bluuebunny/crossref_metadata_2025 huggingface dataset:
Model for predicting evaporation from a row crop with incomplete cover
Authors: Ritchie Joe T.
Published: February 2008

A model is presented for calculating the daily evaporation rate from a crop surface. It applies to a row crop canopy situation in which the soil water supply to the plant roots is not limited and the crop has not come into an advanced stage of maturation or senescence. The crop evaporation rate is calculated by adding the soil surface and plant surface components (each of these requiring daily numbers for the leaf area index), the potential evaporation, the rainfall, and the net radiation above the canopy. The evaporation from the soil surface Es is calculated in two stages: (1) the constant rate stage in which Es is limited only by the supply of energy to the surface and (2) the falling rate stage in which water movement to the evaporating sites near the surface is controlled by the hydraulic properties of the soil. The evaporation from the plant surfaces Ep is predicted by using an empirical relation based on local data, which shows how Ep is related to Eo through the leaf area index. The model was used to obtain the total evaporation rate E = Es + Ep of a developing grain sorghum (Sorghum bicolor L.) canopy in central Texas. The results agreed well with values for E measured directly with a weighing lysimeter.
Viscous flow model for groundwater movement
Authors: Yen Ben Chie , Hsie Chung Hsiung
Published: February 2008

A viscous flow model with nonuniform spacing between plates can be used to simulate two‐dimensional laminar flow in heterogeneous porous media. Such a model can also be used to study the effects of aquifer thickness on flow in homogeneous porous media. Mathematical expressions have been developed from equations of motion and continuity for flow in porous media and for flow between closely spaced nonparallel plates to verify the theoretical background of such model simulations. The modeling is valid for groundwater flow that obeys Darcy's law and viscous flow between plates with the Reynolds number within the Stokes range. Other limitations and restrictions are also discussed.
Application of discriminant analysis in design review
Authors: DeCoursey Donn G.
Published: February 2008

Discriminant analysis is a multivariate technique that uses a group of variables (discriminators) to obtain maximum separation between different groups of data. The discriminant function, a linear combination of the discriminators, obtained by this analysis may be used to assign an individual observation to the group that it most nearly resembles. Discriminant analysis was used to analyze factors related to the adequacy of standard slope protection on small dams. The structures were divided into two groups: one group that visibly needed additional slope protection and one group that appeared to be designed satisfactorily. The analysis showed that a linear combination of the fetch length, the surface area to length ratio (average width), and the plasticity index of the surface material on the dam could be used to distinguish between the two groups about 85% of the time. The equation defined by these parameters was scaled for cost and number of structures, and can be used to assign structures to the two groups such that the additional protection can be most economically provided.
Effect of intra‐aggregate diffusion on oscillatory flow dispersion in aggregated media
Authors: Farrell D. A. , Larson W. E.
Published: February 2008

A theoretical study of oscillatory flow dispersion in aggregated media examines the effect of aggregate size, the coefficient of diffusion, and the frequency of the oscillations in fluid velocity on the separate contribution of intra‐aggregate diffusion to dispersion. The study is concerned primarily with the effect of radial diffusion within the aggregates that gives rise to a pulsating sink‐source feature in the dispersion process. The analysis shows that for selected dispersion phenomena the contribution of this reservoir or capacitance factor on intra‐aggregate porosity can be substantial. For example, when atmospheric turbulence produces an appreciable mass flow of air within a loose soil mulch, the component of dispersion directly attributable to radial diffusion within the soil aggregates may be greater than molecular diffusion by an order of magnitude.
Water table drawdown due to a pumped well in an unconfined aquifer
Authors: Streltsova T. D. , Rushton K. R.
Published: February 2008

A general solution of the water table drawdown for unsteady radial flow to a pumped well is considered. Tabulated values for the free surface function are calculated for the range of parameters occurring in practical situations. A comparison with the available solution of Boulton is made, an appraisal of the assumptions being introduced in the derivation of the solutions. A numerical example of unsteady radial flow in an unconfined aquifer with details of the main part of the computer program is presented.
Relationship between the carbon isotope composition of soil CO2 and dissolved carbonate species in groundwater
Authors: Rightmire Craig T. , Hanshaw Bruce B.
Published: February 2008

To understand the carbonate geochemistry of an aquifer system, it is helpful to determine the sources of carbon in the dissolved carbonate species. Samples of ground litter, soil organic matter, soil CO2, and groundwater were collected in the area of recharge to the principal artesian aquifer of central Florida and were analyzed for 13C content. Analytical results yield consistent 13C/12C values for soil organic matter, δ13CPDB = 23 ±1‰. The 13C/12C ratio of the litter samples ranges from δ13CPDB of −18.2 to −29.5‰ and indicates the presence of both Calvin and Hatch‐Slack cycle plants. The 13C/12C of the soil CO2 ranges from −14.7 to −21.3‰, which is consistent with the trend observed in the litter. The relationship between 13C/12C of the dissolved carbonate and the percent calcite saturation indicates that the δ13CPDB of the source CO2 is within the range of −25 ± 5‰, as is expected for a humid, subtropical environment.
On the analysis of ‘slug test’ data
Authors: Papadopulos Stavros S. , Bredehoeft John D. , Cooper Hilton H.
Published: February 2008

Methods of analyzing ‘slug test’ data are reviewed, and additional type curves for the analysis of test data from formations with very low storage coefficients are presented.
Determinants of use of water‐based recreational facilities
Authors: Holman Mary A. , Bennett James T.
Published: February 2008

A model is developed to explain the use of water‐abased recreational facilities for 15 different recreational activities. The results are then employed to obtain a relative ranking of factors that contribute most to the use of facilities. From an empirical study on data obtained from the Fort Worth District, ILS. Army Corps of Engineers, the factors that contribute to use can be ranked as follows: (1) distance variables, which serve as a surrogate for travel time and cost; (2) population near the site, a measure of demand potential; (3) facilities provided at the site; (4) fees; (5) measures of quality of the site; and (6) seasonal variables.
Evaporation retardation by monomolecular layers
Authors: Lou Y. S. , Rasmussen G. P.
Published: February 2008

An analytical theory based on the kinetic theory of discrete particles has been developed to describe the movement of water molecules through a monolayer. A simplified model based on the theory shows the rate of evaporation through a monolayer to be a function of the length of the hydrocarbon chain molecules, the arrangement of the monolayer molecules, the thickness of the surface diffusion sublayer, and the temperature of the water.
Picloram movement from a Chaparral Watershed
Authors: Davis E. A. , Ingebo P. A.
Published: February 2008

After a brush control treatment of soil‐applied pellets of picloram (9.3 lb acid equivalent per acre) on a 2.1‐acre side slope of a 46‐acre chaparral watershed in central Arizona, picloram was detected in the stream water at a gaging station at the outlet of the watershed. Maximum measured concentrations (350–370 ppb) occurred during the first 3 months after treatment and were associated with heavy rainfall. After 14 months and 40 inches of accumulated rainfall, picloram was no longer detected in the stream water. An estimated 4.5% of the picloram applied was lost to stream water. Direct use of stream water from the outlet of the treated watershed when picloram levels were 46–370 ppb could have damaged sensitive crops such as cotton.
Alternative methods of estimating snow water parameters
Authors: Reese David L. , Mayland H. F. , Beockway Charles E.
Published: February 2008

A recurrence analysis technique using probability and contingency relationships of snow depth, water equivalent, and snow density is presented. Three methods of estimating snow water parameters at site A by recurrence and the presently used regression techniques are based on (1) the value from the previous month at site A, (2) the value from a reference site, and (3) the month to previous month contingency parameter of the reference course. The recurrence technique (Pearson type 3) when it was tested on three central Idaho snow courses was most useful when method 3 was used to estimate snow depth and either method 1 or 3 was used to estimate the water equivalent. Correlation of estimated values to measured values indicated equal reliability of recurrence and regression analysis when the three methods were used. The recurrence technique can successfully be used in estimating snow water parameters and their probability of occurrence. This technique like the regression technique requires a basic data set before it can be applied.
Dissipation of heat from a thermal effluent
Authors: Mumford Warren , Czapski Ulrich , Felon Mark
Published: February 2008

The relative, magnitudes of surface cooling and lateral diffusion and advection from a thermal effluent are investigated. Data have been gathered at Nine Mile Point, east of Oswego, New York.,An estimate of the energy balance of this plume is made. The effective lateral diffusion coefficient obtained from this budget is larger than most values published. Also, surface cooling is suggested to be larger than that estimated by a Dalton type formula. This suggestion is supported by an estimate of advection of sensible heat above the plume. A modification of the temperature of the air over the plume is indicated by the data, although no increase in vapor pressure is observed. However, the variance of the vapor pressure in both time and space suggests a high degree of turbulence.
Cross correlation of the logarithms of estimates of mean streamflows
Authors: Moss Marshall E.
Published: February 2008

A methodology is presented that yields estimates of the cross‐correlation coefficients of the logarithms of estimates of mean discharges at two gaging stations with records that are not completely concurrent. The correlation coefficients of the logarithms of the estimates are found to differ only slightly from the correlation coefficients of the estimates themselves.
The estimation of vertical eddy diffusivities below the thermocline in lakes
Authors: Powell Thomas , Jassby Alan
Published: February 2008

Mathematical models of the spatial and temporal variation of passive substances in lakes and oceans require a quantitative formulation of vertical turbulent transport. Methods of estimating vertical eddy diffusivity coefficients in lakes for such substances as temperature, inorganic ions, or biologically active materials are briefly reviewed. One widely used method, the McEwen method, is discussed, and it is shown how this method can lead to erroneous results. Another method, the flux gradient method, is examined and compared with the McEwen method in specific case studies of thermal energy transfers. Lack of agreement between values obtained by the McEwen method and the flux gradient method has led some investigators to postulate‐a flux of thermal energy into the deep layers of a lake by density currents. An alternative explanation of the discrepancy is offered by noting that deepwater turbulent mixing may result from a microstructure of layers and sheets caused by, for example, a Kelvin‐Helmholtz shear instability in the flows or other instability mechanisms.
Surface temperatures of Lake Erie
Authors: Webb M. S.
Published: February 2008

Data from 58 airborne radiation thermometer surveys obtained over a 6‐year period have been used to map the spatial patterns of the mean surface temperature of Lake Erie by month. Its southern location within the Great Lakes system and the large differences in water depth between its three basins have proved to be important controls affecting the surface temperature regime. Except in winter, when it is largely ice covered, the surface of Lake Erie is warmer than the surfaces of any of the other Great Lakes. The month‐by‐month relationship between the mean surface temperature and the mean air temperature for a nearby climatological station has been demonstrated.
Steady state flow in rigid networks of fractures
Authors: Wilson Charles R. , Witherspoon Paul A.
Published: February 2008

The finite element has been used to develop two numerical methods of calculating the flow characteristics of rigid networks of planar fractures. One method uses triangular elements to investigate details of laminar flow in fractures of irregular cross section combined with that of a permeable rock matrix. The other method uses line elements and is designed only for flow in networks of planar fractures in an impermeable matrix. As an example of the application of the finite element approach the line element method was used to develop a series of dimensionless graphs that characterize seepage in idealized fracture systems beneath dams. These methods treat two‐dimensional flow in the laminar regime for networks of fractures of arbitrary orientation and aperture distribution.
Sensitivity analysis of input parameters in numerical modeling of steady state regional groundwater flow
Authors: Gillham R. W. , Farvolden R. N.
Published: February 2008

A finite element model was used to examine the sensitivity of computed hydraulic head values to changes in the hydraulic conductivity of subsurface flow systems. Steady state saturated flow in nonuniform anisotropic cross sections was considered. From an examination of several hypothetical cross sections it was apparent that the sensitivity analysis procedure could be useful in locating those areas of the flow system that are most sensitive to changes in conductivity and in determining those components of conductivity that have the greatest effect on the hydraulic head distribution. Consequently, a sensitivity analysis could be very useful in designing efficient hydraulic conductivity measurement programs. One method that has frequently been used to determine conductivities is to adjust the conductivity components in a numerical model until the computed head values agree with field measurements. Information is presented that indicates that this procedure could lead to erroneous conclusions. By using the sensitivity analyses, a method was developed for determining the quantitative value of ratios of conductivity components from field measurements of hydraulic head. In principle, the number of head measurements must be equal to the number of unknown conductivity ratios. The accuracy of the results suggests that the method should be evaluated in a field situation.
Public acceptance of renovated waste water: Myth and reality
Authors: Baumann Duane D. , Kasperson Roger E.
Published: February 2008

There is little evidence to support the widespread belief among many water management officials that public opposition constitutes an important obstacle concerning the adoption of renovated waste water for municipal supply.
On the synthesis of random field sampling from the spectrum: An application to the generation of hydrologic spatial processes
Authors: Mejía José M. , Rodríguez‐Iturbe Ignacio
Published: February 2008

A procedure for the synthesis of processes exhibiting temporal and spatial variability is presented. The method involves the addition of harmonics of random frequencies that are sampled from the spectral density function or the radial spectral density function. The process obtained is asymptotically Gaussian and ergodic. An estimate of the error in time or space averages due to the nonergodicity of the process as a function of the number of harmonics is also included.
Transverse mixing in an ice‐covered river
Authors: Engmann J. E. O. , Kellerhals Rolf
Published: February 2008

The effect of an ice cover on transverse mixing in the Lesser Slave River (Alberta) is investigated on the basis of data from two tracer tests. The tests took place under similar conditions of flow depth, one under open water conditions and the other under ice. Average transverse exchange (or mixing) coefficients for the reach Ez are computed by using a curvilinear coordinate system and the moments technique of Aris. The normalized exchange coefficient k = Ez/u* R for ice‐covered conditions is found to be approximately 50% smaller than the corresponding coefficient for open water conditions. Since an ice cover reduces the product u*R (friction velocity times hydraulic radius) by a factor of approximately 2(2)1/2, if depth remains constant, the results indicate that an ice cover can reduce the mixing capacity of a river substantially. The importance of accounting for depth and width variations in computing mixing coefficients is discussed and illustrated. Bend‐induced spiral motions appear to delay vertical mixing until transverse mixing is completed.
A coupled heat and moisture transport model for Arctic soils
Authors: Guymon Gary L. , Luthin James N.
Published: February 2008

The thermal and moisture regimes of arctic and subarctic soils act in parallel in a complex manner and must be considered together. The problem of moisture movement and storage in these soils is complicated by water undergoing a phase change during freezing and thawing and by the presence of ice‐rich permafrost. A one‐dimensional model of these processes is developed and is based on an equivalent quasilinear variational functional for the Richards equation and the heat conduction equation including convective components. The variational functional is solved by a finite element analog. Convergence and stability are investigated, and it is concluded that the numerical procedure is convergent and stable in general.
Screen theory for wells and soil drainpipes
Authors: Selim M. Sami , Kirkham Don
Published: February 2008

A theoretical solution is given for steady flow in a confined aquifer to a well tube having equally distributed screens. It is shown, quantitatively, by use of Darcy's law and Laplace's equation, that more flow results if a given total length of screen is utilized in a number of sections over the full length of the well tube than if the given length of well screen is all used at the bottom of the tube. For a pumped well of 0.25‐ft radius, 200‐ft radius of influence, 50‐ft thickness of aquifer, and 25‐ft length of screen the use of the screen in five 5‐ft‐long sections equally distributed over the well tube results in 25% more well how than if the 25‐ft length of screen is all in one piece at the lower 25 ft of the aquifer. If the screen is used in ten 2.5‐ft sections rather than in the single 25‐ft length, the increase will be 33%; and for an ‘infinite’ number of sections (the 25 ft of the 50‐ft well pipe still being impervious) the flow increase will be 45%. It is shown that the basic theory also applies to seepage flow to the joints between individual lengths of drainpipes used in land drainage. The results are presented in tables and graphs having dimensionless parameters so that the flow for a particular flow system may be found in any units. Mathematically, the problem is of the mixed boundary value type.
Predicting the municipal demand for water
Authors: Berry Dale W. , Bonem Gilbert W.
Published: February 2008

In 1967 one of the authors of this paper found that a regression equation relating per‐capita daily municipal water use to per‐capita income was a relatively good fit for data for a number of cities and towns in New Mexico. In 1974 this equation was fitted again for 1970 data for New Mexico towns, and the regression equation was practically identical with that found in 1967. Thus per‐capita income seems to be a good predictor of per‐capita municipal water use. Price (the water rate) and climatological variables were not significant in the regression, perhaps as a result of insufficiently precise data.
A tax system for groundwater management
Authors: Maddock T. , Haimes Y. Y.
Published: February 2008

A tax scheme is developed that will create an incentive among users to conserve groundwater and reduce the external diseconomies that pumping produces. Quotas are established for wells by using an agricultural management model. If a user pumps more than the quota established for his well, he may be assessed a tax; if a user pumps less than his quota, he may be entitled to a rebate. However, taxes are collected and redistributed in such a way that zero taxes are accumulated from year to year.
Effect of solute dispersion on thermal convection in a porous medium layer, 2
Authors: Rubin Hillel
Published: February 2008

In some situations associated with geothermal activity, groundwater motions are affected by convection currents due to large temperature gradients. In such cases, usually saline hot water is located in the deep layers of the aquifer from which salt and heat are transferred to the upper layers. In part 1 of this study the parameters of the two‐dimensional flow field stability were determined. In this paper, further analysis of the phenomenon in three dimensions is presented. It was found that the convection cells have the shape of rolls whose axes are perpendicular to the steady state flow velocity. However, there is also a possibility of overstability of the flow field caused by rolls whose axes are parallel to the steady state velocity. The parameters of these two kinds of instability were determined in this study.
The effect of urbanization on floods of different recurrence interval
Authors: Hollis G. E.
Published: February 2008

Studies have shown that the urbanization of a catchment can drastically change the flood characteristics of a river. Published results are synthesized to show the general relationship between the increase in flood flows following urbanization and both the percentage of the basin paved and the flood recurrence interval. In general, (1) floods with a return period of a year or longer are not affected by a 5% paving of their catchment, (2) small floods may be increased by 10 times by urbanization, (3) floods with a return period of 100 yr may be doubled in size by a 30% paving of the basin, and (4) the effect of urbanization declines, in relative terms, as flood recurrence intervals increase.
Transformations of fluxes and forces describing the simultaneous transport of water and heat in unsaturated porous media
Authors: Raats P. A. C.
Published: February 2008

Balances of mass for the water in n distinct phases and a balance of heat for the medium as a whole are formulated. Following Philip and de Vries, it is assumed that the flux of water in each phase is proportional to the gradient of the pressure in that phase and that the diffusive component of the flux of heat is proportional to the gradient of the temperature. Clapeyron equations are used to express the gradient of the pressure in any phase in terms of the gradient of the pressure in a reference state and of the temperature. The reference state may be the water in one of the phases or the water in some measuring device such as a tensiometer or a psychrometer. Expressions for the total flux of water and for the diffusive flux of heat plus the convective flux of heat associated with the conversion from any phase to the reference state are shown to satisfy the Onsager reciprocal relations. A theorem due to Meixner is used to delineate the class of fluxes and forces that preserves these relations. In particular, it is shown that if the gradients of water content and temperature are used as the driving forces, the Onsager relations are no longer satisfied.
An identification approach to subsurface hydrological systems
Authors: Distefano Nestor , Rath Amitav
Published: February 2008

A method for the optimal determination of the transmissivity function in a model of a horizontal two‐dimensional saturated aquifer, using time histories of the heads at a number of observation points, is developed. In this method the transmissivity function is assumed to be represented by a continuous spline surface over the entire domain of the aquifer and is given in terms of unknown nodal values disposed over a rectangular grid. These nodal values are then determined by requirements of optimality, i.e., by minimization of an error functional denoting the deviations of the observed and predicted heads at several strategically distributed observation wells. The method is complemented by using a hierarchical identification approach which consists of gradually increasing the number of nodal values employed in the analytical representation of the transmissivity function. Finally, a numerical example involving the determination of the transmissivity map of an aquifer by employing simulated head histories is presented to illustrate the feasibility of the proposed method.
A portfolio approach to public water project decision making
Authors: Neely Walter P. , North Ronald M.
Published: February 2008

Federal water resources projects are presently selected on the basis of the benefit‐cost ratio (BCR), which is an indicator of the economic feasibility of individual projects. From this initial feasibility test one may rank all feasible projects by descending BCR to produce a portfolio of feasible projects which maximizes the BCR within a constrained budget. The portfolio approach proposed in this study is superior to other approaches for project selection, especially when it is combined with an evaluation system to maximize net present value (NPV). Linear and integer programing techniques are combined with empirical data on Tennessee Valley Authority water resources projects to illustrate the superiority and usefulness of the portfolio approach in project selection for implementation. The portfolio approach maximizes NPV and simplifies the application of budget‐planning procedures in choosing projects when budget levels are variable or otherwise uncertain.
Relation of the consumptive use coefficient to the description of vegetation
Authors: Culler R. C. , Hanson R. L. , Jones J. E.
Published: February 2008

Evapotranspiration from three reaches of the Gila River floodplain in Arizona was measured by the water budget during 1963–1971. Initially, the vegetation consisted of salt cedar and mesquite with densities of canopy ranging from 10 to 100%. The phreatophytes were removed from the study reaches in stages during 1967–1971. Perennial grass seed was applied but did not become established, and the postclearing vegetation was primarily annuals. Comparison of the evapotranspiration data from various reaches and comparison of data from before and after clearing required the application of an empirical equation. A consumptive use coefficient related to the description of vegetation was applied to an existing potential evapotranspiration equation based on macroclimatic observations. Initially, the vegetation description consisted of plant identification and canopy dimensions obtained by use of black and white aerial photography and ground measurements. In 1967, remote sensing in the form of color infrared aerial photography became available and densitometric interpretation was used to develop a spectral signature as the vegetation descriptor.
Is there a difference in the finite element method?
Authors: Pinder George F. , Gray William G.
Published: February 2008

The finite element approximation of the convective diffusive transport equation can be expressed in terms of well‐known finite difference notation. Examination of the relationship obtained reveals that in contrast to finite difference schemes, which approximate the differential equation at a point, the finite element method can be interpreted as an approximation of the integrated form of this equation.
Hydrology of the North Cascades Region, Washington: 1. Runoff, precipitation, and storage characteristics
Authors: Rasmussen Lowell A. , Tangborn Wendell V.
Published: February 2008

The time and space distributions of measured precipitation and measured runoff and of spring storage, which is approximately equal to the subsequent summer runoff of snowmelt and stored groundwater, have been analyzed for the North Cascades region of Washington. Neither precipitation nor runoff shows a consistent relationship with altitude, chiefly because of precipitation‐shadowing effects in this region of high relief. The relationship between mean annual precipitation and altitude is improved considerably when a topographic mean altitude is used instead of the actual altitude of the weather station. However, the improvement is not sufficient to explain a number of discrepancies that still occur. Some of the scatter in a precipitation‐altitude plot appears to be due to a deficient precipitation catch by high‐altitude gages. When the dependence of runoff on precipitation was examined on an annual, seasonal, and monthly basis, it was found that only a few low‐altitude gages correlated well with basin runoff. In several instances, annual (water year) runoff could be better predicted from winter precipitation than from annual precipitation. Precipitation and runoff were tested for changes with time and both appeared to have been increasing slightly but not at a statistically significant level. When the summer (May–September) fraction of the total annual runoff is plotted against mean basin altitude, a consistent, physically reasonable, mildly curvilinear relationship is revealed. On the basis of this relationship, by using several drainages with diverse area‐altitude profiles the spring storage versus altitude distribution can be estimated for each basin. The area‐altitude distribution is used instead of the mean altitude in this calculation because of the apparent nonlinear relationship between runoff and altitude.
Identification of linear systems response by parametric programing
Authors: Neuman Shlomo P. , De Marsily Ghislain
Published: February 2008

Experience indicates that in the identification of the impulse response function of a linear hydrologic system the results are extremely sensitive to minor errors in the input‐output data. In particular, low‐amplitude random errors in these data tend to cause severe oscillations in the response function, thereby making it often impossible to obtain a physically realizable solution by conventional methods. Artificial filtering of the input‐output records may help, but since the extent of noise is seldom known a priori, one cannot be sure about the proper choice of a cutoff frequency. Such filtering also causes a loss of data at the end points of the record and is therefore undesirable when the number of data points is small. Filtering the response function itself is only effective in eliminating high‐frequency oscillations, and it is far less effective when the frequency of the oscillations is relatively low. Clearly, the ultimate goal of identification is to determine a solution which optimizes the predictive capabilities of the linear model. To achieve this goal, it is not sufficient that an observed output be correctly reproduced from a given input; an equally important criterion of optimality is that the shape of the response function be physically plausible. It is shown that one way to obtain a stable and physically realizable response function from a relatively short input‐output record is to use parametric linear programing. According to this approach, the problem is formulated as a multicriterion decision process under uncertainty in a manner analogous to that previously described by one of the authors in connection with the inverse problem of groundwater hydrology. Parametric programing serves as a means of generating a continuous set of alternative solutions to the identification problem together with a bicriterion function representing these alternatives. The shape of this bicriterion curve is then used as a guide by the hydrologist in selecting a particular solution when he is relying on his own value judgment. If none of the alternative solutions appears to be physically plausible at this stage, the hydrologist has a further option of imposing modality constraints to eliminate undesirable low‐frequency oscillations from the response function. The method is illustrated by two examples, and the results are compared with those obtained by another approach developed previously by one of the authors.
Evapotranspiration from a shortgrass prairie subjected to water and nitrogen treatments
Authors: Lauenroth W. K. , Sims Phillip L.
Published: February 2008

Evapotranspiration was estimated by the water balance method for three water and nitrogen treatments and a control in a shortgrass prairie in northeastern Colorado in 1971,1972, and 1973. Nitrogen was applied at a rate of 150 kg/ha to maintain soil mineral nitrogen levels greater than or equal to 50 kg/ha above control levels with and without supplemental water. The water treatment maintained soil water potential greater than −0.8 bar during the growing season and was applied with and without nitrogen. Evapotranspiration for the control and unwatered nitrogen treatments was not different and ranged from 118 to 226 mm over the 3 years. The 3‐year averages of evapotranspiration for the water and water plus nitrogen treatments were 505 and 578 mm, respectively. Evapotranspiration for the water plus nitrogen treatment agreed with potential evapotranspiration predicted by Penman's model.
Analytical three‐dimensional transient modeling of effluent discharges
Authors: Yeh Gour‐Tsyh , Tsai Yun‐Jui
Published: February 2008

A transient, three‐dimensional turbulent diffusion equation describing the concentration distribution of a substance or heat in a time‐dependent flow field is solved analytically. Two models are considered; one treats both the depth and the width of a water body as being finite, while the other deals with finite depth but with infinite width. In the search for solutions the method of Green's function is utilized to the optimum advantage. The solutions are developed for cases in which the velocity field can be described as any integratable function of time. For practical applications the velocity is assumed to be the sum of a constant and a harmonic component. There are no limitations on the type of source conditions. Results are compared with field measurements and show the models to be capable of simulating the dye distribution in tidal water bodies. The models should provide the engineering community with a quick and easy way of predicting the distribution of effluent discharges. They should obviate the need of using tedious and time‐consuming numerical models, as occasions often arise in which such complicated models may not be warranted.
Wetting front pressure head in the infiltration model of Green and Ampt
Authors: Neuman Shlomo P.
Published: February 2008

A theoretical expression relating the wetting front pressure head in the infiltration model of Green and Ampt (1911) to soil characteristics is derived. This expression is identical to that previously suggested by Bouwer (1964) on the basis of an analogy with horizontal flow. It differs from a more complete expression recently proposed by Morel‐Seytoux and Khanji (1974) in that the effect of air mobility is neglected, the need for determining the functional relationship between the relative permeability of air and water saturation thus being avoided.
Link slope distribution in channel networks
Authors: Flint Jean‐Jacques
Published: February 2008

The link slope distribution for given magnitude links from 18 basins in the Appalachian Plateau changes from a left skewed, to a normal, to a right skewed distribution resembling a log normal distribution as the average stream gradient decreases. Variations in the link slope distribution can be partly explained by the decrease in the tendency of streams to move downward with a change in available relief or distance and by the effects of local geologic and geomorphic conditions prevailing in a basin. Downstream interior link slopes vary with magnitude following a power function. Their scatter about the log of the power function is constant in most basins. Based on these elementary properties of link slopes and the probability of occurrence of links of any one magnitude, a general model representing the distribution and expectation of interior link slopes for an entire channel network is formulated. The observed interior link slope distributions for different basins vary in shape from a monotonic decrease in frequencies with increasing stream gradient to a unimodal and sometimes bimodal distribution when exterior links are included. In spite of the large changes in the shape of the histograms for different basins, the theoretical distributions provide a good reproduction of the data.
Numerical predictions of two‐dimensional transient groundwater flow by the method of characteristics
Authors: Wiggert D. C. , Wylie E. B.
Published: February 2008

Unsteady flow in a confined or leaky aquifer can be analyzed by replacing the two‐dimensional space domain with a latticework of line elements which intersect at nodal points. Continuity and momentum principles are applied to each line element separately, resulting in a system of hyperbolic equations which can be solved by the method of characteristics. Upon combination of the continuity relation and compatibility conditions at each node an explicit solution for the time‐variable piezometric heads and seepage velocities is obtained. An inertia multiplier is introduced in the momentum equation, which varies inversely with the magnitude of the fluid acceleration. The time step, proportional to the multiplier, thus assumes large values, while the method continues to provide accurate, stable results. Numerical examples are compared with analytical solutions, and a nonhomogeneous regional aquifer analysis agrees favorably with a finite element model. The numerical scheme provides ease of programing, reduced computer storage requirements, and reasonable central processing times.
Infiltration analysis and perturbation methods: 2. Horizontal absorption
Authors: Babu D. K.
Published: February 2008

Perturbation methods are employed to analyze the horizontal absorption of moisture in unsaturated soils. The present study applies to absorption under the general diffusivity function, subject to constant boundary concentration. The concept of the wetting front moving with a finite velocity plays a fundamental role in this set of papers. The solution emerges as a series of terms that can be explicitly calculated in terms of the integrals involving diffusivity functions. The examples of exponential and constant diffusivity functions, as well as the case of Yolo light clay, are computed to one or two terms to exhibit the advantages over, and the good agreement with, other published data of Parlange, Philip, etc. The method possesses great potential, and in a subsequent paper the study of vertical infiltration will be presented by utilizing the perturbation mechanism.
Spectral analysis of hydrometeorological time series
Authors: Shahane Ashok N. , Thomas Daniel , Bock Paul
Published: February 2008

As a part of the interdisciplinary methodology for exploring the characteristic behavior of the hydrometeorological components of the United States, spectral analysis (consisting of spectral density and cross‐spectral density techniques) is employed to provide statistical information in the frequency domain. The spectral density technique is applied to analyze the 5 years of mean monthly time series of atmospheric vapor transport ∇·Q, atmospheric precipitable water ΔW, runoff R, precipitation P, evapotranspiration E, and change in storage ΔS for 76 drainage basins of the United States, and on an experimental basis, cross‐spectral techniques are tried for these time series in 10 large combined drainage basins. The outcome from the spectral density analysis provides information about the spatial variation in the periodic properties of the ∇·Q, R, P, ΔS, and E time series over the United States, whereas the cross‐spectral analysis illuminates the cross‐correlation characteristics of the hydrometeorological data in light of the variations in coherence, partial coherence, and leading and lagging phase angles.
Annual and seasonal flow variations through the Straits of Mackinac
Authors: Quinn Frank H.
Published: February 2008

The present emphasis on Great Lakes water quality studies requires a knowledge of the average and variability of the net flow between Lakes Michigan and Huron. Average annual and average monthly flows through the Straits of Mackinac were computed for the 1950–1966 period by use of a water budget technique applied to Lakes Michigan and Huron. In addition, water budget computations were compared with a 100‐day period of current meter observations taken in 1973. The computations and measurements agreed quite closely, within approximately 2%. A variation of greater than 500% was found between the maximum and minimum annual flows observed during the 17‐year computation period. The gross residence or flushing time for Lake Michigan was determined by two methods. The first determination used the mean annual flow through the straits, resulting in a flushing time of 137 years. The second procedure using the results of the current study, which found a deep return flow into Lake Michigan through the straits during stratification, gave a flushing time of 69 years.
Convective‐dispersive solute transport with a combined equilibrium and kinetic adsorption model
Authors: Cameron D. R. , Klute A.
Published: February 2008

A given chemical may react at different rates with various soil constituents and be involved in several kinds of reactions. A combination of equilibrium and kinetic adsorption models is hypothesized to describe the nature of the overall reaction. An analytical solution to the one‐dimensional convectivedispersive transport equation with a combination linear Freundlich isotherm and first‐order reversible kinetic adsorption model is developed. The individual and combined effects of the model parameters on the breakthrough curves and retention profiles are examined. The combination equilibrium‐kinetic model is shown to be applicable to pesticide, nutrient, and metal transport in soils.
Regionalized drought flow hydrographs from a mature glaciated plateau
Authors: Brutsaert Wilfried , Nieber John L.
Published: February 2008

The drought or base flow characteristics of six basins in the Finger Lakes region are obtained by considering for each available record the lower envelope of |dQ/dt| as a function of Q, where Q is the flow rate. This procedure avoids the uncertainty regarding a proper time reference after each rainfall event, and it eliminates the effects of evapotranspiration. The results suggest that among several expressions, Boussinesq's nonlinear solution of free surface groundwater flow is best suited to parameterize the observed hydrographs. The obtained parameters can be related to the basin characteristics, viz., drainage area and the total stream length, in accordance with relationships derived on the basis of the Dupuit‐Boussinesq aquifer model. This result allows the determination of drought flow parameters for ungaged sites within the region.
Extension of the similarity hypothesis used for modeling the soil water characteristics
Authors: Mualem Yechezkel
Published: February 2008

Two independent domains models are derived by using an extended similarity hypothesis according to which the pore water distribution function is interpreted to be ƒ(r, ρ) = h(r)h(ρ). When this hypothesis is applied to the Néel diagram and the Mualem diagram, it yields two different models which permit prediction of the hysteretical relationship from only one branch of the main hysteresis loop. The models yield an extremely simple formula for the relationship between the boundary drying and wetting curves. Moreover, a universal nondimensional hysteresis is derived for all soils. Comparison with experiments shows that the model which uses the Néel diagram fails to reproduce a reasonable shape of the hysteresis curves. However, much better results are achieved by the second model, which uses the Mualem diagram. In some cases the predicted curves are in very good agreement with the observed ones. For soils in which blockage against air entry plays a significant role the model is less efficient as a predictive tool. It yields poor results in the region of high water content, while the predicted curves are very close to the measured ones in the range of low water content.
Comparison of the two‐ and three‐parameter log normal distributions used in streamflow synthesis
Authors: Charbeneau Randall J.
Published: February 2008

A direct solution is found for the algebraic system of equations relating the statistics of an observed flow sequence to those of the three‐parameter log normal distribution. This solution can be used to compare the two‐ and three‐parameter log normal distributions.
Characterization of urban runoff
Authors: Whipple W. , Berger B. B. , Gates C. D. , Ragan R. M. , Randall C. W.
Published: February 2008

Unrecorded pollution and nonpoint sources are too important to be neglected in water quality analysis, but the findings in the literature have been too scattered in place and time, and too diversely reported, to have been fully accepted. Such pollution is usually referred to as nonpoint source pollution, or in developed areas as urban runoff, in spite of the fact that considerable parts of it are delivered by large storm sewers and may originate partly from unrecorded urban point sources. For convenience, this usual terminology is employed in this paper. The work of each of five participating institutes was designed to evaluate urban runoff pollution from areas within that state and to relate those findings to differences in land use. Results have been reported in detail in the separate reports by the respective investigators. This report summarizes these findings and then draws conclusions which the five principal investigators agreed upon.
On the choice of the ‘appropriate model’ for water resources planning and management
Authors: Rogers Peter
Published: February 2008

The use of symbolic models has become widespread in water resources planning and management. The operations research literature, however, gives little guide as to the choice of the most appropriate model for any situation. This paper outlines a method for comparing models of differing complexity applied to a given situation. The hypothesis that simpler models are more appropriate than more representative but more complex models is tested on two simple irrigation examples.
Numerical model for saturated‐unsaturated flow in deformable porous media: 3. Applications
Authors: Narasimhan T. N. , Witherspoon P. A.
Published: February 2008

This is the third and conclusive part of a three‐paper series and describes the application of a numerical model for saturated‐unsaturated flow in deformable porous media. In all, 10 illustrative examples are presented not only to demonstrate the validity of the method but also to highlight the fundamental unity that exists in the sic principles of the fields of hydrogeology, soil mechanics, and soil physics. The chosen examples involve such diverse phenomena as soil consolidation, infiltration, and drainage and generation of fluid pressures due to cyclic loading such as earthquakes.