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At least 613 records · Page 34Linked to original sources
USGS1975

Experimental abrasion of detrital gold

The physical breakdown and abrasion rates of gold were studied using a tumbler to simulate natural high-energy environments. The gold fragments were tumbled for periods ranging from 30 to 240 h with different combinations of sand, cobbles, and water at velocities of 0.5 and 2.0 mi/h (0.85 and 3.22 km/h). With sand and gravel, the common bedload of the rivers that deposited the gold-bearing Tertiary sedimentary rocks of the Sierra Nevada, gold is abraded at rates of 0.015 to 0.007 percent (by weight) per hour of travel (at 0.5 mi/h or 0.845 km/h). Cobbles, rather than sand, are responsible for most of the physical changes and abrasion of the gold. Ten gold fragments tumbled for 120 h with cobbles and water (no sand) were broken down to 68 recoverable fragments and lost about 25 percent of their weight to particles smaller than could be recovered using conventional panning techniques. Gold tumbled for 120 h with sand and water lost less than 1 percent of its weight. Gold was abraded faster by wet sand than by dry sand. Velocity appears to be more important as a factor in abrasion of gold than travel distance a fourfold increase in velocity produced a tenfold increase in hourly abrasion rates of gold. Scanning electron microscope examination of the gold fragments after the tumbling experiments revealed differences in surface texture between fragments tumbled with (1) sand, (2) sand and cobbles, and (3) cobbles only.

Journal of Research of the U.S. Geological Survey↗
USGS2010

The aquatic turtle assemblage inhabiting a highly altered landscape in southeast Missouri

Turtles are linked to energetic food webs as both consumers of plants and animals and prey for many species. Turtle biomass in freshwater systems can be an order of magnitude greater than that of endotherms. Therefore, declines in freshwater turtle populations can change energy transfer in freshwater systems. Here we report on a mark–recapture study at a lake and adjacent borrow pit in a relict tract of bottomland hardwood forest in the Mississippi River floodplain in southeast Missouri, which was designed to gather baseline data, including sex ratio, size structure, and population size, density, and biomass, for the freshwater turtle population. Using a variety of capture methods, we captured seven species of freshwater turtles (snapping turtle Chelydra serpentina ; red-eared slider Trachemys scripta ; southern painted turtle Chrysemys dorsalis ; river cooter Pseudemys concinna ; false map turtle Graptemys pseudogeographica ; eastern musk turtle Sternotherus odoratus ; spiny softshell Apalone spinifera ) comprising four families (Chelydridae, Emydidae, Kinosternidae, Trinoychidae). With the exception of red-eared sliders, nearly all individuals captured were adults. Most turtles were captured by baited hoop-nets, and this was the only capture method that caught all seven species. The unbaited fyke net was very successful in the borrow pit, but only captured four of the seven species. Basking traps and deep-water crawfish nets had minimal success. Red-eared sliders had the greatest population estimate (2,675), density (205/ha), and biomass (178 kg/ha). Two species exhibited a sex-ratio bias: snapping turtles C. serpentina in favor of males, and spiny softshells A. spinifera in favor of females.

Missouri↗
USGS2016

Habitat selection by juvenile Mojave Desert tortoises

Growing pressure to develop public lands for renewable energy production places several protected species at increased risk of habitat loss. One example is the Mojave desert tortoise ( Gopherus agassizii ), a species often at the center of conflicts over public land development. For this species and others on public lands, a better understanding of their habitat needs can help minimize negative impacts and facilitate protection or restoration of habitat. We used radio-telemetry to track 46 neonate and juvenile tortoises in the Eastern Mojave Desert, California, USA, to quantify habitat at tortoise locations and paired random points to assess habitat selection. Tortoise locations near burrows were more likely to be under canopy cover and had greater coverage of perennial plants (especially creosote [ Larrea tridentata ]), more coverage by washes, a greater number of small-mammal burrows, and fewer white bursage ( Ambrosia dumosa ) than random points. Active tortoise locations away from burrows were closer to washes and perennial plants than were random points. Our results can help planners locate juvenile tortoises and avoid impacts to habitat critical for this life stage. Additionally, our results provide targets for habitat protection and restoration and suggest that diverse and abundant small-mammal populations and the availability of creosote bush are vital for juvenile desert tortoises in the Eastern Mojave Desert.

California↗
USGS2021

Remote sensing-based actual evapotranspiration assessment in a data-scarce area of Brazil: A case study of the Urucuia Aquifer System

The large groundwater reserves of the Urucuia Aquifer System (UAS) enabled agricultural development and economic growth in the western Bahia State, in northeastern Brazil. Over the last several years, concern has grown around the aquifer’s diminishing water levels, and water balance (WB) studies are in demand. Considering the lack of measured actual evapotranspiration (ET a ), a major component of the water cycle, this work uses the Operational Simplified Surface Energy Balance (SSEBop) model to estimate ET a , and compares it to basin-scale estimates from the Soil Moisture Accounting Procedure (SMAP) monthly model and from an annual WB closure method, based on gridded meteorological data and the Gravity Recovery and Climate Experiment (GRACE) product. Additionally, a comparative assessment of different versions of the SSEBop parameterization was performed. Moderate Resolution Imaging Spectroradiometer (MODIS) imagery was used to implement eight different versions of the SSEBop algorithm over the UAS between 2000 and 2013. SSEBop and SMAP ET a yielded similar seasonal patterns, with correlation coefficient (r) up to 0.65, mean difference (MD) of 0.8 mm/month and mean absolute difference (MAD) of 18.5 mm/month. Comparison of SSEBop annual ET a estimates to annual SMAP and WB closure estimates yielded low MD (12.1 and −7.3 mm/year, respectively) and MAD (82.5 and 82.8 mm/year, respectively), but also low r values (0.00 and 0.37, respectively). The comparison of the different SSEBop versions indicated the need to incorporate a calibration step of the aerodynamic heat resistance (r ah ) parameter. SSEBop results were also used for land cover and drought monitoring. Analysis indicates that agriculture, associated with an increasing trend of atmospheric evaporative demand, is responsible for the decrease in groundwater levels and streamflow in the studied time period.

Urucuia Aquifer System↗
USGS2002

Global modeling of land water and energy balances. Part III: Interannual variability

The Land Dynamics (LaD) model is tested by comparison with observations of interannual variations in discharge from 44 large river basins for which relatively accurate time series of monthly precipitation (a primary model input) have recently been computed. When results are pooled across all basins, the model explains 67% of the interannual variance of annual runoff ratio anomalies (i.e., anomalies of annual discharge volume, normalized by long-term mean precipitation volume). The new estimates of basin precipitation appear to offer an improvement over those from a state-of-the-art analysis of global precipitation (the Climate Prediction Center Merged Analysis of Precipitation, CMAP), judging from comparisons of parallel model runs and of analyses of precipitation-discharge correlations. When the new precipitation estimates are used, the performance of the LaD model is comparable to, but not significantly better than, that of a simple, semiempirical water-balance relation that uses only annual totals of surface net radiation and precipitation. This implies that the LaD simulations of interannual runoff variability do not benefit substantially from information on geographical variability of land parameters or seasonal structure of interannual variability of precipitation. The aforementioned analyses necessitated the development of a method for downscaling of long-term monthly precipitation data to the relatively short timescales necessary for running the model. The method merges the long-term data with a reference dataset of 1-yr duration, having high temporal resolution. The success of the method, for the model and data considered here, was demonstrated in a series of model-model comparisons and in the comparisons of modeled and observed interannual variations of basin discharge.

Journal of Hydrometeorology↗
USGS2015

Monitoring and modeling wetland chloride concentrations in relationship to oil and gas development

Extraction of oil and gas via unconventional methods is becoming an important aspect of energy production worldwide. Studying the effects of this development in countries where these technologies are being widely used may provide other countries, where development may be proposed, with some insight in terms of concerns associated with development. A fairly recent expansion of unconventional oil and gas development in North America provides such an opportunity. Rapid increases in energy development in North America have caught the attention of managers and scientists as a potential stressor for wildlife and their habitats. Of particular concern in the Northern Great Plains of the U.S. is the potential for chloride-rich produced water associated with unconventional oil and gas development to alter the water chemistry of wetlands. We describe a landscape scale modeling approach designed to examine the relationship between potential chloride contamination in wetlands and patterns of oil and gas development. We used a spatial Bayesian hierarchical modeling approach to assess multiple models explaining chloride concentrations in wetlands. These models included effects related to oil and gas wells (e.g. age of wells, number of wells) and surficial geology (e.g. glacial till, outwash). We found that the model containing the number of wells and the surficial geology surrounding a wetland best explained variation in chloride concentrations. Our spatial predictions showed regions of localized high chloride concentrations. Given the spatiotemporal variability of regional wetland water chemistry, we do not regard our results as predictions of contamination, but rather as a way to identify locations that may require more intensive sampling or further investigation. We suggest that an approach like the one outlined here could easily be extended to more of an adaptive monitoring approach to answer questions about chloride contamination risk that are of interest to managers.

Montana, North Dakota↗
USGS2012

Synthesis study of an erosion hot spot, Ocean Beach, California

A synthesis of multiple coastal morphodynamic research efforts is presented to identify the processes responsible for persistent erosion along a 1-km segment of 7-km-long Ocean Beach in San Francisco, California. The beach is situated adjacent to a major tidal inlet and in the shadow of the ebb-tidal delta at the mouth of San Francisco Bay. Ocean Beach is exposed to a high-energy wave climate and significant alongshore variability in forcing introduced by varying nearshore bathymetry, tidal forcing, and beach morphology ( e.g. , beach variably backed by seawall, dunes, and bluffs). In addition, significant regional anthropogenic factors have influenced sediment supply and tidal current strength. A variety of techniques were employed to investigate the erosion at Ocean Beach, including historical shoreline and bathymetric analysis, monthly beach topographic surveys, nearshore and regional bathymetric surveys, beach and nearshore grain size analysis, two surf-zone hydrodynamic experiments, four sets of nearshore wave and current experiments, and several numerical modeling approaches. Here, we synthesize the results of 7 years of data collection to lay out the causes of persistent erosion, demonstrating the effectiveness of integrating an array of data sets covering a huge range of spatial scales. The key findings are as follows: anthropogenic influences have reduced sediment supply from San Francisco Bay, leading to pervasive contraction ( i.e. , both volume and area loss) of the ebb-tidal delta, which in turn reduced the regional grain size and modified wave focusing patterns along Ocean Beach, altering nearshore circulation and sediment transport patterns. In addition, scour associated with an exposed sewage outfall pipe causes a local depression in wave heights, significantly modifying nearshore circulation patterns that have been shown through modeling to be key drivers of persistent erosion in that area.

California↗
USGS1999

Formation of natural gas hydrates in marine sediments 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

The stability of submarine gas hydrates is largely dictated by pressure and temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of deep marine sediments may also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our conceptual model presumes that gas hydrate behaves in a way analogous to ice in a freezing soil. Hydrate growth is inhibited within fine-grained sediments by a combination of reduced pore water activity in the vicinity of hydrophilic mineral surfaces, and the excess internal energy of small crystals confined in pores. The excess energy can be thought of as a "capillary pressure" in the hydrate crystal, related to the pore size distribution and the state of stress in the sediment framework. The base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature (nearer to the seabed) than would be calculated from bulk thermodynamic equilibrium. Capillary effects or a build up of salt in the system can expand the phase boundary between hydrate and free gas into a divariant field extending over a finite depth range dictated by total methane content and pore-size distribution. Hysteresis between the temperatures of crystallization and dissociation of the clathrate is also predicted. Growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, and lenses in muds; cements in sands) can largely be explained by capillary effects, but kinetics of nucleation and growth are also important. The formation of concentrated gas hydrates in a partially closed system with respect to material transport, or where gas can flush through the system, may lead to water depletion in the host sediment. This "freeze-drying" may be detectable through physical changes to the sediment (low water content and overconsolidation) and/or chemical anomalies in the pore waters and metastable presence of free gas within the normal zone of hydrate stability.

Journal of Geophysical Research B: Solid Earth↗
USGS2010

Inelastic off-fault response and three-dimensional dynamics of earthquake rupture on a strike-slip fault

Large dynamic stress off the fault incurs an inelastic response and energy loss, which contributes to the fracture energy, limiting the rupture and slip velocity. Using an explicit finite element method, we model three-dimensional dynamic ruptures on a vertical strike-slip fault in a homogeneous half-space. The material is subjected to a pressure-dependent Drucker-Prager yield criterion. Initial stresses in the medium increase linearly with depth. Our simulations show that the inelastic response is confined narrowly to the fault at depth. There the inelastic strain is induced by large dynamic stresses associated with the rupture front that overcome the effect of the high confining pressure. The inelastic zone increases in size as it nears the surface. For material with low cohesion (~5 MPa) the inelastic zone broadens dramatically near the surface, forming a "flowerlike" structure. The near-surface inelastic strain occurs in both the extensional and the compressional regimes of the fault, induced by seismic waves ahead of the rupture front under a low confining pressure. When cohesion is large (~10 MPa), the inelastic strain is significantly reduced near the surface and confined mostly to depth. Cohesion, however, affects the inelastic zone at depth less significantly. The induced shear microcracks show diverse orientations near the surface, owing to the low confining pressure, but exhibit mostly horizontal slip at depth. The inferred rupture-induced anisotropy at depth has the fast wave direction along the direction of the maximum compressive stress.

Journal of Geophysical Research B: Solid Earth↗
USGS2025

Review: The hydrogeology of critical mineral resources relevant to the energy transition

Attaining the goals of the international treaty on climate change (the Paris Agreement) will greatly increase the demand for the critical minerals required to implement clean-energy technologies. This poses both challenges and opportunities to the hydrogeologic community from several perspectives. Here, important insights that the hydrogeological sciences have to offer for mineral exploration, mineral production, and addressing environmental issues related to mining and mine decommissioning are summarized. This study focuses on copper, cobalt, lithium, and rare earths to represent the broad spectrum of critical minerals and illustrate their relevance by referring to projected demands and production rates. The current understanding of the hydrogeologic processes that form major deposits of these minerals are then summarized. Ore is defined as the naturally occurring material from which minerals of economic value can be extracted, where most ore deposits are the products of complex hydrogeologic couplings between fluid flow, heat transport, solute transport, chemical reactions, and mechanical deformation. Exploration models for the discovery of deeper, hidden deposits are potentially informed by hydrogeologic theory and hydrogeochemical processes. Hydrogeologic understanding and methods are also essential to production and recovery. Longstanding challenges are mine dewatering and (conversely) mine water supply, as well as mineral-extraction practices such as spoil heap leaching and in situ mining. New challenges arise from element extraction from subsurface brines. Finally, the quantity of water use and potential environmental impacts of mining on water quality are at the core of ‘social license’: the approval and acceptance of society to mining activities.

Hydrogeology Journal↗
USGS2021

Effect of an algal amendment on the microbial conversion of coal to methane at different sulfate concentrations from the Powder River Basin, USA

Biogenic methane is estimated to account for one-fifth of the natural gas worldwide and there is great interest in controlling methane from different sources. Biogenic coalbed methane (CBM) production relies on syntrophic associations between fermentative bacteria and methanogenic archaea to anaerobically degrade recalcitrant coal and produce methanogenic substrates. However, very little is known about how differences in geochemistry, hydrology, and microbial community composition influence subsurface carbon utilization and CBM production. The addition of an amendment consisting of microalgal biomass has previously been shown to increase CBM production while providing the possibility of a closed-loop fossil system where waste (production water) is used to grow algae to ultimately produce energy (methane). However, the efficiency of enhancing CBM production under different redox conditions remains unresolved. In this study, we focused on the U.S. Geological Survey's Birney test site (Montana, USA) that has nine wells vertically accessing four coal seams with varying geochemistry (low and high sulfate (SO 4 2− )) and methane production rates. We used organic matter (OM) in the form of algal biomass to discern the effect of this amendment on OM degradation and microbially enhanced CBM production potential under different geochemical constraints. We tracked changes in community composition, OM composition, organic carbon (OC) concentration, methane production, and nutrients in batch systems over six months. Methane production was detected only in microcosms from low SO 4 2− wells (168 to 800 μg methane per gram of coal). The OC consumption varied across time for all wells and the variation was greatest for the low SO 4 2− wells. Different groups of syntrophic bacteria were associated with net‑carbon consuming microcosms, and specifically Syntrophorhabdus was identified with several different statistical methods as a potentially important coal degrader. Results from this study provide insight into potential coal-degraders, the compositional changes in some of the different OM fractions, and trends in carbon consumption related to methane production across coal seams along the vertical SO 4 2− gradient.

Montana, Wyoming↗
USGS1999

Climatic impact of glacial cycle polar motion: Coupled oscillations of ice sheet mass and rotation pole position

Precessional motion of Earth's rotation axis relative to its orbit is a well-known source of long-period climatic variation. It is less well appreciated that growth and decay of polar ice sheets perturb the symmetry of the global mass distribution enough that the geographic location of the rotation axis will change by at least 15 km and possibly as much as 100 km during a single glacial cycle. This motion of the pole will change the seasonal and latitudinal pattern of temperatures. We present calculations, based on a diurnal average energy balance, which compare the summer and winter temperature anomalies due to a 1° decrease in obliquity with those due to a 1° motion of the rotation pole toward Hudson Bay. Both effects result in peak temperature perturbations of about 1° Celsius. The obliquity change primarily influences the amplitude of the seasonal cycle, while the polar motion primarily changes the annual mean temperatures. The polar motion induced temperature anomaly is such that it will act as a powerful negative feedback on ice sheet growth. We also explore the evolution of the coupled system composed of ice sheet mass and pole position. Oscillatory solutions result from the conflicting constraints of rotational and thermal stability. A positive mass anomaly on an otherwise featureless Earth is in rotational equilibrium only at the poles or the equator. The two polar equilibria are rotationally unstable, and the equatorial equilibrium, though rotationally stable, is thermally unstable. We find that with a plausible choice for the strength of coupling between the thermal and rotational systems, relatively modest external forcing can produce significant response at periods of 10 4 –10 6 years, but it strongly attenuates polar motion at longer periods. We suggest that these coupled oscillations may contribute to the observed dominance of 100 kyr glacial cycles since the mid-Pleistocene and will tend to stabilize geographic patterns that are suitable to glaciations.

Journal of Geophysical Research B: Solid Earth↗
USGS1987

Hydraulics and basin morphometry of the largest flash floods in the conterminous United States

The maximum rainfall-runoff floods measured by indirect methods in small basins (0.39-370 km 2 ) in the conterminous United States are examined. This analysis identified twelve floods that were the largest ever measured. These floods all occurred in semiarid to arid areas. For eleven of the twelve largest rainfall-runoff floods measured in small basins by the slope-area method, values of hydraulic depth; hydraulic radius; width-depth ratio; n value; mean velocity; velocity-head coefficient; Froude number; water-surface, energy, and channel slopes; shear stress; and unit stream power are tabulated. Estimated composite n values weighted by subsection conveyance range from 0.028 to 0.048 with a mean of 0.038. Mean velocities ranged from 3.47 to 9.97 m s −1 . Froude numbers ranged from 0.81 to 2.49, with 9 of 12 floods having values greater than 1.00. Water-surface, energy, and channel slopes vary considerably for each flood. Energy slope always was less than water-surface slope by values of 1–104%. Channel slope was greater than energy slope in eight floods. Shear stresses ranged between 61 and 855 N m −2 , and unit stream power from 212 to 8131 w m −1 . Floods in these small basins produced shear stresses and unit stream powers several hundred times greater than floods in large rivers. Floods on other small streams, with smaller unit discharges, produced greater shear stresses and stream powers. This indicates that the force of a flood is controlled by the depth-slope product, not absolute discharge. In the twelve watersheds studied, basin relief ranged from 165 to 1280 m, elongation ratios ranged from 0.55 to 0.80, the number of first-order streams (basin magnitude) ranged from 10 to 4297, drainage density ranged from 4.1 to 10.9 km km −2 , basin slope ranged from 0.0043 to 0.2486, relief ratio ranged from 0.0097 to 0.34, ruggedness number ranged from 0.69 to 7.17, and first-order channel frequency ranged from 5.1 to 38.6 km −2 . Elongation ratios were larger, and drainage density and first-order channel frequency lower, than other small flash-flood prone basins in the United States. These twelve basins have neither the most favorable morphometric characteristics which contribute to flash-flood peaks, nor did the storms causing these flash floods have the greatest short-duration intensities. Maximum flood peaks originate from an optimal combination of basin morphology and physiography, and storm intensity.

conterminous United States↗
USGS2019

Estimating the pressure-limited dynamic capacity and costs of basin-scale CO2 storage in a Saline Formation

Deployment of carbon capture and storage (CCS) could be necessary to be able to satisfy baseload electricity demand, maintain diversity in the energy mix, and achieve mitigation of carbon dioxide (CO 2 ) emissions at lowest cost ( IPCC, 2015 ; U.S. DOE, 2016 ). If basin-, regional- or national-scale deployment of CCS is needed, it may be possible to store only a small fraction of the captured CO 2 in oil and natural gas reservoirs. The vast majority would likely have to be stored in saline formations. Pressure buildup as a result of injecting CO 2 into such reservoirs is expected to be an important source of risk associated with CO 2 storage, and could constrain dynamic storage capacities (maximum injection rates) to be far below estimates based on access to theoretical storage resources. Estimates of CO 2 storage costs based on an assumption of practical availability of the theoretical storage resource could lead to underestimation of the costs of CO 2 storage. In this study, simulation results suggest that the pressure-limited dynamic CO 2 storage capacity of the Mount Simon Sandstone could be less than 4% of the theoretical storage resource in this saline formation, and storage costs could be an order of magnitude higher than recent estimates. However, consideration of the geologic heterogeneity in this deep saline formation allowed definition of a high injectivity zone, and estimated costs of CO 2 storage in this “sweet spot” of the reservoir approached recent estimates that did not include costs for pressure management.

Illinois, Indiana, Kentucky↗
USGS2000

Stress resistance strategy in an arid land shrub: interactions between developmental instability and fractal dimention

This paper investigates allocation of energy to mechanisms that generate and preserve architectural forms (i.e. developmental stability, complexity of branching patterns) and productivity (growth and reproduction) in response to environmental disturbances (i.e. grazing and resource availability). The statistical error in translational symmetry was used to detect random intra-individual variability during development. This can be thought of as a measure of developmental instability caused by stress. Additionally, we use changes in fractal complexity and shoot distribution of branch structures as an alternate indicator of stress. These methods were applied to Anthyllis cytisoides L., a semi-arid environment shrub, to ascertain the effect of grazing and slope exposure on developmental traits in a 2×2 factorial design. The results show that A. cytisoides maintains developmental stability at the expense of productivity. Anthyllis cytisoides was developmentally more stable when grazed and when on south-facing, as opposed to north-facing slopes. On the contrary, shoot length, leaf area, fractal dimension and reproductive-to-vegetative allocation ratio were larger in north- than in south-facing slopes. As a consequence, under extreme xeric conditions, shrub mortality increased in north-facing slopes, especially when not grazed. The removal of transpiring area and the reduction of plant competition favoured developmental stability and survival in grazed plants. Differences between grazed and ungrazed plants were most evident in more mesic (north-facing) areas.

Journal of Fish Diseases↗
USGS2014

Application of near-surface geophysics as part of a hydrologic study of a subsurface drip irrigation system along the Powder River floodplain near Arvada, Wyoming

Rapid development of coalbed natural gas (CBNG) production in the Powder River Basin (PRB) of Wyoming has occurred since 1997. National attention related to CBNG development has focused on produced water management, which is the single largest cost for on-shore domestic producers. Low-cost treatment technologies allow operators to reduce their disposal costs, provide treated water for beneficial use, and stimulate oil and gas production by small operators. Subsurface drip irrigation (SDI) systems are one potential treatment option that allows for increased CBNG production by providing a beneficial use for the produced water in farmland irrigation. Water management practices in the development of CBNG in Wyoming have been aided by integrated geophysical, geochemical, and hydrologic studies of both the disposal and utilization of water. The U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL) and the U.S. Geological Survey (USGS) have utilized multi-frequency airborne, ground, and borehole electromagnetic (EM) and ground resistivity methods to characterize the near-surface hydrogeology in areas of produced water disposal. These surveys provide near-surface EM data that can be compared with results of previous surveys to monitor changes in soils and local hydrology over time as the produced water is discharged through SDI. The focus of this investigation is the Headgate Draw SDI site, situated adjacent to the Powder River near the confluence of a major tributary, Crazy Woman Creek, in Johnson County, Wyoming. The SDI system was installed during the summer of 2008 and began operation in October of 2008. Ground, borehole, and helicopter electromagnetic (HEM) conductivity surveys were conducted at the site prior to the installation of the SDI system. After the installation of the subsurface drip irrigation system, ground EM surveys have been performed quarterly (weather permitting). The geophysical surveys map the heterogeneity of the near-surface geology and hydrology of the study area. The geophysical data are consistent between surveys using different techniques and between surveys carried out at different times from 2007 through 2011. This paper summarizes geophysical results from the 4-year monitoring study of the SDI system.

Wyoming↗
USGS2005

Nearshore wave-induced cyclical flexing of sea cliffs

[1] Evolution of a tectonically active coast is driven by geomorphically destructive energy supplied by ocean waves. Wave energy is episodic and concentrated; sea cliffs are battered by the geomorphic wrecking ball every 4-25 s. We measure the response of sea cliffs to wave assault by sensing the ground motion using near-coastal seismometers. Sea cliffs respond to waves in two distinct styles. High-frequency motion (20 Hz) reflects the natural frequency of the sea cliff as it rings in response to direct wave impact. Low-frequency motion in the 0.1-0.05 Hz (10-20 s) band consistently agrees with the dominant nearshore wave period. Integrating microseismic velocities suggests 50 ??m and 10 ??m displacements in horizontal and vertical directions, respectively. Displacement ellipsoids exhibit simultaneous downward and seaward sea cliff motion with each wave. Video footage corroborates the downward sea cliff flex in response to the imposed water load on the wave cut platform. Gradients in displacement amplitudes documented using multiple seismometers suggest longitudinal and shear strain of the flexing sea cliff on the order of 0.5-4 ?? strains during each wave loading cycle. As this sea cliff flexure occurs approximately 3 million times annually, it has the potential to fatigue the rock through cyclical loading. Local sea cliff retreat rates of 10 cm/yr imply that a given parcel of rock is flexed through roughly 109 cycles of increasing amplitude before exposure to direct wave attack at the cliff face. Copyright 2005 by the American Geophysical Union.

Journal of Geophysical Research F: Earth Surface↗
USGS2023

Effect of feeding history on metabolic rate of largemouth bass (Micropterus nigricans): implications for bioenergetics models

Metabolic rate is a key parameter in fish energy budgets that strongly influences the output of bioenergetics models. In this study, we tested the hypothesis that metabolic rate varies with growth history of age-1 largemouth bass Micropterus nigricans Cuvier, 1828. Two groups of fish were fed alternating maintenance or ad libitum rations of fathead minnow Pimephales promelas Rafinesque, 1820, so that over a 9-week period, initial and ending size of fish was similar. After 9 weeks, oxygen consumption was measured using static, closed respirometry. Although final body weight was similar between the two groups (means, 104–108 g), specific oxygen consumption for fish fed maintenance rations (0.094 mg O 2 g −2 h −1 ) was 38% less than that measured for fish fed ad libitum (0.152 mg O 2 g −2 h −1 ). Bioenergetics estimates of food consumption were similar to observed values for fish fed ad libitum (∼7% error), but for fish fed maintenance rations, the model overestimated food consumption by 65%. By accounting for changes in metabolic rate owing to reduced feeding, error in model estimates of food consumption was reduced. These findings shed new insight into factors associated with consumption-dependent error in bioenergetics models and highlight the importance of feeding history on metabolic rate of fish. Incorporating growth-dependent metabolism into bioenergetics models can improve model accuracy and allow fisheries biologists to make more informed decisions regarding fish growth and energetics.

Canadian Journal of Zoology↗