bluuebunny/crossref_metadata_2025 huggingface dataset:
Groundwater contour mapping in Venice by stochastic interpolators: 1. Theory
Authors: Gambolati Giuseppe , Volpi Giampiero
Published: February 2008

An adaptation of the kriging technique (Matheron, 1969, 1970) is developed and used to map the hydraulic head field z of three major aquifers underlying the Venetian lagoon. Available records come from a fairly small number of observation wells unevenly scattered across the mainland, Venice, and the littoral. The event to be reconstructed is conceptually idealized as the sum of (1) a deterministic component m giving the main trend of z and (2) a stochastic component e giving the natural dispersion of z around m with zero mean, constant variance, and high autocorrelation. Both m and e are dependent on the observation scale. A physically based expression for m is selected including the consideration of additional information related to the general hydrogeological context. To reduce the complexity of the choice, some unknown coefficients ak are introduced in m and determined ‘a priori’ by a best fit technique, for instance, the least squares method. The relationship between m and ak is not necessarily linear. The dispersion e is then assessed by a linear optimal stochastic interpolator, i.e., by a linear combination of the observed values with the requirement that the variance of the interpolation error E be minimal. In the absence of instrument errors the interpolator reproduces the measured quantity in the observation points, while in the remainder of the field it provides an estimate z* with a standard deviation σ whose magnitude depends on the dispersion of the given z around m as well as on the quantity and distribution of the measurements. A prerequisite for a plausible model is that the reduced errors (z−z*)/σ have zero mean and unit variance, i.e., the estimates are not affected by systematic errors and (z−z*) is consistent with the corresponding σ. Validation of the interpretation models selected for each of the three Venetian aquifers shows that the present approach yields accurate results provided the trend is correctly assessed.
Use of specific conductance and contact time relations for separating flow components in storm runoff
Authors: Pilgrim David H. , Huff Dale D. , Steele Timothy D.
Published: February 2008

The difference between the dissolved‐solids concentration in base flow and in storm flow has often been used as the basis for separating components of flow. However, an analysis that explicitly relates the amount of time that runoff water has been in contact with watershed soils to the resulting dissolved‐solids concentration shows that simple mass balance chemistry methods for hydrograph separation are misleading. Field studies of surface and subsurface storm flow, when coupled with laboratory determination of the relationship between contact time and dissolved solids content of a soil water mixture, suggest that the residence time of infiltrated water is as short as a few hours in the cases studied. In those cases, hydrograph separation methods based on the simple mass balance equation for the dissolved solids will yield considerable overestimates of the base flow component.
A method of estimating parameters and assessing reliability for models of steady state Groundwater flow: 2. Application of statistical analysis
Authors: Cooley Richard L.
Published: February 2008

Techniques of nonlinear regression were applied to estimate the hydrogeologic parameters (values of transmissivity or hydraulic conductivity), recharge, discharge, and boundary fluxes for steady state groundwater flow models of two field areas: Truckee Meadows, Nevada, and a cross section in the Hula Basin, Israel. Statistical techniques were used to estimate the degree of nonlinearity of the models, the goodness of fit of the models to field data, and the reliability of predictions to be made with the models. Goodness of fit was determined by analyzing the reliability and significance of computed parameters and the reliability of the computed head distribution. It was found that both of the field cases analyzed behaved at least approximately linearly based on Beale's measure of nonlinearity; that variable reliability of observed head data had to be incorporated into the analysis for Truckee Meadows; that residuals, transformed to eliminate heteroskedasticity and intercorrelation, may be independently normally distributed in the case of Truckee Meadows (testing was not carried out for Hula Basin because of the possible lack of model fit); and that the standard errors for parameters for both cases were large, indicating nonuniqueness of the solution, even though model fit was good for Truckee Meadows and fair for Hula Basin. The reliability of the predicted drawdown distribution and pumping rate was estimated for a gravel pit operation in Truckee Meadows. In spite of the nonuniqueness problem, predictions of these quantities were not significantly different at a level of significance of 0.05 from the observed values.
Generation and evaluation of alternative plans for regional wastewater systems: An imputed value method
Authors: Nakamura Masahisa , Brill Downey E.
Published: February 2008

A branch‐and‐bound method for use in planning regional wastewater treatment systems is extended to include a methodology for generating and evaluating alternative plans. Since many planning issues are related to a specific configuration of regional facilities, economic trade‐offs among alternative plans are evaluated using imputed values of individual facilities or groups of them. The imputed values, or bounds on them, are calculated from information contained in the branch‐and‐bound tree using an ‘imputed value incidence matrix.’ The general approach, which can be applied to other public facility location problems, is designed to aid an analyst in gaining more insights into the problem under study than obtainable from conventional optimization methods. The procedure is designed for use within a larger planning process where the steps are to generate, to evaluate, and to elaborate on alternative plans. The method is illustrated using the regional wastewater system for DuPage County, Illinois.
Estimation of drainage density from topological variables
Authors: Gardiner V.
Published: February 2008

Existing methods for the estimation of drainage density are generally inadequate, being either laborious or expensive or of low effectiveness. Methods are examined by which grid square drainage density may be estimated from topological variables, a sample of 400 grid squares from Devon, England, being used in the study. Principal components analysis of these data yields interpretable components that allow prediction of 82% of the total variation in stream length, employing a multiple relationship. A simple regression relationship affords prediction of 68% of the variation in stream length. The mode of sampling employed and the use of polynomial regression do not markedly change the effectiveness of these relationships, and sufficient published work exists to suggest that the method may be widely applicable.
An improved aerodynamic evaporation technique for large lakes with application to the International Field Year for the Great Lakes
Authors: Quinn Frank H.
Published: February 2008

An improved bulk transfer technique was developed for large‐lake evaporation based upon recent boundary layer research near the air‐water interface. A variable bulk transfer coefficient, dependent upon atmospheric stability, is given as a function of the nondimensional wind speed gradient, the potential temperature gradient, and the Monin‐Obukhov length. The technique, which requires the same data as the simplified mass transfer equation, can be readily applied to large lakes throughout the world. This technique has been applied to the Lake Ontario data set collected during the International Field Year for the Great Lakes. The inclusion of stability increases calculated evaporation during the unstable high‐evaporation months and decreases calculated condensation during the stable late spring months to more realistic levels. Comparisons between the Lake Hefner mass transfer equation and the technique recommended here indicate that the mass transfer equation may overestimate Lake Ontario evaporation by approximately 20%.
A generalized solution for solute flow in soils with mobile and immobile water
Authors: De Smedt F. , Wierenga P. J.
Published: February 2008

An analytical solution is presented for the movement of a solute through a porous medium which is leached at a constant rate. The solution takes into account transfer into an immobile water fraction. The generalized solution is valid for both finite or semi‐infinite media and for concentration or flux type boundary conditions. The solution consists of a convolution integral of two functions. The first function is the derivative with respect to injected pore volume of the corresponding analytical solution of the solute transfer equation without transfer into immobile water. The second function is the J function, for which series approximations are presented. The influence of the boundary conditions on the solution is discussed.
Multiobjective dynamic programing with application to a reservoir
Authors: Tauxe George W. , Inman Robert R. , Mades Dean M.
Published: February 2008

The analysis of water resource problems often involves noncommensurable objectives. Where this is the case, no clear‐cut optimum solution exists, but rather a whole set of technologically efficient ‘noninferior’ solutions exists. A water resources decision maker, who reflects society's preferences, chooses the single noninferior solution preferred to all the others. Multiobjective dynamic programing is introduced as an extension of dynamic programing which can provide the decision maker with the entire noninferior set of solutions as well as the explicit trade‐offs between noncommensurable objectives at all objective levels to aid him in the decision‐making process. The technique makes possible the quantitative analysis of multiple‐objective problems which would provide great difficulties for the existing methods. An example of such a problem is presented and solved by multiobjective dynamic programing. The problem involved the generation of the noninferior set and trade‐off curves for the operation of a reservoir considering three objectives.
The geochemistry of the Fox Hills‐Basal Hell Creek Aquifer in southwestern North Dakota and northwestern South Dakota
Authors: Thorstenson Donald C. , Fisher Donald W. , Croft Mack G.
Published: February 2008

The Late Cretaceous Fox Hills Formation and the basal portion of the overlying Hell Creek Formation constitute an important aquifer in the Fort Union coal region. Throughout most of southwestern North Dakota and northwestern South Dakota the aquifer is at depths ranging from 1000 to 2000 ft, except for exposures along the Cedar Creek anticline. Water flows in the aquifer from southwest to northeast, with flow rates of a few feet per year. The recharge and discharge areas of the aquifer are separated by a north‐south trending transition zone in which significant changes in water chemistry occur. Dissolved constituents in the recharge area (the western part of the study area) are Na+ = 18 mmol/l, Cl− = 0.7 mmol/1, SO42− = 2.7 mmol/1, and HCO3− = 13 mmol/l (δ13C = −12‰) with pH = 8.5. Ca2+, Mg2+, and K+ are each less than 0.1 mmol/l, dissolved O2 = 0, and traces of H2S and CH4 are present. Computer modeling and carbon isotope data suggest the following reactions in the recharge area. CO2 derived from lignitic carbon reacts to dissolve carbonate minerals, with cations then being exchanged for Na+ on clay minerals. The high pH in the aquifer is the result of buffering by carbonate‐ion exchange equilibria. In the discharge area, pH values have declined to 8.3, Cl− has increased from 0.7 to 5.5 mmol/l, with a parallel increase in Na+ SO42− has essentially disappeared, HCO3− has increased from 13 to 21 mmol/l (δ13C = −9‰), CH4 has attained concentrations greater than 0.5 mmol/l, and small amounts of He are present. Traces of H2S are present, and Ca2+, Mg2+, and K+ concentrations remain low throughout the aquifer: These changes can be accounted for by reactions in the aquifer: (1) sulfate reduction to pyrite with lignitic material as the carbon source and (2) continuous buffering of pH by the carbonate‐ion exchange equilibria. Chemical and hydrologic data suggest that the increase in NaCl results from upward movement of small volumes of water into the Fox Hills aquifer from the transition zone eastward. Redox reactions in the aquifer are closely analogous to those observed in pore waters of reducing marine sediments. Reactions approach but do not achieve true thermodynamic equilibrium. Measurements of redox potential suggest a downgradient decrease in redox potential. The measurements are not amenable to quantitative interpretation.
Reliability‐constrained reservoir control problems: 1. Methodological issues
Authors: Sniedovich Moshe
Published: February 2008

A dynamic programing solution procedure is developed for a class of reliability‐constrained reservoir control problems associated with constraints defined over the entire life of the reservoir. Certain methodological issues involved in the modeling, analysis, and solution of reservoir control problems are raised, and it is shown how the proposed model can be used to evaluate heuristic release strategies. A simple numerical example is presented.
An evaluation of some record reconstruction techniques
Authors: Hirsch Robert M.
Published: February 2008

There are many methods available for reconstructing streamflow records for sites where no record or only a short record exists. The methods described and evaluated herein rely on transfer of information from nearby stream gages. The methods involve (1) the use of drainage area ratios, (2) the use of estimates of monthly means and standard deviations based on regional streamflow‐basin characteristics models, and (3) two different methods of using the cross‐correlation of flow records. The methods are evaluated in terms of their ability to estimate some statistics of the annual yields of a reservoir located at the site for which the record is reconstructed. The analysis indicates that useful estimates of flows and reservoir yields may be made without any at‐site measurements provided that good regional information transfer models are available.
Space, time, and the third dimension (model error)
Authors: Moss Marshall E.
Published: February 2008

The space‐time tradeoff of hydrologic data collection (the ability to substitute spatial coverage for temporal extension of records or vice versa) is controlled jointly by the statistical properties of the phenomena that are being measured and by the model that is used to meld the information sources. The control exerted on the space‐time tradeoff by the model and its accompanying errors has seldom been studied explicitly. The technique, known as Network Analyses for Regional Information (NARI), permits such a study of the regional regression model that is used to relate streamflow parameters to the physical and climatic characteristics of the drainage basin.

The NARI technique shows that model improvement is a viable and sometimes necessary means of improving regional data collection systems. Model improvement provides an immediate increase in the accuracy of regional parameter estimation and also increases the information potential of future data collection. Model improvement, which can only be measured in a statistical sense, cannot be quantitatively estimated prior to its achievement; thus an attempt to upgrade a particular model entails a certain degree of risk on the part of the hydrologist.
Use of principal component analysis to identify homogeneous precipitation stations for optimal interpolation
Authors: Morin Guy , Fortin Jean‐Pierre , Sochanska Wanda , Lardeau Jean‐Pierre , Charbonneu Raymond
Published: February 2008

The Eaton River precipitation network was set up as one of the Quebec International Hydrologic Decade projects in 1965. At the end of the decade, in 1975, 30 stations had been in operation for most of the period in this 248‐mi2 (643 km2) basin. After a principal components analysis of the data from 14 of the 30 stations on 10‐day precipitation totals, it was found that the stations could be divided into three groups, the composition and geographic distribution of which change from season to season. It was also possible to identify which stations were redundant and could be closed should it become necessary. Application of optimal interpolation, season by season, to a 30‐ and a 5‐station network showed that the precision of point interpolation varies more from season to season for the same network than from the 30‐ to the 5‐station network for the same season. In fact, errors of interpolation caused by microclimatic irregularities and by observational errors in the initial data are greater than those resulting from the reduction of the network from 30 to 5 stations.
Monetizing benefits under alternative river recreation use allocation systems
Authors: Loomis John B.
Published: February 2008

An optimal capacity, when the binding use constraint is ecological damage, and monetization of recreational benefits, under alternative means of rationing that capacity, were conceptually and empirically developed. The model was developed by first estimating the demand to float Westwater Canyon, derived from a modified travel cost model. Recreational benefits of $6,500 under a hypothetical capacity of 50 trips, when pricing was used to allocate the permits, and a range of benefits from as low as $880 to an expected value of $3,690, if a lottery system is used, were estimated using this model. The monetization of the efficiency losses associated with more equitable allocation systems allows managers to be more objective in making the equity‐efficiency trade‐offs involved in picking a recreation use allocation system.
Organic solute‐mineral surface interactions: A new method for the determination of groundwater velocities
Authors: Ciccioli Paolo , Cooper William T. , Hammer Paul M. , Hayes J. M.
Published: February 2008

When the adsorption processes affecting the migration rates of organic solutes in groundwater systems are considered in detail, it can be shown that the use of multiple tracers should allow accurate calculation of the groundwater velocity even when all the tracers are retarded to some extent by interactions with mineral surfaces in the aquifer and even when the extent of that retardation is not known beforehand. It should be required only that the tracers be members of a series of compounds whose surface interaction energies vary regularly, this condition being met, for example, by compounds in the series C2ClnF6−n Experimental studies aimed at testing this concept show that two series of tracers behave as expected on laboratory columns (limestone and sand), thus indicating the fundamental validity of the approach. Further, the nature of the interactions between the mineral surfaces and the tracer molecules can be shown in these cases, at least, to be nonspecific, the strength of the interaction depending only on the polarizability of the tracer molecule. It seems likely that other satisfactory tracers can be selected using this criterion and that the approach should be applicable even to systems involving many different mineral surface types.
Stochastic parameter estimation procedures for hydrologie rainfall‐runoff models: Correlated and heteroscedastic error cases
Authors: Sorooshian Soroosh , Dracup John A.
Published: February 2008

A maximum likelihood estimation procedure is presented through which two aspects of the streamflow measurement errors of the calibration phase are accounted for. First, the correlated error case is considered where a first‐order autoregressive scheme is presupposed for the additive errors. This proposed procedure first determines the anticipated correlation coefficient of the errors and then uses it in the objective function to estimate the best values of the model parameters. Second, the heteroscedastic error case (changing variance) is considered for which a weighting approach, using the concept of power transformation, is developed. The performances of the new procedures are tested with synthetic data for various error conditions on a two‐parameter model. In comparison with the simple least squares criterion and the weighted least squares scheme of the HEC‐1 of the U.S. Army Corps of Engineers for the heteroschedastic case, the new procedures constantly produced better estimates. The procedures were found to be easy to implement with no convergence problem. In the absence of correlated errors, as theoretically expected, the correlated error procedure produces the exact same estimates as the simple least squares criterion. Likewise, the self‐correcting ability of the heteroschedastic error procedure was effective in reducing the objective function to that of the simple least squares as data gradually became homoscedastic. Finally, the effective residual tests for detection of the above‐mentioned error situations are discussed.
Metagame analysis of the Garrison Conflict
Authors: Hipel Keith W. , Fraser Niall M.
Published: February 2008

Metagame analysis is a type of game theory which can be employed for assessing the political feasibility of large‐scale water resources projects. The Garrison Diversion Unit, a planned irrigation scheme in North Dakota has caused a complex international controversy which is analyzed by using metagame analysis. Based upon the options available to the participants in the conflict and also the preferences of the participants, metagame analysis is used to predict possible feasible political solutions to the Garrison conflict. In addition, metagame analysis provides a framework for systematically studying the Garrison dispute so that the political complexities of the problem can be understood and put into proper perspective.
Adaptive filtering through detection of isolated transient errors in rainfall‐runoff models
Authors: Kitanidis Peter K. , Bras Rafael L.
Published: February 2008

Real‐time river discharge forecasting models operate under widely different wet and dry regimes, producing sequences of highly nonstationary prediction residuals. Errors in the mean areal precipitation estimation are often magnified due to model approximations and nonlinear behavior and result in significant effective input errors which propagate as transient signals through the system. Normal operation of a feedback scheme based on the Kalman filter with stationary error statistics cannot account for such discrepancies leading to local divergence between expected and observed prediction residuals. An adaptive filtering methodology which explicitly accounts for transient errors in the prediction due to errors in the estimation of the effective rainfall is presented. The filter operates normally under the assumption of only stationary or slowly varying noise, while a generalized likelihood ratio test is used to detect the presence of transient errors. When such errors are detected, estimates of their timing and magnitude are obtained, and the forecasts are appropriately corrected. An illustrative example of the procedure operation is given.
Reliability programing in reservoir management: 1. Single multipurpose reservoir
Authors: Simonovic Slobodan P. , Mariño Miguel A.
Published: February 2008

This paper presents the application of reliability programing techniques to a multipurpose reservoir. The approach, in allowing reliabilities to be considered as decision variables, explicitly considers the trade‐off between benefits and risk. The number of probability constraints is, in theory, not limited. A three‐level solution algorithm is proposed. The solution can be obtained for a reservoir with few purposes (for example, water supply, irrigation, etc.) and random inflow and demands. The procedure is illustrated with an example of a reservoir management problem with constraints on the probabilities of not exceeding the specified maximum storage and minimum volume of the reservoir. The output of the program gives the optimal values of reservoir releases and the optimal risk levels (flood risk and drought risk), which are valuable information for decision makers. When the number of constraints becomes large, however, computational requirements may limit the applicability of the algorithm to higher‐dimensional problems.
Modeling daily river flows with precipitation input
Authors: Miller Robert B. , Bell William , Ferreiro Osvaldo , Wang Richard Yng‐Yuh
Published: February 2008

A univariate time series of daily average river flows is compared to a regression model that incorporates precipitation in a nonlinear fashion. The regression model produces superior predictions to those of the time series model. The regression model forms the basis for simulations that permit comparisons of model parameters and precipitation as contributors to variation in river flow.
Contribution of hypolimnetic water on metalimnetic dissolved oxygen minima in a reservoir
Authors: Nix J.
Published: February 2008

A minimum in the dissolved oxygen distribution of numerous lakes and reservoirs has been observed to develop in the metalimnion during the stratified period. This minimum is usually explained by the accumulation of organic matter from the overlying layer of water. The introduction of organic matter from the interflow of storm water is also a likely contributor to the accelerated oxygen depletion within the metalimnion. Data are presented that demonstrate that even during low flow periods, water containing reduced species in the deeper upstream section of DeGray Reservoir, Arkansas, is being incorporated into a density current and transported advectively through the metalimnetic region. This mechanism may contribute significantly to the development of metalimnetic dissolved oxygen minima in reservoirs with similar stratification and flow characteristics to DeGray Reservoir.
Physical basis of stochastic models of annual flows
Authors: Salas Jose D. , Smith Ricardo A.
Published: February 2008

The main objective of this paper is to demonstrate that annual streamflow time series can be represented by autoregressive and moving average (ARMA) processes. The method follows the conceptual representation of a watershed given by Fiering (1967).
Model for planning water‐energy systems
Authors: Lall Upmanu , Mays Larry W.
Published: February 2008

A mathematical programing model which has a nonlinear objective function and linear constraints is developed for the planning of composite regional water‐energy systems and is solved using the largescale generalized reduced‐gradient technique. Three interacting subsystems (the water subsystem, the power generation subsystem, and the coal and synthetic natural gas subsystem) are modeled to define the interlinked water‐energy system. The objective of the model is to minimize the sum of the capital, operating, and distribution costs incurred in meeting future water, gas, coal and power demands within a region. The nonlinear objective function represents an improvement over existing models, as it permits analysis of nonlinear system response and economies of scale. The model is applied to a region located in northeastern Texas.
An integral transform method for the linearized Boussinesq Groundwater Flow Equation
Authors: Daly Charles J. , Morel‐Seytoux H. J.
Published: February 2008

An analytical procedure is developed for the determination of potentiometric head in nonhomogeneous aquifers. Both steady and unsteady flow conditions are considered. The analytical procedure is based upon the use of orthogonal functions. It consists essentially of assuming an appropriate orthogonal series for both the aquifer properties and the unknown potentiometric head. The technique is applied to several one‐ and two‐dimensional flow problems where conditions are described by the linearized Boussinesq equation. The result of the analysis is the expression of potentiometric heads in analytic form. Subsequent use of Darcy's law yields accurate, analytic equations for the associated velocity fields. Such representations of the flow field are a potential benefit for prediction of mass transport in groundwater since velocity is known as a continuous function of space and time. Other useful features of the orthogonal series approach include its straightforward application. The approach is also shown to eliminate the introduction of discretization errors associated with the use of node systems which are required by many alternative numerical methods.
Compatibility of Canadian snowfall and snow cover data
Authors: Goodison B. E.
Published: February 2008

The accuracy and compatibility of Canadian snowfall and snow survey data were investigated in the Cold Creek research basin in southern Ontario. Problems in obtaining compatible point measurements of snowfall precipitation from gauge and ruler measurements are discussed. However, it is shown that correction of gauge measurements (MSC Nipher, Universal, Fischer and Porter) of snowfall water equivalent for catch variations caused by environmental factors, notably wind speed, results in compatible storm or seasonal totals. Accurate statistics of basin snow cover were determined from snow courses specifically sited in relation to basin land use. At the time of peak accumulation, which might occur at any time during the winter, there was a statistically significant difference in snow cover between land use categories. Mean basin snow cover was calculated by weighting the snow survey measurements in proportion to basin land use. The need to consider the effect of changing land use on snow course measurements is demonstrated. Results show that as an alternative to direct snow survey measurements, accumulated precipitation may be used to estimate snow cover up to peak accumulation. Net snow cover determined from accumulated corrected gauge data less short‐term melt losses and snow evaporation was within the confidence limits of the basin mean snow cover measured during the winter. Compatible results are only achieved when precipitation measurements are corrected for gauge catch variations and snow survey data are representative of basin land use.
Analysis of the reciprocity concept in a porous medium
Authors: Falade G. K.
Published: February 2008

The general reciprocity relation was proved to be valid for flow of fluid through porous medium, the validity was demonstrated for flow within a semi‐infinite domain and also for a finite domain bounded by impermeable boundaries. A graphical analysis of the reciprocity relation was presented for the bounded system.
Flow in aquifers with clay laminae: 1. The comprehensive potential
Authors: Strack O. D. L.
Published: February 2008

A description is given of steady flow in a system of homogeneously permeable aquifers that are separated by thin impervious clay laminae. Restriction is made to laminae that do not overlap one another. A steady state two‐dimensional Dupuit‐Forchheimer model is formulated to predict piezometric heads in the aquifers. The flow below the laminae may be confined or unconfined, and the possible occurrence of perched conditions above the laminae is taken into account. A new potential is introduced, with a gradient equal to minus the vectorial sum of the discharges in the upper and lower aquifers. This potential is referred to as the comprehensive potential and is determined by solving a boundary value problem of the Poisson equation. Application of the comprehensive potential makes it possible to establish heads along the edges of the clay laminae without the use of an iterative procedure. Two flow problems are solved as examples of the technique presented in this paper.
Regional flood frequency estimation and network design
Authors: Greis Noel P. , Wood Eric F.
Published: February 2008

The use of probability weighted moments has been investigated for improving estimates of flood recurrence quantile events in both gauged and ungauged basins. Regional estimates at gauged sites are improved over more conventional methods such as method of moments and maximum likelihood estimation. An improved method for ungauged basins is proposed which incorporates both probability weighted moment techniques with more traditional mean peak flow estimation. The question of network design in terms of number of sites and number of years of record is reexamined in light of the probability weighted moment techniques.
The response of groundwater to artificial recharge schemes
Authors: Latinopoulos P.
Published: February 2008

Analytic solutions are presented for the groundwater flow in an unconfined aquifer under seasonal artificial recharge schemes of variable duration. The results can be used for a preliminary assessment of the response of groundwater to artificial recharge. Variations in storage and outflow from the aquifer, apart from the siting of recharge, are also highly dependent on both the aquifer characteristics and the duration of recharge.
A screening model to quantify resilience
Authors: Fiering Myron B.
Published: February 2008

Concurrent advances in statistics and biology have introduced similar concepts to these disciplines: the use of robust estimators and the investigation of resilient ecosystems, respectively. This paper and those following in this series explore the application of these concepts of water resource systems. The emphasis here is on the concept of a resilient water resource system, or one which does not respond precipitously to a major ‘surprise’ during the course of its economic life. The general flatness of the response surface in the vicinity of the global optimum is explored, leading to suggestions for selection of small‐, intermediate‐, and large‐scale system design. The conclusions indicate that systems characterized by a small number of design options are somewhat more brittle and are more sensitive to optimization procedures, while systems which contain significant redundancies are relatively insensitive to the identification of global optima and lend themselves more readily to negotiations in the institutional and political spheres.
Modeling of leachate organic migration and attenuation in groundwaters below sanitary landfills
Authors: Sykes J. F. , Soyupak S. , Farquhar G. J.
Published: February 2008

A model for predicting the concentrations of leachate organics, measured as chemical oxygen demand, in groundwaters below sanitary landfill sites is developed. Simultaneous Michaelis‐Menten substrate utilization and microbial mass production equations, with convection and dispersion included for the former, were used for the modeling of biodegradation. For substrate concentrations significantly less than the half utilization rate coefficient and for microbial populations approaching a steady state the Michaelis‐Menten equations are reduced to a first‐order reaction kinetic model. The nonlinear model equations are solved using a Galerkin finite element technique, with a Newton Raphson iteration procedure being used to solve the resulting matrix equations. Model sensitivity studies are undertaken to determine the extent to which COD reduction might vary in the field with respect to time and space. The results indicate that substantial removal of leachate organics can be expected within short distances of the landfill even under the conditions of widely varying biological parameters. Model results are compared to the leachate organic reduction occurring below the Canadian Forces Base Borden sanitary landfill.
Atmospheric deposition processes and their importance as sources of nutrients in a chaparral ecosystem of southern California
Authors: Schlesinger William H. , Gray John T. , Gilliam Frank S.
Published: February 2008

Precipitation and dry fallout were collected over a 2‐year period in the Santa Ynez Mountains, Santa Barbara County, California, and analyzed for nutrient content. Mean annual depositions of Ca (2.2 kg/ha), K (0.7 kg/ha), NH4+‐N (0.5 kg/ha), and NO3−‐N (1.5 kg/ha) were largely derived from dryfall; depositions of Na (7.2 kg/ha), Mg (1.2 kg/ha), and SO4=‐S (3.6 kg/ha) were important in both rainfall and dry fallout. These atmospheric inputs are equal to or larger than the typical annual losses reported in runoff from mature chaparral shrublands, but on the basis of these inputs, more than 70 years may be necessary to replace the nitrogen losses measured in volatilization and runoff after fire. The depositions of NO3−‐N and SO4=‐S at this remote site may be indicative of the natural levels of these ions which, in many other areas of California, are derived from anthropogenic sources.
The Policy Delphi and Public Involvement Programs
Authors: Baumann Nancy , Ervin Osbin , Reynolds Gerald
Published: February 2008

Involvement of the public in water resources planning is generally required by federal law. However, the specific approach and techniques for involvement are left to the discretion of agencies participating in the particular project. This has resulted in considerable debate and experimentation aimed at discovery of effective public involvement techniques. This paper posits the Policy Delphi as one such technique, elaborates the major assumptions and rationale of the technique, and reports on an application of the approach in a water resources planning project of the U.S. Army Corps of Engineers. The Policy Delphi proved to be a useful component of the public involvement program in this case, providing both planners and the wider public with informed opinion about water resources issues and alternatives. Methodological issues for consideration in future applications of the technique to water resources planning are discussed.
Stochastic analysis of spatial variability in two‐dimensional steady groundwater flow assuming stationary and nonstationary heads
Authors: Mizell Steve A. , Gutjahr Allan L. , Gelhar Lynn W.
Published: February 2008

Two‐dimensional steady groundwater flow in a confined aquifer with spatially variable transmissivity T is analyzed stochastically using spectral analysis and the theory of intrinsic random functions. Conditions that ensure a stationary (statistically homogeneous) head process are derived, and using two convenient forms for the covariance function of the ln T process, the head covariance function is studied. In addition, the head variogram is obtained for a particular nonstationary case, and the asymptotic head variogram is derived under very general conditions. Results are compared to those obtained by Gelhar (1976) for one‐ and two‐dimensional phreatic flow and Bakr et al. (1978) for one‐ and three‐dimensional confined flow. Multidimensional flow analysis results in a significantly reduced head variance. The head correlation remains high over much greater distances than the ln T correlation. The variogram obtained when stationary heads are assumed is identical to that obtained for nonstationary heads for dimensionless lag distances up to 2½ times the correlation scale of the log transmissivity. The variogram for nonstationary heads continues to grow logarithmically as lag distance increases, independent of the form of the input covariance in the nonstationary case. The conditions for stationarity are contrasted with the corresponding results obtained for the one‐ and three‐dimensional cases of Gutjahr and Gelhar (1981). The head variance calculated from the stationary theory is found to agree with that of previous Monte Carlo simulations.
A comparison of four streamflow record extension techniques
Authors: Hirsch Robert M.
Published: February 2008

One approach to developing time series of streamflow, which may be used for simulation and optimization studies of water resources development activities, is to extend an existing gage record in time by exploiting the interstation correlation between the station of interest and some nearby (long‐term) base station. Four methods of extension are described, and their properties are explored. The methods are regression (REG), regression plus noise (RPN), and two new methods, maintenance of variance extension types 1 and 2 (MOVE.l, MOVE.2). MOVE.l is equivalent to a method which is widely used in psychology, biometrics, and geomorphology and which has been called by various names, e.g., ‘line of organic correlation,’ ‘reduced major axis,’ ‘unique solution,’ and ‘equivalence line.’ The methods are examined for bias and standard error of estimate of moments and order statistics, and an empirical examination is made of the preservation of historic low‐flow characteristics using 50‐year‐long monthly records from seven streams. The REG and RPN methods are shown to have serious deficiencies as record extension techniques. MOVE.2 is shown to be marginally better than MOVE.l, according to the various comparisons of bias and accuracy.
Bank stability and channel width adjustment, East Fork River, Wyoming
Authors: Andrews E. D.
Published: February 2008

Frequent surveys of eight cross sections located in self‐formed reaches of the East Fork River, Wyoming, during the 1974 snowmelt flood showed a close relation between channel morphology and scour and fill. Those cross sections narrower than the mean reach width filled at discharges less than bankfull and scoured at discharges greater than bankfull. Those cross sections wider than the mean reach width scoured at discharges less than bankfull and filled at discharges greater than bankfull. The accumulation and depletion of sand‐sized bed material in a cross section was concentrated in the near‐bank parts of the stream channel and thus significantly influenced bank stability and retreat. In those cross sections that scour at discharges greater than bankfull, the basal bank material is eroded and the banks become undercut and unstable. Conversely, in those cross sections that fill at discharges greater than bankfull, the basal bank material is covered by the accumulated sand‐size material and is not eroded. Streambanks in these cross sections are moderately inclined and stable. A resurvey in the summer of 1980 of the cross sections located in straight reaches showed that those cross sections which scoured at discharges greater than bankfull had become 2–4 feet wider, whereas those cross sections which filled at discharges greater than bankfull were unchanged. Thus bank stability and to some extent the adjustment of stream channel width in the East Fork River study reach appears to be controlled by the processes of scour and fill.
Erosion, redeposition, and delivery of sediment to midwestern streams
Authors: Wilkin Donovan C. , Hebel Susan J.
Published: February 2008

While sediment in surface waters may be one of our more serious water quality problems, the sources of this sediment are not well defined. Sediment control programs for water quality are presently concentrating on the application of best management practices (BMP's) across the watershed with little regard to location. The authors have studied sediment movement patterns in a midwestern watershed using fallout cesium‐137 techniques and have concluded these programs may be largely ineffective. The implications from this work are that cropped floodplains are the most severely eroded lands in the watershed, followed by cropped lands bordering the floodplains. Most of the eroded sediment either originates on or is delivered directly to the active floodplain and hence to the stream. The authors conclude that the majority of cropped uplands may not be nearly as important in determining sediment levels in streams as is generally thought.
Response surface parameter sensitivity analysis methods for postcalibration studies
Authors: Sorooshian Soroosh , Arfi Farid
Published: February 2008

This paper addresses the role of parameter sensitivity analysis for postcalibration studies of conceptual rainfall‐runoff models. Two sensitivity measures, namely, concentricity and interaction, which characterize the shape of the response surface in the neighborhood of the converged point were developed. When used conjunctively, the two measures provide some useful information related to the geometry of the response surface in two‐parameter subspaces. The role of these measures for postestimation purposes is demonstrated in the case of a four‐parameter model using synthetically generated data.
A point process model of summer season rainfall occurrences
Authors: Smith James A. , Karr Alan F.
Published: February 2008

A point process model of summer season rainfall occurrences is developed. The model, which is termed an RCM process, is a member of the family of Cox processes (Poisson processes for which the rate of occurrence of events varies randomly over time). Model development is based on counts and interarrival time statistics estimated from Potomac River basin rainfall data. The counting parameters used are the conditional intensity function, index of dispersion, and counts spectrum; the interarrival time parameters are the coefficient of variation and the autocorrelation function. Explicit results are presented for the counts and interarrival time parameters of RCM processes. Of particular importance in this paper is the interpretation of clustering suggested by the form of the RCM process. For the RCM process the rate of occurrence alternates between two states, one of which is 0, the other positive. During periods when the intensity is 0, no events can occur. The form of the intensity process suggests that clustering of summer season rainfall occurrences in the Potomac River basin results from the alternation of wet and dry periods. Computational results are presented for two extensions of the RCM process model of rainfall occurrences: a marked RCM process model of rainfall occurrences and associated storm depths and a bivariate RCM process model of rainfall occurrences at two sites.
A cluster model for flood analysis
Authors: Cervantes J. E. , Kavvas M. L. , Delleur J. W.
Published: February 2008

A two‐level and two‐dimensional nonhomogeneous point stochastic process is developed to model the flood peaks of a hydrograph. The model is a cluster process of the Neyman‐Scott type and presents the occurrences of flood generating mechanisms (FGM) at the precipitation level as the triggers for clusters of flood peaks at the runoff level. The FGMs are studied in terms of their times of occurrence τ and their volumes ν. The volume of a FGM corresponds to the volume of precipitation in the precipitation cluster that originates at the occurrence time of the FGM. Thus, each precipitation cluster at the precipitation level is represented by its origin time and by its volume as a point in a time volume plane, τ = (τ, ν). The FGM points in the time volume plane of the precipitation level form a two‐dimensional process,Nc(τ), with a nonhomogeneous rate of occurrence λ(τ). It is assumed thatNc(τ) is a Poisson process. The FGMs, in turn, generate a two‐dimensional subsidiary process,Ns(t |τ), in the runoff level. This process represents the occurrences of flood peaks at timetwith magnitudemas a point in the time magnitude plane t = (t, m), determined by the conditional rate of occurrence μ(t|τ), and is also assumed to be a Poisson process. The statistical properties of the flood cluster processN(t), defined as the total number of flood peaks, are found in terms of the probability generating functional of the process. Using a nonparametric methodology, the two‐dimensional parameters λ(τ) and μ(t|τ) are estimated. The theoretical rate of occurrence, the theoretical covariance density, and the theoretical probability mass function of the process are compared with the respective empirical functions obtained for several stations located in the Ohio River Basin. A good fit is found for the analyzed stations as the first two moments and the two‐dimensional probability mass function of the flood peak process are preserved.