San Francisquito Creek Baylands Landscape Change Metrics Analysis

San Francisco Estuary Institute (SFEI) | June 21st, 2016

The goal of this study is to develop a high level overview of the physical and ecological changes to lower San Francisquito Creek and the surrounding tidal marshes and mu

The goal of this study is to develop a high level overview of the physical and ecological changes to lower San Francisquito Creek and the surrounding tidal marshes and mudflats (referred to here as “baylands”) since the beginning of intensive European-American settlement. Building upon a previous reconnaissance-level historical ecology study (Hermstad et al. 2009), this study analyzes the changes in key landscape features (or landscape metrics) within lower San Francisquito Creek and baylands through comparisons of reconstructed historical (mid-1800s) and contemporary (2011/2012) conditions. The results from this study are intended to provide baseline information that can be used to help with developing restoration and flood control redesign alternatives and appropriate habitat restoration targets. This study is one component of the Flood Control 2.0 project, a regional effort funded by the U.S. EPA to help design flood control channels at the Bay interface that support tidal habitats while maintaining the required level of flood protection. Emerging strategies for flood protection focus on reconnecting channels to floodplains and tidal marshes and using available dredged sediment as a resource to increase marsh elevations and help keep pace with sea level rise. Lower San Francisquito Creek is one of three implementation projects that have partnered with Flood Control 2.0 to assess the benefits of an integrated approach for flood control and habitat management at the Bay interface.

San Joaquin River Restoration Program

San Joaquin River Restoration Program | December 13th, 2007

San Luis National Wildlife Refuge Complex Final Comprehensive Conservation Plan and Environmental Assessment

U.S. Fish and Wildlife Service (FWS) | July 31st, 2024

This Comprehensive Conservation Plan (CCP) will guide the management of the Merced National Wildlife Refuge (NWR), San Luis NWR and Grasslands Wildlife Management Area (W

This Comprehensive Conservation Plan (CCP) will guide the management of the Merced National Wildlife Refuge (NWR), San Luis NWR and Grasslands Wildlife Management Area (WMA) for the next 15 years. Located in Merced County, California (Figure 1-1), these three units are managed and administered by the San Luis National Wildlife Refuge Complex (the Complex). A fourth unit, the San Joaquin River NWR, is also managed and administered by the Complex but already has a CCP for its management, which was completed in 2006 and amended in 2022. For the sake of this document, the term Complex refers to the San Luis NWR, Merced NWR and Grasslands WMA only. The Complex comprises just four of the 568 refuges that currently make up the U.S. Fish and Wildlife Service (USFWS or the Service) National Wildlife Refuge System (NWRS or Refuge System). The mission of the NWRS is to conserve a network of lands and water for the conservation and management of fish, wildlife and plant resources of the United States for the benefit of present and future generations. As part of the Refuge System, the three units—Merced NWR, San Luis NWR and Grasslands WMA—addressed in this CCP provide important habitat for a unique assemblage of both wetland- (particularly waterfowl and other waterbirds) and upland-dependent wildlife species of California’s Central Valley. This CCP is divided into five chapters: Chapter 1, Introduction and Background; Chapter 2, Comprehensive Conservation Planning Process; Chapter 3, Refuge Resources; Chapter 4, Refuge Management Direction; and Chapter 5, Implementation. Click here for full appendices.

Scattered tree death contributes to substantial forest loss in California

Nature Portfolio (Springer Nature) | January 20th, 2024

In recent years, large-scale tree mortality events linked to global change have occurred around the world. Current forest monitoring methods are crucial for identifying m

In recent years, large-scale tree mortality events linked to global change have occurred around the world. Current forest monitoring methods are crucial for identifying mortality hotspots, but systematic assessments of isolated or scattered dead trees over large areas are needed to reduce uncertainty on the actual extent of tree mortality. Here, we mapped individual dead trees in California using sub-meter resolution aerial photographs from 2020 and deep learning-based dead tree detection. We identified 91.4 million dead trees over 27.8 million hectares of vegetated areas (16.7-24.7% underestimation bias when compared to field data). Among these, a total of 19.5 million dead trees appeared isolated, and 60% of all dead trees occurred in small groups ( ≤ 3 dead trees within a 30 × 30 m grid), which is largely undetected by other state-level monitoring methods. The widespread mortality of individual trees impacts the carbon budget and sequestration capacity of California forests and can be considered a threat to forest health and a fuel source for future wildfires.

Scenarios of climate adaptation potential on protected working lands from management of soils

Environmental Research Letters (IOP) | September 30th, 2019

Management of protected lands may enhance ecosystem services that conservation programs were designed to protect. Practices that build soil organic matter on agri

Management of protected lands may enhance ecosystem services that conservation programs were designed to protect. Practices that build soil organic matter on agricultural lands also increase soil water holding capacity, potentially reducing climatic water deficit (CWD), increasing actual evapotranspiration (AET) and increasing groundwater recharge (RCH). We developed nine spatially-explicit land use and conservation scenarios (2001–2100) in the LUCAS land use change model to address two questions for California working lands (cropland and rangeland): How does land use change limit opportunities to manage soils for hydrologic climate adaptation benefits? To what extent and where can soil management practices increase climate adaptation on protected working lands? Hydrologic benefits [Σ(ΔCWD, ΔAET, ΔRCH)] due to soil management were simulated in the Basin Characterization Model (a state-wide water balance model) for two Representative Concentration Pathway 8.5 climate models. LUCAS simulated land conversion and new conservation easements with potential for maximum hydrologic benefits. Climate drove differences in lost potential for water benefits due to urbanization (33.9–87.6 m3 × 106) in 2050. Conflict between development pressure and potential hydrologic benefits occurred most in Santa Clara County in the San Francisco Bay Area and Shasta County in Northern Sacramento Valley. Hydrologic benefits on easements were similar in magnitude to losses from development. Water savings from management of California Land Conservation (a.k.a. Williamson) Act contract lands were an order of magnitude greater, totaling over 460 m3 × 106 annually in a drier climate by 2050. Few counties provide most benefits because of soil properties, climate and land area protected. The increase in hydrologic benefits varies by agricultural practice and adoption rate, land use type and configuration, and terms of conservation agreements. The effectiveness of programs designed to improve climate adaptation at county to state scales will likely increase by taking this variability into consideration.

Scientist and Stakeholder Views on the Delta Ecosystem

Public Policy Institute of California (PPIC) | April 22nd, 2013

There is broad scientific recognition that a wide range of ecosystem stressors are responsible for the declines in native fish populations in the Sacramento–San Joaquin

There is broad scientific recognition that a wide range of ecosystem stressors are responsible for the declines in native fish populations in the Sacramento–San Joaquin Delta. But science and policymaking have been at odds about the roles of different stressors and the potential of various management actions to improve ecosystem health. In the summer of 2012, PPIC conducted two confidential surveys on the impact of ecosystem stressors: one sought input from scientific experts and the other focused on stakeholders and policymakers. This report analyzes the results and examines the implications of both surveys.

Scrutinizing the Delta Cross Channel

CALFED | June 1st, 2001

Seasonal and Long-Term Clarity Trend Assessment of Lake Tahoe, California–Nevada

U.S. Geological Survey (USGS) | July 20th, 2022

The clarity of Lake Tahoe, observed using a Secchi disk on a regular basis since the late 1960s, continues to be a sentinel metric of lake health. Water clarity is influe

The clarity of Lake Tahoe, observed using a Secchi disk on a regular basis since the late 1960s, continues to be a sentinel metric of lake health. Water clarity is influenced by physical and biological processes and has declined in the five decades of monitoring, revealing differences between summer (June–September) and winter (December–March). This document summarizes key findings of a study of Lake Tahoe water clarity, including long-term variability and the relative importance of several influencing variables and processes. This study, prepared in cooperation with the Nevada Division of Environmental Protection, focused on (1) an apparent divergence in clarity trends between summer and winter periods, (2) observed changes in in-lake physical and ecological variables that may influence or control seasonal and annual clarity trends, and (3) five research hypotheses regarding lake clarity that were developed by Lake Tahoe management agencies. Previously collected data were used to complete this study. Trend analysis confirmed that winter clarity stabilized (that is, there is no longer a statistically significant trend up or down) during the last 20 years. Evaluation of clarity for selected months in the 50-year Secchi disk clarity dataset showed that only two summer months, July and August, had statistically significant decreases in clarity from 2000–19. Different subsets of available data were analyzed to reveal the presence or absences of trends for each season, decade, and month. Five hypotheses related to lake clarity were part of the study described by this report. Hypothesis 1 stated that clarity is controlled predominantly by the distribution and volumetric density of fine particles in suspension. This hypothesis was studied using available data describing in-lake fine (0–20 micrometers) particles from 2008–19. Water clarity was negatively correlated with in-lake particle abundance, with particles in the 1.0-4.6 μm range having the greatest effect, consistent with light-scattering theory. Estimated abundances of diatoms of the genus Cyclotella also were found to be negatively correlated with clarity. Data limitations precluded a complete investigation of hypothesis 2, which stated that the observed improvements in winter water clarity are a response to decreasing fine suspended-sediment concentrations in the lake resulting from load reductions from upland sources in and near urbanized areas. Data describing fine-sediment loading from urban areas to the lake were only available since 2014, and only once or twice per month. A slight, statistically significant, negative correlation was identified between urban fine-particle loading and monthly lake clarity with a 4-month lag. Particle abundance in monitored streams is highly correlated with simultaneous particle abundance in the lake.

Sediment Mobility and River Corridor Assessment for a 140-Kilometer Segment of the Main-Stem Klamath River Below Iron Gate Dam, California

U.S. Geological Survey (USGS) | January 26th, 2021

This river corridor assessment documents sediment mobility and river response to flood disturbance along a 140-kilometer segment of the main-stem Klamath River below Iron

This river corridor assessment documents sediment mobility and river response to flood disturbance along a 140-kilometer segment of the main-stem Klamath River below Iron Gate Dam, California. Field and remote sensing methods were used to assess fundamental indicators of active sediment transport and river response to a combination of natural runoff events and reservoir releases during the study period from 2005 to 2019. Discharge measurements at two gaged sites and bed-material samples at two ungaged sites provided direct and indirect evidence of mobile bed conditions, scour and fill, and surface flushing of fine sediment. Available remote-sensing datasets collected in 2005, 2009, 2010, and 2016 were used to determine sediment storage, flood inundation boundaries, and provide indirect evidence of flood-induced scour. These datasets validate channel-maintenance flows defined by Shea and others (2016). During the study period, flows greater than or equal to 6,030 cubic feet per second mobilized the substrate, caused localized scour, and flushed fine sediment from bar surfaces. Flows greater than or equal to 10,400 cubic feet per second stripped vegetation from bars and floodplains and produced deeper scour. Flood disturbance within the study reach is produced by the combined effect of natural flows and reservoir releases, which resulted in mobile bed conditions during the study period. Periodic scour and substrate disturbance are considered by the U.S. Fish and Wildlife Service to be integral for managing disease-induced mortality of juvenile and adult salmonids. Substrate conditions conducive to parasites that host infectious diseases, particularly Ceratonova shasta, occur periodically. Additional studies are required to determine whether disease prevalence can be mitigated by well-timed reservoir releases. Study results are useful for interpreting linkages among physical and biological processes and for evaluating the effectiveness of flow management targeted to improve river bed conditions for endangered salmonid populations.

Selenium in White Sturgeon from North San Francisco Bay: The 2015-2017 Sturgeon Derby Study

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

This report presents the findings from a study evaluating selenium concentrations in white sturgeon (Acipenser transmontanus) tissues collected during the 2015-2017 Sturg

This report presents the findings from a study evaluating selenium concentrations in white sturgeon (Acipenser transmontanus) tissues collected during the 2015-2017 Sturgeon Derby events in North San Francisco Bay. The goal of this study was to investigate the distribution of selenium among sturgeon tissues to inform the toxicological and regulatory interpretation of selenium measured in non-lethally collected tissues, including muscle plugs and fin rays. This technical report provides documentation of the study and presents its major findings.