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Source-linked reports with geographic coverage including California.

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USGS2022

Chapter 1: General conceptual model for climate change in the Upper San Francisco Estuary

This report is a collaboration by many state and federal agencies working in the Upper San Francisco Estuary to analyze the potential impacts of climate change to different ecosystems found here. Management stategies for ecological values in the face of climate change require reliable and focused information. In this technical report, our focus is on the Upper San Francisco Estuary (SFE), which contains the Sacramento-San Joaquin Delta and Suisun Bay. This area is home to three interconnected ecosystems: open water, floodplain, and tidal marsh. For this geographical area, we have decades of in-depth monitoring information and scientific investigations that have been successfully used to address a number of management needs. In 2019, the Interagency Ecological Program established a diverse work team to improve our ability to anticipate and respond to climate change impacts. The charge to the group was to: • synthesize science relevant to climate change, • determine important knowledge gaps, and • identify ecosystem metrics for climate change. We focus our analyses on the likely impacts of climate change on interconnected aquatic habitats. We illustrate how changes in habitats are likely to affect diverse species. In this report we describe ecological trends attributable to climate change and likely future impacts. We address four principal questions: 1. How have the habitats and biotic communities changed due to climatic trends and events? 2. How are estuarine habitats, flora, and fauna likely to change as climate change trends continue? 3. What are key metrics to document ecosystem change as a result of climate change? 4. How should our monitoring change to improve information value? Our work builds on the similar work of the San Francisco Baylands Goals Project (Goals Project 2015), which addressed climate change impacts to wetlands downstream of the confluence of the Sacramento and San Joaquin Rivers. We aim to contribute to an integrated baseline understanding of climate change impacts for the entire San Francisco Estuary.

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USGS2022

Floodplains and climate change

Floodplains are landscape features that are periodically inundated by water from adjacent rivers (Opperman et al. 2010). Ecologically, functional floodplains are characterized by three primary elements: connectivity, flow regime, and spatial scale. Water quantity flowing over floodplains can vary greatly. Based on a flood’s effects on the floodplain, three flood categories have been defined: floodplain-activation floods, floodplain-maintenance floods, and floodplainresetting floods (Box 1). Several physical parameters determine the types of ecosystems on floodplains and the species they will support; these include temperature, water depth, water velocity, and hydrologic connectivity (Opperman et al. 2010). Natural ecosystems commonly found on floodplains include annual vegetation, forests, seasonal wetlands, and permanent ponds or wetlands (Whipple et al. 2012). Floodplains provide many valuable ecosystem services: attenuation of flood flows which reduces flood risk, filtration of surface water, recreation, fisheries, agriculture, biodiversity, food availability, and groundwater recharge, which contributes to more-sustained and cooler dry-season flows (Opperman et al. 2010). -------------------------------------------------------------------------------------------------------------- Box 1 Floodplain-activation flood A small magnitude flood that occurs relatively frequently and produces characteristic ecological benefits such as food-web productivity and habitat creation for native fish spawning and rearing. Floodplain-maintenance flood A higher magnitude flood that, in addition to providing ecological benefits, results in geomorphic changes including bank erosion and deposition on the floodplain. Floodplain-resetting flood A very high-magnitude flood that occurs rarely and results in extensive geomorphic changes, such as the scouring of floodplain surfaces and changes in channel location due to avulsion. ----------------------------------------------------------------------------

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USGS2022

Bivalves

Bivalves are important as consumers of pelagic and demersal food resources. With sufficient biomass, they can compete with and, in some cases, outcompete other members of the pelagic food web for food resources such as phytoplankton and zooplankton. We include bivalves in the San Francisco Estuary (SFE) and Delta in the FLOAT MAST because they have been and continue to be an important member of the food web. Changes in the bivalves over the last 40 years have led us to hypothesize that bivalves may limit food resources for Delta Smelt and other pelagic fish species (Kimmerer and Thompson 2014, Sommer et al 2007). We will discuss the two bivalves with the largest biomass, the estuarine bivalve Potamocorbula amurensis (hereafter Potamocorbula ) and the freshwater bivalve Corbicula fluminea (hereafter Corbicula ). The distribution of these two species together covers the full range of salinities between the Golden Gate and the upstream reaches of the SR and SJR. The species overlap in the region of X2. Both species’ distributions expand or contract when the salinity distribution changes and do so in near synchrony with each other at a salinity of approximately 2. It is this interaction of both bivalves at their threshold levels of salinity within the ecologically sensitive low salinity zone (LSZ) in addition to their distribution in the rest of the system that determines each species effect on the food web.

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USGS2022

Repeat magnetotelluric measurements to monitor The Geysers steam field in northern California

The Geysers in northern California is the world’s largest electricity generating steam field. To help understand changes in the steam reservoir, repeat magnetotelluric (MT) measurements are being collected once a year from 2021-2023. These data will be compared and modeled to provide 4-D images of changes within the reservoir. Joint inversion with passive seismic data will be done to further constrain changes observed in the geophysical models. This study describes the first repeat survey and provides comparisons with MT data collected in 2017. In April 2021, 41 of the 42 MT stations collected in 2017 were repeated in addition to 14 new stations in the southern part of the steam field. Calculating residual phase tensors from MT responses between the two surveys shows compartmentalized changes within the steam field. Changes are observed at periods longer than 1 second with the largest changes of up to 30 percent observed at periods of 30 seconds. The residual phase tensors also show good repeatability between the surveys for periods less than 1 second, with changes on the order of 1 percent. To model the data, the preferred 3D resistivity volume that resulted from the inversion of the 2017 data is employed as the starting model for inversion of the new data. The two resulting inversion models are then subtracted to identify areas of change within the reservoir.

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USGS2022

Are canned sardines or dry cat food more effective as bait for capturing Northwestern Pond Turtles (Actinemys marmorata) and Red-eared Sliders (Trachemys scripta elegans)?

During an occupancy study of Northwestern Pond Turtles ( Actinemys marmorata ) and Red-eared Sliders ( Trachemys scripta elegans ) in California’s Sacramento Valley in 2018, we tested the relative effectiveness of 2 bait types: sardines packed in soybean oil and Meow Mix ® Original Choice dry cat food. We sampled 116 sites with 2 traps each: one baited with sardines and one baited with dry cat food. Sardines were 1.7 (95% confidence interval, 1.2–2.6) times more effective than dry cat food at capturing turtles in our study, and 63% of all captured turtles were caught in traps baited with sardines. Despite the slightly lower capture rate in traps baited with dry cat food, the significantly lower cost of cat food (about one-tenth the cost of sardines) makes it an appealing alternative bait if cost-effectiveness is a primary concern.

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USGS2022

Introduction to the Delta Smelt flow alteration white papers

The management of the quantity and timing of freshwater flow into and through the San Francisco Estuary (SFE) is a perennial source of controversy in California. It is well known that freshwater outflow is a major environmental driver in estuarine ecosystems, including the SFE. However, the estuary is also the hub of California’s water distribution system, which supplies water to over 25 million Californians and a multibillion-dollar agricultural industry. This tension between water supply and maintaining flows to maintain environmental quality is at the core of the controversy.

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USGS2022

Estimates of kappa in the San Francisco Bay area

Site characterization is a critical component of seismic hazards studies, especially in the development and use of ground motion models (GMMs). One such parameter, kappa ( Κ 0 ), represents local site attenuation and effectively describes regional variations in ground motion [1]. However, estimates of Κ 0 are limited. We estimate the site parameter Κ 0 for 296 broadband and accelerometer stations in the San Francisco Bay area using 225 local events with M>3.5. We first invert for kappa on the high-frequency slope of every record at a station, which represents full attenuation effects [2]. We then perform weighted regression of kappa versus distance to obtain expected kappa at the site ( Κ 0 ). We find that Κ 0 varies extensively in the San Francisco Bay area, with values ranging from 0.004-0.113 s, thus representing the heterogeneous geologic conditions in the region. Κ 0 estimates from this study will be useful to consider in future seismic hazard analyses and ground motion studies in the Bay Area.

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USGS2022

UAS-based tools for mapping and monitoring hydrothermal systems: An example from Mammoth Lakes, California

Unoccupied Aerial Systems (UAS) can accommodate a variety of tools for mapping and monitoring hydrothermal systems (e.g., magnetic, gas, photogrammetry, and thermal infrared [TIR]). These platforms offer increased speed, coverage area, and uniformity compared to ground-based measurements, as well as lower flight height – and therefore higher resolution – than occupied aircraft. We adapted a suite of tools for use with UAS and implemented these methods in a study focused on the area around Shady Rest Park, Mammoth Lakes, California, within the Long Valley Caldera. This location, which contains tree kills, gas vents, soil gas emissions, heated ground, and hydrothermal alteration, is the site of ongoing efforts to monitor changes in the surface expression of the local hydrothermal system. The methods applied in this study include: (1) airborne visible imagery for surficial mapping and the creation of high-resolution digital elevation models; (2) airborne magnetic measurements; (3) airborne TIR imagery; (4) airborne gas emission measurements; and (5) ground-based gravity measurements. We conducted these surveys in May and October of 2021, in part to establish baseline TIR and gas data against which future changes to the hydrothermal system may be assessed. UAS-based magnetic and ground-based gravity data were collected to map subsurface geology and to characterize potential subsurface controls on thermal anomalies and gas emissions. Results of these efforts at mapping and monitoring the hydrothermal system at Mammoth Lakes demonstrate how an integrated UAS- and ground-based approach may be applied more broadly to study other known or potential hydrothermal and volcanic systems. We consider the benefits and limitations of each method, particularly the TIR and gas sensors, which have less well-developed processing techniques in place for UAS applications. By integrating results from several of these different methods, however, the limitations facing each individual approach may be mitigated, and a better understanding of the hydrothermal system may be reached.

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USGS2022

Physical and geochemical architecture and age of the Pliocene Bicycle Lake basalt, southeastern Fort Irwin, California

The informally named Bicycle Lake basalt forms a volcanic field in southeastern Fort Irwin, California, disrupted by three east-striking faults and linked cross-faults of the Eastern California Shear Zone, and its distribution provides a framework for assessing volcanic field development, groundwater resources, and fault offsets. Previous geochronologic studies yielded ages ranging from ~2.9-5.6 Ma, and a new cycle of dating reported herein yields a more robust age of ~4.55 Ma. No vents or dikes have been identified for the basalt. No interstratified sedimentary rocks have been identified, not even aeolianites, implying that the field was monogenic and short-lived. Thickness of the field varies from 1 m at distal edges to as much as 20-35 m (projected in cross-section) in the central part of the field. The field consists of lava flows <8 m thick, and the relative abundance of flows <2 m thick and 3-8 m thick varies across the field, as does the interstratification of <3 m thick cosets of <1 m thick flows. Most flows are basaltic andesite with minor basalt. Within stratigraphic sequences, variations in major oxides and trace element geochemistry indicate interstratification of basalt with basaltic andesite, but also different compositions of interstratified basaltic andesite. The local abundance of basalt or different compositions of basaltic andesite varies. The distribution of compositions suggests minor changes in the composition of magma erupted and minor sector partitioning of flow paths during growth of the field. The basalt has been deformed as a result of transpressional stress transferred from the Coyote Lake to Bicycle Lake faults, which formed NW- striking reverse faults and faulted kink folds along with broad arching of the basalt. Restoring separation along the Coyote Canyon and Bicycle Lake faults indicates some flows of the basalt field traveled at least 10 km from their inferred source.

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USGS2021

Marine paleoseismic evidence for seismic and aseismic slip along the Hayward-Rodgers Creek fault system in northern San Pablo Bay

Distinguishing between seismic and aseismic fault slip in the geologic record is difficult, yet fundamental to estimating the seismic potential of faults and the likelihood of multi-fault ruptures. We integrated chirp sub-bottom imaging with targeted cross-fault coring and core analyses of sedimentary proxy data to characterize vertical deformation and slip behavior within an extensional fault bend along the Hayward-Rodgers Creek fault system in northern San Pablo Bay. We identified and traced four key seismic horizons (R1–R4), all younger than approximately 1400 CE, that cross the fault and extend throughout the basin. A stratigraphic age model was developed using detailed down-core radiocarbon and radioisotope dating combined with measurements of anthropogenic metal concentrations. The onset of hydraulic mining within the Sierra Nevada in 1852 CE left a clear geochemical and magnetic signature within core samples. This key time horizon was used to calculate a local reservoir correction and reduce uncertainty in radiocarbon age calibration and models. Vertical fault offset of strata younger than the most recent surface-rupturing earthquake on the Hayward fault in 1868 CE suggest near-surface vertical creep is occurring along the fault in northern San Pablo Bay at a rate of approximately 0.4 mm/yr. In addition, we present evidence of at least one and possibly two coseismic events associated with growth strata above horizons R1 and R2, with median event ages estimated to be 1400 CE and 1800 CE, respectively. The timing of both these events overlaps with paleoseismic events on adjacent fault sections, suggesting the possibility of multi-fault rupture.

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USGS2021

Post-seismic relaxation following the 2019 Ridgecrest, California, earthquake sequence

The 2019 Ridgecrest, California, earthquake sequence involved predominantly right‐lateral strike slip on a northwest–southeast‐trending subvertical fault in the 6 July M 7.1 mainshock, preceded by left‐lateral strike slip on a northeast–southwest‐trending subvertical fault in the 4 July M 6.4 foreshock. To characterize the postseismic deformation, we assemble displacements measured by Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar. The geodetic measurements illuminate vigorous postseismic deformation for at least 21 months following the earthquake sequence. The postseismic transient deformation is particularly well constrained from survey‐mode GPS (sGPS) in the epicentral region carried out during the weeks after the mainshock. We interpret these observations with mechanical models including afterslip and viscoelastic relaxation of the lower crust and mantle asthenosphere. During the first 21 months, up to several centimeters of horizontal motions are measured at continuous GPS and sGPS sites, with amplitude that diminishes slowly with distance from the mainshock rupture, suggestive of deeper afterslip or viscoelastic relaxation. We find that although afterslip involving right‐lateral strike slip along the mainshock fault traces and their deeper extensions reach a few decimeters, most postseismic deformation is attributable to viscoelastic relaxation of the lower crust and mantle. Within the Basin and Range crust and mantle, we infer a transient lower crust viscosity several times that of the mantle asthenosphere. The transient mantle asthenosphere viscosity is &#x223C; 1.3 &#xD7; 10 17 &#x2009;&#x2009; Pa &#x2009; s ">

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USGS2021

Golden eagle population surveys in the vicinity of the Altamont Pass Wind Resource Area, California, 2014–21

Golden Eagles ( Aquila chrysaetos ) are among the highest profile species killed by collisions with wind turbines at the Altamont Pass Wind Resource Area (APWRA) in the northern Diablo Range of west-central California. Understanding the distribution, site occupancy, and nesting status of eagles near the APWRA is needed to identify and minimize possible population-level impacts. We established a broad-scale survey design across a 5,185-km square-kilometer region of the Diablo Range, including the APWRA, to monitor site occupancy, abundance, and reproduction of Golden Eagles. During the study period we identified as many as 230 territorial pairs of Golden Eagles in the study area, up to 21 of which overlapped with the APWRA in any given year. On average, we detected a similar density of pairs at sites surveyed in the APWRA (1 pair per 17.8 km 2 surveyed) relative to sites surveyed in the surrounding region (1 pair per 20.3 km 2 surveyed). In 2020 and 2021, estimates of the proportion of pairs that successfully fledged at least one young (nesting success) were 0.27 and 0.26, respectively, which were above the seven-year average (0.22). On average, eagle pairs monitored in the APWRA had similar reproductive output (0.37 young fledged per pair) relative to pairs monitored outside of the APWRA (0.30 young fledged per pair). We observed a substantially higher proportion of territorial subadult pair members at the APWRA (mean = 29 percent of 16 pairs aged) relative to pairs monitored and aged in the surrounding region (mean = 3 percent of 122 pairs), indicating potentially higher rates of adult mortality or displacement at territories overlapping with the APWRA. Emergent threats to eagles in the study region, including a severe wildfire that impacted over 60 historical breeding territories in 2020, may interact with existing threats to affect population status and thus warrants further investigation. Our study provides wind energy developers, land managers, and regulatory agencies with key information on the spatial distribution, habitat quality, and population status of Golden Eagles needed to promote compatible wind energy production and long-term conservation of this federally protected wildlife species.

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USGS2021

Geostatistical mapping of salinity conditioned on borehole logs, Montebello Oil Field, California

We present a geostatistics-based stochastic salinity estimation framework for the Montebello Oil Field that capitalizes on available total dissolved solids (TDS) data from groundwater samples as well as electrical resistivity (ER) data from borehole logging. Data from TDS samples ( n = 4924) was coded into an indicator framework based on falling below four selected thresholds (500, 1000, 3000, and 10,000 mg/L). Collocated TDS-ER data from the surrounding groundwater basin were then employed to produce a kernel density estimator to establish conditional probabilities for ER data ( n = 8 boreholes) falling below the selected TDS thresholds within the Montebello Oil Field area. Directional variograms were estimated from these indicator coded data, and 500 TDS realizations from conditional indicator simulation were generated for the subsurface region above the Montebello Oil Field reservoir. Simulations were summarized as 3D maps of median TDS, most likely salinity class, and probability for exceeding each of the specified TDS thresholds. Results suggested TDS was below 500 mg/L in most of the study area, with a trend toward higher values (500 to 1000 mg/L) to the southwest; consistent with the average regional groundwater flow direction. Discrete localized zones of TDS greater than 1000 mg/L were observed, with one of these zones in the greater than 10,000 mg/L range; however, these areas were not prevalent. The probabilistic approach used here is adaptable and is readily modified to include additional data and types and can be employed in time-lapse salinity modeling through Bayesian updating.

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USGS2021

Birds not in flight: Using camera traps to observe ground use of birds at a wind-energy facility

Context: Camera trapping is increasingly used to collect information on wildlife occurrence and behaviour remotely. Not only does the technique provide insights into habitat use by species of interest, it also gathers information on non-target species. Aims: We implemented ground-based camera trapping to investigate the behaviours of ground-dwelling birds, a technique that has largely been unutilised for studying birds, especially in wind-energy facilities. Methods: We used camera traps to monitor activities of Agassiz’s desert tortoises ( Gopherus agassizii ) at their self-constructed burrows in a wind-energy facility near Palm Springs, California, USA. While doing so, we collected data on numerous burrow commensals, including birds. Key results: Monitoring from late spring to mid-autumn in one year showed regular use of tortoise burrows and the immediate area by 12 species of birds, especially passerines. The most abundant species, as indicated by the number of photographs, but not necessarily individuals, was the rock wren ( Salpinctes obsoletus ), with a total of 1499 events. Birds appeared to use the interior or proximate vicinity of burrows for gathering nesting material, displaying, feeding, dust bathing and other activities. Of the bird species observed, 10 are known to be occasional casualties of turbine-blade strikes. The minimum known-age of a burrow had a positive relationship with bird counts. Conclusions: Using camera traps focused at ground level can be a useful tool in avian conservation efforts because it is an effective technique for measuring bird presence, activity and behaviour in altered habitats such as wind farms, especially for those species that are low flyers or ground dwellers. Implications: Acquiring data over the long term by using ground-based monitoring with camera traps could add to our understanding of avian behaviour and habitat use in relation to wind-energy infrastructure and operations, and help determine the vulnerability of avifauna that utilise the area.

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USGS2021

Geochronologic, isotopic, and geochemical data from pre-Cretaceous plutonic rocks in the Lane Mountain area, San Bernardino County, California

Pre-Cretaceous, predominantly dioritic plutonic rocks in the Lane Mountain area, California, intrude metasedimentary and metavolcanic rocks considered part of the El Paso terrane. New geochronologic (uranium-lead zircon), geochemical, and isotopic data provide a reliable basis for dividing these pre-Cretaceous plutonic rocks into two mappable suites of Permian–Triassic and Late Jurassic ages. The 26 Permian–Triassic samples included in this report have a mean age of ~248 mega-annum (Ma), range in composition from monzodiorite to quartz monzonite and granodiorite, and have a mean initial 87 Sr/ 86 Sr ratio (Sri) of ~0.7045. The 22 Late Jurassic samples have a mean age of ~149 Ma, range in composition from gabbro to granite, and have a mean Sr i of ~0.7055. Accurate mapping of these two plutonic suites and their detailed field relations with the associated metamorphic rocks is essential for resolving the geologic history and regional tectonic significance of the Lane Mountain area. The sub-0.706 Sr i values of both plutonic suites at Lane Mountain are consistent with previous suggestions that the El Paso terrane is allochthonous and did not develop on Precambrian continental lithosphere. Both suites are considered parts of northwest-trending magmatic arcs interpreted to have formed above east-dipping subduction zones along the evolving North American continental margin, and both arcs are interpreted to cross a major east-west-trending boundary between the El Paso terrane and rocks considered part of ancestral North America in the San Bernardino Mountains area to the south. The El Paso terrane thus appears to have been attached to the San Bernardino Mountains area at least since Permian–Triassic time, although the boundary probably has been modified by Cenozoic faulting.

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