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At least 235 records · Page 13Linked to original sources

USGS2004

Modeling sorption of divalent metal cations on hydrous manganese oxide using the diffuse double layer model

Manganese oxides are important scavengers of trace metals and other contaminants in the environment. The inclusion of Mn oxides in predictive models, however, has been difficult due to the lack of a comprehensive set of sorption reactions consistent with a given surface complexation model (SCM), and the discrepancies between published sorption data and predictions using the available models. The authors have compiled a set of surface complexation reactions for synthetic hydrous Mn oxide (HMO) using a two surface site model and the diffuse double layer SCM which complements databases developed for hydrous Fe (III) oxide, goethite and crystalline Al oxide. This compilation encompasses a range of data observed in the literature for the complex HMO surface and provides an error envelope for predictions not well defined by fitting parameters for single or limited data sets. Data describing surface characteristics and cation sorption were compiled from the literature for the synthetic HMO phases birnessite, vernadite and δ-MnO 2 . A specific surface area of 746 m 2 g −1 and a surface site density of 2.1 mmol g −1 were determined from crystallographic data and considered fixed parameters in the model. Potentiometric titration data sets were adjusted to a pH IEP value of 2.2. Two site types (≡XOH and ≡YOH) were used. The fraction of total sites attributed to ≡XOH ( α ) and p K a2 were optimized for each of 7 published potentiometric titration data sets using the computer program FITEQL3.2. p K a2 values of 2.35±0.077 (≡XOH) and 6.06±0.040 (≡YOH) were determined at the 95% confidence level. The calculated average α value was 0.64, with high and low values ranging from 1.0 to 0.24, respectively. p K a2 and α values and published cation sorption data were used subsequently to determine equilibrium surface complexation constants for Ba 2+ , Ca 2+ , Cd 2+ , Co 2+ , Cu 2+ , Mg 2+ , Mn 2+ , Ni 2+ , Pb 2+ , Sr 2+ and Zn 2+ . In addition, average model parameters were used to predict additional sorption data for which complementary titration data were not available. The two-site model accounts for variability in the titration data and most metal sorption data are fit well using the p K a2 and α values reported above. A linear free energy relationship (LFER) appears to exist for some of the metals; however, redox and cation exchange reactions may limit the prediction of surface complexation constants for additional metals using the LFER.

Applied Geochemistry↗

USGS2019

Estimating offsets for avian displacement effects of anthropogenic impacts

Biodiversity offsetting, or compensatory mitigation, is increasingly being used in temperate grassland ecosystems to compensate for unavoidable environmental damage from anthropogenic developments such as transportation infrastructure, urbanization, and energy development. Pursuit of energy independence in the United States will expand domestic energy production. Concurrent with this increased growth is increased disruption to wildlife habitats, including avian displacement from suitable breeding habitat. Recent studies at energy-extraction and -generation facilities have provided evidence for behavioral avoidance and thus reduced use of habitat by breeding waterfowl and grassland birds in the vicinity of energy infrastructure. To quantify and compensate for this loss in value of avian breeding habitat, it is necessary to determine a biologically-based currency so that the sufficiency of offsets in terms of biological equivalent value can be obtained. We describe a method for quantifying the amount of habitat needed to provide equivalent biological value for avifauna displaced by energy and transportation infrastructure, based on the ability to define five metrics: impact distance, impact area, pre-impact density, percent displacement, and offset density. We calculate percent displacement values for breeding waterfowl and grassland birds and demonstrate the applicability of our avian-impact offset method using examples for wind and oil infrastructure. We also apply our method to an example in which the biological value of the offset habitat is similar to the impacted habitat, based on similarity in habitat type (e.g., native prairie), geographical location, land use, and landscape composition, as well as to an example in which the biological value of the offset habitat is dissimilar to the impacted habitat. We provide a worksheet that informs potential users how to apply our method to their specific developments and a framework for developing decision-support tools aimed at achieving landscape-level conservation goals.

Ecological Applications↗

USGS2018

Exploring the impacts of seagrass on coupled marsh-tidal flat morphodynamics

Intertidal coastal environments are prone to changes induced by sea level rise, increases in storminess, temperature, and anthropogenic disturbances. It is unclear how changes in external drivers may affect the dynamics of low energy coastal environments because their response is non-linear, and characterized by many thresholds and discontinuities. As such, process-based modeling of the ecogeomorphic processes underlying the dynamics of these ecosystems is useful, not only to predict their change through time, but also to generate new hypotheses and research questions. Here, we used a three-point dynamic model to investigate how seagrass might affect the behavior of coupled marsh-tidal flat systems. The model directly incorporates ecogeomorphological feedbacks among wind waves, salt marsh vegetation, allochthonous sediment loading, seagrasses and sea level rise. The model was applied to examine potential behaviors of salt marsh systems in the Virginia coastal bays. Differences due to the presence or absence of seagrass and stochastic vs. constant drivers lead to the emergence of complex behaviors in the coupled salt marsh-tidal flat system. In intertidal areas without seagrass, small tidal flats are unlikely to expand and provide enough sediment to the salt marshes to combat sea level rise. However, as the tidal flat expands, the concurrent increase in sediment supply due to wave-induced processes allows for the salt marsh to maintain pace with sea level at the expense of salt marsh extent. The presence of seagrass has two effects: (1) it decreases near bed shear stresses thus reducing the sediment flux to the salt marsh platform; (2) it reduces the wave energy acting on the salt marsh scarp, thus reducing boundary erosion. Model results indicate that the reductions in wave power and near bed shear stresses when seagrass is present provide an overall stabilizing effect on the coupled marsh-tidal flat system; but as water depth increases due to sea level rise or as external sediment supply increases, light conditions decline and the system reverts to that of a bare tidal flat.

Frontiers in Environmental Science↗

USGS2026

Neutron scattering reveals fractionation of natural gas mixtures in unconventional petroleum reservoir pores: Perspectives on energy resource recovery and storage

In unconventional petroleum reservoirs hydrocarbon fluids are hosted by both mineral and organic matter pores. These pores can have diameters that range from microns to less than a single nanometer and, for unconventional reservoirs, there is evidence that small pores ( <20 nm diameter) may constitute a large proportion of the available space. Understanding subsurface volumes and how fluids behave in them can be helpful for predicting hydrocarbon production and storage in the subsurface. One area with knowledge gaps regarding hydrocarbon behavior in small pores is the possibility for mixtures to fractionate (i.e., unmix) based on pore size or pore type. Mixture fractionation as a function of pore size could impact recovery of hydrocarbons, drive compositional shifts during production, and limit fluid storage within candidate reservoirs. To investigate natural gas fractionation in small geologic pores, we applied total neutron scattering to probe methane-ethane mixtures at reservoir pressures (up to ≈30 MPa) and temperature (60°C) within a sample from the Upper Cretaceous Niobrara Formation. Neutron scattering data reveal only minor fractionation occurs between methane and ethane in 20-nm diameter sample mesopores. Increased fractionation is observed for sample micropores, with up to 72% (±1% at 1-sigma) methane found in 2 nm diameter pores following injection of a 50%-50% methane-ethane mixture. These data provide rarely available direct experimental observations of hydrocarbon mixture behavior under nanoconfinement in a sample from an important unconventional petroleum reservoir. Our results are discussed in the context of evaluating hydrocarbon resources in unconventional reservoir meso- and micropores, reconciling observed gas composition changes during production, and more broadly, understanding subsurface pore volumes within an energy storage framework.

Fuel↗

USGS2022

Mapping actual evapotranspiration using Landsat for the conterminous United States: Google Earth Engine implementation and assessment of the SSEBop model

The estimation and mapping of actual evapotranspiration (ETa) is an active area of applied research in the fields of agriculture and water resources. Thermal remote sensing-based methods, using coarse resolution satellites, have been successful at estimating ETa over the conterminous United States (CONUS) and other regions of the world. In this study, we present CONUS-wide ETa from Landsat thermal imagery-using the Operational Simplified Surface Energy Balance (SSEBop) model in the Google Earth Engine (GEE) cloud computing platform. Over 150,000 Landsat satellite images were used to produce 10 years of annual ETa (2010–2019) at unprecedented scale. The accuracy assessment of the SSEBop results included point-based evaluation using monthly Eddy Covariance (EC) data from 25 AmeriFlux stations as well as basin-scale comparison with annual Water Balance ETa (WBET) for more than 1000 sub-basins. Evaluations using EC data showed generally mixed performance with weaker (R 2 < 0.6) correlation on sparsely vegetated surfaces such as grasslands or woody savanna and stronger correlation (R 2 > 0.7) over well-vegetated surfaces such as croplands and forests, but location-specific conditions rather than cover type were attributed to the variability in accuracy. Croplands performed best with R 2 of 0.82, root mean square error of 29 mm/month, and average bias of 12%. The WBET evaluation indicated that the SSEBop model is strong in explaining the spatial variability (up to R 2 > 0.90) of ETa across large basins, but it also identified broad hydro-climatic regions where the SSEBop ETa showed directional biases, requiring region-specific model parameter improvement and/or bias correction with an overall 7% bias nationwide. Annual ETa anomalies over the 10-year period captured widely reported drought-affected regions, for the most part, in different parts of the CONUS, indicating their potential applications for mapping regional- and field-scale drought and fire effects. Due to the coverage of the Landsat Path/Row system, the availability of cloud-free image pixels ranged from less than 12 (mountainous cloud-prone regions and U.S. Northeast) to more than 60 (U.S. Southwest) per year. However, this study reinforces a promising application of Landsat satellite data with cloud-computing for quick and efficient mapping of ETa for agricultural and water resources assessments at the field scale.

Remote Sensing of Environment↗

USGS2020

An integrated feasibility study of reservoir thermal energy storage in Portland, Oregon, USA

In regions with long cold overcast winters and sunny summers, Deep Direct-Use (DDU) can be coupled with Reservoir Thermal Energy Storage (RTES) technology to take advantage of pre-existing subsurface permeability to save summer heat for later use during cold seasons. Many aquifers worldwide are underlain by permeable regions (reservoirs) containing brackish or saline groundwater that has limited beneficial use due to poor water quality. We investigate the utility of these relatively deep, slow flowing reservoirs for RTES by conducting an integrated feasibility study in the Portland Basin, Oregon, USA, developing methods and obtaining results that can be widely applied to groundwater systems elsewhere. As a case study, we have conducted an economic and social cost-benefit analysis for the Oregon Health and Science University (OHSU), a teaching hospital that is recognized as critical infrastructure in the Portland Metropolitan Area. Our investigation covers key factors that influence feasibility including 1) the geologic framework, 2) heat and fluid flow modeling, 3) capital and maintenance costs, 4) the regulatory framework, and 5) operational risks. By pairing a model of building seasonal heat demand with an integrated model of RTES resource supply, we determine that the most important factors that influence RTES efficacy in the study area are operational schedule, well spacing, the amount of summer heat stored (in our model, a function of solar array size), and longevity of the system. Generally, heat recovery efficiency increases as the reservoir and surrounding rocks warm, making RTES more economical with time. Selecting a base-case scenario, we estimate a levelized cost of heat (LCOH) to compare with other sources of heating available to OHSU and find that it is comparable to unsubsidized solar and nuclear, but more expensive than natural gas. Additional benefits of RTES include energy resiliency in the event that conventional energy supplies are disrupted (e.g., natural disaster) and a reduction in fossil fuel consumption resulting in a smaller carbon footprint. Key risks include reservoir heterogeneity and a possible reduction in permeability through time due to scaling (mineral precipitation). Lastly, a map of thermal energy storage capacity for the Portland Basin yields a total of 87,000 GWh, suggesting tremendous potential for RTES in the Portland Metropolitan Area.

Oregon↗

USGS2015

Data regarding hydraulic fracturing distributions and treatment fluids, additives, proppants, and water volumes applied to wells drilled in the United States from 1947 through 2010

Comprehensive, published, and publicly available data regarding the extent, location, and character of hydraulic fracturing in the United States are scarce. The objective of this data series is to publish data related to hydraulic fracturing in the public domain. The spreadsheets released with this data series contain derivative datasets aggregated temporally and spatially from the commercial and proprietary IHS database of U.S. oil and gas production and well data (IHS Energy, 2011). These datasets, served in 21 spreadsheets in Microsoft Excel (.xlsx) format, outline the geographical distributions of hydraulic fracturing treatments and associated wells (including well drill-hole directions) as well as water volumes, proppants, treatment fluids, and additives used in hydraulic fracturing treatments in the United States from 1947 through 2010. This report also describes the data—extraction/aggregation processing steps, field names and descriptions, field types and sources. An associated scientific investigation report (Gallegos and Varela, 2014) provides a detailed analysis of the data presented in this data series and comparisons of the data and trends to the literature.

Data Series↗

USGS2018

Collision and displacement vulnerability to offshore wind energy infrastructure among marine birds of the Pacific Outer Continental Shelf

Marine birds are vulnerable to collision with and displacement by offshore wind energy infrastructure (OWEI). Here we present the first assessment of marine bird vulnerability to potential OWEI in the California Current System portion of the U.S. Pacific Outer Continental Shelf (POCS). Using population size, demography, life history, flight heights, and avoidance behavior for 62 seabird and 19 marine water bird species that occur in the POCS, we present and apply equations to calculate Population Vulnerability, Collision Vulnerability, and Displacement Vulnerability to OWEI for each species. Species with greatest Population vulnerability included those listed as species of concern (e.g., Least Tern [ Sternula antillarum ], Marbled Murrelet [ Brachyramphus marmoratus ], Pink-footed Shearwater [ Puffinus creatopus ]) and resident year-round species with small population sizes (e.g., Ashy Storm-Petrel [ Oceanodroma homochroa ], Brandt's Cormorant [ Phalacrocorax penicillatus ], and Brown Pelican [ Pelecanus occidentalis ]). Species groups with the greatest Collision Vulnerability included jaegers/skuas, pelicans, terns and gulls that spend significant amounts of time flying at rotor sweep zone height and don't show macro-avoidance behavior (avoidance of entire OWEI area). Species groups with the greatest Displacement Vulnerability show high macro-avoidance behavior and low habitat flexibility and included loons, grebes, sea ducks, and alcids. Using at-sea survey data from the southern POCS, we combined species-specific vulnerabilities described above with at-sea species densities to assess vulnerabilities spatially. Spatial vulnerability densities were greatest in areas with high species densities (e.g., near-shore areas) and locations where species with high vulnerability were found in abundance. Our vulnerability assessment helps understand and minimize potential impacts of OWEI infrastructure on marine birds in the POCS and could inform management decisions.

Journal of Environmental Management↗

USGS2018

Induced earthquake families reveal distinctive evolutionary patterns near disposal wells

The timing of events in seismic sequences can provide insights into the physical processes controlling fault slip. In southern Kansas, the rate of earthquakes rose rapidly starting in 2013 following expansion of energy production into the area, demanding the disposal of large volumes of wastewater into deep wells. Seismicity catalogs that are complete to low magnitudes can provide insights into the physical processes that induce seismicity near wastewater disposal. We develop a catalog of over 130,000 earthquakes recorded in southern Kansas from mid‐March 2014 through December 2017 by applying a matched filter algorithm to an original catalog of 5,831 template earthquakes. Detections have nearly identical waveforms to their associated template event and represent slip on nearly co‐located sections of a fault. We select template events with at least 100 associated detections and examine the characteristics of these prolific families of earthquakes. We find that families located close (<10 km) to areas with significant volumes of injected fluids have near‐Poissonian interevent times and the families remain active over longer durations. Families farther from high‐volume injection wells show strong clustering of interevent times and shorter sequence durations. We conclude that increasing pore fluid pressures from nearby disposal of large volumes of wastewater is the primary driver of these long duration episodes, with earthquake‐earthquake interactions driving sequences at greater distance from the wells.

Kansas↗

USGS1985

Remote sensing; a geophysical perspective

In this review of developments in the field of remote sensing from a geophysical perspective, the subject is limited to the electromagnetic spectrum from 0.4 mu m to 25 cm. Three broad energy categories are covered: solar reflected, thermal infrared, and microwave.The reflected solar region has been the most intensely studied. Photointerpretation of images from individual spectral bands or from color composites remains the most widely used method of analysis. New instrumentation and digital processing, based on analysis of laboratory and field spectra, provide significant advances that are beginning to be applied to resource exploration. Color compositing techniques have been effectively used to detect the characteristic spectral reflectance features of iron oxides and hydroxyl-bearing materials in satellite multispectral data for mapping areas of hydrothermal alteration. Airborne spectrometers can now detect individual spectral features of many minerals which are diagnostic of different stages of hydrothermal alteration. Evolution was from discrimination, based on empirical experience, to mineralogic identification and leading to quantification. Current developments also indicate new, promising extensions to vegetated terrains.Advances in thermal infrared studies are due to development of thermal models that permit mapping of physical property variations and to detection of spectral differences that provide important compositional information. Analysis techniques are still in their infancy, and thermal satellite data remain appropriate only for regional investigations.Microwave data have been acquired mainly with radar systems, which can provide very high resolution from space, but use of textural and slope information has had limited application. Long-wavelength radiation has been shown to penetrate dry materials, and this may be applicable in extremely arid regions.

Geophysics↗

USGS2014

Geochemistry of groundwater in the Beaver and Camas Creek drainage basins, eastern Idaho

The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, is studying the fate and transport of waste solutes in the eastern Snake River Plain (ESRP) aquifer at the Idaho National Laboratory (INL) in eastern Idaho. This effort requires an understanding of the natural and anthropogenic geochemistry of groundwater at the INL and of the important physical and chemical processes controlling the geochemistry. In this study, the USGS applied geochemical modeling to investigate the geochemistry of groundwater in the Beaver and Camas Creek drainage basins, which provide groundwater recharge to the ESRP aquifer underlying the northeastern part of the INL. Data used in this study include petrology and mineralogy from 2 sediment and 3 rock samples, and water-quality analyses from 4 surface-water and 18 groundwater samples. The mineralogy of the sediment and rock samples was analyzed with X-ray diffraction, and the mineralogy and petrology of the rock samples were examined in thin sections. The water samples were analyzed for field parameters, major ions, silica, nutrients, dissolved organic carbon, trace elements, tritium, and the stable isotope ratios of hydrogen, oxygen, carbon, sulfur, and nitrogen. Groundwater geochemistry was influenced by reactions with rocks of the geologic terranes—carbonate rocks, rhyolite, basalt, evaporite deposits, and sediment comprised of all of these rocks. Agricultural practices near and south of Dubois and application of road anti-icing liquids on U.S. Interstate Highway 15 were likely sources of nitrate, chloride, calcium, and magnesium to groundwater. Groundwater geochemistry was successfully modeled in the alluvial aquifer in Camas Meadows and the ESRP fractured basalt aquifer using the geochemical modeling code PHREEQC. The primary geochemical processes appear to be precipitation or dissolution of calcite and dissolution of silicate minerals. Dissolution of evaporite minerals, associated with Pleistocene Lake Terreton, is an important contributor of solutes in the Mud Lake-Dubois area. Oxidation-reduction reactions are important influences on the chemistry of groundwater at Camas Meadows and the Camas National Wildlife Refuge. In addition, mixing of different groundwaters or surface water with groundwater appears to be an important physical process influencing groundwater geochemistry in much of the study area, and evaporation may be an important physical process influencing the groundwater geochemistry of the Camas National Wildlife Refuge. The mass-balance modeling results from this study provide an explanation of the natural geochemistry of groundwater in the ESRP aquifer northeast of the INL, and thus provide a starting point for evaluating the natural and anthropogenic geochemistry of groundwater at the INL.

Idaho↗

USGS2019

One hundred pressing questions on the future of global fish migration science, conservation, and policy

Migration is a widespread but highly diverse component of many animal life histories. Fish migrate throughout the world's oceans, within lakes and rivers, and between the two realms, transporting matter, energy, and other species (e.g., microbes) across boundaries. Migration is therefore a process responsible for myriad ecosystem services. Many human populations depend on the presence of predictable migrations of fish for their subsistence and livelihoods. Although much research has focused on fish migration, many questions remain in our rapidly changing world. We assembled a diverse team of fundamental and applied scientists who study fish migrations in marine and freshwater environments to identify pressing unanswered questions. Our exercise revealed questions within themes related to understanding the migrating individual's internal state, navigational mechanisms, locomotor capabilities, external drivers of migration, the threats confronting migratory fish including climate change, and the role of migration. In addition, we identified key requirements for aquatic animal management, restoration, policy, and governance. Lessons revealed included the difficulties in generalizing among species and populations, and in understanding the levels of connectivity facilitated by migrating fishes. We conclude by identifying priority research needed for assuring a sustainable future for migratory fishes.

Frontiers in Ecology and Evolution↗

USGS1988

Assessment of the role of bottomland hardwoods in sediment and erosion control

Drainage and clearing of bottomland hardwoods have long been recognized by the U.S. Environmental Protection Agency (EPA) and the U.S. Fish and Wildlife Service (Service) as important impacts of Federal water projects in the lower Mississippi River Valley. More recently, the water quality impacts of such projects (e.g., increases in sediments, nutrients, and pesticides) have also become of concern. In 1984, in an effort to better define problems concerning wetland losses and water degradation, EPA initiated a cooperative project with the Western Energy and Land Use Team (now the National Ecology Research Center) of the Service. Three phases of the project were identified: 1. To collect existing literature and data; 2. To select, develop, and test the utility of methods to quantify the relationships between land use, cover types, soils, hydrology, and water quality (as represented by sediment); and 3. To apply selected methodologies to several sites within the Yazoo Basin of Mississippi to determine the, potential effectiveness of various management alternatives to reduce sediment yield, increase sediment deposition, and improve water quality. Methods development focused on linking a simulation of water and sediment movement to a computerized geographic information system. We had several objectives for the resulting model. We desired that it should: 1. Estimate the importance of bottomland and hardwoods as a cover type that performs the functions of erosion and sediment control, 2. Simulate effects of proportions of ' various cover types and their specific spatial configurations, 3. Be applicable to moderately large spatial areas with minimal site-specific calibration, 4. Simulate spatial patterns of sediment loss-gain over time, and 5. Represent both sediment detachment and transport. While it was recognized that impacts and management alternatives could be sorted roughly into landscape measures and channel measures, the decision was made to focus study efforts mainly on landscape measures. Landscape measures include altered drainage and flooding patterns, altered cover types (e.g., conversion of bottomland hardwoods to agricultural crops, reforestation of cropland to bottomland hardwoods, and creation of riparian buffer strips), altered cropping and tillage patterns, altered routing of water, and creation of buffer strips along wetlands and channel margins. Channel measures include vegetative bank stabilization, grade control structures, and regulation of channel water volume and velocity. During the first year of the study, EPA decided not to fund the third phase of the project. This required considerable rescoping of the project with the result that application of the sediment mobilization, routing, and deposition models to various management alternatives and portions of the Yazoo Basin was somewhat restricted. We believe, however, that this report will provide a good understanding of the various modes of sediment mobilization, transport, and deposition within the Yazoo Basin, as well as of the role of bottomland hardwoods. The model developed in this study could be applied to a variety of management or mitigation alternatives prior to implementation to determine their relative effectiveness. Policy, political, and socio-economic consequences of any proposed management/mitigation practice, however, must ultimately be taken into consideration by those charged with management of water resources within the Yazoo Basin before any practice is implemented. This study makes no effort to judge the feasibility of management alternatives in this regard.

Report↗

USGS2004

The global short-period wavefield modelled with a Monte Carlo seismic phonon method

At high frequencies (∼1 Hz), much of the seismic energy arriving at teleseismic distances is not found in the main phases (e.g. P , PP , S , etc.) but is contained in the extended coda that follows these arrivals. This coda results from scattering off small-scale velocity and density perturbations within the crust and mantle and contains valuable information regarding the depth dependence and strength of this heterogeneity as well as the relative importance of intrinsic versus scattering attenuation. Most analyses of seismic coda to date have concentrated on S -wave coda generated from lithospheric scattering for events recorded at local and regional distances. Here, we examine the globally averaged vertical-component, 1-Hz wavefield (>10° range) for earthquakes recorded in the IRIS FARM archive from 1990 to 1999. We apply an envelope-function stacking technique to image the average time–distance behavior of the wavefield for both shallow (≤50 km) and deep (≥500 km) earthquakes. Unlike regional records, our images are dominated by P and P coda owing to the large effect of attenuation on PP and S at high frequencies. Modelling our results is complicated by the need to include a variety of ray paths, the likely contributions of multiple scattering and the possible importance of P -to- S and S -to- P scattering. We adopt a stochastic, particle-based approach in which millions of seismic phonons are randomly sprayed from the source and tracked through the Earth. Each phonon represents an energy packet that travels along the appropriate ray path until it is affected by a discontinuity or a scatterer. Discontinuities are modelled by treating the energy normalized reflection and transmission coefficients as probabilities. Scattering probabilities and scattering angles are computed in a similar fashion, assuming random velocity and density perturbations characterized by an exponential autocorrelation function. Intrinsic attenuation is included by reducing the energy contained in each particle as an appropriate function of traveltime. We find that most scattering occurs in the lithosphere and upper mantle, as previous results have indicated, but that some lower-mantle scattering is likely also required. A model with 3 to 4 per cent rms velocity heterogeneity at 4-km scale length in the upper mantle and 0.5 per cent rms velocity heterogeneity at 8-km scale length in the lower mantle (with intrinsic attenuation of Q α = 450 above 200 km depth and Q α = 2500 below 200 km) provides a reasonable fit to both the shallow- and deep-earthquake observations, although many trade-offs exist between the scale length, depth extent and strength of the heterogeneity.

Geophysical Journal International↗

USGS2004

SutraGUI, a graphical-user interface for SUTRA, a model for ground-water flow with solute or energy transport

This report describes SutraGUI, a flexible graphical user-interface (GUI) that supports two-dimensional (2D) and three-dimensional (3D) simulation with the U.S. Geological Survey (USGS) SUTRA ground-water-flow and transport model (Voss and Provost, 2002). SutraGUI allows the user to create SUTRA ground-water models graphically. SutraGUI provides all of the graphical functionality required for setting up and running SUTRA simulations that range from basic to sophisticated, but it is also possible for advanced users to apply programmable features within Argus ONE to meet the unique demands of particular ground-water modeling projects. SutraGUI is a public-domain computer program designed to run with the proprietary Argus ONE? package, which provides 2D Geographic Information System (GIS) and meshing support. For 3D simulation, GIS and meshing support is provided by programming contained within SutraGUI. When preparing a 3D SUTRA model, the model and all of its features are viewed within Argus 1 in 2D projection. For 2D models, SutraGUI is only slightly changed in functionality from the previous 2D-only version (Voss and others, 1997) and it provides visualization of simulation results. In 3D, only model preparation is supported by SutraGUI, and 3D simulation results may be viewed in SutraPlot (Souza, 1999) or Model Viewer (Hsieh and Winston, 2002). A comprehensive online Help system is included in SutraGUI. For 3D SUTRA models, the 3D model domain is conceptualized as bounded on the top and bottom by 2D surfaces. The 3D domain may also contain internal surfaces extending across the model that divide the domain into tabular units, which can represent hydrogeologic strata or other features intended by the user. These surfaces can be non-planar and non-horizontal. The 3D mesh is defined by one or more 2D meshes at different elevations that coincide with these surfaces. If the nodes in the 3D mesh are vertically aligned, only a single 2D mesh is needed. For nonaligned meshes, two or more 2D meshes of similar connectivity are used. Between each set of 2D meshes (and model surfaces), the vertical space in the 3D mesh is evenly divided into a user-specified number of layers of finite elements. Boundary conditions may be specified for 3D models in SutraGUI using a variety of geometric shapes that may be located freely within the 3D model domain. These shapes include points, lines, sheets, and solids. These are represented by 2D contours (within the vertically-projected Argus ONE view) with user-defined elevations. In addition, boundary conditions may be specified for 3D models as points, lines, and areas that are located exactly within the surfaces that define the model top and the bottoms of the tabular units. Aquifer properties may be specified separately for each tabular unit. If the aquifer properties vary vertically within a unit, SutraGUI provides the Sutra_Z function that can be used to specify such variation.

Open-File Report↗

USGS2011

Evaluating the potential for remote bathymetric mapping of a turbid, sand-bed river: 1. Field spectroscopy and radiative transfer modeling

Remote sensing offers an efficient means of mapping bathymetry in river systems, but this approach has been applied primarily to clear-flowing, gravel bed streams. This study used field spectroscopy and radiative transfer modeling to assess the feasibility of spectrally based depth retrieval in a sand-bed river with a higher suspended sediment concentration (SSC) and greater water turbidity. Attenuation of light within the water column was characterized by measuring the amount of downwelling radiant energy at different depths and calculating a diffuse attenuation coefficient, K d . Attenuation was strongest in blue and near-infrared bands due to scattering by suspended sediment and absorption by water, respectively. Even for red wavelengths with the lowest values of K d , only a small fraction of the incident light propagated to the bed, restricting the range of depths amenable to remote sensing. Spectra recorded above the water surface were used to establish a strong, linear relationship ( R 2 = 0.949) between flow depth and a simple band ratio; even under moderately turbid conditions, depth remained the primary control on reflectance. Constraints on depth retrieval were examined via numerical modeling of radiative transfer within the atmosphere and water column. SSC and sensor radiometric resolution limited both the maximum detectable depth and the precision of image-derived depth estimates. Thus, although field spectra indicated that the bathymetry of turbid channels could be remotely mapped, model results implied that depth retrieval in sediment-laden rivers would be limited to shallow depths (on the order of 0.5 m) and subject to a significant degree of uncertainty.

Water Resources Research↗

USGS2003

Petroleum system and production characteristics of the Muddy (J) Sandstone (Lower Cretaceous) Wattenberg continuous gas field, Denver basin, Colorado

Wattenberg field is a continuous-type gas accumulation. Estimated ultimate recovery from current wells is 1.27 tcf of gas from the Lower Cretaceous Muddy (J) Sandstone. Mean gas resources that have the potential to be added to these reserves in the next 30 yr are 1.09 tcf; this will be primarily through infill drilling to recover a greater percentage of gas in place and to drain areas that are isolated because of geologic compartmentalization. Greatest gas production from the Muddy (J) Sandstone in Wattenberg field occurs (1) from within the most permeable and thickest intervals of Fort Collins Member delta-front and nearshore-marine sandstones, (2) to a lesser extent from the Horsetooth Member valley-fill channel sandstones, (3) in association with a large thermal anomaly that is delineated by measured temperatures in wells and by vitrinite reflectance contours of 0.9% and greater, (4) in proximity to the bounding Mowry, Graneros, and Skull Creek shales that are the hydrocarbon source rocks and reservoir seals, and (5) between the Lafayette and Longmont right-lateral wrench fault zones (WFZs) with secondary faults that act as conduits in areas of the field. The axis of greatest gas production is north 25 to 35 degrees northeast, which parallels the basin axis. Recurrent movement along five right-lateral WFZs that crosscut Wattenberg field shifted the Denver basin axis to the northeast and influenced depositional and erosional patterns of the reservoir and seal intervals. Levels of thermal maturity within the Wattenberg field are anomalously high compared to other areas of the Denver basin. The Wattenberg field thermal anomaly may be due to upward movement of fluids along faults associated with probable igneous intrusions. Areas of anomalous high heat flow within the field correlate with an increased and variable gas-oil ratio. Debra Higley has 5 years experience in uranium exploration and 20 years as a petroleum geologist with the U.S. Geological Survey. Her research interests include and integrate reservoir characterization, thermal maturation studies, and petroleum resource assessment in basins in North and South America. She received a B.S. degree in geology from Mesa State College (Colorado) and an M.S. degree in geochemistry and Ph.D. in geology from the Colorado School of Mines.Dave Cox is vice president of Reservoir Engineering for Questa Engineering in Golden, Colorado. He has 25 years experience in the oil and gas industry, primarily in reservoir engineering and property evaluations, and has analyzed reservoirs in 31 states of the United States and 19 other countries. He is an expert in coalbed methane, tight gas reservoirs, and enhanced oil recovery. He has B.S. and M.S. degrees in petroleum engineering from the Colorado School of Mines. Robert Weimer has taught courses in stratigraphy, regional and field geology, and energy resource exploration and development for 43 years. He earned B.A. and M.A. degrees from the University of Wyoming and his Ph.D. from Stanford University. He has been a visiting professor at universities in Calgary, Canada; Adelaide, Australia; and Bandung, Indonesia. He is currently professor emeritus, Colorado School of Mines. Weimer has been honored for teaching excellence, blending basic and applied research, national and international continuing education, and service to scientific societies and to state and national boards.

Colorado↗

USGS1980

Need for new sensors to map lithologic units

One of the most important contributions that remote sensing can make to mineral energy explorations to provide data from satellites to augment regional geological mapping. Geologic maps, which show information on the subsurface, are the main basis for formulating models of resource genesis that guide exploration. However, conventional compilation procedures are time-consuming and therefore often slow the pace of exploration, especially in large, inaccessible areas. Landsat Multispectral Scanner (MSS) images have been applied to a wide variety of specific geological problems, including discrimination of lithologic and delineation of previously unrecognized tectonic features. However, these lithologic distinctions are based on brightness, spectral reflectance, and, less commonly, the morphology of the unit, which in the wavelength region of MSS images are only rarely diagnostic of specific mineralogical content. Limonite is the only lithological material that can be identified be analyzing MSS spectral radiance.

Sixth Annual Pecora Symposium and Exposition↗