bluuebunny/crossref_metadata_2025 huggingface dataset:
A timber‐water simulation model for lodgepole pine watersheds in Colorado Rockies
Authors: Betters David R.
Published: February 2008

A deterministic, dynamic joint production simulation model was developed to predict annual timber and water yields over an extended time period. The model provides for testing the long‐term effects of various managerial strategies and thus acts as an aid to analyzing and studying proposed management plans. The simulation may be applied to lodgepole pine subalpine watersheds along the Colorado Rocky Mountain Front Range region. The input requirements for the simulation include initial stand conditions, stable site characteristics, watershed location along the Front Range, and the proposed timber‐harvesting schedule. The simulator was tested by comparing model predictions to observed records of two Colorado watersheds. The average error of estimation in predicting long‐term water yields was about 14%.
The large‐scale regional plant hypothesis: Discriminant analysis
Authors: Marsden James R. , Pingry David E. , Whinston Andrew
Published: February 2008

This paper pedagogically outlines (1) means to check the consistency of data collected for large‐scale data ‘banks’ and (2) a basic consideration of the regional treatment plant efficiency hypothesis giving the approach and technique rather than expounding the ‘results.’ Implementation of pollution control acts has required the compilation of vast amounts of data. Up to this point, emphasis has been on data collection and storage. The present suggested approach is one which could easily provide the means to move in the direction of checking the consistency of the data and identifying cases for special study.
Infiltration analysis and perturbation methods: 1. Absorption with exponential diffusivity
Authors: Babu D. K.
Published: February 2008

Simple perturbation methods are employed to analyze the horizontal absorption of moisture in unsaturated soils. The special case treated assumes the diffusivity to be an exponential function of the concentration and the concentration at the boundaries to be constant. The solution emerges as an explicitly determined power series in the Boltzmann variable.

The resulting profiles are compared with some others found in the existing literature. A discussion about the relevance and advantages of this type of analysis forms the concluding part of the paper.
Algorithm for solar radiation on mountain slopes
Authors: Swift Lloyd W.
Published: February 2008

A generalized algorithm provides the daily total of potential solar radiation on any sloping surface at any latitude. The algorithm can be coded as subroutines of a computer model that requires solar radiation as a variable. The required inputs are Julian dates and the latitude, inclination, and aspect of the slope. In addition to computing potential solar radiation, the routine provides estimates of actual radiation on any slope on the basis of measured solar radiation for a nearby horizontal surface that has the same cloud cover.
A proposed algorithm for the solution of the large‐scale inverse problem in groundwater
Authors: Chang Shin , Yeh William W‐G.
Published: February 2008

This paper introduces a new algorithm for the solution of the problem of parameter identification associated with a two‐dimensional unsteady state groundwater flow. The parameters to be identified are functions of the space variables. It is assumed that some observations on the dependent variable of the governing equation are available. The unknown parameters are directly identified from observations. An implicit finite difference scheme is used to approximate the original partial differential equation. A least squares criterion function is employed. The identification problem is then formulated as a standard quadratic programing representation by quasi‐linearization. The formulation is further modified by a simple matrix operation which drastically reduces the dimension of the constraint set. The new algorithm is shown to be very effective in solving the large‐scale inverse problem, and it is easily implemented, rapidly convergent, and able to handle any inequality constraints, a feature that is essential for such a problem.
Atmospheric input of some cations and anions to forest ecosystems in North Carolina and Tennessee
Authors: Swank Wayne T. , Henderson Gray S.
Published: February 2008

The atmospheric contributions of elements in precipitation and dry fallout to forest ecosystems were measured at two sites in the southern Appalachians. At both sites, relative mean annual concentrations of cations in bulk precipitation were in the order Ca > Na > K > Mg. At the Coweeta Hydrologic Laboratory in North Carolina, average annual inputs of Ca++, Na+, K+, Mg++, and NH4‐N in 1970–1973 were 4.88, 3.52, 1.62, 1.01, and 0.52 kg/ha/yr, respectively. At Walker Branch, Tennessee, the inputs of these elements during the same time period were 15.73, 3.89, 2.99, 2.94, and 2.37 kg/ha/yr. The inputs Of NO3‐N, PO4‐P, and Cl−in 1972–1973 were 2.88, 0.19, and 8.53 kg/ha/yr at Coweeta. Inputs of NO3‐N and PO4‐P were 4.61 and 0.55 kg/ha at Walker Branch over the same period. One reason for differences in bulk precipitation chemistry was greater dry fallout for some cations at Walker Branch than at Coweeta. For both sites, dry fallout associated with local land use activities influenced seasonal concentrations of bulk precipitation except for Na+, which appeared to be partly derived from marine sources. Total inputs of elements are considered to be minimum estimates for both forest ecosystems due to sampling and analytical methods.
An analysis of the numerical solution of the transport equation
Authors: Gray William G. , Pinder George F.
Published: February 2008

Various finite difference and finite element methods for solving the one‐dimensional convective‐dispersive equation are investigated. A Fourier series analysis is performed to determine the dissipative and dispersive characteristics of these numerical methods. The analysis indicates that the commonly observed phenomenon of overshoot of a concentration pulse is due to the inability of the numerical schemes to propagate the small wavelengths which are important to the description of the front. Furthermore, the numerical smearing of a sharp front is due to dissipation of these small wavelengths. The finite element method was found to be superior to finite difference methods for solution of the convective‐dispersive equation.
Designing regionalized waste water treatment systems
Authors: Whitlatch Elbert E. , ReVelle Charles S.
Published: February 2008

The problem of determining the optimal number, location, and level of treatment for regional domestic sewage treatment plants along an estuary or river is considered. The formulation is one of minimizing the sum of treatment and transport (piping and pumping) costs such that water quality improvement goals for dissolved oxygen are met. Restrictions may also be placed upon the overall level of treatment (required secondary, required uniform, or least cost) if desired. An optimization procedure is developed which utilizes dynamic programing, linear programing, and heuristic location techniques in a series of steps which lead to progressively improved (lower total cost) solutions. The location procedure is intended for use by an engineer‐planner during the design stage and requires his participation and skilled judgment during the course of the algorithm. The technique is illustrated for the Delaware estuary for 22 domestic waste sources, nine potential regional sewage treatment plant sites, and 22 industrial waste sources. Results of the case study show considerable savings over previous nonregional treatment schemes.
Polluter Discriminant Analysis
Authors: Tock Donald G. , Wright Gordon P.
Published: February 2008

A unique water pollution data base for the U.S. coastal waterways and Great Lakes that has been evolving since 1965 is discussed in this paper. The pollution statistics in this data base are used to develop a model, using multiple discriminant techniques, to determine which pollution incident report variables will discriminate the polluter who reports his spill from the polluter who does not report his spill. The results of the analysis as given in this paper indicate that as few as nine variables, out of a possible 60 variables, provide reasonable discriminatory power.
Similarity of the mean motion of fluid particles dispersing in a natural channel
Authors: Day Terry J. , Wood Ian R.
Published: February 2008

The mean longitudinal motion of fluid particles dispersing in a natural river channel for distances up to 800 widths on a small mountain stream and up to approximately 1200 widths on the Missouri River is shown to be different from that predicted by a Taylor type dispersion model. The dispersing cloud is shown to exhibit the characteristics of a self‐similar process, with constant velocity ratios and geometric form, and a dimensionless time‐concentration curve is developed. Based upon the dimensionless coordinates of this form and the linearity of its scaling parameters, a method for prediction of the dispersion pattern is developed.
Water storage variations in the conterminous United States
Authors: Court Arnold , Elliott Stythe T.
Published: February 2008

Variations through the year in the contents of two dozen storage reservoirs in the conterminous United States are shown in Figure 1, which is patterned after the map by Busby [1963] of ‘normal monthly distribution of runoff’ for 20 well‐distributed streams. The lakes and reservoirs chosen for tabulation were the ‘representative group’ used by Langbein [1959] and are listed in Table 1.

For each reservoir the average contents at the end of each month during 1961–1970 were computed from annual tabulations and expressed as percentages of usable capacity (given in Table 1). These percentages, in turn, were shown on cartesian graphs for the October through September water year; polar (circular) diagrams, while they are perhaps more appropriate, might be harder to interpret. Results were consistent with those of the only other similar tabulations which were found for the states of California and Texas and are published by their respective water agencies.
The applicability of planetary boundary layer theory to calculate regional evapotranspiration
Authors: Brutsaert Wilfried , Mawdsley John A.
Published: February 2008

A formulation is obtained for the calculation of evapotranspiration from a region even when the water supply to the surface may be limited. The theoretical model is based on general similarity principles for a steady uniform boundary layer under any conditions of atmospheric stability. The resulting mass transfer formulae have the advantage that the necessary data (‘rawinsonde’) are often routinely published or otherwise easily available. In contrast, most presently used methods for the determination of evapotranspiration either require a special experimental setup for rarely available data or are purely empirical without a firm physical base. The proposed method can be applied in hydrologic simulation for drought studies and for the determination of antecedent moisture conditions in flood prediction.
A note on long waves in shallow channels with running water
Authors: Green Theodore
Published: February 2008

Long waves moving upstream in a channel with nonuniform cross‐channel depth and current distributions are determined for cases in which wave advection due to the current is approximately balanced by wave refraction due to varying water depth. An expansion based on this balance is introduced which can be carried to any desired order. The method is shown to apply in wide, shallow channels.
Dispersion of water pollutants in a turbulent shear flow
Authors: Yeh Gour‐Tsyh , Tsai Yun‐Jui
Published: February 2008

A steady state two‐dimensional turbulent diffusion equation describing the concentration distribution of a substance from a line source in a shear flow field is solved analytically. A similar formulation may be developed for any other kinds of sources. In the study the velocity and eddy diffusivity are assumed to be variables given by the power law approximations, and the depth of the water body is assumed finite, with no‐flux boundary conditions applied at the water surface and bottom. This represents a first step toward analytical water quality modeling which realistically includes the effects of both the finiteness in water depth and the nonhomogeneity in velocity and diffusivity. Results from the present model are compared with those obtained from the finite depth constant coefficient model and from the infinite depth constant coefficient model. They show significant and realistic differences in the prediction of concentration patterns. The effects of nonhomogeneous velocity and diffusivity are cancelled out by the effect of boundary reflection far away from the source.
Laboratory study of unsteady energy transfer in surface layers of stratified water
Authors: Viskanta R. , Parkin J. R.
Published: February 2008

A Mach‐Zehnder interferometer was used to study the energy transfer in the surface layers of stratified water cooled from above. Laboratory measurements of the unsteady temperature distributions indicate that the thermal structure between the interface and the stable region is controlled by a buoyancy induced flow which is established a small distance below the surface. The thermal structure is quite complex and the column of water can be separated into several regions: (1) the surface skin layer, (2) the thermal boundary layer, (3) the convective layer, (4) the interfacial entrainment layer, and (5) the stable region. In the skin layer (z < 0.2 mm) there exists a relatively sharp temperature gradient, and energy is transported by molecular diffusion. Turbulent diffusion contributes to the energy transport in the thermal boundary layer (0.2 < z < 3 mm), while in the convective layer, heat is transferred primarily by turbulent diffusion and free convection circulation. An unsteady energy transport model is developed by lumping the convective terms with the spatially dependent turbulent diffusivity. A simple expression for the diffusivity based on the kinetic energy equation is derived for the equilibrium layer. This expression is then used in a polynomial to obtain the vertical diffusivity profile. The theoretical model predicts behavior which is consistent with experimental results and in good agreement with measured vertical temperature profiles.
A comparison of modeling and statistical evaluation of hydrologic change
Authors: Langford K. J. , McGuinness J. L.
Published: February 2008

The U.S. Department of Agriculture Hydrograph Laboratory model of watershed hydrology is adapted for use on a research watershed where land use changed drastically as a result of reforestation and subsequent thinning. Eight years of measured runoff from a mature forest are used to estimate two of the model parameters; the remaining 39 are based on physical measurements. Model simulations properly evaluated both the magnitude and statistical significance of the hydrologic changes with much less data than were needed for standard statistical analyses.
On solving the nonlinear diffusion equation: A comparison of perturbation, iterative, and optimal techniques for an arbitrary diffusivity
Authors: Parlance J.‐Y. , Babu D. K.
Published: February 2008

A recent solution determined by Babu for an arbitrary soil‐water diffusivity is compared with two earlier solutions. It is shown that the perturbation solution is identical to the iterative result when Cisier's (1974) correction is used. It is also shown that a result obtained by optimization, which is numerically indistinguishable from either the perturbation or iterative result, has a much simpler analytical form.
Hydrology of small watersheds in Wisconsin's driftless area
Authors: Sartz Richard S. , Curtis Willie R. , Tolsted David N.
Published: February 2008

Steep unglaciated terrain and a peculiar land use pattern give the upper Mississippi Valley's unglaciated region a distinctive hydrology. Catchments smaller than 250 ha normally have no perennial streams but may have many springs that flow for short distances and then reenter the ground. Land use has been shown to influence the surface hydrology greatly. Tilled cropland is the principal source of flood runoff and stream sediment. Runoff from forest land is minimal regardless of its slope or condition. The occurrence and movement of groundwater are complex, perched water bodies and dry pockets being intermixed with water tables that rise and fall in rapid response to rainfall and snowmelt and in close synchronization with spring flow. Snowmelt produces a distinctive diurnal pattern of both overland flow and groundwater rise, sometimes in midwinter. Overland flow usually peaks about midafternoon and diminishes to near zero a few hours later. The groundwater peak comes early in the morning of the next day. We found little difference in the daily timing of overland flow from north‐ and south‐facing catchments once the melt period had begun. Larger catchments responded to both rainfall and snowmelt much the same as smaller experimental catchments.
Distributed numerical model for estimating runoff and sediment discharge of ungaged rivers 1. The information system
Authors: Gupta S. K. , Solomon S. I.
Published: February 2008

The need for a distributed numerical model for information transfer on runoff and sediment discharge from a gaged river section to any section of the river or its tributaries is discussed. The methodology of developing the information system, which forms the basic structure for the development of such a model, is briefly described. The advantages of the proposed information system are presented, and suggestions to further improve it are made.
Storm depth‐area relations from digitized radar returns
Authors: Frederick Ralph H. , Myers Vance A. , Auciello Eugene P.
Published: February 2008

The point‐derived precipitation frequency values depicted on maps must be converted to areal values for engineering and design work. Sparsity of data for quantifying this relation will be overcome as the National Weather Service implements its program to digitize radar return at its primary radar sites. A prototype project converts digitized radar data to precipitation. By averaging precipitation thus derived over discrete area sizes, depth‐area reduction curves are derived. While the data sample is presently very limited, this prototype can be applied to the expected accumulation of data from the future National Weather Service operational program.
Sensitivity analysis in aquifer studies
Authors: Aguado Eduardo , Sitar Nicholas , Remson Irwin
Published: February 2008

A method is presented for determining in which areas detailed knowledge of aquifer characteristics and conditions is most critical to the success of a management plan. These questions are answered by using sensitivity analysis to determine how variations in parámeters and input data affect the optimal solution of a linear programing management model. The model uses either finite element or finite difference approximations of the groundwater equations as constraints. The optimal locations and discharge rates of wells were determined for dewatering a rectangular area to a specified level while minimizing steady state total pumping rate. The area is in a small aquifer having constant head boundaries. Sensitivity analysis showed that the optimal steady state solution is most sensitive to hydraulic conductivity at and near the aquifer boundaries parallel to the length of the dewatered area. Thus field exploration and testing should be concentrated on determination of hydraulic conductivity in those areas.
Water table response to a sequence of recharges
Authors: Chu Shu Tung
Published: February 2008

Water table behavior under subsurface drainage conditions was analyzed by considering water table fluctuations in response to a sequence of recharge events. The derived solution is applicable to a nonhomogenous soil profile. An iteration procedure was introduced to illustrate the application of the theoretical results. Agreement between theoretical analysis and field data was shown to be adequate.
A modified optimization method of estimating aquifer parameters
Authors: Navarro Agustin
Published: February 2008

A modified optimization method for estimating transmissivity and storativity parameters has been utilized for the fast calibration of mathematical models of transient aquifers. The method provides ‘usable solutions’ at an intermediary point between the minimization of residuals in the water budget equations and the similitude of solutions to field estimations of parameters T and S. Four field examples of the use of the method are given and discussed in terms of relative accuracy of results.
Determination of transport model parameters in groundwater aquifers
Authors: Murty V. V. N. , Scott V. H.
Published: February 2008

The hydrodynamic dispersion coefficients in groundwater aquifers can be determined from observed values of solute concentrations. For a two‐dimensional aquifer in which the concentrations of a solute are known an algorithm is developed to determine the values of longitudinal (∈L) and transverse (∈T) dispersivities. Concentration polynomials are developed by using double interpolation for a set of selected values of longitudinal and transverse dispersivities. With two of the polynomials, Newton's method is used to find the roots which are the values of the longitudinal dispersivity and the ratio of ∈L to ∈T. With more than two polynomials an optimization approach is used in arriving at the values of ∈L and ∈L/∈T. The methods converge to the true values for a good initial estimate of the values.
A water quality planning model with multiple time, pollutant, and source capabilities
Authors: DeLucia R. , McBean E. , Harrington J.
Published: February 2008

The imposition of recent U.S. legislative requirements (Public Law (PL) 92–500) with the 1977 and 1983–1985 water quality goals requires that water quality management plans must weigh both degree of treatment and capacity expansion questions. A planning model capable of reflecting the implications of the pollutant constraints and the scale economies of point source abatement implicit in the legislation is developed. The model captures within a mathematical programing format important characteristics of decisions associated with the time‐related water pollution control goals of PL 92–500. The model's unique features are the utilization of a biomass potential parameter as a measure of water quality and a set of heuristic procedures involving linearization of the waste treatment capacity‐removal curves. These features allow avoidance of nonconvexity problems associated with analogous models. The model also includes the usual BOD, DO, N, and P water quality measures. The model was applied in a recent planning study for the Saint John Basin in Maine.
On oscillation of numerical solution of a modified Richards' Equation
Authors: Krishnamurthi N. , Sunada D. K. , Longenbaugh R. A.
Published: February 2008

Numerical solutions of differential equations should be checked for the conditions of consistency, convergence, and stability. The implicit solutions that satisfy these conditions are sometimes found to be oscillatory about the true solutions. The reasons for these oscillations are explained. A method to derive criteria for nonoscillatory solutions of a nonlinear partial differential equation is outlined. These criteria for modified Richards' equation are presented, and their physical significances are explained.
Topological classifications of drainage networks: An evaluation
Authors: Onesti Lawrence J. , Miller Theodore K.
Published: February 2008

Channel networks for 103 drainage basins ranging in size from 0.65 to 199 km2 were classified according to 9 topologic systems ranging from Strahler's order and Shreve's magnitude to those recently derived by Werner and Smart. Correlation coefficients and coefficients of determination were calculated to test the relationship between these systems and 10 characteristics of drainage basins and stream channels. The results suggest that (1) network properties are closely associated with basin area and with other characteristics primarily determined by area, (2) the hydraulic variables are essentially unrelated to all topologic systems analyzed, and (3) certain newly proposed topologic systems are unrelated to all characteristics tested, including area.
Evaluating the environmental consequences of groundwater contamination: 3. Obtaining contaminant arrival distributions for steady flow in heterogeneous systems
Authors: Nelson R. William
Published: February 2008

The versatility of the new contaminant arrival distributions for determining environmental consequences of subsurface pollution problems is demonstrated through application to a field example involving land drainage in heterogeneous porous materials. Though the four phases of the hydrologic evaluations are complicated because of the material heterogeneity encountered in the field problem, the arrival distributions still effectively summarize the minimal amount of data required to determine the environmental implications. These arrival distributions yield a single graph or tabular set of data giving the consequences of the subsurface pollution problems. Accordingly, public control authorities would be well advised to request that the results of subsurface pollution investigations be provided in the form of arrival distributions and the resulting simpler summary curve or tabulation. Such an objective is most easily accomplished through compliance with the requirements presented by Nelson (1978a) for assuring a complete subsurface evaluation.
Growth of groundwater mounds affected by in‐transit water
Authors: Ortiz N. V. , McWhorter D. B. , Sunada D. K. , Duke H. R.
Published: February 2008

An analytical solution accounting for the reduction in storage capacity caused by in‐transit water is presented for the growth of groundwater mounds in an unconfined aquifer in response to uniform deep percolation from a strip of infinite length but finite width. The solution is obtained by integrating the solution for the analogous case of heat flow in a composite solid with respect to time. The aquifer is homogeneous, isotropic, and infinite in areal extent and rests on a horizontal impermeable base. The results from the analytical solution were compared with those obtained from a numerical model which was previously verified with data obtained from a physical porous media model. Dimensionless curves are presented to afford a relatively simple means of analyzing the growth of groundwater mounds.
Optimal water pricing and storage with cyclical supply and demand
Authors: Riley John G. , Scherer Charles R.
Published: February 2008

Optimal storage of a naturally renewable, seasonally varying resource is considered where demand is price sensitive and seasonal and social resources are required for storage and processing prior to consumption. The particular application is water supply, where the demand and supply fluctuations are generally out of phase. Using a Lagrangian analytical framework, net willingness to pay is maximized subject to fundamental constraints that characterize water supply and storage. The purpose of this work is to integrate the literatures of peak load pricing and optimal reservoir planning and operation, noting that price is both an active form of ‘soft’ demand management and an effective information signal for efficient allocation of (nonwater) resources in the management of water supply. Results indicate that although demand is assumed to vary continuously with time, the optimal rate structure is approximated by a policy in which the price of water is adjusted at only a few points in the cycle. In contrast with the usual discrete time model, the duration of each subperiod of constant pricing is endogenously determined. It is also shown that owing to the introduction of storage, off‐peak prices as well as the peak season price may be held above marginal operating costs, thereby bearing part of the capacity costs.
Optimal weekly releases from a seasonal reservoir: 1. Deterministic future
Authors: Laufer F. , Morel‐Seytoux Hubert J.
Published: February 2008

A technique was developed to maximize the returns from the operation of a seasonal alpine reservoir for the production of electrical energy. The emphasis rests on a comprehensive approach to the problem, and the following fields were considered: hydrology, power economics, operations research, and decision theory. The solution technique to determine the optimal releases strategy is first developed for the deterministic case. It is based on the solution of the system of equations given by the Kuhn‐Tucker conditions. As the direct solution of this system of equations is complicated, an alternative approach was devised. The operation period is divided into two parts: the drawdown phase and the refill phase. For each of these phases, the optimality conditions are solved by a procedure akin to Masse's constrained calculus of variations, the physical constraints being first ignored, and then introduced in a stepwise manner. A preliminary study of the approximate nature of the optimal releases sequence provides a good starting point in the variational procedure and the number of iterations necessary to arrive at the optimum is reduced to a minimum. The application of the developed technique to a seasonal reservoir fed by an alpine watershed showed that the method is both feasible and attractive. It is also well suited for generalization to the case of an uncertain future; to be presented in a second paper.
Diffusion of dissolved gas in consolidating porous media
Authors: Corapcioglu M. Y.
Published: February 2008

The diffusion of dissolved gas in liquid resulting from soil consolidation is analyzed as a function of time and space. The medium is assumed to be isotropic, finite, and filled with a homogeneous and incompressible fluid. Two cases of consolidation have been considered to determine the fluid velocity expression. The model is useful to predict the concentration of dissolved gas in liquid for laboratory problems.
A conceptual deterministic analysis of the kriging technique in hydrology
Authors: Gambolati Giuseppe , Volpi Giampiero
Published: February 2008

A stochastic approach to interpolating sparse observation records in hydrology referred to as the ‘kriging technique’ has recently been developed by Matheron (1969, 1970) and systematically used in the field by the Ecole des Mines de Paris. Distinct primary features of this method are supposed to be its predictive reliability and its ability to provide an estimation error. In the present paper a deterministic analysis for the kriging technique is given without resorting to a statistical framework. It turns out that a close relationship with the most traditional interpolation schemes may easily be found. The formulation shows that in relation to other commonly used methods, any claim to produce more accurate estimates fails to be proven, since an arbitrary component is necessarily introduced by the decision process of selecting an operative model. It is recognized that a distinct and unique advantage of the kriging technique is its ability to provide an assessment of the interpolation error. An attempt is also made to give a deterministic interpretation for the main trend. The results show that the use of this concept involves an additional component of arbitrariness whose impact upon the final outcome can hardly be predicted a priori. The conclusions of the present analysis suggest that in practical applications the interpretation model is not improved by the use of a main trend, unless its expression reflects some additional information related to the general hydrologic context but not included in the available observations.
Assessment of fitting techniques for the log Pearson type 3 distribution using Monte Carlo Simulation
Authors: Nozdryn‐Plotnicki M. J. , Watt W. E.
Published: February 2008

The distribution parameter space for the log Pearson type 3 distribution has been defined for annual maximum floods at 37 long‐term Canadian flow‐gauging stations. Within this parameter space, log Pearson type 3 independent variates were generated in samples of size 25, 50, and 100. For each sample, parameters and specified quantiles were estimated by using three techniques: the method of maximum likelihood, the method of moments, and a method which preserves the moments of the untransformed flows. The parameter estimates were generally very poor; they were highly biased and exhibited large variances, However, there was no evidence of significant bias in the quantile estimates. On the basis of statistical efficiency, no one method was superior for the whole of the parameter space. The third method was generally superior for negative values of skewness of the logarithmically transformed flows, and the method of moments was the best method for positive values of skewness. The differences in standard error were generally small. The expressions for the standard error of the T‐year flood were found to be biased for N equal to 25, 50, and 100. In general, the asymptotic maximum likelihood relation gave underestimates, whereas the moments relation gave overestimates.
Stochastic optimization of a water supply system
Authors: Bogle M. G. V. , O'Sullivan M. J.
Published: February 2008

Stochastic dynamic programming (DP) is used to find the operating policy with the least expected steady state cost for a water supply system consisting of a reservoir and an alternative source. The set of possible decisions consists of a number of release rules, each expressing release as a function of storage, rather than a number of discrete releases, as in the conventional DP approach. A flexible procedure is developed which permits inflow to be described by piecewise linear probability density functions, and removes the constraint that inflow and release must be multiples of the discrete unit of storage. The techniques are applied to a reservoir‐river system, and through simulation, the results are compared with the solution found by conventional DP.
Identification of aquifer dispersivities in two‐dimensional transient groundwater Contaminant transport: An optimization approach
Authors: Umari Amjad , Willis Robert , Liu Philip L.‐F.
Published: February 2008

The problem of identifying unknown aquifer dispersivities in two‐dimensional transient groundwater contaminant transport from given observations on the concentration field is addressed. This inverse problem is formulated as a general nonlinear programing problem, the purpose of which is to minimize the discrepancy between calculated and observed values of the concentration field. The method of quasilinearization is used to linearize the above problem, and the inverse algorithm becomes the solution of a sequence of linear programs that converge to the solution of the original nonlinear problem. The finite elements method in conjunction with finite differencing is used to discretize the governing differential equations which are then used as constraints for the optimization (mathematical programing) problem stated above. The effect on the inverse problem of the choice of observation points, objective function, number of finite elements, size of time step, and observation errors is studied. The proposed identification algorithm is shown to be fast, stable, and accurate.
Optimization of a dam system for recharging runoff water into the ground
Authors: Nov Amihud , Golany Pinhas
Published: February 2008

This work presents a method for a routine determination of an optimal combination of small dams in mountainous catchments. The method is meant for arid and semiarid climates, where wells are the main source of water. The objective of the dams is to impound runoff water and recharge it, through the reservoirs formed by them, into the ground, thereby augmenting the natural replenishment of groundwater. The objective function calls for a minimization of the cost of the recharged water. The optimization technique is dynamic programing. The method is confined to the mathematical formulation of the optimization procedure. Although this formulation is made in terms of the hydrological and geometrical variables concerned, no reference is made to the hydrological and structural information; it is assumed that this information is available. A purposeful use of this optimization method requires appropriate methods (yet to be proposed) of supplying and processing the vast hydrological information necessary. The results obtained from an application of this method (the cost of the recharged water and a description of the corresponding dam system) are given for different, arbitrarily selected average annual recharge volumes up to the total average annual runoff yield of the catchment. From a rigorous, formal point of view the method violates the principles of dynamic programing. This violation becomes permissible owing to certain controls, inherent in the process, regulating it from within.
A note on the Dual‐Gage and Wyoming Shield Precipitation Measurement Systems
Authors: Hanson Clayton L. , Morris Ronald P. , Coon Delbert L.
Published: February 2008

Analysis of 52 events, which included both snowfall and rainfall, showed that the dual‐gage and the Wyoming shield precipitation measuring systems measured nearly the same amounts at an unprotected site on the Reynolds Creek Experimental Watershed in southwest Idaho. These systems were developed to accurately measure precipitation, more specifically snowfall, under windy conditions. The more legible record traces obtained from the Wyoming shield gage are a good reason for using this shield when installing precipitation gages at windy locations.
Predicting level of dissolved reactive phosphate in the Lafayette River, Virginia, from information on tide, wind, temperature, and sewage discharge
Authors: Montgomery John R.
Published: February 2008

The Lafayette River in Norfolk, Virginia, is a shallow, turbid, urban estuary, polluted with primary treated sewage. The river was sampled monthly from October 1970 to January 1972. Oxygen, temperature, and salinity values are vertically and laterally homogeneous in the Lafayette River. The mean values of dissolved reactive phosphate (DRP) in the Lafayette River for the winter (1970–1971 and 1972) ranged from 2.2 to 5.8 microgram‐atoms per liter (μg‐at/1) and for the summer of 1971, 7.6 μg‐at/l. Multiple linear regression models were prepared to relate the daily changes in phosphate to tide stage, wind component and rate of phosphate discharge (kg/hr) from the Lamberts Point sewage treatment plant. The equations for the August 1971 sample show that the effect of the tide stage is 3 times as important in the determination of the levels of DRP as the rate of flow of DRP from the sewage effluent on the ebbing tide and is equally as important as the rate of flow of DRP from the sewage effluent on the flooding tide. The daily variations in DRP are more noticeable in the summer because of the higher concentrations of phosphate in the Lafayette River during this season. The increase of phosphate on the ebb tide and the decrease on the flood tide over a daily cycle was attributed to a dilution of the waters of the Lafayette River by the water from Hampton Roads. The direct relation of water temperature to the concentration of DRP for the seasonal model was attributed to the increased biochemical activities of the micro‐organisms in the sediment‐water system.
Range of independent mixture models in hydrology
Authors: Zekâi Şen
Published: February 2008

A general formula relating low order statistics of surplus and deficit to range of cumulative departures is proposed on the basis of the independent mixture models. By means of derived expressions the effects of both drought duration and intensity on the range are documented, leading to the conclusion that even if the successive observations are independent, increases in drought duration and intensity cause the range to increase.
An optimal sampling procedure for the collection of residential water use data
Authors: Hanke Steve H. , Mehrez Abraham
Published: February 2008

Sampling theory is used to design an optimal sample of individual residential water users for the United States. The purpose of designing this optimal stratified random sample is to facilitate an efficient nationwide collection of residential water use data which can be analyzed statistically to forecast water use and to determine water system design criteria. This sample is designed in two steps; we select (1) the specific type and number of customers to be sampled at each location and (2) the specific locations to be sampled.
Estimation of parameters and quantiles of Wakeby Distributions: 2. Unknown lower bounds
Authors: Landwehr J. Maciunas , Matalas N. C. , Wallis J. R.
Published: February 2008

An algorithm based on the use of probability weighted moments allows estimation of the parameters, hence quantiles, of the Wakeby distribution. For the case where the lower bound is not known, the performance of the algorithm using unbiased estimates of the probability weighted moments is compared to that using biased estimates. The choice of estimating algorithm, determined as that which minimizes the root mean square error of the quantiles, appears to be unimportant when the upper (flood) quantiles are of interest and the lower bound is not known, in contrast to the lower (drought) quantiles.
On the problem of discretization in Dam Theory
Authors: Lochert P. , Phatarfod R. M.
Published: February 2008

This paper considers the twin problems of the nature of discretization and the size of the unit of discretization in dam theory. It compares the probabilities of emptiness and of fullness of the dam obtained by the discretization schemes suggested by Moran and Doran. It is proved that the probability of emptiness for the former scheme is always greater than that obtained for the latter scheme. The probability distribution of the dam content for the latter scheme is derived for the case when the release is the unit of measurement. Finally, the probabilities of emptiness and of fullness of the dam for the two schemes are compared with the exact values for the Erlangian input case.
Stability of rhodamine WT in saline waters
Authors: Stanbro W. D. , Pyrch D. A.
Published: February 2008

The stability of rhodamine WT dye was investigated in buffered and unbuffered NaCl solutions and in natural waters of varying salinity. Despite previous reports in the literature, no significant decay attributable to salinity effects was seen. The maximum decay observed was 5% after 327 hours.
A systems approach to water resource allocation in international river basin development
Authors: Stone Paula J.
Published: February 2008

A methodology is presented to assist the water resource systems analyst in providing and interpreting technical information to promote coordinated water resource use in international river basin development. The international river basin planning environment is examined to identify the analytical information which can address and satisfy comprehensive decision‐making requirements. This information is organized within a multilevel decomposition framework that permits an analysis of the implications of alternative resource development patterns in terms of nations both achieving their objectives and pursuing development strategies that will lead to feasible basin‐wide resource use. The proposed methodology is applied to an example of international river basin planning with the generation of resource transformation curves, and results are examined for their appropriateness as bases for coordinated development.
Diffusion of a passive scalar with random advection
Authors: Moiyneux John E. , Witten Alan J.
Published: February 2008

To investigate the instantaneous release of a passive additive into a flow, we assume that the concentration of the additive is governed by the one‐dimensional advective diffusion equation in which the advecting flow velocity is a given time‐dependent stochastic process. We determine both the one‐ and two‐space‐time point probability distributions of the random concentration field. This problem, or more elaborate variations of it, is a rather idealized model for a variety of environmentally important flow situations, for example, the accidental or planned release of a contaminant into a river by a power station, and, as such, it has been investigated by a number of authors. Previous treatments, however, have concentrated on deriving information about the statistical moments of the concentration. Although such information is important, it may be inadequate for accessing the true effects of a flow additive on the environment. Our investigation demonstrates the possibility of obtaining a more complete statistical description.
The rotation of a vertical interface in a porous medium
Authors: Verruijt Arnold
Published: February 2008

A solution is given of the problem of the simultaneous flow of two different fluids in a vertical plane, separated from each other by a vertical interface. It is shown that the viscosities of the two fluids influence the motion of the interface only through their average value. A simple formula for the rotation of the interface is derived in terms of the relative density difference.
The transport of a radioactive salt through a semi‐infinite column of porous medium: A physical model
Authors: Lucas Joe Nathan
Published: February 2008

A model study of the transport of radioactive tracer through a porous medium was carried out in columns of sand into which a radioactive salt solution, sodium‐24 chloride, was introduced continuously. Mathematical equations were developed to describe the effluent concentration, for a semi‐infinite column, during the transient phase for variable as well as for the constant input concentration. Furthermore, inspection of the relevant equation for effluent concentrations from long columns indicated that dispersion should be negligible in the steady state. The experimental data of effluent concentrations gave accurate agreement with the theoretical breakthrough curves predicted by the mathematical equations, and with the steady state concentration value.
Choosing among hydrologic regression models: 2. Extensions to the standard model
Authors: Valdés Juan B. , Rodríguez‐Iturbe I. , Vicens Guillermo J.
Published: February 2008

Bayesian methods are used to discriminate among alternative structures of the covariance matrix of the disturbances of hydrologic regression schemes; moreover, the covariance matrix is allowed to be non‐scalar. Different alternative functional forms, which the hydrologic regression may also have, are also discriminated through the proposed methodology.
Modeling soil water changes in a well‐structured, freely draining soil
Authors: Parkes M. E. , O'Callaghan J. R.
Published: February 2008

Changes of soil water content were measured in three monolith lysimeters and compared with changes predicted by a soil water budgeting program and a program incorporating a finite element solution of the unsaturated soil water flow equation. Both models underestimated water uptake during periods of high evapotranspiration. While the physically based model gave accurate estimates of flow from a lysimeter in the absence of root water uptake, the empirical budget provided the more practical approach to long‐term water balance calculations.
Heat and mass transfer in a freezing unsaturated porous medium
Authors: Jame Yih‐Wu , Norum Donald I.
Published: February 2008

A numerical simulation of a laboratory experiment involving coupled heat and mass transfer in a horizontal porous medium column with one end subjected to a temperature below 0°C has been carried out. The model is essentially that of Harlan (1973) and is solved numerically by the finite difference method using the Crank‐Nicholson scheme. The solution yields temperature, liquid water content, and ice content profiles along the column as a function of time. Comparison of the experimental results and the simulation analysis results shows that Harlan's model, with some modification in the hydraulic conductivity of the frozen medium, can be used successfully to simulate numerically the coupled heat and mass transfer processes when ice lensing does not occur.