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Browsing by Author "Contractor, Dinshaw N."

Now showing 1 - 11 of 11
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    Agricultural engineering: hydrologic and water quality modeling of surface water discharges from mining operations
    Herricks, Edwin E.; Shanholtz, Vernon O.; Contractor, Dinshaw N. (Virginia Agricultural Experiment Station, 1975-01)
    Studies were undertaken to develop methods whereby a better understanding of the impact of mining on drainage from a specific area could be achieved.
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    Factors affecting water quality from strip-mined sites
    Connell, J. F.; Contractor, Dinshaw N.; Shanholtz, Vernon O. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1976)
    This project analyzed the parameters that influence the quality of water from strip-mined sites. An instrumented watershed near Beckley, W. Va., provided data on precipitation, stream flow, and water quaIity, both before and during mining operations. This data was analyzed to derive linear relationships between a water-quality parameter and such variables as temperature, current and antecedent precipitation, and the extent of the area disturbed by mining. Mathematical formulae representing sulfate and calcium concentration, alkalinity, turbidity, conductance, and discharge were used in the study. A correlation analysis also was made among the various water-quality parameters. A formula for each water-quality parameter was derived for each of three different conditions: (1) before mining; (2) during mining for the disturbed area alone, and (3) during mining for the entire watershed. The coefficients in the formulae then were refined for minimum error. As is reported in the findings, the coefficients indicate that temperature is not an important water-quality consideration except in the case of alkalinity. The coefficients of the antecedent precipitation terms indicate that, in most cases, surface runoff is the basic mechanism by which the substances affecting water quality are conveyed from the disturbed area into a receiving stream. The findings provide data that can be used in the future for predicting water-quality impacts from strip mining operations at particular sites in the study area.
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    A finite element analysis of dissolved oxygen drawdown and sulfate production in strip mine spoil dams due to pyritic chemical reaction
    Amend, Joseph Henry (Virginia Tech, 1975-05-06)
    The problem of dissolved oxygen drawdown and sulfate production in strip mine spoil dams due to chemical reaction between an excess of pyrite, water, and dissolved oxygen is investigated. A finite element analysis is used to solve the diffusion-convection equation assuming steady state conditions and no internal oxygen sources. Oxygen recharge along the free surface is permitted. The analysis is performed in three steps. Step one calculates the nodal piezometric heads and elemental bulk fluid velocities. Steps two and three determine the nodal dissolved oxygen and sulfate concentrations. Solutions are presented for a wide range of soil permeabilities and dissolved oxygen reaction coefficients. It is found that as the dissolved oxygen reaction coefficients. decreased, the dissolved oxygen deficit decreased and the sulfate concentration increased. From these results it was found that the maximum dissolved oxygen deficit occurs at an internal point in the dam and the maximum sulfate concentration occurs on the downstream face of the dam. The computer program used in the analysis is written in FORTRMi IV computer language and requires a minimum of programming knowledge to implement.
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    GEM, generalized estuary model: a variation on the Schodfield- Krutchoff stochastic model for estuaries
    DePietro, Sandra Ann (Virginia Tech, 1975-08-05)
    In recent years, many mathematical models have been developed to be used as mechanisms for carrying out stream and estuary investigations. In 1971, W.R. Schofield and R.G. Krutchkoff completed work on a stochastic model in an attempt to accurately describe the behavior of an estuary. Through the use of a high-speed computer this one-dimensional model predicts the concentrations of twelve interacting components, subdivided into five biological and seven chemical factors. This is a valuable tool, but from a practical viewpoint, the model is difficult to apply without a fairly strong background in computer science. It is the aim of the present study to simplify the use of the SchofieldKrutchkoff estuary model so that it can be readily accessible to the appropriate personnel, irrespective of their previous exposure to computer programming. Dependent upon the particular estuary studied, it was necessary to make internal program adjustments with respect to boundary conditions, applicable rate constants, tidal lag, and maximum tidal velocity rates. These constants have been replaced by variables for the user to define as input data to the main program segment. The options to choose one of several expressions for the oxygen reaeration rate K₂, whether to weight this equation with wind velocity, vary the volumetric freshwater flow rate with position and request plotted output for each day modeled have also been added.
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    An integrated modular watershed planning model applied to the Upper South River watershed, Waynesboro, Virginia
    Steger, Charles W. (Virginia Tech, 1978-07-01)
    The problems associated with urban development and its resultant effects on environmental quality present increasingly complex decisions for elected and technical officials. Current approaches to modeling often result in the development of models which are too complex to be understood and require such long time periods to be modified that by the time the model is operational the problem has changed. A modular modeling framework is proposed which considers land use, runoff, and water quality and connects these factors to a budgetary function. In addition, the modular configuration facilitates the process of modifying components of the model in response to a changing problem environment. In order to test the feasibility of the proposed modeling approach, the model is applied to the Upper South River watershed, Waynesboro, Virginia. The following three alternative development plans are evaluated: 1. To permit no additional population growth and preserve the area for agriculture and recreation. 2. To permit concentrated development in the form of two new communities each with a population of three thousand persons. 3. To increase the population by three thousands persons but to allow development to continue to follow the existing pattern of urban sprawl. The study concludes by stating that if zoning ordinances and comprehensive plans focus on consolidating development within the framework of existing water and sewer networks, the cost of providing the sewer network for Alternative 2 will be ten million dollars less than Alternative 3 for the same increase in population.
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    A Model for evaluating the effect of land uses on flood flows
    Ross, Burton Blake; Shanholtz, Vernon O.; Contractor, Dinshaw N.; Carr, Jan C. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1978)
    A basic problem facing modelers of natural watershed systems has been that of accounting for heterogeneities that generally are present. It has long been recognized that such factors as soil, cover, management, and slope tend to cause heterogeneity in the runoff response...
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    Model for simulating runoff and erosion in ungaged watersheds
    Ross, Burton Blake; Wolfe, Mary Leigh; Shanholtz, Vernon O.; Smolen, M. D.; Contractor, Dinshaw N. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1982)
    This research, which developed a distributed parameter model for simulating runoff in ungaged areas, can assist in nonpoint pollution control planning efforts. The sediment detachment and transport component of this finite element storm hydrograph model (FESHM) enables its additional use for simulating erosion processes which result from runoff. Though not dependent on calibration, the FESHM, when applied to fieldscale areas, does require extensive information on the field's soils, topography, and cover characteristics. Application of the FESHM, however, is not limited to field-scale areas. Although most research using the model has been conducted on watersheds of 2 to 1,000 acres, it has performed adequately on watersheds as large as 193 square miles. The FESHM's hydrologic section compares favorably with other watershed models currently in use (ANSWERS, H EC-1, TR-20, and USGS State Equations), in terms of data preparation and execution costs. A sediment washload capability has been demonstrated but presently remains unverified. Work is progressing toward verification.
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    Modeling the effect of waste discharges in a small mountain stream
    Hoehn, Robert C.; Childrey, Mitchell R.; Contractor, Dinshaw N. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1975)
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    Numerical studies of unsteady flow of the James River
    Contractor, Dinshaw N.; Wiggert, James M. (Water Resources Research Center, Virginia Polytechnic Institute and State University, 1972)
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    A solution of the two parameter gamma model to relate unit hydrograph features to basin characteristics
    Cruise, James Franklin (Virginia Tech, 1977-11-15)
    The problem of correlating unit hydrograph features to topographic and man-made basin characteristics received attention in this report. The unit graph features considered herein were the peak discharge and the time lag of basin response. In order to facilitate the desired regression analysis, the two-parameter gamma model proposed by Edson was utilized in the investigation. The parameters of the model were obtained by the simultaneous solution of the equations for unit graph peak and lag using observed unit hydrographs for 16 basins in the Piedmont region of North Carolina and 14 basins located in Northern Virginia. In the opinion of many, these parameters are a better measure of the complex relationship which exists between the runoff from a basin and the topographic features of that basin than are the values of the unit graph peak and lag time themselves. The basin characteristics utilized in the investigation were: basin area, length of the longest streamcourse in the basin, average stream slope between points 10 percent and 85 percent downstream of the headwaters, and the percent of the impervious area contained in the basin. This last factor served as a measure of the amount of urban development present in the watershed. The investigation was hampered by a regrettable lack of sufficient data to derive regression equations of good reliability. This fact was due to the reduction of the data into groups by narrow geographical ranges. Thus, the number of stations available for analysis in anyone group was insufficient for purposes of a reliable regression analysis. From the investigation, it appears that the most significant basin characteristics affecting runoff are length, slope, and urban development. The strongest regression equations were derived using those three characteristics. It appears that the length and slope factors give better results when combined in the form (L/√S).
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    Streamflow and water quality modeling of the Chowan River
    Contractor, Dinshaw N.; King, Paul H. (Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University, 1980)
    The Chowan River system in Southeast Virginia consists of three rivers that form two confluences before flowing into Albemarle Sound in North Carolina. This study investigated, by means of numerical simulation, the river's water quality problems related to excessive algal growth. A computer program was developed to determine flow rates, velocities, and depths at 51 computer stations by routing flows through the river system. The output of this flow program provided the input for calculating the concentrations of biochemical oxygen demand (BOD), chemical oxygen demand (COD), dissolved oxygen (DO), and four nitrogen parameters (organic, ammonia, nitrite-nitrate, and algal) at each of the computer stations. The four nitrogen parameters were solved for simultaneously. Measured field data collected in 1974. were used to calibrate the model. The program was then used to simulate algal growth for 1974 and 1975 and was compared with measured data for verification of the program. The program was also used to study management strategies for water quality control. The first such plan was to measure the effects of reducing the concentration of nutrients from overland runoff on algal concentrations at the mouth of the river. Another application of the program assumed the watershed to consist only of forests and nutrient runoff from the forests to be the river's only nonpoint source of pollution. This primeval condition resulted in roughly half the concentrations measured in 1974.