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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...
To measure, predict, and understand the flow of water through the soil and rock of the unsaturated zone. Specifically to advance (1) knowledge of aquifer recharge rates for improved management of water resources, (2) the assessment and quantification of hazards from contaminants near the earth's surface, and (3) the understanding of soil moisture processes in relation to ecological habitat. Results are directed toward large-scale problems of water quality, water availability, land-use evaluation, and environmental impacts of climate change.
Characterizing Groundwater Flow and Chemical Transport in Fractured Rock From Meters to Kilometers: The objectives of my research are to develop a conceptual understanding of geologic, geochemical, and biological processes that affect groundwater flow and chemical transport in complex geologic settings, such as fractured rock and karst aquifers, and to test hypotheses under field scale conditions. Because the geologic complexity of fractured rock and karst aquifers can manifest itself differently over increasingly larger physical dimensions, the formulation of hypotheses and the design of field scale experiments are undertaken over physical dimensions that range from meters to kilometers.
The responsible use of our Nation's ground-water resources requires an ability to predict changes in water quality as a result of human impacts. Prediction of chemical quality in the ground-water environment depends on a detailed understanding of both chemical and hydrologic processes. To determine the spatial and temporal variability of ground-water quality, it is necessary to identify reactions occurring in the system, to define their kinetic and thermodynamic properties, and to determine how the configuration of the hydrologic regime influences ground-water quality. The objectives of this project are to: (1) identify chemical reactions in ground-water systems using observed chemical and isotopic composition of...
There is a general lack of knowledge of fundamental processes governing the fate and transport of anthropogenic organic compounds in surface and ground waters. Interactions of organic contaminants with natural organic coatings on sediments and aquifer porous media are not well understood. Furthermore, abiotic and biological transformations of organic contaminants in surface and ground waters require extensive fundamental investigations if their effects on Water Quality are to be understood. Objectives are to (1) determine physicochemical and biological processes, controlling the fate and transport of organic compounds in surface and ground waters; (2) determine bioavailability of hydrophobic organic contaminants...
My research aims to improve fundamental understanding of gas evolution and multiphase fluid flow within water-saturated, deformable porous media. These processes are governed by concurrent fluid-fluid and fluid-rock interactions such as chemical mass transfer, capillarity, buoyancy, viscous drag, and effective stress. Potential applications for the fundamental knowledge that I aim to generate include geologic radioactive waste storage, carbon sequestration, and hydraulic fracturing.
An important challenge of the 21st century is the global water challenge that is exacerbated by recent droughts and rapid population growth. Water shortages have led to increased reliance on groundwater and broad reductions in groundwater resources. As demands for water resources increase, our understanding of interconnections between the hydrologic cycle and our environment increasingly become more important. Moving into the future, approaches are needed for sustainable management of water resources in order to maintain robust water-dependent systems on earth. Our research aims to better understand local and regional hydrologic processes affecting humans and the environment. Our focus is on the development of...
Advance the utility of environmental models by improving how models are tested against data and how they are used to understand simulated processes, predictions and prediction uncertainty. This includes ways of making models more transparent and refutable. Making a model transparent means that tests of model adequacy are clearly defined and conducted and the importance of different aspects of the model to predictions of interest are readily apparent. Thus, in more transparent models it is easier to determine what data and simulated processes dominate model development, predictions, and measures of prediction uncertainty. I consider sensitivity analysis to be a primary way of making models more transparent. Making...
<p>The overall objective of my research is to understand the movement and quality of surface and groundwater using geochemical approaches. Some key issues that are considered in this research are the environmental aspects of energy and mineral resources, climate change, and carbon cycling and sequestration. The geochemical approaches that are used in this research include the use of isotopic tracers, trace elements, and radioisotopes. My research has focused on the sampling and analysis of produced waters from geologic carbon sequestration studies, geochemical characterization of sediment transport in the coastal zone, the environmental chemistry of mercury in coastal regions, and water quality analysis for samples...
1) To better understand linkages between climate (and other perturbations such as land use change and fire) and variably saturated subsurface flow with focus on hydrologically extreme environments including arid to semiarid regions and subarctic to arctic permafrost systems, and 2) to simulate/predict hydrologic and related impacts resulting from system change by integrating cutting-edge data from remote sensing and geophysical methods into innovative numerical models.
Toxic contaminants and naturally occurring substances found in the subsurface can exist in multiple phases, and undergo complex reactions including biodegradation. A comprehensive and quantitative understanding of the processes controlling the fate and transport of subsurface contaminants is necessary to develop policies and strategies for managing water-quality conditions in different land use and environmental settings. Numerical models that simulate flow, transport, and reactions are useful tools for understanding the fate of chemicals in the subsurface when used in conjunction with field and laboratory studies. The research efforts of this project consider flow and chemical behavior in the saturated and unsaturated...
Improve our understanding of groundwater flow and transport by developing and using environmental tracers to characterize groundwater flow and transport, and by developing new methods for combining tracer analysis and groundwater model calibration.
My goal is to improve the quality of groundwater modeling both inside and outside the USGS by making it easier for modelers to create models and to examine the results of those models. I do this, in part, by writing graphical user interfaces for the models. Another important aspect of my work is to provide support for modelers who have run into technical difficulties.
Various processes within the unsaturated zone affect ground-water availability and portability, as well as concentrations of water vapor and trace gases in the atmosphere. The rate at which precipitation or applied irrigation water infiltrates, its redistribution following infiltration, and the partitioning of the redistributed soil moisture between ground-water recharge and evapotranspiration affect the rate at which the ground-water reservoir is replenished and the degree to which ground water might be contaminated by chemical applications, spills, or disposal. Consequently, knowledge of and methods to quantitatively measure and predict these processes are needed to determine the impact of such societal practices...
The goal of my research is to develop innovative approaches for the detection trace gases and expanding our understanding of their environmental cycles. Dissolved gases can be used as age tracers and climate markers, provide information about biological activity and recharge conditions, and provide unique fingerprints of superficial activity in aquifer systems. This sort of information is valuable to both scientific and resource management communities, and there are many benefits to enhancing our knowledge of the class of compounds.
Develop, enhance, and extend theory and methods to investigate and characterize fluid flow, solute transport, heat transport, and stress/deformation changes in fractured and porous media for application to diverse areas, including the assessment of groundwater availability in bedrock terrains, remediation of contaminated sites, and evaluation of potential hazards such as induced seismicity from fluid injection.
Research Objectives: Brian uses field and laboratory measurements combined with numerical modeling to understand hydrologic processes and problems in disturbed landscapes. His research seeks to understand water and solute movement, plant community recovery, and the changes in hydrologic processes and associated water resources after landscape disturbances. Brian's work spans multiple scales, investigating the plot- and catchment-scale processes that dictate the emergent behaviors observed at watershed scales. Additional research interests include hydrologically-driven slope failure, sediment transport, soil physics, contaminant transport, and surface-water/groundwater interaction.
The responsible use of our Nation's ground-water resources requires an ability to predict changes in water quality as a result of human impacts. Prediction of chemical quality in the ground-water environment depends on a detailed understanding of both chemical and hydrologic processes. To determine the spatial and temporal variability of ground-water quality, it is necessary to identify reactions occurring in the system, to define their kinetic and thermodynamic properties, and to determine how the configuration of the hydrologic regime influences ground-water quality. The objectives of this project are to: (1) identify chemical reactions in ground-water systems using observed chemical and isotopic composition of...
Apply reactive transport models in groundwater to gain understanding of the processes controlling the fate of geochemical species. Develop and apply methods to incorporate small scale information into large scale simulations of groundwater transport in order to formulate more robust modeling approaches and results. Quantify the uncertainty inherent in reactive transport models including both the uncertainty of model parameters as well as the uncertainty in conceptualization of the problem.
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...