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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...
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, All tags...
Many difficult problems in river mechanics may have stemmed from inadequate understanding of the multiplicity and interaction of fluvial processes. Some of the problems may have been solved, but in a very simplified, approximate way. Many efforts have been directed, but without apparent success, to fully account for the causes, occurrences, and mechanisms of catastrophic events, such as flash floods, debris flows, and channel changes resulting from torrential storms, sudden snow or glacier melt, dam break, volcanic eruptions, and earthquakes. Such failures may be partially attributed to the deficiency and incompleteness of existing empirical formulas (or models) representing the relationships between various processes...
Climate displays an often-unrecognized order in both time and space. What may appear as a random sequence of precipitation at a point or within a watershed is actually the local expression of a broad integrated system of weather processes that are active on scales of 100’s to 1000’s of kilometers. Only when climate forcings and hydrologic responses are considered from a regional perspective does the order become evident. Understanding these regional processes provides a sound basis for national, regional, and local hydrologic analysis, resource management, and hazard assessment/mitigation. The objectives of this research are (1) to identify and quantify relations between large-scale atmospheric circulation and sea-surface...
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...
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...
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...
Sediment moves through a river system in response to specific events and changing conditions in the drainage basin. The movement of sediment is usually discontinuous. Episodes of movement are separated by periods of storage that can range from less than a year to more than one thousand. Understanding the movement and storage of sediment in rivers is important to navigation, flood control, and other aspects of river engineering, as well as to the prediction of the fate of contaminants adsorbed on sediment particles. This project's objectives are to assess: (1) changes in river sediment loads over periods of decades or longer, and the factors (natural or artificial) that cause the changes; (2) rates at which sediment...
The geometry and pattern of river channels adjust to significant changes in the water discharge, size, and quantity of sediment supplied to the channel. When the quantity of water and sediment over a period of years remains relatively constant, the channel geometry and pattern vary about a mean of quasi-equilibrium conditions. Major watershed alterations that change the supply of water, sediment, and size of sediment reaching the channel necessitate an adjustment of the channel geometry and pattern. That is, the channel is transformed from one quasi-equilibrium state to another. Between the two quasi-equilibrium states, there is a period of instability and adjustment. The dynamics and rate of river channel adjustment...
This project focuses on sediment erosion and deposition processes associated with disturbed watersheds and the essential processes needed to predict evolution of river systems. The objectives are to understand: a. Spatial and temporal character of rainfall and the transformation of rainfall into runoff, which controls erosion and deposition. b. Hillslope runoff processes characterized by shallow, unsteady flow where the relative roughness causing friction can be much greater than, for example, in perennial channels with nearly steady flow. c. Geomorphic and scale effects of channel networks on the prediction of the runoff hydrographs. d. Coupling of biologic and geomorphologic processes to predict erosion and...
Technical solutions to the problem of investigating and managing waste movement and disposal in regulated rivers, estuaries, and embayments require qualitative and quantitative assessment of the interactions between waste constituents undergoing dynamic transport. Mathematical, numerical, computer-simulation models offer one very powerful solution. Because water is both the vehicle by which the waste constituents are transported and the media in which the constituent interactions occur, the temporal and spatial variations of the flow appreciably govern the interactions both qualitatively and quantitatively. Design of the desired simulation models depends in large measure upon accurate mathematical/numerical representation...
To anticipate the effects of potential climate change (natural or anthropogenic) on hydrology and to assess hydrologic trends will require an understanding of past long-term hydrologic variability. There also is a critical need for data on extreme floods for better understanding flood processes, in engineering hydrology, flood-hazard mitigation, and other disciplines requiring flood-risk assessments. Probably the best information on hydrologic variability and extreme floods is provided by paleohydrologic and other proxy data analyzed with the help of hydrologic models. Methods for extending existing climatic and hydrologic records over long-time scales are needed. A relatively new approach, one that complements...
The regional nature of hydrologic processes is generally defined in terms of shared meteorological and basin characteristics. Inferences have been attempted by regressing the parameters of hydrologic interest against these characteristics. Such analyses have not been able to fully explain the variations, extremes or persistence of discharge patterns observed within a geographic area. An accounting of anthropogenic effects on basin characteristics needs to be made. Longer term influences such as decadal to centennial, and millennial climatic fluctuations need to be considered, and the stochastic structure of the hydrologic process itself needs to be studied. The objectives of this project are (1.) to develop secular...
The acquisition and meaningful interpretation of sediment data from areas disturbed by land-use activities or natural processes are two of the most deficient areas of recognizing nonpoint-source pollution in the United States. The comparison of sediment data from disturbed and undisturbed areas provides a means to (1) evaluate the effects that land-use activities cause, (2) investigate the geomorphic processes that regulate the detachment and transport of sediment, and (3) develop strategies for remedial action to reduce excessive sediment discharges. This information is especially necessary to minimize sediment discharges and sorbed chemical loads from surface-mine, industrial, agricultural, and urban areas. Objectives...