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Predicting the outcome of flow and sediment transport events quantitatively has been difficult due to the complex nature of stream systems and the effects of woody vegetation on flow and sediment transport. Interactions between channel and floodplain flow, sediment transport, and woody vegetation have important implications for the health of riparian vegetation and as well as for contaminant transport and deposition. The goal of my research is to develop methods for the application and testing of predictive, process-based models (no empirically adjusted coefficients) that compute the flow and sediment transport from fluid mechanical theory for (1) known channel and floodplain topography and (2) measured tree and...
This project studies evaporation, groundwater mixing, surface-water circulation, groundwater/surface-water interactions, contaminant migration and remediation, and other hydrochemical and biologic processes. The isotope variations are related to (1) purely physical processes, (2) heterogeneous chemical equilibria, and (3) reaction kinetics. The isotope effects of many of these processes are not sufficiently understood or quantified to make the most effective use of stable isotope techniques in hydrologic research. This project aims to develop theoretical and instrumental mass spectrometric techniques through experimental investigation, and to test applications in suitable field locations to improve the utility of...
Uranium mill tailings and related forms of low-level radioactive waste contain elevated contents of naturally occurring radionuclides that have been brought to the surface, processed for the recovery of uranium and/or other components and then disposed of in near-surface impoundments. The long-term fate of the tailings and their constituents will be determined by surficial earth processes. Project objectives are to study the chemical form in which radionuclides and selected stable elements are retained in surficial earth materials, particularly uranium mill tailings, and to identify processes operating in natural aqueous and terrestrial systems that may influence the transport of these constituents from these earth...
Recent increases in the atmospheric concentrations of carbon dioxide and methane have emphasized the need for a more complete understanding of the processes that control carbon transfer among air, land, and water. Knowledge of the amount, rate and chemical form of carbon transfer across environmental interfaces, such as the land-air and water-air interfaces, is of particular importance. These fluxes are commonly controlled by a combination of physical, biological, and chemical processes at or near the interface. Isolation of the primary mechanisms that determine carbon transfer across the interface allows for development of process-based models that can be used for carbon mass transfer estimates at the ecosystem...
The overall objective of this project is to determine the role of chemical processes associated with dissolved organic carbon (DOC) on the transport and reactivity of both naturally occurring and anthropogenic compounds. Defining the roles of DOC in environmental and geochemical processes is critical to understanding the nature and quality of the Nation’s water resources, and is important for future management of these resources. This field of study has increased in relevancy as numerous environmental problems have been linked to processes involving organic matter. My project attempts to meet these needs by focusing on the chemical mechanisms controlling the fate, transport, and reactivity of naturally occurring...
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The “Hydroecology of Flowing Waters” project was initiated in 1998 with the aim to improve understanding of how stream and river corridors function naturally in ways that produce valuable ecosystem services (e.g. flood attenuation, carbon and nutrient storage and contaminant removal, habitat value for fish and wildlife, recreation). The research is increasingly focused on how aquatic ecosystem services can be better protected in the face of degradation resulting from accelerating land use and climate change. Central to the research is the investigation of interactions between physical and biological processes, e.g. how land use change affects hydraulics and channel geomorphology in ways that produce cascading...
Uncertainty in application of physically based surface-water hydrologic models is a function of adequacy of the conceptualization of the processes involved and of the quantity and quality of data available to use as input to the model. In any type of modeling exercise, even if the physical processes are well understood, spatial heterogeneities make application of the model on a basin-wide scale problematic, and it is almost always necessary to use some form of spatial averaging to obtain 'effective' input variables. The over-all goal of our research is to investigate: (1) Model output errors as a function of model complexity and uncertainty in model input, (2) Derivation of simplified yet physically based models...
There are a variety of ground-water resource and contamination problems that involve determining the state of ground water and detecting or predicting changes in the ground-water environment. Most approaches to ground-water monitoring network design avoid a rigorous formulation of the monitoring objectives and fail to consider the important processes controlling the movement of ground water and migration of ground-water contaminants. It is unlikely that such approaches to network design will be able to effectively and efficiently monitor the subsurface environment in the face of limited resources. This research aims to develop statistically sound and simulation based methods for ground-water monitoring network design....
The overarching objective of this Project is to determine how and why biogeochemical cycles of macronutrients (i.e. C, Fe, S, etc…) and those for certain trace contaminants (e.g. Hg, Se, As, etc…) covary at the ecosystem and regional scales. General approaches to this end include: comparing and contrasting key biogeochemical pathways both within the sub-habitats of a given ecosystem and among systems that involve a wide range of land-use practices, fostering collaborations with other USGS and non-USGS scientists on projects that are regional in scope, have a fundamental biogeochemical/microbiological focus, and that balance basic environmental research with management / society ‘needs-driven’ research expanding...
Geophysical data are recorded for water wells and test holes, but interpretation is subject to significant uncertainties. The data are used in ground-water models to evaluate potential waste disposal sites and the effects of ground-water contamination and to guide development of aquifers, including geothermal reservoirs. The development of quantitative log-interpretation techniques to derive more accurate data and to evaluate the statistical uncertainty in the data will reduce costs in ground-water investigations. Project objectives are to (1) evaluate presently available logging equipment and log-interpretation packages and develop improved instrumentation and analytical techniques for specific ground-water problems...
Categories: Project; Tags: Fractured Rock, Hydrogeology
Project research is focused on two general objectives: first, to better understand the basic physics of coupled flow and sediment transport in geophysical flows; second, to develop practical tools based on that understanding that can be used in a predictive manner to aid in the management of the Nation’s rivers. Within the context of this overarching pair of long-term goals, the project has a number of specific shorter-term objectives, some of which are research oriented, and others of which are related to technology transfer or consultation on specific riverine issues. Our current research objectives are as follows: 1) Develop and test physically based methods for predicting the initiation, development, and response...
Biogeochemical processes associated with the microbial community (algae, bacteria, fungi) constitute the interface between solute transport and biotic production in riverine environments. Identifying and estimating the role of biotic processes such as nitrification and denitrification by bacteria, nutrient uptake and production by epilithic algal films and decomposition of particulate and dissolved organic matter, as well as abiotic processes such as absorption, are important for understanding the linkage between terrestrial, riparian, hyporheic and in-channel contributions to the nutrient chemistry of a drainage network. Relative biotic response to solutes in transport between pristine and anthropogenically modified...
Categories: Project; Tags: Ecology, Solute Transport
Many persistent organic compounds are hazardous to human and ecological health. The transport characteristics of these compounds across environmental phases are strongly influenced by adsorption and partition interactions with the individual phases. Quantification of process rates and partition constants of organic pollutants in air, water, soil, and biota is an important step in defining the level of organic contaminants in environmental systems and their potential impact on environmental quality. Project objectives are to delineate and quantify processes affecting the movement and distribution of persistent organic compounds in hydrogeologic systems. Specifically: (1) determine the sorptive capacity of soil and...
Categories: Project; Tags: Contaminants, Organic Compounds
Natural water systems provide a wide range of conditions within which to examine the geochemical behavior and cycling of trace elements and nutrients relative to hydrochemically important mineral reactions. Processes of mineral dissolution, alteration and genesis exert strong controls on the concentrations of chemical species in natural water systems and thus on water quality. Chemical composition of atmospheric precipitation input to terrestrial watersheds affects mineral reaction rates and may regulate reaction pathways and products. Knowledge of the geochemical behavior and cycles of major elements, trace elements, and nutrients is essential in order to understand and predict the consequences of deliberate or...
Ground-Water solute-transport simulation modeling is an important tool that aids in the analysis of ground-water contamination problems, both actual and potential. Accidental spills, leakage, and waste disposal operations can lead to ground-water contamination. The ability to analyze and predict the movement of solutes in ground-water systems is necessary to assess the effects of a contamination situation or properly design a waste-disposal operation. Laboratory experiments are essential to understanding geochemical reactions in the field and for obtaining the necessary reaction coefficients and rate constants used in transport models. Simulation modeling also is used to compare alternative strategies for aquifer...
Delineate and quantify processes affecting the movement and distribution of pollutants in hydrogeologic systems. (1) Determine the sorptive capacity of soil and sediment for compounds of interest that are dissolved in water; (2) identify the roles of soil and sediment organic matter and mineral components in sorption of pollutants; (3) examine the interaction of natural organic matter with mineral surfaces and its consequent effect on sorption of compounds of interest; (4) characterize the effect of dissolved organic matter on the solubility and mobility of organic contaminants in natural water; and (5) determine the characteristics of pyrogenic soil components (black carbon) and its effects on fate and transport...
Categories: Project; Tags: Contaminants, Organic Compounds
Uranium mill tailings and related forms of low-level radioactive waste contain elevated contents of naturally occurring radionuclides that have been brought to the surface, processed for the recovery of uranium and/or other components and then disposed of in near-surface impoundments. The long-term fate of the tailings and their constituents will be determined by surficial earth processes. Project objectives are to study the chemical form in which radionuclides and selected stable elements are retained in surficial earth materials, particularly uranium mill tailings, and to identify processes operating in natural aqueous and terrestrial systems that may influence the transport of these constituents from these earth...
Regional assessment of the chemical character of ground water requires that unbiased estimates of the chemical species in ground water be obtained. With recent regulations regarding ground-water contamination and disposal of toxic wastes, it is necessary that the methods for assessment of man-induced versus natural chemical character are not biased by experimental design, and that estimates of chemical species present in ground water are not influenced to a large degree by temporal variation and sample collection strategies. It is a requirement as well that populations which are compared are homogeneous in terms of statistical parameters. Implementing statistical design techniques early in the water-quality assessments...
Categories: Project
Reconstructions of continental paleoclimates of the Pleistocene Epoch have relied almost exclusively on packrat midden, lacustrine, and speleothem records. The isotopic (deuterium, oxygen-18, carbon-13) record of calcitic veins marking the sites of fossil ground-water discharge, have not been utilized. Preliminary work indicates that such veins contain continuous dateable records of Pleistocene paleoclimate and paleohydrology. The paleohydrologic interpretations should also be pertinent to selection of sites for the disposal and long term isolation of toxic wastes. Project objectives are: (1) infer paleoclimate and paleohydrology of selected regions based on variations in isotopic content of calcitic veins of ground...
This project seeks to quantify, predict, and project the relative role of plant physiology, among other ecosystem drivers, on carbon, nutrient, and trace-metal biogeochemistry. Approaches span landscape-to-molecular scales as necessary to understand how human and stochastic alterations of wetland structure influence wetland function. Research sites represent a wide range of salinity and management conditions, from rice agriculture to coastal and restored wetlands. Primary goals include evaluating management and modeling approaches to quantify wetland carbon sequestration, greenhouse gas budgets and/or mercury methylation and export.


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