta ecosystem … in a manner that protects and enhances … the values of Delta as an evolving place”. The economic, ecological, and social costs of scientific uncertainty in water management controversies are significant - and to some degree unavoidable. Scientific findings that relate fishes and flows increasingly guide decisions on how to manage flows for the well-being of threatened or endangered species in the Delta. Many studies – and management decisions – rely on correlations between water flows and fish populations. But the decisions warrant fuller understanding of precisely how the flows affect the fishes. Knowledge of these underlying mechanisms is likely to facilitate adaptive management by clarifying uncertainty and risk, by creating specific expectations for outcomes and by strengthening testable hypotheses. This report therefore recommends, first and foremost (there are other recommendations as well), redoubling effects to identify causes and effects concerning fishes and flows in the Delta.

Flows and Fishes in the Sacramento-San Joaquin Delta Research Needs in Support of Adaptive Management

Delta Stewardship Council (Delta Council) | August 15th, 2015

Food Web Fuel Differs Across Habitats and Seasons of a Tidal Freshwater Estuary

Estuaries and Coasts (Springer) | July 11th, 2020

Estuarine food webs are fueled by multiple different primary producers. However, identifying the relative importance of each producer to consumers is difficult, particula

Estuarine food webs are fueled by multiple different primary producers. However, identifying the relative importance of each producer to consumers is difficult, particularly for fishes that utilize multiple food sources due to both their mobility and their generally high trophic levels. Previous studies have documented broad spatial differences in the importance of primary producers to fishes within the Upper San Francisco Estuary, California, including separation between pelagic and littoral food webs. In this study, we evaluated the importance of primary producers to adult fishes in three closely spaced subregions that represented disparate habitat types (a tidal wetland channel, a turbid backwater channel, and a deep open-water channel), each a potential outcome of local restoration projects. Using stable isotope analysis coupled with a Bayesian mixing model, we identified significant differences in primary-producer contribution to fishes and invertebrates across habitats and seasons, especially in the relative contribution of submersed aquatic vegetation and phytoplankton. Most fishes utilized multiple primary producers and showed little segregation between pelagic and littoral food webs among habitats. Availability of primary producers differs seasonally and across multiple spatial scales, helping to buffer environmental variability and thus enhancing food web resilience. Ecosystem restoration may improve with emphasis on restoring a wide variety of primary producers to support consumers.

Food Webs of the Delta, Suisun Bay, and Suisun Marsh: An Update on Current Understanding and Possibilities for Management

University of California, Davis (UC Davis) | October 1st, 2016

This paper reviews recent research findings on food web processes since 2008. It also highlights the idea of a changing baseline with respect to food web function. New re

This paper reviews recent research findings on food web processes since 2008. It also highlights the idea of a changing baseline with respect to food web function. New research indicates that interactions between habitat-specific food webs vary across the current landscape. For example, based on early work in the south Delta, the food web associated with underwater vegetation was thought to provide little support to species of concern; however, data from other regions of the estuary suggest that this conceptual model may not apply across the entire region. Habitat restoration has been proposed as a method of re-establishing historic food web processes to support species of concern. Benefits are likely for species that directly access such restored habitats, but are less clear for pelagic species. Several issues require attention to further improve the knowledge of food webs needed to support effective management, including: (1) synthesis of factors responsible for low pelagic biomass; (2) monitoring and research on effects of harmful algal blooms; (3) broadening the scope of long-term monitoring; (4) determining benefits of tidal wetland restoration to species of concern, including evaluations of interactions of habitat-specific food webs; and (5) interdisciplinary analysis and synthesis. The only certainty is that food webs will continue to change in response to the changes in the physical environment and new species invasions.

Forests and Water in the Sierra Nevada: Sierra Nevada Watershed Ecosystem Enhancement Project

University of California, Merced (UC Merced) | November 21st, 2011

In this white paper on the Sierra Nevada Watershed Ecosystem Enhancement Project (SWEEP), we make the case that upstream management of Sierra Nevada forests can significa

In this white paper on the Sierra Nevada Watershed Ecosystem Enhancement Project (SWEEP), we make the case that upstream management of Sierra Nevada forests can significantly increase the value of downstream water resources by shifting water towards higher value uses and optimizing the timing of runoff. The focus of this paper is on the west-side mixed-conifer forests at elevations of about 1500-3600 m (5000-12,000 ft), which are highly productive owing to the availability of sufficient water, predominance of above-freezing temperatures and presence of other conditions necessary for growth.  California has a Mediterranean climate, with wet winters and dry summers. Precipitation falling as rain on Sierra Nevada forests enters the soil and is partitioned between evapotranspiration and runoff. Much of the rainfall leaves the forest as evapotranspiration, owing to ample water storage in the subsurface and temperatures that allow growth year round. At higher elevations, e.g. above elevations of 1800-2100 m depending on both latitude and microclimate, which are dominated by snow rather than rain, the snowpack provides an important seasonal storage of water that, together with subsurface-water storage, provides the water needed for forest growth over the summer and fall. Forest thinning to reduce vegetation and thus evapotranspiration will result in a higher fraction of precipitation, particularly snowmelt, leaving the mountain forest as runoff. Historically, the unique character of Sierra Nevada forests was defined by its tall trees, relatively mild climate and low forest density. In many areas, current forest densities are much higher than historical values. Forest thinning can also influence the timing of snowmelt and runoff. That is, a less-dense canopy can allow snow to reach the ground rather than be held in the canopy; and strategic spacing of forest openings will limit early season sunlight reaching the forest floor and retard snowmelt.  In this paper we review the forest hydrology literature relevant to management of conifer forests in the Sierra snow zone, as that management affects the timing and amount of snowmelt runoff. In order to understand the conceptual and practical challenges, we summarize the key elements of forest energy budget, with specific reference to the Sierra Nevada, and describe several relevant case studies. Although principles that govern the mountain water cycle are well known and models of water and energy balance are informed by field measurements in some areas, there is a severe knowledge gap that limits quantitative predictions of the effects of forest thinning on Sierra Nevada water and energy cycles. Nevertheless, generalizations from reviews of paired catchment studies carried out elsewhere suggest that Sierra Nevada conifer forests contain ecological attributes with a high potential for water-yield gains. Historical studies of forest harvesting in the Sierra Nevada have shown increases of between 14 and 34% in snow accumulation. Treatments that increase snow accumulation help increase water yield during low flows, when water resources’ economic and ecosystem values are highest.  Preliminary estimates based on average climate information suggest that in the Sierra Nevada, treatments that would reduce forest cover by 40% of maximum levels across a watershed could increase water yields by about 9%. Note that this white paper focused on forest management effects on the water balance. Impacts on wildlife habitat, forest health, and fire behavior were not analyzed. The projections and models reported here are designed to describe the potential for modifying water yield and timing. Before implementation of any strategy, a wider consideration of the consequences on forest structure and function would be necessary.  Because of the potential for water-yield increases and extended snow storage, the SWEEP project has developed a plan to evaluate forest thinning related to water yield in representative headwater catchments in the Sierra Nevada, as a basis for extending these treatments to broader areas of the Sierra Nevada. To that end, we outline an experiment that could be carried out in the Onion Creek Experimental Forest, Tahoe National Forest, Placer County, California that could test silvicultural treatments designed to modify the water balance of mixed-conifer, snow-dominated catchments. The treatments are based on a leaf area index (LAI) approach (O’Hara 1998) to forest management, which is well-suited to water yield and timing objectives. Our initial estimates are that treatments could increase water yield as much as 16% and extend snow storage, i.e. delay snowmelt, by days to weeks. 

Formation and prevention of pipe scale from acid mine drainage at iron Mountain and Leviathan Mines, California, USA

Applied Geochemistry (Elsevier) | April 1st, 2020

Pipelines carrying acid mine drainage (AMD) to treatment plants commonly form pipe scale, an Fe(III)-rich precipitate that forms inside the pipelines and requires periodi

Pipelines carrying acid mine drainage (AMD) to treatment plants commonly form pipe scale, an Fe(III)-rich precipitate that forms inside the pipelines and requires periodic and costly cleanout and maintenance. Pipelines at Iron Mountain Mine (IMM) and Leviathan Mine (LM) in California carry acidic water from mine sources to a treatment plant and have developed pipe scale. Samples of scale and AMD were collected from both mine sites for mineralogical, microbiological, and chemical analysis. The scale mineralogy was primarily schwertmannite with minor amounts of poorly crystalline goethite. Although the bulk composition of the scale was similar along the length of the pipeline at IMM, the number of iron-oxidizing bacteria and concentrations of associated trace elements decreased along the flow path inside the pipeline. Laboratory batch experiments with unfiltered AMD from IMM and LM showed that Fe(II) oxidation was driven by microbial activity when the pH was <5. A remediation strategy of decreasing the pH to <2.2 was tested through geochemical modeling and laboratory experiments. These experiments indicated that scale formation could be prevented by decreasing the pH, which could be achieved at IMM by mixing source waters. However, the presence of Fe(III)-rich scale in a pipeline buffers the pH to higher values that may affect the efficacy of this remedial approach.