bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative characterization of channel network structure
Authors: Smart J. S.
Published: February 2008

The most commonly used quantitative parameters for characterizing channel networks are derived from a Horton analysis (bifurcation ratios, stream length ratios, and so forth). Although these parameters give useful information about individual networks, they are generally ineffective in distinguishing differences in network structure due to lithologic controls and degree of maturity. As Shreve has noted, this failure is due in part to the random nature of network topology and link lengths and in part to the fact that the Horton analysis tends to average out many of the details that characterize such differences. Parameters derived from considerations of statistical geometric similarity, on the other hand, are relatively successful in characterizing network structure. For a simple example, let le and li be the mean exterior and interior link lengths, respectively, and ae and ai be the means of the associated drainage areas. Four dimensionless parameters that can be constructed from this set are λ = le/li α = ae/ai Ke = le2/ae and Ki = li2/ai. Data on λ, α, Ke and Ki for natural networks drawn from different geologic populations indicate that these quantities are effective in detecting differences due to varying lithology and degree of maturity.
Conditional chance‐constrained model for reservoir control
Authors: Lane Morton
Published: February 2008

This paper presents a model for designing the optimum control policies of a reservoir serving an agricultural demand area. Policies are designed to maximize the expected agricultural benefits to the area. The demand for irrigation water depends on both the crops planted and the rainfall in the area. Explicit account is taken of both, particularly the stochastic nature of the rainfall, which is characterized as a joint log normally distributed random variable. The problem lends itself to a conditional chance‐constrained formulation. However, the dependency of the rainfall distributions and agricultural functions does not lead to conveniently solvable deterministic equivalents. As a result, decision rules are defined for each of a series of sequences of rainfall intervals. The problem then reduces to linear programing form. The novelty of the approach lies in the fact that the decision rules are conditional rules whose parameters depend on previous observations of the random variable.
Determination of the discharge policy for existing reservoir networks under differing objectives
Authors: LeClerc Guy , Marks David H.
Published: February 2008

The discharge policy for a network of eight small existing reservoirs used for recreational activities and for water supply of a city downstream of the network is determined by using optimization techniques. A linear programing problem is formulated by using a linear operating rule, and chance‐constrained programing is adopted to account for the stochasticity of the inflows. Two objective functions are introduced to study the cost of a more equitable distribution of the losses due to surface drawdowns than the most efficient distribution, which minimizes the total summation of the individual drawdowns. A case study on the Rivière du Nord, Quebec, Canada, is presented. The results show that the linear operating rule is valid for existing reservoir analysis; it is also observed that chance‐constrained programing may have serious ineptitudes for design purposes and for analysis of large existing reservoir networks. The approach, however, is a desirable management tool for systems of small reservoirs, primarily as a screening model.
Multiple‐Objective Optimization in Water Resource Systems
Authors: Vemuri V.
Published: February 2008

Multiple‐objective optimization problems naturally arise in resource management projects. A chief difficulty with multiple‐objective optimization is that it is no longer clear what one means by an optimal solution. A possible remedy to this situation is to refine the concept of ‘optimal solution’ by introducing the so‐called ‘noninferior solution set.’ Then optimization, in a multiple‐objective context, boils down to determining the set of noninferior solutions. Determination of the noninferior set is facilitated by relating it, in a one‐to‐one manner, to a family of auxiliary scalar optimization problems. For a certain class of problems the entire noninferior set can be obtained by solving the auxiliary scalar problem. This procedure is illustrated by means of a problem that commonly occurs in water resource planning and management.
Multiobjectives in water resource systems analysis: The Surrogate Worth Trade Off Method
Authors: Haimes Yacov Y. , Hall Warren A.
Published: February 2008

The problem of noncommensurable multiobjective functions in water resource systems is discussed. Potential strategies in multiobjective decision theory are summarized. A new method for solving non‐commensurable multiobjective functions, namely, the surrogate worth trade off method, is developed. Procedures for the derivation of the trade off functions and the surrogate worth functions are developed and analyzed. Major characteristics and advantages of the surrogate worth trade off method are summarized. In particular, the trade off and surrogate worth functions are constructed in the functional space, where an interaction with the decision maker takes place, and only then these functions are transformed into the decision space. The Reid and Vemuri multiobjective problem in water resources has been chosen as an example and was successfully solved via the surrogate worth trade off method.
Filter pore‐size effects on the analysis of Al, Fe, Mn, and Ti in water
Authors: Kennedy Vance C. , Zellweger Gary W. , Jones Blair F.
Published: February 2008

Fine‐grained particulate material can pass through a 0.45‐μm membrane filter and cause major errors up to an order of magnitude or more in the determination of Al, Fe, Mn, and Ti dissolved in natural waters. Other elements enriched in clay‐size sediments but normally very low in solution concentration may also be affected.
Field test of a modified numerical model for water uptake by root systems
Authors: Feddes R. A. , Bresler E. , Neuman S. P.
Published: February 2008

Data obtained from careful water balance studies on water uptake by the roots of red cabbage are compared with results obtained from a modified numerical model of Nimah and Hanks. In the modified model the air dry moisture content at the soil surface may vary with time depending on meteorological conditions. The maximum possible rate of evapotranspiration is calculated by considering both meteorological conditions and crop properties. Data are quoted to suggest that the coefficient of the root sink may sometimes vary exponentially with depth. A period of 7 weeks was simulated, and the calculated weekly moisture profiles did not agree completely with those measured in the field. On the other hand, the calculated cumulative rates of evaporation and transpiration were in excellent agreement with the field data. When the original model was used without the suggested modifications, the agreement of these rates with the field data was not as good, an indication that some of these modifications actually improve the predictive capabilities of the model.
Hydrogeochemistry of carbonate groundwaters of an urban area
Authors: Long David T. , Saleem Z. A.
Published: February 2008

A comparison of the groundwater chemical data from the shallow dolomite aquifer of Northeastern Illinois Metropolitan Area (NIMA) from August 1972 through April 1973 with data collected 12–40 yr earlier indicates that concentrations of all ions have increased, the greatest increase occurring in the south‐eastern part of the area where the overburden is thinnest. The largest increases are 843, 142, and 91% in Cl−, SO42−, and Na+, respectively. However, the spatial distribution of the groundwater chemical types has remained the same with time. The groundwater was found to be apparently supersaturated with respect to calcite and dolomite; however, the two saturation indices were reduced by 20 and 30%, respectively, after considering the effect of ion pairings. The chemical character of the groundwater is controlled, among other factors, by the change of carbon dioxide content of the water along the groundwater flow path. A model for the solution of dolomite based on the standard equations for carbonate equilibrium is presented. The application of the model to the study area indicates that a variety of geologic conditions between the dolomite aquifer and the overlying glacial drift prevail in the area.
Water table position as affected by soil air pressure
Authors: Linden D. R. , Dixon R. M.
Published: February 2008

Air pressures in the unsaturated soil and hydraulic heads beneath a shallow water table were measured during border irrigations. Air pressures rose during the irrigation, thereby increasing the hydraulic heads. The increased hydraulic heads were not uniformly distributed under the border strip but varied in the cross‐slope and with‐slope directions and thus caused groundwater redistribution. Cross‐slope and with‐slope variations in air pressures also caused variations in infiltration and groundwater recharge.
Relative importance of meteorological variables in snowmelt
Authors: Zuzel John F. , Cox Lloyd M.
Published: February 2008

To improve predictive equations of the snowmelt process, we need to better understand the relative importance of various meteorological parameters. Factor analysis and regression analysis were used to determine the effectiveness of wind, air temperature, vapor pressure, and net radiation in predicting snowmelt. Analyses of meteorological and snowmelt data collected at a site near Boise, Idaho, in May 1973 showed that the standard error of daily snowmelt prediction could be decreased 13% by using vapor pressure, net radiation, and wind in predictive equations rather than just air temperature.
Transient free surface flow to a well: An analysis of theoretical solutions
Authors: Gambolati Giuseppe
Published: February 2008

Several simplifying assumptions are in general required to solve analytically the set of differential equations controlling transient free surface flow to a fully penetrating gravity well. Results based on the linearization technique as well as on the delayed yield concept provide the most advanced theoretical developments to date. A review of available solutions is presented together with some complementary interpretations of their physical behavior and an analysis of the interrelations between the corresponding basic theories. If the elastic storage coefficient S8 is markedly less than the specific yield Sy, the vertical fluid transport is predominant in a cylindrical zone of the water table aquifer included between two regions where flow is essentially radial and is controlled by two different Theis equations. Its boundary surfaces move in time far from the well. If S8 is of the same order of or greater than Sy, the vertical components always tend to become subordinate throughout the aquifer, which at any instant basically behaves as an artesian formation. The physical meaning of Boulton's (1955) delay index 1/α is extensively discussed. It is shown that, contrary to Neuman's (1975) conclusions, the true physical α does not vary linearly with the logarithm of the radial distance r from the pumping well, but it is almost linearly related to 1/r and becomes practically constant at some distance from the well (equal to twice the aquifer thickness if the medium is isotropic). An empirical delay index is also found by equating Boulton's (1963) solution and the linearized average drawdown. Its expression enables us to use the classical delayed yield solution to compute the average piezometric decline with an accuracy equal to that of the linearization approach whose final outcome is, however, more complex and needs more computational time for its numerical evaluation. The two major assumptions underlying the present solutions, which are generally more accurate than the Dupuit‐Boussinesq equation, essentially require small water table drawdowns and an aquifer of infinite areal extent.
The generation of runoff from subarctic snowpacks
Authors: Dunne Thomas , Price Anthony G. , Colbeck Samuel C.
Published: February 2008

A physically based model of the movement of water through snowpacks was used to calculate hydrographs generated by diurnal waves of snowmelt on the tundra and in the boreal forest of subarctic Labrador. The model was tested against measured hydrographs from hillside plots that sampled a range of aspect, gradient and length, vegetative cover, and snow depth and density. The model yielded good results, particularly in the prediction of peak runoff rates, though there was a slight overestimate of the lag time. A comparison of predictions with field measurements indicated that given the ranges over which each of the controls is likely to vary, the two most critical factors controlling the hydrograph are the snow depth and the melt rate, which must be predicted precisely for short time intervals. Permeability of the snowpack is another important control, but it can be estimated closely from published values.
A simple tube‐type water profile sampler
Authors: Gilbert R. G. , Miller J. B.
Published: February 2008

A plexiglass tube‐type water profile sampler was designed for use in relatively shallow bodies of water, such as farm ponds, small recreational lakes, irrigation canals, and the surface 2 m of larger lakes and rivers. The sampler is a plexiglass tube with holes drilled at intervals (side ports) corresponding to water layers which are to be sampled. To obtain a water sample, the tube (open at both ends and with the side ports closed) was gently lowered vertically into the water. With the top stoppered, the tube was raised and its bottom stoppered just under the water surface. While the tube is held vertically, the water profile samples are rapidly and easily obtained after removing the top stopper and successively collecting from top to bottom the water sample from each side port. Dissolved oxygen (DO) profiles of the ponds measured with an oxygen probe directly in the ponds were similar to DO profiles of water samples collected with the tube sampler. Chemical and biological analyses of water samples obtained with the tube‐type sampler and two other standard type water samplers (Kemmerer and Van Dorn) were compared. The analyses revealed that similar relative results were obtained from water samples collected with all three samplers, but the tube‐type sampler was more desirable for obtaining water profile samples because of its simplicity of design and operation, especially in small ponds.
Comparison of linear systems and finite difference flow‐routing techniques
Authors: Keefer Thomas N.
Published: February 2008

A single‐input linear system model and a multiple‐input linear system model are compared to a finite difference model. Comparisons are based on the ability of the models to predict discharge at the downstream end of a 24.14‐km reach of prismatic channel. Four types of channels and two slopes covering a wide range of conditions are evaluated. The single‐input model compares favorably in cases where flood wave celerity does not vary greatly with discharge. The multiple‐input model can be made to compare favorably in all cases. Linear model parameters cannot be set accurately without calibration, except in the case of rectangular channels. The single‐input model is approximately one sixth as costly as the finite difference model, and the multiple‐input model is approximately one half as costly for the conditions investigated.
Areal differentiation of snow cover in east central Ontario
Authors: Adams W. P.
Published: February 2008

Vegetationally based patterns of snow depth, density, and water equivalent are identified by using snow course, grid, and unaligned random sample measurements. The limitations of extrapolations from point measurements to general characteristics of regional snow cover are discussed for an area in which midwinter melt is a feature of snow cover evolution. The snow cover of the vegetation zones was most distinct in terms of water equivalent and least distinct in terms of density. Measurements of depth proved to have a high predictive value for water equivalents. The validity of generalizations from point measurements, even in terms of quite coarse measures of snow cover characteristics, is limited in areas such as this to a short period following the time of measurement.
Atmospheric sulfate additions and cation leaching in a Douglas fir ecosystem
Authors: Cole Dale W. , Johnson D. W.
Published: February 2008

Precipitation sulfuric acid input was small in comparison to sulfate and cation transfers within the ecosystem studied. Most of the annual incoming hydrogen ions were removed in the forest canopy, presumably through an exchange process. Therefore canopy leaching appears to be most strongly affected by acid rainfall, whereas soil leaching appears to be dominated by mechanisms internal to the ecosystem, such as carbonic acid leaching and sulfur release from decomposing litter.
Numerical analysis of two‐dimensional infiltration and redistribution
Authors: Perrens S. J. , Watson K. K.
Published: February 2008

The two‐dimensional flow equation for the movement of water in unsaturated porous materials is used to study an infiltration‐redistribution sequence in which the surface flux is spatially nonuniform. A numerical analysis based on a finite difference scheme involving the use of iterative alternating direction implicit techniques is found to describe the two‐dimensional flow process satisfactorily. The program incorporates an interpolation‐type hysteresis model which enables temporal as well as spatial variations of flux to be simulated. The flow regime is discussed with reference to two porous materials which have contrasting hydrologic characteristics. The two‐dimensional profile distributions of water content and pressure head are represented at significant times by a series of perspective diagrams.
Survey results on the benefits of water pollution abatement in the Merrimack River Basin
Authors: Oster Sharon
Published: February 2008

A report on and an analysis of a survey of individuals' willingness to pay for water pollution abatement in the Merrimack River Basin are presented. The survey included 200 residents of the basin; data were collected on socioeconomic attributes of the respondents as well as their willingness to pay and their expected use of a clean river. The average (mean) willingness to pay for pollution abatement in the basin was found to be fairly high, about $12.00/yr per person. Home ownership, increases in income, and family size were all related to increased willingness to pay.
Analysis of a capillary hysteresis model based on a one‐variable distribution function
Authors: Mualem Y. , Morel‐Seytoux H. J.
Published: February 2008

Parlange's (1976) model corresponds to a special case of Mualem's similarity hypothesis ƒ(ψw, ψd) = h(ψw)l(ψd) in which h(ψ) is set at unity for all ψ values. Interpreted in terms of the soil water domain theory this assumption implies that the relative pore volume of the domains is distributed uniformly in respect to the wetting radius (or to ψw). In this paper the proper mathematical equation is derived for calibrating the model from the experimental main drying curve. The applicability of Parlange's model for the soil water hysteresis is theoretically analyzed and extensively tested for different types of porous media. Theoretical hysteretic curves derived by direct implementation of Parlange's model are compared with experiments. These comparisons show that Parlange's model contradicts well‐known properties of the soil moisture characteristics. The good results reported by Parlange are not obtained when actual measured curves of the hysteresis loop are used. Whether the main branch of hysteresis for wetting or for drying is used in calibration, one obtains badly distorted shapes of hysteresis curves. Parlange's suggestion for calibrating the model on the basis of the main drying curve plus one additional point from the main wetting curve is considered too arbitrary to be reliable.
Approximation of a normal distribution by a three‐parameter log normal distribution
Authors: Burges Stephen J. , Hoshi Kiyoshi
Published: February 2008

A procedure is given where mixed normal and log normal populations exist; the normal populations can be approximated with three‐parameter log normal (3PLN) distributions to facilitate multivariate stochastic hydrologic disaggregation or generation approaches. Approximations can be made by assuming an arbitrary small value of skew G (0.05‐0.01). For G ≤ 0.1 the appropriate parameters for a 3PLN distribution can be approximated as dimensionless location parameter α = a/μx ≃ 1 − CV(3G−l+ G/9); σy ≃ G/3 − 7G3/324; µy ≃ ln (3σx/G) − (G2/54).
A comparison of two formula types for calculating long‐wave radiation from the atmosphere
Authors: Aase J. K. , Idso S. B.
Published: February 2008

Measurements of long‐wave radiation at Sidney, Montana, indicated that both an analytically derived equation and an empirically derived equation for clear‐sky conditions adequately predict the long‐wave radiation flux at that site for screen level air temperatures above 0°C. However, for air temperatures below 0°C the analytical equation always underestimated the true radiation, while the empirical equation just slightly underestimated it, then match it, and then overestimated it, as air temperature decreased from 0° to −37°C. These discrepancies in the below 0°C temperature regime indicate that the equations may need some modification to conform more closely to reality for low‐temperature conditions.
Effect of pH on the adsorption of trace radioactive cesium by sediments
Authors: Elprince A. M.
Published: February 2008

The adsorption of trace radioactive cesium by sediments from the Savannah River Plant area follows a theoretically expected linear relationship between ln Kd* and the pH of the equilibrium solution, where Kd* is the equilibrium distribution coefficient: Cs adsorbed (meq g−1)/Cs+ in solution (meq ml−1). Theoretically, the slope of these plots is proportional to the fraction of surface area occupied by pH dependent charges. Experimentally, the slope becomes zero after removal of hydroxy Al interlayers with citrate pretreatment. Hydroxy Al interlayers are thus the main source for the pH dependent charges making Cs+ adsorption pH dependent.
Sampling and chemical interpretation of precipitation for mass balance studies
Authors: Lewis William M. , Grant Michael C.
Published: February 2008

From an analytical viewpoint, total dry and wet precipitation consists of three fractions: (1) dissolved materials in aqueous precipitation, (2) the water‐soluble component of dry precipitation, and (3) the water‐insoluble component of either wet or dry precipitation. Methods of precipitation collection and processing greatly affect the separation of these components. A literature survey shows that fraction 3 has typically been ignored and that samplers currently in use lead to a highly variable mixture of the three fractions. Major causes of interpretational ambiguity include (1) variable leaching of dry fallout, (2) particle formation and chemical repartitioning in aqueous precipitation, (3) height, texture, and composition of the collector surfaces, (4) relation of collector surfaces to natural environmental surfaces, (5) contamination by birds, insects, pollen, and organometallic release from local vegetation, (6) sample storage, and (7) failure to analyze insoluble particles. A literature survey also shows that most collectors currently in use are of insufficient size to collect samples large enough to support broad‐spectrum analysis on a weekly basis. The minimum satisfactory size of collectors is computed from (1) average rain chemistry, (2) sensitivity of standard chemical tests for chemical species of biological interest, and (3) volume required for each analysis. The computations show that collectors should have an area of at least 1200 cm2 in regions of average chemistry and as much as 8300 cm2 in cold climates with minimal aqueous precipitation. A design is given for a collector which combines large size with other desirable features.
Some aspects of Florida convective rainfall
Authors: Ulanski Stanley L. , Garstang Michael
Published: February 2008

A dense network of rain gages in an area of 660 km2 in south Florida was operated for the summers of 1971 and 1973. More than 3 times as much rain fell in this network in the summer of 1973 than in 1971. The two periods are examined in order to understand the controls in convective rainfall which produce such contrasting amounts. It is found that the total duration and intensity of rain was about the same in both years. Well‐organized thunderstorms of large extent account for the bulk of the rainfall. These large storms occurred with a greater frequency in 1973 than in 1971. Days with single showers produced more rain than multishower days. The critical variable in determining convective rainfall amount is the size of the individual storm. These large storms appear to eliminate competition for the available moisture supply and are more efficient in converting that moisture to rainfall.
Stochastic analysis of steady state groundwater flow in a bounded domain: 1. One‐dimensional simulations
Authors: Smith Leslie , Freeze R. Allan
Published: February 2008

A stochastic analysis of one‐dimensional steady state groundwater flow through a bounded domain is carried out by using Monte Carlo simulation techniques. The flow domain is divided into a finite set of discrete blocks. Hydraulic conductivity values in neighboring blocks are autocorrelated by assuming the spatial variations in conductivity can be represented by a first‐order nearest‐neighbor stochastic process model. An integral scale is defined to characterize the average distance over which conductivity values in the block system are autocorrelated. This model leads to a realistic representation of the spatial variations in hydraulic conductivity in a discrete block medium. Results of the simulations provide estimates of the output distributions in hydraulic head. It is shown that the ratio of the integral scale for conductivity to the distance between boundary points is a fundamental parameter in modeling the stochastic behavior of a bounded statistically homogeneous medium. The output distributions on the prediction variables must be interpreted in light of this parameter. The standard deviation in hydraulic head increases with an increase in either the standard deviation in hydraulic conductivity or the strength of the correlation between neighboring conductivity values. The standard deviation in head does not significantly depend upon the block size or the total number of blocks included along the flow line, provided a sufficiently accurate representation of the autocorrelation function is made. Although direct comparisons cannot be made, the Monte Carlo solution shows a similar behavior to the spectral solution of the stochastic flow equation in one dimension.
A square grid transport model relating land use exports to nutrient loads in rivers
Authors: Cluis D. A. , Couillard D. , Potvin L.
Published: February 2008

The present transport model relates a nutrient‐oriented land use data bank to mass discharges of total nitrogen and total phosphorus on an annual or seasonal basis. This bank is based upon already available Canadian statistics distributed upon drainage units of the Universal Transverse Mercator square grid system; it contains for both types of sources (direct and diffuse) information on the intensities and spatial distributions of the produced loads. Using two constants only, the contribution of a drainage unit to a downstream site can be written as L = CTk [P + (CI × NP)], where P and NP represent the point and nonpoint production of nutrients; CI is an internal transfer coefficient of nonpoint sources to the river, CT a transport coefficient from one unit to the following unit, and k a distance expressed in number of units covered. Stable sets of coefficients were obtained for each season, reflecting the hydrological regime and differences in mobility of phosphorus and nitrogen. Once it is calibrated, the model can be used to assess the relative contributions of each type of land use and predict the effect of impoundments or changes in land use.
The compressibility and hydraulic diffusivity of a water‐steam flow
Authors: Grant Malcolm A. , Sorey Michael L.
Published: February 2008

Physical parameters are defined for a flow of water and steam in a porous medium: dynamic and kinematic viscosity, density, and compressibility. These permit single‐phase pressure transient theory to be applied to two‐phase flow provided that the pressure changes are not too large.
Barometric fluctuations in wells tapping deep unconfined aquifers
Authors: Weeks Edwin P.
Published: February 2008

Water levels in wells screened only below the water table in unconfined aquifers fluctuate in response to atmospheric pressure changes. These fluctuations occur because the materials composing the unsaturated zone resist air movement and have capacity to store air with a change in pressure. Consequently, the translation of any pressure change at land surface is slowed as it moves through the unsaturated zone to the water table, but it reaches the water surface in the well instantaneously. Thus a pressure imbalance is created that results in a water level fluctuation. Barometric effects on water levels in unconfined aquifers can be computed by solution of the differential equation governing the flow of gas in the unsaturated zone subject to the appropriate boundary conditions. Solutions to this equation for two sets of boundary conditions were applied to compute water level response in a well tapping the Ogallala Formation near Lubbock, Texas from simultaneous microbarograph records. One set of computations, based on the step function unit response solution and convolution, resulted in a very good match between computed and measured water levels. A second set of computations, based on analysis of the amplitude ratios of simultaneous cyclic microbarograph and water level fluctuations, gave inconsistent results in terms of the unsaturated zone pneumatic properties but provided useful insights on the nature of unconfined‐aquifer water level fluctuations.
Multiobjective dynamic programing: A classic problem redressed
Authors: Tauxe George W. , Inman Robert R. , Mades Dean M.
Published: February 2008

The problem of noncommensurable multiple‐objective functions in water resources and potential methods for solving such multiobjective problems are discussed. A new method, namely, multiobjective dynamic programing (MODP), that borrows from conventional dynamic programing is developed. It generates the entire noninferior solution set of the multiobjective problem, and it can be used to generate the trade‐off ratios between objectives. The trade‐off ratios are actually a by‐product of the MODP method and are available explicitly between all objectives. The noninferior solution set is obtained solely in terms of the objectives rather than in terms of the individual decisions that influence each objective, thus facilitating the decision maker's task in choosing the preferred solution. The Reid‐Vemuri multi‐objective problem in water resources was chosen as an example and was successfully solved using MODP.
On a model of a nonlinear feedback system for river flow prediction
Authors: Ozaki T.
Published: February 2008

A nonlinear system with feedback is proposed as a dynamic model for the hydrological system, whose input is the rainfall and whose output is the discharge of river flow. Parameters and orders of the model are estimated using Akaike's information criterion. Its application to the prediction of daily discharges of Kanna River and Bird Creek is discussed.
Marketable permits for the control of phosphorus effluent into Lake Michigan
Authors: David M. , Eheart W. , Joeres E. , David E.
Published: February 2008

Transferable discharge permits (TDP) can be used to achieve desired abatement levels at costs that approach the minimum. The emphasis in the discussion is on the implementation of such a system, the public choice problem in its adoption, and an assurance that regardless of which polluters provide waste treatment there is a mechanism for equitable sharing in the costs ofthat abatement. The argument is applied to phosphorus abatement in the Wisconsin portion of the Lake Michigan basin. The level of demand and supply for TDP's among 53 waste treatment plants is simulated, and the necessary steps to create a market are outlined. Enforcement, price changes, and future adjustments in the permissible effluent loading are shown to be compatible with the marketing process proposed.
Mass transport: 1. A stochastic analysis of macroscopic dispersion
Authors: Smith Leslie , Schwartz Franklin W.
Published: February 2008

Conventional modeling of mass transport in groundwater systems usually involves use of the dispersion‐convection equation with large values of porous medium dispersivity to account for macroscopic dispersion. This work describes a modeling concept which accounts for macroscopic dispersion not as a large‐scale diffusion process but as mixing caused by spatial heterogeneities in hydraulic conductivity. The two‐dimensional spatially autocorrelated hydraulic conductivity field is generated as a first‐order nearest‐neighbor stochastic process. Analysis of a variety of hypothetical media shows that over finite domains a population of tracer particles convected through this statistically homogeneous conductivity field does not have the normal distribution and does not yield the constant dispersivity that classic theory would predict. This problem occurs because of insufficient spatial averaging in the macroscopic velocity field by the moving tracer particles. Our analyses suggest that the diffusion model for macroscopic dispersion may be inadequate to describe mass transport in geologic units. Sensitivity analysis with the model has shown that features of transport, such as first arrival of a tracer, are dependent on porous medium structure and that even when the statistical features of porous media are known, considerable uncertainty in the model result can be expected.
Large‐sample methods for decision analysis of gamma variates
Authors: Krzysztofowicz Roman , Yakowitz Sidney
Published: February 2008

It is widely recognized that Bayes decision analysis with gamma variables leads almost invariably to fairly troublesome computational difficulties. The purpose of this paper is to show how these difficulties can be circumvented by the use of certain results of decision theory in conjunction with some specialized developments on series expansions. Specifically, the posterior law will be approximated by the computationally and analytically convenient bivariate normal distribution. The approximation technique derived here is compared to exact formulas through statistical measures as well as comparative performance in water resource management contexts.
Real‐time forecasting with a conceptual hydrologic model: 2. Applications and results
Authors: Kitanidis Peter K. , Bras Rafael L.
Published: February 2008

The results from an application of a conceptual hydrologic model, combined with filtering and statistical estimation methods, to real‐time forecasting of river discharges are very encouraging. The use of feedback significantly improves the overall forecasting capability of the model even when the model and input error statistics are not perfectly known. Identification of these statistics through adaptive filtering techniques is practical and further improves the performance of the model. Comparison with a simple linear adaptive ‘black box’ model is very favorable for the conceptual hydrologic model, especially for forecast lead times comparably to the response time of the catchment. The results emphasize the importance of using a realistic model of uncertainty accounting for the nonstationarity in the rainfall‐runoff process.
A derivation of the macroscopic solute transport equation for homogeneous, saturated, porous media: 2. Reactive solutes at low concentration
Authors: Chu Shu‐Yuan , Sposito Garrison
Published: February 2008

The macroscopic transport equation for a reactive solute at low concentration in a homogeneous, saturated, porous medium is derived on the basis of a rigorous cumulant expansion applied to the equation of mass balance for the solute both in the liquid phase and in the solid phase. The derivation includes a detailed consideration of the molecular‐kinetic picture of adsorption. The commonly neglected fact that all adsorption phenomena in natural porous media also are exchange phenomena is emphasized, as is the important distinction between uniform and nonuniform adsorbing surfaces. For the uniform case, where there is only one type of adsorption site on the solid matrix, the expression for the macroscopic transport equation is identical in form with the standard dispersion‐convection equation incorporating a first‐order kinetic adsorption model. For the nonuniform case, where there is more than one type of adsorption site, the macroscopic transport equation derived in this paper and the conventional dispersion‐convection equation are no longer identical. The difference between the two equations is discussed briefly.
Stochastic modeling of mass transport in a random velocity field
Authors: Tang D. H. , Schwartz Franklin W. , Smith Leslie
Published: February 2008

The purpose of this paper is to develop and solve a stochastic transport equation which is based directly on a stochastic representation of the velocity field. This equation, which describes the spatial and temporal variation in ensemble mean concentration, is similar in form to the advection‐dispersion equation. Of particular note are the coefficients of the second‐order terms, which are termed ensemble dispersion coefficients. For a simple system where neighboring velocities are uncorrelated, these coefficients vary as a function of the mean velocity, the variance in velocity, and travel distance of the tracer. For cases where the spatial correlation in velocity can be approximated by an exponentially decaying function, ensemble dispersion coefficients ultimately reach a constant value. If ensemble averages and spatial averages for a realization are equivalent, the ensemble dispersion coefficients can be related to the process of dispersion in a single realization. A hybrid deterministic‐probabilistic technique used to solve the stochastic equation has been verified with a one‐dimensional analytic solution. The results of trials with the numerical model show how variability in ensemble mean concentration is controlled by the coefficients in the stochastic transport equation for two different types of loading functions. The generality of the model makes it suitable for application to media with very different spatial structure.
Moisture and heat transport in hysteretic, inhomogeneous porous media: A matric head‐based formulation and a numerical model
Authors: Milly P. Christopher D.
Published: February 2008

A general, physically based formulation of water and energy transport in partially saturated soil must account for the coupling between the fields of matric potential ψ and temperature T. The formulation by de Vries (1958) is converted to one that employs ψ and T as the dependent variables. This conversion facilitates a significant generalization of the theory to accommodate the omnipresent complications of hysteresis and inhomogeneity. The limitations of the assumptions of local thermodynamic equilibrium are discussed. A finite element solution algorithm for the one‐dimensional equations is outlined and tested on a variety of problems. The computational results demonstrate the reliability of the numerical model.
Determination of bedload transport using naturally magnetic tracers: First experiences at Squaw Creek, Gallatin County, Montana
Authors: Ergenzinger P. J. , Custer S. G.
Published: February 2008

Pebbles and cobbles constitute an important part of the sediment discharge of many streams. Data on the movement of this coarse bedload is important to a variety of studies including analysis of total sediment yield, resevoir‐filling rates, bridge erosion, and trout‐spawning habitat. Despite the importance of knowledge regarding coarse bedload transport, measurement remains difficult and unreliable. A new detector has been constructed which records the movement of naturally magnetic pebbles and cobbles. The detector was installed at a log sill in the bed of Squaw Creek, Gallatin County, Montana, to evaluate the detector under natural conditions. During a flood in May 1981 the detector recorded the passage of magnetic particles larger than 32 mm. Extrapolation of the data allows estimation of total bedload transport. Based on the composition of an unvegetated gravel bar upstream of the detector and on measurements of turbidity during the flood, bedload accounted for approximately 66% of the solid material leaving the drainage basin. Since many coarse bed streams probably contain material as magnetic as the andesitic rocks in Squaw Creek, the procedure should be widely applicable.
Contamination of successive samples in portable pumping systems
Authors: Thomas Robert B. , Eads Rand E.
Published: February 2008

Automatic discrete sample pumping systems used to monitor water quality should deliver to storage all materials pumped in a given cycle. If they do not, successive samples will be contaminated, a severe problem with highly variable suspended sediment concentrations in small streams. The cross‐contamination characteristics of two small commonly used portable pumping samplers are compared to each other and to reference measurements under conditions of sudden and severe changes in suspended sediment concentrations. The pressure‐vacuum sampler showed greater cross contamination, especially when changing from high to zero concentrations, than the peristaltic sampler. Both samplers, however, cross‐contaminated to some degree. The contamination was primarily due to the sand size particles rather than to the finer sizes.
Effects of Clearcutting and Slash Burning on Streamwater Chemistry and Watershed Nutrient Budgets in Southwestern British Columbia
Authors: Feller M. C. , Kimmins J. P.
Published: February 2008

Two small forested watersheds near Haney in southwestern British Columbia were partially clearcut, and the slash on one of them was subsequently burned. Streamwater chemistry was monitored in these treated watersheds and an undisturbed control watershed for 2 years prior to treatment and up to 9 years after treatment. The chemical parameters that were studied responded differently to the treatments, but there was a general pattern of increased concentrations and fluxes in Streamwater for the first 2–3 years following treatment followed by a decline to, and sometimes below, pretreatment values. The most pronounced increases were observed for K and NO3. It was not possible to determine the exact causes of these changes in concentrations and fluxes, due to the great variability in the ecosystems present. This variability precluded determination of statistically significant changes in annual terrestrial nutrient fluxes and pools. Stream nutrient exports usually were <10 kg/ha/yr for each of N, P, K, and Mg, <20 kg/ha/yr for Na and Cl, and <30 kg/ha/yr for Ca. These values were considerably less than nutrient exports in harvested logs and in losses to the atmosphere during the slashburn. Clearcutting and burning caused greater nutrient losses than Clearcutting alone, particularly in the case of N, where the Clearcutting and Clearcutting and burning treatments resulted in total losses of 245 kg/ha and 1293 kg/ha, respectively, for the first two years after treatment.
A Sensitivity Analysis of a Numerical Model for Estimating Evapotranspiration
Authors: Camillo P. J. , Gurney R. J.
Published: February 2008

A simulation approach has been used to study the sensitivity of evaporation, estimated with an energy and moisture balance model, to the meteorological data used to drive the model. The numerical model solves the surface energy balance equation. Daily evaporation is calculated by integrating the instantaneous fluxes. A Monte Carlo method is used to apply random errors to the meteorological data, and constant biases are also applied. This was done for both bare and wheat fields. Previous sensitivity studies have used analytical methods, ignoring the interaction of the meteorological measurements, their biases, and the feedback mechanisms which couple the energy and moisture fluxes. The method described here removes these restrictions and does not require linearity and differentiability in the evaporation estimation technique. The numerical method was shown to produce results generally similar to those expected analytically for random errors under near‐potential conditions. Measurement biases produced larger errors in evaporation than random errors. The method will be applicable for dry conditions, where an analytical approach is not feasible.
Landfill Leachate Migration Through Shallow Unconfined Aquifers
Authors: Ostendorf David W. , Noss Richard R. , Lederer David O.
Published: February 2008

We model the transport of a simply reactive contaminant through a landfill and initially pure, underlying, shallow, one‐dimensional unconfined aquifer with a plane, sloping bottom under steady hydraulic conditions in the assumed absence of dispersion and downgradient dilution. The user population and a presumedly constant contaminant loading factor determine the pollution input to the groundwater system, and we model the near field response as a single linear reservoir whose output comprises the far field source term at the downgradient edge of the landfill. The far field analysis yields a method of characteristics solution valid in the vicinity of the source location with frame speeds modified by recharge, head loss, bottom slope, and linear adsorption, and concentrations reflecting first‐order reaction kinetics. We calibrate and test the near and far field models against conservative chloride and first‐order reactive bicarbonate data at the Babylon, New York landfill with accurate and physically plausible results.
Time‐Variant Differences in Chemistry Among Four Small Streams
Authors: Teti Patrick
Published: February 2008

Concentrations of the major cations and silica were monitored in four small British Columbia Coast Mountain streams during the 1976 snowmelt season. The four streams could be grouped into three unique classes using logarithmically transformed calcium and potassium concentrations. The two most similar basins fed streams that were chemically indistinguishable. The next most similar basin yielded runoff that was chemically similar to the other two except for unusually low K+ concentration, possibly due to a shortage of biotite in the bedrock. The fourth stream had unusually high Ca++, Mg++, Na+, and silica concentrations due to the long residence time of groundwater from metamorphic rocks in its basin. Another different feature of that basin was the earlier depletion of its spring snowpack due to its south aspect. Time‐variant differences in chemistry among streams were measured as changing ratios of solute concentrations over time. Differences among streams were time‐variant due to time variance of interbasin runoff components. The relative contribution of groundwater increased in the basin with the metamorphic rocks and decreased in the other three basins over the summer. The chemical differences among streams were reflected in solute loads as well as solute concentrations. Therefore the major components of variable runoff and solute sources in the study area were high runoff and low solute yield from three basins on granite and low runoff but high solute yield from a basin on metamorphic rocks.