Filters: Contacts: {oldPartyId:17096} (X)
108 results (260ms)
Filters
Date Range
Extensions Types Contacts
Categories Tag Types |
Using long-term data records, this project is focused on two problems of importance to water resources managers. First, long-term streamflow records are being used to a) identify broad regional to national trends in floods and low-flows and relate them to possible causes (climate change, water management changes, land-cover changes, and ground-water level change) and b) determine whether there are patterns that relate to watershed size or climate characteristics. It is often stated in the popular press and in official publications on global climate change that we can expect increased variability, including larger and/or more frequent floods, and deeper and longer droughts, as a result of greenhouse warming. This...
Our research focuses on developing methods to analyze volcano-hydrothermal systems and on the application of these methods to particular volcanic systems in the western United States. Specific research questions include (1) What are the modes of heat and mass transport from magma to the shallow subsurface? (2) What are the pressure, temperature, and fluid-saturation conditions between magma and the land surface? (3) What controls the permeability of volcanoes? How does it vary in space and time? What role do temporal variations in permeability play in the evolution of volcanogenic hydrothermal systems and episodes of volcanic unrest? (4) How well-coupled are various fluid flow, transport, and mechanical deformation...
Categories: Project;
Tags: Geothermal Resources,
Groundwater Flow and Transport,
Hydrogeology,
Volcanic Hazards
The NRP had its beginnings in the late 1950's. Since that time, the program has grown to encompass a broad spectrum of scientific investigations. The sciences of hydrology, mathematics, chemistry, physics, ecology, biology, geology, and engineering are used to gain a fundamental understanding of the processes that affect the availability, movement, and quality of the Nation's water resources. Results of NRP's long-term research investigations often lead to the development of new concepts, techniques, and approaches that are applicable not only to the solution of current water problems, but also to future issues that may affect the Nation's water resources. Basic tools of hydrology that have been developed by the...
Categories: Project;
Types: ScienceBase Project;
Tags: Acid Mine Drainage,
Aquatic Habitat,
Arid Land Hydrology,
Carbon Cycle,
Contaminant Reactions and Transport,
Understanding the effects of climatic variability is important to development of water resources, mitigation of flood hazards, and interpretation of geomorphic surfaces. Climatic variability, which is characterized by temporal changes in variability of seasonal climate that spans decades or centuries, may be more important to water-resources evaluations than changes in mean climatic conditions. Changes in variability of climate has a large effect on the probability of occurrence of extreme events, such as floods or droughts. Understanding of climatic variability and its effect on the landscape is of paramount importance for estimation of flood frequency, sediment transport rates, and long-term watershed and channel...
This project is focused on developing objective methods for evaluating USGS hydrologic-data-collection activities; such methods are needed so that activities can be modified when necessary and the efficiency of USGS operations maximized.
Categories: Project;
Tags: Statistical Hydrology
The goal of my biodegradation research is to understand the processes controlling the rate of biodegradation of contaminants in the subsurface. This understanding will form the basis of methods to increase degradation rates without causing further degradation of groundwater quality. Recent work has focused on the fate of crude oil and agricultural nitrate contamination in the subsurface. Specific objectives for the crude oil research include: (a) determine the rate that contaminants are transported from the source zone; (b) provide an estimate of how long the spilled oil will continue to pollute the groundwater; and (c) determine the fate of products of biodegradation or so-called “secondary water quality impacts”...
Modeling of watershed response to normal and extreme climatic conditions or to changes in the physical conditions of a watershed requires the simulation of a variety of complex hydrologic processes and process interactions. Some of these processes are well understood at a point or for a small area; others are poorly understood at all scales. Increasing spatial and temporal variability in climate and watershed characteristics with an increase in watershed area adds significantly to the degree of difficulty in investigating and understanding these processes. Research is needed to better define these processes and to develop techniques to simulate these processes and their interactions at all watershed scales. Project...
The overall objective of the MoWS research group is to gain better understanding of the precipitation-runoff processes and use this knowledge to develop improved hydrologic models. The main research topics include: 1) Add functionality and improvements to the MoWS simulation models being developed and integrate with other hydrologic, hydraulic, and climate models. 2) Enhance the models to use the best and latest topographic, climate, geologic, and land-use data sets as direct input to process algorithms to increase the physical nature and temporal and spatial resolution of model input. 3) Develop national model structure and calibration strategy for national model application.
The objectives of my research are (1) to synthesize observational estimates of continental water and energy fluxes and storage; (2) to construct global computational models of continental water and energy fluxes and storage; (3) to identify physical controls, natural and anthropogenic, on spatial and temporal variability of water and energy fluxes and storage; and (4) to elucidate the hydrologic causes and effects of Earth-system variability and change, including climatic, biospheric, and geodetic processes.
Categories: Project;
Tags: Climate Change,
Evapotranspiration,
Hydroclimatology (including droughts and floods)
Our research seeks to evaluate and understand the processes that control and respond to changes in the level of CO 2 in the atmosphere. Our interests include the natural cycling of CO 2 and carbon through plants, soils, seawater, rocks, and sediments. We study the causes and effects of past geologic changes in atmospheric CO 2 levels, and the ongoing effects of human actions on CO 2 and climate.
The purpose of my research group is to develop new methods and applications of environmental isotopes to solve problems of national importance. In specific, the overall goal is to use environmental isotopes, combined with other biogeochemical measurements and hydrologic and biogeochemical modeling, to increase our understanding of biogeochemical and hydrological processes, nutrient and organic matter sources, subsurface flowpaths, and water age distributions in diverse environments. Many of our studies piggyback on the sampling efforts of major monitoring programs to investigate causes of hypoxia and food web problems. Our work provides critical scientific support for these monitoring programs. A long-term career...
Organic substances in streams affect the water quality and uses of the water. To determine the effect of organic substances on water quality, the physical, chemical, and biological processes involved in the transport and degradation of these substances must be understood. Procedures for measuring or estimating the rate coefficients describing these processes must be developed. Models using these coefficients must then be developed for predicting the fate of organic substances in streams and their effect on water quality. Project objectives are: (1) to study the fundamentals of volatilization, dispersion, and sorption on sediments of organic substances in water; (2) to develop sub-models of these processes including...
Categories: Project;
Tags: Organic Compounds
Movement of toxic and radioactive substances in aquifer systems occurs in all three phases and is controlled by both hydrologic and chemical forces. Solute movement can be greatly affected not only by physical dispersion, but by other factors such as exchange sorption, chemical kinetics, and ionic distributions. Movement of gases and particulate material in the unsaturated zone are controlled by many additional factors. Knowledge of how these physical and geochemical factors affect prediction of movement of toxic and radioactive wastes is only generally known for ideal systems. This project's objective is to develop field methods and techniques that will yield values for physical and geochemical factors of regional...
Categories: Project;
Tags: Groundwater Flow and Transport,
Radioisotopes,
Solute Transport,
Unsaturated Zone
a) Developing defensible conceptual models of processes influencing the mass transfer of inorganic contaminants between aqueous and solid phases. b) Translating conceptual models into quantitative models that can be used to predict the influence of mass-transfer processes on contaminant fate and transport in field applications. c) Developing approaches to obtain parameters required to describe contaminant mass transfer in quantitative fate and transport models that are, to the maximum extent possible, independent of field observations. d) Testing these approaches in laboratory experimental studies, field experimental studies, and field-scale plume characterization studies.
Efficient management of ground-water aquifers and geothermal reservoirs requires accurate estimates of the hydraulic properties of water-bearing formations. These are needed to predict water- level changes, aquifer storage capacity, and the rate of movement of chemical species or thermal energy. Analytical models, properly applied, can often be used to estimate the hydraulic and transport properties of complex aquifer systems. This project's objective is to obtain analytical solutions to specific problems of flow and transport in water- bearing formations that can be used for evaluating the hydraulic and transport properties of aquifers and geothermal reservoirs.
The mechanisms that control the composition of river-borne materials are only imperfectly understood, because both erosion and the subsequent transport of material by rivers are mediated by a wide variety of highly-linked chemical, biological, and physical processes. Moreover, in developed river systems, such as those in the United States, these processes are subject to pervasive human- related perturbations. This project studies weathering, erosion, and atmospheric-exchange processes which are the sources of dissolved and particulate material in rivers and trace substances in the atmosphere; studies chemical partitioning of various phases during transport in rivers and estuaries; describes the dispersal pathways...
To elucidate and quantitatively explain the behavior of hydrogeologic systems typically characterized by hydrogeologic and physics-based complexity and data scarcity, for purposes of developing theory when needed, and with a focus on practical management (use and preservation) of water-resource systems to benefit humankind.
Categories: Project;
Tags: Contaminants,
Groundwater Flow and Transport,
Groundwater Hydraulics,
Hydrogeology
Aquatic humic substances and other classes of dissolved organic material present in natural waters can control the biogeochemistry of trace metals and other solutes and can influence ecological processes in lakes and streams. The nature and reactivity of the dissolved organic material is in turn influenced by biological, chemical, and physical processes occurring in the aquatic environment. Recent advances in isolating and characterizing different fractions of the dissoloved organic carbon (DOC) and in measuring rates of microbial processes can be used to advance the understanding of the dynamic relationship between aquatic biota and dissolved organic material and trace metals in different environments. Project...
To study the mechanisms, pathways, and rates of transformation of carbon and nitrogen compounds (natural and contaminant) mediated by microorganisms in aquatic habitats and identify factors controlling these transformations and to examine the effect that these transformations have upon other biogeochemical processes.
Categories: Project;
Tags: Carbon Cycling and Sequestration,
Ecology,
Microbiology (Activity and Transport),
Nitrogen Cycling
Permeability – the ease of fluid flow through porous media – varies about 17 orders of magnitude in geologic media. My research concerns fluid and solute transport in the low part of the of the range (~ 10-19 – 10-25 m2), where measurements are difficult, standard relations such as Darcy’s law are unverified, and unfamiliar phenomena that include osmosis and ultrafiltration affect movement of water and solutes. Testing can sample only small volumes of low-permeability formations, and finding ways to characterize them on regional scales – and thereby detect leakage through fractures and faults - is especially important for problems such as repository siting, CO2 and other waste injection, and protection of aquifers....
|