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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 1,783 records · Page 99Linked to original sources
USGS2001

Scientific and social landscapes: New frameworks and forums for water management and sustainability

The Two Decades of Water Law and Policy Reform conference examines the agenda for reforming and improving water law that has developed during the past two decades in the West, assesses what has (and has not) been accomplished by pursuing these reforms, and explores lessons and implications for future water law and policy. The papers and discussion provide analysis and lessons that can guide the new administration, Congress, federal agencies, state governments, and communities as they seek to find policy solutions to the challenges posed by the tremendous economic and demographic changes occurring in the West, in order to ensure the sustainability of the region’s unique environment. Specific sessions focus on reforms such as improving the scientific and technical basis for water management, water conservation and efficiency, protecting environmental values in meeting water demands, and creating new models of governance for water issues.

Conference Paper↗
USGS1999

Behaviour and ecology of sea ducks

In November 1995... a full-day symposium on the biology of sea ducks was held. The papers in this volume were presented at this symposium. It is hoped that by synthesizing this information, more informed management decisions for sea ducks may emerge. The symposium contents help to emphasize the seriousness of some conservation issues facing sea ducks, notably the possible endangerment of the eastern population of Barrow's Goldeneye and the dwindling number of eider ducks in the Nearctic, while also providing new data on the behaviour and habitat use of this beautiful group of ducks.

Occasional Paper of the Canadian Wildlife Service↗
USGS1987

The use of the National Water Data Exchange in support of estuarine and coastal programs

The National Water Data Exchange (NAWDEX) was established by the U.S. Geological Survey in 1976. Its program is directed toward improving the exchange of water and water -related data collected and made available by hundreds of federal and non-federal agencies throughout the United States. This paper describes the NAWDEX program and the services which can be provided to assist coastal and estuarine programs.

Conference Paper↗
USGS2017

Some results from ModEM3DMT, the freely available OSU 3D MT inversion code

At the 3DEM-5 workshop in 2013, we presented a paper entitled "ModEM: developing 3D EM inversion for the masses", outlining our then recent development of a modular system for inversion of EM geophysical data, called ModEM. As promised in that presentation, we made a version of the code that is suitable for 3D modeling and inversion of magnetotelluric data freely available for academic use shortly thereafter. There are now over 250 registered users, of ModEM3DMT from around the globe. To date at least 50 publications cite use of ModEM for 3D inversion of real MT datasets to address diverse problems in applied and basic Earth Science research at a range of scales. Here we present an overview of some of these results, focusing on studies that the authors have been involved in, and are thus most familiar to us.

Conference Paper↗
USGS1963

Simple measurements of morphological changes in river channels and hillslopes

One of the principal types of observational evidence on climatic changes in the recent geologic past is in river position and elevation. It is well known that river channels, particularly those flowing through alluvium or on relatively soft bedrock, tend to develop flood plains by lateral migration of the channel. Abandoned flood plains at elevations distinctly above the present river channel are the origin of river terraces, widespread through the world but particularly noticeable in arid regions. Climatic change is one of the causes of the abandonment of flood plains and the consequent formation of river terraces. Therefore, the identification and stratigraphy of river terraces is one of the methods by which climatic changes in the recent geologic past can be studied. There are, of course, morphologic changes in river channels of a more subtle nature. Even when a channel is progressively degrading-a trend which will eventually result in the formation of a river terracethere are no obvious criteria by which the current changes in a river channel can be positively identified. For this reason simple techniques, which will aid in the direct observation of current changes in a channel’s position, can be helpful in identifying the nature of changes in progress. It is the purpose of this paper to describe some relatively simple techniques which have been found to be useful in observing morphological changes on slopes and in channels. The methods have been tested primarily in arid climates but to some extent they can also be useful even where vegetation is prominent.

Conference Paper↗
USGS2001

Recommended features of protocols for long-term ecological monitoring

In 1991, the National Park Service (NPS) selected seven parks to serve as prototypes for development of a long-term ecological monitoring program. Denali National Park and Preserve was one of the prototype parks selected. The principal focus of this national program was to detect and document resource changes and to understand the forces driving those changes. One of the major tasks of each prototype park was to develop monitoring protocols. In this paper, we discuss some lessons learned and what we believe to be the most important features of protocols. One of the many lessons we have learned is that monitoring protocols vary greatly in content and format. This variation leads to confusion about what information protocols should contain and how they should be formatted. Problems we have observed in existing protocols include (1) not providing enough detail, (2) omitting critical topics (such as data management), and (3) mixing explanation with instructions. Once written, protocols often sit on the shelf to collect dust, allowing methods changes to occur without being adequately considered, tested, or documented. Because a lengthy and costly research effort is often needed to develop protocols, a vision of what the final product should look like is helpful. Based on our involvement with the prototype monitoring program for Denali (Oakley and Boudreau 2000), we recommend key features of protocols, including a scheme for linking protocols to data in the data management system and for tracking protocol revisions. A protocol system is crucial for producing long-term data sets of known quality that meet program objectives.

Conference Paper↗
USGS1991

Effects of oil pollution on marine bird populations

Worldwide oil pollution has killed millions of marine birds in this century but it has been difficult to directly link these losses to population declines. Estimated bird losses from acute spills and chronic pollution are not precise because we usually do not know the proportion of birds killed at sea that are detected on beach surveys or the origin of those birds. Data required to assess effects on populations (abundance, distribution, productivity, recruitment and mortality rates) are inadequate or absent for many species. Local populations may sometimes be devastated by oil pollution, but whether these losses are biologically significant to global populations, especially in light of natural or human-induced sources of mortality, is debatable. In this paper. We review the evidence for effects of oil on marine bird populations, discuss four case histories, and address the debate concerning short- and long-term effects on avian populations.

Conference Paper↗
USGS2017

Wave dynamics and flooding on low-lying tropical reef-lined coasts

Many tropical islands and coasts are lined with coral reefs. These reefs are host to valuable ecosystems that support abundant marine species and provide resources for fisheries and recreation. As a flood defense, reefs protect coastlines from coastal storm damage and flooding by reducing the majority of incident wave energy. However, during storm and large swell conditions, coastal wave-driven flooding and overwash still occur due to high water levels, (infra) gravity waves, and/or low-frequency wave resonance. The wave and flooding effects cause erosion, damage to infrastructure, agricultural crops, and salinization of precious drinking water supplies. These impacts, which are likely to increase due to climate change and ongoing development on the islands, may cause many low-lying tropical islands and coastal areas to become uninhabitable before the end of the century. This paper investigates aspects of wave dynamics for the case of a small island in the tropical Pacific Ocean, shows projections of flooding under climate change scenarios, and outlines approaches to generalize the results to other islands, including mitigation options.

Conference Paper↗
USGS2004

History and effects of hatchery salmon in the Pacific

There has been a long history of production of hatchery salmon along the Pacific coast - from California’s first efforts in the 1870s using eggs from chinook and rainbow trout to the recent large-scale production hatcheries for pink salmon in Japan and the Russian Far East. The rationale for this production has also varied from replacement of fish lost in commercial ocean harvests to mitigation and restoration of salmon in areas where extensive habitat alteration has reduced salmonid viability and abundance. Over the years, we have become very successful in producing a certain type of product from salmon hatcheries, but until recently we seldom questioned the impacts the production and release of hatchery fish may have on freshwater and marine aquatic ecosystems and on the sustainability of sympatric wild salmon populations. This paper addresses the history of hatcheries around the Pacific Rim and considers potential negative implications of hatchery-produced salmon through discussions of biological impacts and biodiversity, ecological impacts and competitive displacement, fish and ecosystem health, and genetic impacts of hatchery fish as threats to wild populations of Pacific salmon.

Speaking for the Salmon↗
USGS2010

Topographic evolution of sandbars: Flume experiment and computational modeling

Measurements of sandbar formation and evolution were carried out in a laboratory flume and the topographic characteristics of these barforms were compared to predictions from a computational flow and sediment transport model with bed evolution. The flume experiment produced sandbars with approximate mode 2, whereas numerical simulations produced a bed morphology better approximated as alternate bars, mode 1. In addition, bar formation occurred more rapidly in the laboratory channel than for the model channel. This paper focuses on a steady-flow laboratory experiment without upstream sediment supply. Future experiments will examine the effects of unsteady flow and sediment supply and the use of numerical models to simulate the response of barform topography to these influences.

Conference Paper↗
USGS2012

Using computational modeling of river flow with remotely sensed data to infer channel bathymetry

As part of an ongoing investigation into the use of computational river flow and morphodynamic models for the purpose of correcting and extending remotely sensed river datasets, a simple method for inferring channel bathymetry is developed and discussed. The method is based on an inversion of the equations expressing conservation of mass and momentum to develop equations that can be solved for depth given known values of vertically-averaged velocity and water-surface elevation. The ultimate goal of this work is to combine imperfect remotely sensed data on river planform, water-surface elevation and water-surface velocity in order to estimate depth and other physical parameters of river channels. In this paper, the technique is examined using synthetic data sets that are developed directly from the application of forward two-and three-dimensional flow models. These data sets are constrained to satisfy conservation of mass and momentum, unlike typical remotely sensed field data sets. This provides a better understanding of the process and also allows assessment of how simple inaccuracies in remotely sensed estimates might propagate into depth estimates. The technique is applied to three simple cases: First, depth is extracted from a synthetic dataset of vertically averaged velocity and water-surface elevation; second, depth is extracted from the same data set but with a normally-distributed random error added to the water-surface elevation; third, depth is extracted from a synthetic data set for the same river reach using computed water-surface velocities (in place of depth-integrated values) and water-surface elevations. In each case, the extracted depths are compared to the actual measured depths used to construct the synthetic data sets (with two- and three-dimensional flow models). Errors in water-surface elevation and velocity that are very small degrade depth estimates and cannot be recovered. Errors in depth estimates associated with assuming water-surface velocities equal to depth-integrated velocities are substantial, but can be reduced with simple corrections.

Conference Paper↗
USGS2015

Identifying sediment sources in the sediment TMDL process

Sediment is an important pollutant contributing to aquatic-habitat degradation in many waterways of the United States. This paper discusses the application of sediment budgets in conjunction with sediment fingerprinting as tools to determine the sources of sediment in impaired waterways. These approaches complement monitoring, assessment, and modeling of sediment erosion, transport, and storage in watersheds. Combining the sediment fingerprinting and sediment budget approaches can help determine specific adaptive management plans and techniques applied to targeting hot spots or areas of high erosion.

Conference Paper↗
USGS1990

Reevaluation of large-scale dispersivities for a waste chloride plume: Effects of transient flow

This paper investigates the effects of transient groundwater flow on dispersion of a waste chloride plume in the basaltic aquifer beneath the Idaho (USA) National Engineering Laboratory. In an early application of numerical modeling techniques to the two-dimensional simulation of field-scale plumes, previous investigators identified longitudinal and transverse dispersivities using an independently calibrated steady-state flow model and matching contours of observed and simulated concentrations. The unusual result of calibrated transverse dispersivity (140 m) being significantly larger than longitudinal dispersivity (90 m) has been attributed to spatial heterogeneity, the fractured nature of the aquifer, and to the use of a two-dimensional model. New calibrations of the solute-transport model are performed on point concentration observations using a flow model incorporating transient recharge conditions that cause significant fluctuations in velocity. Under transient flow conditions, lowest calibration errors are achieved with significantly larger dispersivities than previously hypothesized, and with the longitudinal component larger than the transverse component. Unfortunately, the sensitivity of the model calibration error to dispersivity is low. Incorporating transient flow in this two-dimensional porous-media model does not significantly improve our understanding of the processes controlling chloride transport at this site.

Conference Paper↗
USGS1990

Effectiveness of the addition of alkaline materials at surface coal mines in preventing or abating acid mine drainage--Part 1. Geochemical considerations

The addition of alkaline materials to supplement deficient "neutralization potential" (NP) of mine spoil, and thus to prevent or abate acid mine drainage, has riot been successful at most surface coal mines in Pennsylvania. A basic problem may have been improper accounting for acid‐production potential and thus inadequate addition rates of calcium carbonate (CaCO 3 ), calcium oxide (CaO) , or calcium hydroxide [ Ca (OH) 2 ] at many mines. The commonly used acid‐base accounting method is based on the following overall reaction: FeS 2 + 2 CaCO 3 + 3.75 O 2 + 1.5 H 2 O --> Fe(OH) 3 + 2 SO 4 -2 + 2 Ca +2 +2 CO 2 (g), where the acidity from 1 mole of pyrite (FeS2) is neutralized by 2 moles of CaCO 3 . This method presumes that gaseous carbon dioxide (CO 2 ) will exsolve, and therefore may underestimate by up to a factor of 2 the quantity of CaCO 3 required to neutralize the "maximum potential acidity" (MPA) in the mine spoil. This paper reviews some geochemical reactions involving FeS 2 and various alkaline additives that support the argument that the acid‐base accounting method for computing MPA from overburden analyses should be revised. Considering the stoichiometry of the following overall reaction: FeS 2 + 4 CaCO 3 + 3.75 O 2 + 3.5 H 2 O --> Fe(OH) 3 + 2 SO 4 -1 + 4 Ca +2 + 4 HCO 3 - , 4 moles of CaCO 3 are required to neutralize the maximum potential acidity produced by the oxidation of 1 mole of FeS 2 . Therefore, the multiplication factor for computing MPA from the overburden sulfur concentration, in weight percent, should be increased from 31.25 to 62.5.

Conference Paper↗
USGS2017

Numerical simulations of sand production in interbedded hydrate-bearing sediments during depressurization

Geomechanical behavior of hydrate-bearing sediments during gas production is complex, involving changes in hydrate-dependent mechanical properties. When interbedded clay layers are present, the complexity is more pronounced because hydrate dissociation tends to occur preferentially in the sediments adjacent to the clay layers due to clay layers acting as a heat source. This would potentially lead to shearing deformation along the sand/clay contacts and may contribute to solid migration, which hindered past field-scale gas production tests. This paper presents a near-wellbore simulation of sand/clay interbedded hydrate-bearing sediments that have been subjected to depressurization and discusses the effect of clay layers on sand production.

Conference Paper↗
USGS2011

Mechanics of flow and sediment transport in delta distributary channels

Predicting the planform and dimensions of a channel downstream from a confluence of two smaller channels with known sediment and water supplies is a fundamental, well-studied problem in geomorphology and engineering. An analogous but less well understood problem is found well downstream of such confluences, where large river channels split into two or more distributary channels on a river delta. In this case, both the flow and sediment supplies in the downstream distributaries are set by the dynamics near the bifurcation of the upstream channel and by downstream boundary conditions. Over time, the pattern of erosion and deposition in the distributary channels gives rise to variations in the amount of water and sediment routed into them. In the simplest case, this results in channel switching on deltas, but in a more general sense these dynamics produce a rich suite of interesting morphologic change contributing both to the evolution of the channel distributary network and the overall evolution of the delta. As part of a study to develop a better understanding of these processes, we conducted a field study measuring the detailed morphology of the Hong-Luoc junction on the Red River downstream of Hanoi, Vietnam. This junction was selected for such a study because it has a 1,000-year history, modern observations suggest that it is currently switching (changing the proportion of sediment and streamflow provided to each of the distributary channels), and hydrologic configuration of the junction allows for the study of two bifurcations and one confluence in a single junction complex. In this paper, our morphologic observations are used in computational flow models to show how flow and sediment transport changes as a function of total discharge upstream of the junction. This is a key component of understanding how the junction attains stability over a range of flows or how imbalances in the distribution of flow and sediment transport lead to destabilization of the channel bifurcation.

Conference Paper↗
USGS2017

Statistical relative gain calculation for Landsat 8

The Landsat 8 Operational Land Imager (OLI) is an optical multispectral push-broom sensor with a focal plane consisting of over 7000 detectors per spectral band. Each of the individual imaging detectors contributes one column of pixels to an image. Any difference in the response between neighboring detectors may result in a visible stripe or band in the imagery. An accurate estimate of each detector’s relative gain is needed to account for any differences between detector responses. This paper describes a procedure for estimating relative gains which uses normally acquired Earth viewing statistics.

Conference Paper↗
USGS2015

Synoptic evaluation of scale-dependent metrics for hydrographic line feature geometry

Methods of acquisition and feature simplification for vector feature data impact cartographic representations and scientific investigations of these data, and are therefore important considerations for geographic information science (Haunert and Sester 2008). After initial collection, linear features may be simplified to reduce excessive detail or to furnish a reduced-scale version of the features through cartographic generalization (Regnauld and McMaster 2008, Stanislawski et al. 2014). A variety of algorithms exist to simplify linear cartographic features, and all of the methods affect the positional accuracy of the features (Shahriari and Tao 2002, Regnauld and McMaster 2008, Stanislawski et al. 2012). In general, simplification operations are controlled by one or more tolerance parameters that limit the amount of positional change the operation can make to features. Using a single tolerance value can have varying levels of positional change on features; depending on local shape, texture, or geometric characteristics of the original features (McMaster and Shea 1992, Shahriari and Tao 2002, Buttenfield et al. 2010). Consequently, numerous researchers have advocated calibration of simplification parameters to control quantifiable properties of resulting changes to the features (Li and Openshaw 1990, Raposo 2013, Tobler 1988, Veregin 2000, and Buttenfield, 1986, 1989). This research identifies relations between local topographic conditions and geometric characteristics of linear features that are available in the National Hydrography Dataset (NHD). The NHD is a comprehensive vector dataset of surface 18 th ICA Workshop on Generalisation and Multiple Representation, Rio de Janiero, Brazil 2015 2 water features within the United States that is maintained by the U.S. Geological Survey (USGS). In this paper, geometric characteristics of cartographic representations for natural stream and river features are summarized for subbasin watersheds within entire regions of the conterminous United States and compared to topographic metrics. A concurrent processing workflow is implemented using a Linux high-performance computing cluster to simultaneously process multiple subbasins, and thereby complete the work in a fraction of the time required for a single-process environment. In addition, similar metrics are generated for several levels of simplification of the hydrographic features to quantify the effects of simplification over the various landscape conditions. Objectives of this exploratory investigation are to quantify geometric characteristics of linear hydrographic features over the various terrain conditions within the conterminous United States and thereby illuminate relations between stream geomorphological conditions and cartographic representation. The synoptic view of these characteristics over regional watersheds that is afforded through concurrent processing, in conjunction with terrain conditions, may reveal patterns for classifying cartographic stream features into stream geomorphological classes. Furthermore, the synoptic measurement of the amount of change in geometric characteristics caused by the several levels of simplification can enable estimation of tolerance values that appropriately control simplification-induced geometric change of the cartographic features within the various geomorphological classes in the country. Hence, these empirically derived rules or relations could help generate multiscale-representations of features through automated generalization that adequately maintain surface drainage variations and patterns reflective of the natural stream geomorphological conditions across the country.

Conference Paper↗