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At least 1,261 records · Page 70Linked to original sources
USGS2005

The influence of ozone on atmospheric emissions of gaseous elemental mercury and reactive gaseous mercury from substrates

Experiments were performed to investigate the effect of ozone (O 3) on mercury (Hg) emission from a variety of Hg-bearing substrates. Substrates with Hg(II) as the dominant Hg phase exhibited a 1.7 to 51-fold increase in elemental Hg (Hgo) flux and a 1.3 to 8.6-fold increase in reactive gaseous mercury (RGM) flux in the presence of O3-enriched clean (50 ppb O3; 8 substrates) and ambient air (up to ???70 ppb O3; 6 substrates), relative to clean air (oxidant and Hg free air). In contrast, Hgo fluxes from two artificially Hgo-amended substrates decreased by more than 75% during exposure to O3-enriched clean air relative to clean air. Reactive gaseous mercury emissions from Hg o-amended substrates increased immediately after exposure to O 3 but then decreased rapidly. These experimental results demonstrate that O3 is very important in controlling Hg emissions from substrates. The chemical mechanisms that produced these trends are not known but potentially involve heterogenous reactions between O3, the substrate, and Hg. Our experiments suggest they are not homogenous gas-phase reactions. Comparison of the influence of O3 versus light on increasing Hgo emissions from dry Hg(II)-bearing substrates demonstrated that they have a similar amount of influence although O3 appeared to be slightly more dominant. Experiments using water-saturated substrates showed that the presence of high-substrate moisture content minimizes reactions between atmospheric O3 and substrate-bound Hg. Using conservative calculations developed in this paper, we conclude that because O3 concentrations have roughly doubled in the last 100 years, this could have increased Hgo emissions from terrestrial substrates by 65-72%. ?? 2005 Elsevier Ltd. All rights reserved.

Conference Paper↗
USGS2009

Understanding CO 2 Plume Behavior and Basin-Scale Pressure Changes during Sequestration Projects through the use of Reservoir Fluid Modeling

Large scale geologic sequestration tests are in the planning stages around the world. The liability and safety issues of the migration of CO 2 away from the primary injection site and/or reservoir are of significant concerns for these sequestration tests. Reservoir models for simulating single or multi-phase fluid flow are used to understand the migration of CO 2 in the subsurface. These models can also help evaluate concerns related to brine migration and basin-scale pressure increases that occur due to the injection of additional fluid volumes into the subsurface. The current paper presents different modeling examples addressing these issues, ranging from simple geometric models to more complex reservoir fluid models with single-site and basin-scale applications. Simple geometric models assuming a homogeneous geologic reservoir and piston-like displacement have been used for understanding pressure changes and fluid migration around each CO 2 storage site. These geometric models are useful only as broad approximations because they do not account for the variation in porosity, permeability, asymmetry of the reservoir, and dip of the beds. In addition, these simple models are not capable of predicting the interference between different injection sites within the same reservoir. A more realistic model of CO 2 plume behavior can be produced using reservoir fluid models. Reservoir simulation of natural gas storage reservoirs in the Illinois Basin Cambrian-age Mt. Simon Sandstone suggest that reservoir heterogeneity will be an important factor for evaluating storage capacity. The Mt. Simon Sandstone is a thick sandstone that underlies many significant coal fired power plants (emitting at least 1 million tonnes per year) in the midwestern United States including the states of Illinois, Indiana, Kentucky, Michigan, and Ohio. The initial commercial sequestration sites are expected to inject 1 to 2 million tonnes of CO 2 per year. Depending on the geologic structure and permeability anisotropy, the CO 2 injected into the Mt. Simon are expected to migrate less than 3 km. After 30 years of continuous injection followed by 100 years of shut-in, the plume from a 1 million tonnes a year injection rate is expected to migrate 1.6 km for a 0 degree dip reservoir and over 3 km for a 5 degree dip reservoir. The region where reservoir pressure increases in response to CO 2 injection is typically much larger than the CO 2 plume. It can thus be anticipated that there will be basin wide interactions between different CO 2 injection sources if multiple, large volume sites are developed. This interaction will result in asymmetric plume migration that may be contrary to reservoir dip. A basin- scale simulation model is being developed to predict CO 2 plume migration, brine displacement, and pressure buildup for a possible future sequestration scenario featuring multiple CO 2 storage sites within the Illinois Basin Mt. Simon Sandstone. Interactions between different sites will be evaluated with respect to impacts on pressure and CO 2 plume migration patterns. ?? 2009 Elsevier Ltd. All rights reserved.

Conference Paper↗
USGS2011

A feasibility study of geological CO2 sequestration in the Ordos Basin, China

The Shaanxi Province/Wyoming CCS Partnership (supported by DOE NETL) aims to store commercial quantities of CO2 safely and permanently in the Ordovician Majiagou Formation in the northern Ordos Basin, Shaanxi Province, China. This objective is imperative because at present, six coal-to-liquid facilities in Shaanxi Province are capturing and venting significant quantities of CO2. The Wyoming State Geological Survey and the Shaanxi Provincial Institute of Energy Resource and Chemical Engineering conducted a feasibility study to determine the potential for geological CO2 sequestration in the northern Ordos Basin near Yulin. The Shaanbei Slope of the Ordos Basin is a huge monoclinal structure with a high-priority sequestration reservoir (Majiagou Formation) that lies beneath a 2,000+ meter-thick sequence of Mesozoic rocks containing a multitude of lowpermeability lithologies. The targeted Ordovician Majiagou Formation in the location of interest is more than 700 meters thick. The carbonate reservoir is located at depths where pressures and temperatures are well above the supercritical point of CO2. The targeted reservoir contains high-salinity brines (20,000-50,000 ppm) that have little or no economic value. The targeted reservoir is continuous as inferred from well logs, and cores show that porosity ranges from 1 to 15% with average measured porosity of 8%, and that permeability ranges from 1-35 md. This paper focuses on calculations that will help evaluate the capacity estimates through the use of high-resolution multiphase numerical simulation models, as well as a more simple volumetric approach. The preliminary simulation results show that the Ordovician Majiagou Formation in the Ordos Basin has excellent potential for geological CO2 sequestration and could store the CO2 currently emitted by coal-to-liquid facilities in Shaanxi Province for hundreds of years (i.e., 9 Mt/year CO2; 450 Mt over a 50-year period at one injection site). ?? 2011 Published by Elsevier Ltd.

Conference Paper↗
USGS2006

Groundwater-supported evapotranspiration within glaciated watersheds under conditions of climate change

This paper analyzes the effects of geology and geomorphology on surface-water/-groundwater interactions, evapotranspiration, and recharge under conditions of long-term climatic change. Our analysis uses hydrologic data from the glaciated Crow Wing watershed in central Minnesota, USA, combined with a hydrologic model of transient coupled unsaturated/saturated flow (HYDRAT2D). Analysis of historical water-table (1970-1993) and lake-level (1924-2002) records indicates that larger amplitude and longer period fluctuations occur within the upland portions of watersheds due to the response of the aquifer system to relatively short-term climatic fluctuations. Under drought conditions, lake and water-table levels fell by as much as 2-4 m in the uplands but by 1 m in the lowlands. The same pattern can be seen on millennial time scales. Analysis of Holocene lake-core records indicates that Moody Lake, located near the outlet of the Crow Wing watershed, fell by as much as 4 m between about 4400 and 7000 yr BP. During the same time, water levels in Lake Mina, located near the upland watershed divide, fell by about 15 m. Reconstructed Holocene climate as represented by HYDRAT2D gives somewhat larger drops (6 and 24 m for Moody Lake and Lake Mina, respectively). The discrepancy is probably due to the effect of three-dimensional flow. A sensitivity analysis was also carried out to study how aquifer hydraulic conductivity and land-surface topography can influence water-table fluctuations, wetlands formation, and evapotranspiration. The models were run by recycling a wet year (1985, 87 cm annual precipitation) over a 10-year period followed by 20 years of drier and warmer climate (1976, 38 cm precipitation). Model results indicated that groundwater-supported evapotranspiration accounted for as much as 12% (10 cm) of evapotranspiration. The aquifers of highest hydraulic conductivity had the least amount of groundwater-supported evapotranspiration owing to a deep water table. Recharge was even more sensitive to aquifer hydraulic conductivity, especially in the lowland regions. These findings have important implications for paleoclimatic studies, because the hydrologic response of a surface-water body will vary across the watershed to a given climate signal. ?? 2005 Elsevier B.V. All rights reserved.

Conference Paper↗
USGS2004

Development of an AMS method to study oceanic circulation characteristics using cosmogenic 39Ar

Initial experiments at the ATLAS facility [Nucl. Instr. and Meth. B 92 (1994) 241] resulted in a clear detection of cosmogenic 39Ar signal at the natural level. The present paper summarizes the recent developments of 39Ar AMS measurements at ATLAS: the use of an electron cyclotron resonance (ECR) positive ion source equipped with a special quartz liner to reduce 39K background, the development of a gas handling system for small volume argon samples, the acceleration of 39Ar8+ ions to 232 MeV, and the final separation of 39Ar from 39K in a gas-filled spectrograph. The first successful AMS measurements of 39Ar in ocean water samples from the Southern Atlantic ventilation experiment (SAVE) are reported. Published by Elsevier B.V.

Conference Paper↗
USGS2011

A working environment for digital planetary data processing and mapping using ISIS and GRASS GIS

Since the beginning of planetary exploration, mapping has been fundamental to summarize observations returned by scientific missions. Sensor-based mapping has been used to highlight specific features from the planetary surfaces by means of processing. Interpretative mapping makes use of instrumental observations to produce thematic maps that summarize observations of actual data into a specific theme. Geologic maps, for example, are thematic interpretative maps that focus on the representation of materials and processes and their relative timing. The advancements in technology of the last 30 years have allowed us to develop specialized systems where the mapping process can be made entirely in the digital domain. The spread of networked computers on a global scale allowed the rapid propagation of software and digital data such that every researcher can now access digital mapping facilities on his desktop. The efforts to maintain planetary missions data accessible to the scientific community have led to the creation of standardized digital archives that facilitate the access to different datasets by software capable of processing these data from the raw level to the map projected one. Geographic Information Systems (GIS) have been developed to optimize the storage, the analysis, and the retrieval of spatially referenced Earth based environmental geodata; since the last decade these computer programs have become popular among the planetary science community, and recent mission data start to be distributed in formats compatible with these systems. Among all the systems developed for the analysis of planetary and spatially referenced data, we have created a working environment combining two software suites that have similar characteristics in their modular design, their development history, their policy of distribution and their support system. The first, the Integrated Software for Imagers and Spectrometers (ISIS) developed by the United States Geological Survey, represents the state of the art for processing planetary remote sensing data, from the raw unprocessed state to the map projected product. The second, the Geographic Resources Analysis Support System (GRASS) is a Geographic Information System developed by an international team of developers, and one of the core projects promoted by the Open Source Geospatial Foundation (OSGeo). We have worked on enabling the combined use of these software systems throughout the set-up of a common user interface, the unification of the cartographic reference system nomenclature and the minimization of data conversion. Both software packages are distributed with free open source licenses, as well as the source code, scripts and configuration files hereafter presented. In this paper we describe our work done to merge these working environments into a common one, where the user benefits from functionalities of both systems without the need to switch or transfer data from one software suite to the other one. Thereafter we provide an example of its usage in the handling of planetary data and the crafting of a digital geologic map. ?? 2010 Elsevier Ltd. All rights reserved.

Conference Paper↗
USGS2004

Recycling of construction debris as aggregate in the Mid-Atlantic Region, USA

Reclaimed asphalt pavement (RAP) and portland cement concrete (RPCC) are abundant and available substitutes for natural aggregate in many areas. This paper presents an overview of factors that affect recycled aggregate cost, availability, and engineering performance, and the results of a survey of business practices in the Mid-Atlantic region. For RAP, processing costs are less than those for virgin natural aggregate. Use of efficient asphalt pavement stripping technology, on-site reclamation, and linked two-way transport of asphalt debris and processed asphalt paving mix between asphalt mix plants and paving sites has led to extensive recycling of asphalt pavement in the Mid-Atlantic region of the US. Most of the sites that recycle asphalt pavement (RAP) are located in or near urban areas close to important transportation corridors. RPCC is a viable aggregate source in urban settings where unit costs for processed aggregate from RPCC and natural aggregate are comparable. Disposal fees charged at RPCC recycling sites help defray processing costs and the significantly lower tipping fees at recycling sites versus landfill disposal sites encourage recycling of construction debris as aggregate. Construction contractors and construction debris recycling centers, many of which have the ability to crush and process concrete debris at the job site, produce most RPCC. Production of RPCC aggregate from construction debris that is processed on site using portable equipment moved to the construction site eliminates transportation costs for aggregate and provides an economic incentive for RPCC use. Processing costs, quality and performance issues, and lack of large quantities where needed limit RPCC use. Most RPCC suppliers in the Mid-Atlantic area are located in counties with population densities greater than 400 people/km2 (1036 people/mile2) and that have high unit-value costs and limited local availability of natural aggregate. ?? 2004 Published by Elsevier B.V.

Conference Paper↗
USGS2001

Identification of a new degradation product of the antifouling agent Irgarol 1051 in natural samples

A main degradation product of Irgarol [2-(methylthio)-4-(tert-butylamino)-6-(cyclopropylamino)-s-triazine], one of the most widely used compounds in antifouling paints, was detected at trace levels in seawater and sediment samples collected from several marinas on the Mediterranean coast. This degradation product was identified as 2-methylthio-4-tert-butylamino-s-triazine. The unequivocal identification of this compound in seawater samples was carried out by solid-phase extraction (SPE) coupled on-line with liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS). SPE was carried out by passing 150 ml of seawater sample through a cartridge containing a polymeric phase (PLRP-s), with recoveries ranging from 92 to 108% (n=5). Using LC-MS detection in positive ion mode, useful structural information was obtained by increasing the fragmentor voltage, thus permitting the unequivocal identification of this compound in natural samples. Method detection limits were in the range of 0.002 to 0.005 ??g/l. Overall, the combination of on-line SPE and LC-APCI-MS represents an important advance in environmental analysis of herbicide degradation products in seawater, since it demonstrates that trace amounts of new polar metabolites may be determined rapidly. This paper reports the LC-MS identification of the main degradation product of Irgarol in seawater and sediment samples. ?? 2001 Elsevier Science B.V. All rights reserved.

Conference Paper↗
USGS1997

Amplitude versus offset modeling of the bottom simulating reflection associated with submarine gas hydrates

A bottom simulating seismic reflection (BSR) that parallels the sea floor occurs worldwide on seismic profiles from outer continental margins. The BSR coincides with the base of the gas hydrate stability field and is commonly used as indicator of natural submarine gas hydrates. Despite the widespread assumption that the BSR marks the base of gas hydrate-bearing sediments, the occurrence and importance of low-velocity free gas in the sediments beneath the BSR has long been a subject of debate. This paper investigates the relative abundance of hydrate and free gas associated with the BSR by modeling the reflection coefficient or amplitude variation with offset (AVO) of the BSR at two separate sites, offshore Oregon and the Beaufort Sea. The models are based on multichannel seismic profiles, seismic velocity data from both sites and downhole log data from Oregon ODP Site 892. AVO studies of the BSR can determine whether free gas exists beneath the BSR if the saturation of gas hydrate above the BSR is less than approximately 30% of the pore volume. Gas hydrate saturation above the BSR can be roughly estimated from AVO studies, but the saturation of free gas beneath the BSR cannot be constrained from the seismic data alone. The AVO analyses at the two study locations indicate that the high amplitude BSR results primarily from free gas beneath the BSR. Hydrate concentrations above the BSR are calculated to be less than 10% of the pore volume for both locations studied.

Conference Paper↗
USGS2003

Arsenic behavior in newly drilled wells

In the present paper, inorganic arsenic species and chemical parameters in groundwater were determined to investigate the factors related to the distribution of arsenic species and their dissolution from rock into groundwater. For the study, groundwater and core samples were taken at different depths of two newly drilled wells in Huron and Lapeer Counties, Michigan. Results show that total arsenic concentrations in the core samples varied, ranging from 0.8 to 70.7 mg/kg. Iron concentration in rock was about 1800 times higher than that of arsenic, and there was no correlation between arsenic and iron occurrences in the rock samples. Arsenic concentrations in groundwater ranged from <1 to 171 ??g/l. The arsenic concentration in groundwater depended on the amount of arsenic in aquifer rocks, and as well decreased with increasing depth. Over 90% of arsenic existed in the form of As(III), implying that the groundwater systems were in the reduced condition. The results such as high ferrous ion, low redox potential and low dissolved oxygen supported the observed arsenic species distribution. There was no noticeable difference in the total arsenic concentration and arsenic species ratio between unfiltered and filtered (0.45 ??m) waters, indicating that the particulate form of arsenic was negligible in the groundwater samples. There were correlations between water sampling depth and chemical parameters, and between arsenic concentration and chemical parameters, however, the trends were not always consistent in both wells. ?? 2003 Elsevier Science Ltd. All rights reserved.

Conference Paper↗
USGS2003

Implications of crustal permeability for fluid movement between terrestrial fluid reservoirs

A classic paper by Rubey [Geol. Soc. Amer. Bull 62 (1951) 1111] examined various hypotheses regarding the origin of sea water and concluded that the most likely hypothesis was volcanic outgassing, a view that was generally accepted by Earth scientists for the next several decades. More recent work suggests that the rate of subduction of water is much larger than the volcanic outgassing rate, lending support to hypotheses that either ocean volume has decreased with time, or that the imbalance is offset by continuous replenishment of water by cometary impacts. These alternatives are required in the absence of additional mechanisms for the return of water from subducting lithosphere to the Earth's surface. Our recent work on crustal permeability suggests a large capacity for water upflow through tectonically active continental crust, resulting in a heretofore-unrecognized degassing pathway that can accommodate the water-subduction rate. Escape of recycled water via delivery from the mantle through zones of active metamorphism eliminates the mass-balance argument for the loss of ocean volume or extraterrestrial sources. ?? 2003 Elsevier Science B.V. All rights reserved.

Conference Paper↗
USGS2002

Supporting user-defined granularities in a spatiotemporal conceptual model

Granularities are integral to spatial and temporal data. A large number of applications require storage of facts along with their temporal and spatial context, which needs to be expressed in terms of appropriate granularities. For many real-world applications, a single granularity in the database is insufficient. In order to support any type of spatial or temporal reasoning, the semantics related to granularities needs to be embedded in the database. Specifying granularities related to facts is an important part of conceptual database design because under-specifying the granularity can restrict an application, affect the relative ordering of events and impact the topological relationships. Closely related to granularities is indeterminacy, i.e., an occurrence time or location associated with a fact that is not known exactly. In this paper, we present an ontology for spatial granularities that is a natural analog of temporal granularities. We propose an upward-compatible, annotation-based spatiotemporal conceptual model that can comprehensively capture the semantics related to spatial and temporal granularities, and indeterminacy without requiring new spatiotemporal constructs. We specify the formal semantics of this spatiotemporal conceptual model via translation to a conventional conceptual model. To underscore the practical focus of our approach, we describe an on-going case study. We apply our approach to a hydrogeologic application at the United States Geologic Survey and demonstrate that our proposed granularity-based spatiotemporal conceptual model is straightforward to use and is comprehensive.

Conference Paper↗
USGS1989

Depositional aspects and a guide to Paleocene coal-bearing sequences, Powder River Basin

The Paleocene coal-bearing sequences in the northern Powder River Basin are contained in the Tongue River Member of the Fort Union Formation and include anomalously thick (54 m) subbituminous coals. These thick coals have been the target of exploration and development for the past few decades. For the past decade, these coals have also been the object of depositional modeling studies [Law, 1976; Galloway, 1979; Flores, 1981, 1983, 1986; Ethridge and others, 1981; Ayers and Kaiser, 1984; Warwick, 1985; Ayers, 1986; Moore, 1986; Warwick and Stanton, 1988]. Intensive modeling of these coals has resulted in two major schools of thought. Firstly, Galloway [1979], Flores [1981, 1983, 1986], Ethridge and others [1981], Warwick [1985], Moore [1986], and Warwick and Stanton [1988] believe that the coals formed from peat that accumulated in swamps of fluvial systems. The fluvial systems are interpreted as a basin axis trunktributary complex that drained to the north-northeast into the Williston Basin. Secondly, Ayers and Kaiser [1984] and Ayers [1986] believe that the coals formed from peat swamps of deltaic systems. These deltas are envisioned to have prograded east to west from the Black Hills and infilled Lebo lake that was centrally located along the basin axis. In order to explain the low ash content of the thick coals, Flores [1981] proposed that they are formed as domed peats, similar in geomorphology to swamps associated with the modern fluvial systems in Borneo as described by Anderson [1964]. Ethridge and others [1981] suggested that these fluvial-related swamps are platforms well above drainage systems and are fed by ground water that is recharged from surrounding highlands. Warwick [1985], Warwick and Stanton [1988], Satchell [1984], and Pocknall and Flores [1987] confirmed the domed peat hypothesis by investigating the petrology and palynology of the thick coals. The purpose of this paper is to provide a guide to the depositional aspects of the thick coals in the Tongue River Member of the Fort Union Formation and, because of the biases of the field trip leaders, it elaborates on the fluvial origin of the swamps in which the thick coals formed. Case histories of these thick coals and associated sediments in the Gillette, Powder River, and Kaycee-Linch areas of Wyoming and in the Decker-Tongue River area of Montana (fig. 1) are highlighted on this field trip.

Montana, Wyoming↗
USGS2012

Modeling of rock friction 2. Simulation of preseismic slip

The constitutive relations developed in the companion paper are used to model detailed observations of preseismic slip and the onset of unstable slip in biaxial laboratory experiments. The simulations employ a deterministic plane strain finite element model to represent the interactions both within the sliding blocks and between the blocks and the loading apparatus. Both experiments and simulations show that preseismic slip is controlled by initial inhomogeneity of shear stress along the sliding surface relative to the frictional strength. As a consequence of the inhomogeneity, stable slip begins at a point on the surface and the area of slip slowly expands as the external loading increases. A previously proposed correlation between accelerating rates of stable slip and growth of the area of slip is supported by the simulations. In the simulations and in the experiments, unstable slip occurs shortly after a propagating slip event traverses the sliding surface and breaks out at the ends of the sample. In the model the breakout of stable slip causes a sudden acceleration of slip rates. Because of velocity dependency of the constitutive relationship for friction, the rapid acceleration of slip causes a decrease in frictional strength. Instability occurs when the frictional strength decreases with displacement at a rate that exceeds the intrinsic unloading characteristics of the sample and test machine. A simple slider-spring model that does not consider preseismic slip appears to approximate the transition adequately from stable sliding to unstable slip as a function of normal stress, machine stiffness, and surface roughness for small samples. However, for large samples and for natural faults the simulations suggest that the simple model may be inaccurate because it does not take into account potentially large preseismic displacements that will alter the friction parameters prior to instability. Copyright ?? 1979 by the American Geophysical Union.

Conference Paper↗
USGS2023

The spatial distribution of debris flows in relation to observed rainfall anomalies: Insights from the Dolan Fire, California

A range of hydrologic responses can be observed in steep, recently burned terrain, which makes predicting the spatial distribution of large debris flows challenging. Studies from rainfall-induced landslides in unburned areas show evidence of hydroclimatic tuning of landslide triggering, such that the spatial distribution of events is best predicted by the observed rainfall anomaly relative to climatic norms rather than by absolute rainfall. In this paper, we test whether the spatial distribution of debris flows in response to rainfall can be similarly predicted by rainfall anomaly. The 520 km 2 Dolan Fire burn scar in Monterey County, California, USA, spans a sharp hydroclimatic gradient and experienced a widespread storm in January 2021 that triggered floods and debris flows, providing a natural experiment in which to test this hypothesis. In this study, we use remote and field methods to map debris-flow response and examine its spatial heterogeneity. Together with rainfall data, our mapping reveals that the observed anomalies in peak 15-min rainfall intensity (I 15 ) relative to the intensity of the 1-yr return interval storm predict debris-flow occurrence better than the absolute peak I 15 . Our findings indicate that debris-flow processes and threshold rainfall required for debris-flow initiation may be tuned to local hydroclimate.

California↗
USGS2017

Quantifying acoustic doppler current profiler discharge uncertainty: A Monte Carlo based tool for moving-boat measurements

This paper presents a method using Monte Carlo simulations for assessing uncertainty of moving-boat acoustic Doppler current profiler (ADCP) discharge measurements using a software tool known as QUant , which was developed for this purpose. Analysis was performed on 10 data sets from four Water Survey of Canada gauging stations in order to evaluate the relative contribution of a range of error sources to the total estimated uncertainty. The factors that differed among data sets included the fraction of unmeasured discharge relative to the total discharge, flow nonuniformity, and operator decisions about instrument programming and measurement cross section. As anticipated, it was found that the estimated uncertainty is dominated by uncertainty of the discharge in the unmeasured areas, highlighting the importance of appropriate selection of the site, the instrument, and the user inputs required to estimate the unmeasured discharge. The main contributor to uncertainty was invalid data, but spatial inhomogeneity in water velocity and bottom-track velocity also contributed, as did variation in the edge velocity, uncertainty in the edge distances, edge coefficients, and the top and bottom extrapolation methods. To a lesser extent, spatial inhomogeneity in the bottom depth also contributed to the total uncertainty, as did uncertainty in the ADCP draft at shallow sites. The estimated uncertainties from QUant can be used to assess the adequacy of standard operating procedures. They also provide quantitative feedback to the ADCP operators about the quality of their measurements, indicating which parameters are contributing most to uncertainty, and perhaps even highlighting ways in which uncertainty can be reduced. Additionally, QUant can be used to account for self-dependent error sources such as heading errors, which are a function of heading. The results demonstrate the importance of a Monte Carlo method tool such as QUant for quantifying random and bias errors when evaluating the uncertainty of moving-boat ADCP measurements.

Conference Paper↗
USGS2012

Monograph for using paleoflood data in Water Resources Applications

The Environmental and Water Resources Institute (EWRI) Technical Committee on Surface Water Hydrology is sponsoring a Task Committee on Paleoflood Hydrology to prepare a monograph entitled, "Use of Paleoflood and Historical Data in Water Resources Applications." This paper introduces the subject of paleoflood hydrology and discusses the topics, which are expected to be included in the monograph. The procedure for preparing and reviewing the monograph will also be discussed. The paleoflood hydrology monograph will include a discussion of types of hydrologic and paleoflood data, paleostage indicators, flood chronology, modeling methods, interpretation issues, water resources applications and case studies, and research needs. Paleoflood data collection and analysis techniques will be presented, and various applications in water-resources investigations will be provided. An overview of several flood frequency analysis approaches, which consider historical and paleoflood data along with systematic streamflow records, will be presented. The monograph is scheduled for completion and publication in 2001. Copyright ASCE 2004.

Conference Paper↗
USGS2012

Clearwater local scour experiments in a large flume

Local sediment scour experiments have been conducted with 0.114 m, 0.305 m and 0.914 m diameter circular piles in a 6.1 m (20 ft) wide by 6.4 m (21 ft) deep by 38.4 m (126 ft) long flume in the Hydraulics Laboratory at the USGS Conte Laboratory in Turners Falls, MA. All of the tests to date have been in the clearwater scour range of velocities and with two near uniform diameter sediments with median diameters of 0.2 mm and 0.8 mm. All tests were conducted with steady, fully developed flows. This paper describes the procedures and instrumentation used in these tests and outlines the live bed scour experiments that are planned after the completion of the clearwater tests. Copyright ASCE 2004.

Conference Paper↗