bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating the precipitation climate
Authors: Stidd C. K.
Published: February 2008

A method has been developed for estimating climatic expectancies of flood or drought from the mean and variance of a precipitation record. An interrelationship between the distributions of amounts from the various observing periods, e.g., hourly, daily, monthly, is demonstrated, so that any one of these records may be used to estimate the others. The method is based on the cube root normal distribution of precipitation and on an observed tendency for the distribution lines to be parallel. Graphs and tables are provided as an aid to making these estimates. The relationship between monthly, daily, and so forth amounts must be derived in some manner from the frequency spectrum of precipitation rates. This spectrum is shown to have the same profile as the theoretical spectrum for atmospheric pressure; thus the E(f) ∼ f−5/3 spectrum of kinetic energy regulates the relationship between precipitation distributions.
Annual cycle in river water quality: A time series approach
Authors: Edwards A. M. C. , Thornes J. B.
Published: February 2008

Regression, spectral, and cross‐spectral techniques are used to examine the trends and periodicity in a 20‐year record of weekly observations of eight water quality variables in the River Stour, eastern England. Linear regression shows that all except pH. and carbonate hardness have significantly increased over time. A strong annual cycle is present in the data, and cross‐spectral analysis is used to model the relationship between the variables and the water discharge in time. Nitrate and noncarbonate hardness are positively correlated with discharge, whereas carbonate hardness is an inverse function.
Effect of agricultural management of wet sloping soil on nitrate and phosphorus in surface and subsurface water
Authors: Benoit George R.
Published: February 2008

A 12‐plot study in East Franklin, Vermont, was conducted on a poorly drained, sloping Cabot silt loam to evaluate differences in nitrate and phosphate content of water from three cropping systems: (1) a timothy, red clover, Kentucky bluegrass hay‐pasture operation, (2) an alfalfa, hay operation, and (3) a corn silage operation. Six plots were in alfalfa hay, six plots were planted in corn, and the upslope area was in hay‐pasture. Soil samples were collected from the 12 plots in the summers of 1969 and 1970 and analyzed for total soil nitrogen. Surface and subsurface drain effluent samples from the plots and upslope area were analyzed for nitrates and phosphates. The results indicate that draining wet sloping land may decrease total soil nitrogen, that nitrate nitrogen may be lost from organic matter breakdown in cold but unfrozen soil, that nitrates but not phosphates will move both vertically and laterally through the soil to subsurface drains, that surface runoff contains few nitrates but significant concentrations of phosphates, and that more nitrates were lost from fertilized corn plots than from alfalfa plots or hay‐pasture areas.
Dispersion‐affected transport of reacting solutes in saturated porous media: Galerkin Method applied to equilibrium‐controlled exchange in unidirectional steady water flow
Authors: Rubin Jacob , James R. V.
Published: February 2008

Equations describing dispersion and ion exchange affected one‐dimensional transport of solutes in saturated porous media are solved numerically by means of the Galerkin method. It is assumed that water flow is steady and that local chemical equilibrium exists throughout the systems considered. No constancy restrictions are placed on the total concentration of the dissolved ions participating in exchange. The cases treated involve (1) homogeneous or layered systems, (2) exchange reactions with constant or concentration dependent selectivity coefficients, (3) binary or multicomponent exchange, and (4) systems in which one of the exchanging ions is also involved in a precipitation‐dissolution reaction. The results of computations show that the approach presented may be useful in analyzing a variety of solute transport processes of hydrologic interest. They also demonstrate at least for some of the ion transport cases the importance of taking into account the effects of dispersion and ion exchange.
Factors Affecting Draft From a Lloyd Reservoir
Authors: Pegram G. G. S.
Published: February 2008

This paper investigates the effect of input model, size of reservoir, and various input parameters on the probability of zero draft from a discrete reservoir fed by a serially correlated input. It appears that the form of the transition probability matrix describing the input (assumed to be a finite Markov chain) has relatively little effect on the probability of zero draft.
A groundwater profile sampler
Authors: Hansen Edward A. , Harris Alfred Ray
Published: February 2008

A series of fiber glass probes spaced in sand‐packed compartments in a screened well point permits the collection of a number of discrete groundwater samples from predetermined depths in a single borehole.
A conceptual model of hysteresis
Authors: Mualem Yechezkel
Published: February 2008

A conceptual model of the capillary hysteresis phenomenon is suggested. The advantage of this model is that all scanning curves are derived with the aid of simple functions from the main drying curve and the main wetting curves solely. Like the generalized approach of Enderby (1955) the present model takes into account a reversible part of the process. A simple method of predicting the first drying curve and the scanning curves branched out of the first drying curve is also proposed. Results based on this model are compared with laboratory measurements and the general Néel‐Everett independent domain model. The comparison shows that the present model is often in more satisfactory agreement with measurements for cases in which the prediction based on the Néel‐Everett model is poor. The suggested method can be used for solving problems in which hysteresis plays a significant role, the difficulties associated with laboratory determination of the ψ‐θ relationships in the whole domain thus being avoided.
The karstic groundwater basins of the Kaibab Plateau, Arizona
Authors: Huntoon Peter W.
Published: February 2008

The Kaibab plateau north of the Grand Canyon is characterized by the absence of live surface streams because most of the surplus water drains through the groundwater system. Over 95% of the primary porosity that can be attributed to the 4000‐ft sequence of Paleozoic sediments under the plateau occurs in the upper 900 ft of the section. However, almost all the water that discharges from the region exits through perennial karst springs developed in carbonates 3000 ft below the rims of the Grand Canyon and the Marble Canyon. The locations of these springs are fault‐ and joint‐controlled, and they drain between 65 and 97% of the area underlying the Kaibab plateau. The relatively permeable upper Paleozoic rocks in the section collect and transmit water to fault zones where the water enters regional drains dissolved along fractures in the lower carbonates. Flow in the fault zones is largely unconfined and perched above an impermeable shale unit that underlies the lower carbonates. Consequently, the areal extent of the groundwater basins that drain the Kaibab plateau as well as potential saturated zones along the faults can be delineated by using gradients taken from a structural contour map of the top of the shale.
Nonlinear technological functions for aquifers whose transmissivities vary with drawdown
Authors: Maddock T.
Published: February 2008

An algebraic technological function (ATF) is shown to exist for an aquifer whose flow to wells can be remodeled by Boussinesq's equation. Drawdown is shown to be an infinite power series in pumping values, and the ATF is provided by a finite sum of the power series. The number of terms necessary for the finite sum to provide a good approximation to the infinite series is shown to depend on a ratio of drawdown to saturated thickness. The ATF can be used in optimization techniques or as a method for predicting drawdowns from pumping.
Variation of mainstream length with basin area in river networks
Authors: Shreve Ronald L.
Published: February 2008

Mainstream length in river networks from various parts of the world varies statistically in proportion to basin area raised to a power that decreases from about 0.6 for small to medium basins (1–103 km2) to near 0.5 for the largest in the world (nearly 107 km2). This relationship is predicted by the statistical theory of channel networks, which is founded on the basic postulates that (1) natural channel networks in the absence of strong geologic controls are very nearly topologically random and (2) interior and exterior link lengths and associated areas in basins with homogeneous climate and geology have separate statistical distributions that are approximately independent of location. The calculation was carried out by a Monte Carlo method, which produced a random sample of networks from the postulated population, and was checked by analytical results for networks up to magnitude 500. The necessary empirical data on link lengths and associated areas were obtained by measurement on maps of an 80‐km2 basin in relatively flatlying coal‐bearing sandstones in eastern Kentucky. Agreement with observation is excellent for the small to medium basins, but the ratio of predicted to observed mainstream length progressively decreases to about 0.7 for the largest basins. This discrepancy can be accounted for by moderate downstream increase in channel sinuosity and decrease in drainage density. The particular data on link lengths and associated areas used in the calculation have only slight influence because mean link length varies statistically directly as the square root of mean associated area, so that taking data from different areas merely displaces the predicted points nearly parallel to their trend.
A review and evaluation of multiobjective programing techniques
Authors: Cohon Jared L. , Marks David H.
Published: February 2008

Three criteria are established for the evaluation of the utility of multiobjective programing techniques for water resource planning. The criteria are computational efficiency, explicitness of trade offs among objectives, and the amount of information generated for decision making. The multiobjective approaches are classified into generating techniques, techniques which rely on the prior articulation of preferences, and techniques which foster iterative definition of preferences. The methods in the various classes are reviewed and evaluated in terms of the hypothesized criteria. The evaluations are then used in establishing conclusions about the applicability of the multiobjective approaches to water resource problems.
A theory for water flow through a layered snowpack
Authors: Colbeck S. C.
Published: February 2008

A natural snowpack with ice layers is described in terms of an equivalent anisotropic porous medium. The anisotropic permeability is represented as a diagonalized matrix whose principal values can be calculated from a small amount of information about the prototype snowpack. Ice layers increase the transit time for water movement by a factor equal to the ratio of the principal values of permeability. The flow path, volume flux, and wave speed are determined by the slope of the snowpack and principal values of permeability. When a snowpack is assumed to be isotropic, the error in calculating transit time increases with the difference between the principal values of permeability. Usual variations in slope introduce a small change in the transit time.
Analysis of pumping test data from anisotropic unconfined aquifers considering delayed gravity response
Authors: Neuman Shlomo P.
Published: February 2008

Previously a new analytical model was proposed by the author for the delayed response process characterizing flow to a well in an unconfined aquifer. The new approach differs from that of Boulton (1954, 1963, 1970, 1973) and Boulton and Pontin (1971) in that it is based only on well‐defined physical parameters of the aquifer system. As such, it can be used to develop methods for determining the hydraulic properties of anisotropic unconfined aquifers from field drawdown data. Two methods of analysis are described, one based on the matching of field data with theoretical type curves and the other based on the semilogarithmic relationship between drawdown and time. Owing to the reversible nature of the delayed response process as represented by the analytical model, data from recovery tests can be used to deterrnine aquifer transmissivity. All of these methods are illustrated by applying them to pumping test data collected by the French Bureau de Recherches Géologiques et Minières in Gironde (Bonnet et al., 1970). Similar procedures can be used to analyze data from partially penetrating wells, but this method requires that a special set of theoretical curves be developed for each field situation. Such theoretical curves can easily be developed with the aid of a computer program available from the author. An explicit mathematical relationship is derived between Boulton's (1963) delay index, 1/α, and the physical characteristics of the aquifer. It is shown that contrary to the assumption of Boulton the parameter a is not a characteristic constant of the aquifer but decreases linearly with the logarithm of r, the radial distance from the pumping well. This discovery makes it possible to reinterpret the results of pumping tests that were previously obtained with the aid of Boulton's theory without necessarily reexamining the original drawdown data. Results from pumping tests performed by the Bureau de Recherches Géologiques et Minières in Gironde and by Prickett (1965) in Illinois are used to illustrate this last point.
A Hele‐Shaw Analog Study of the seepage of groundwater resting on a sloping bed
Authors: Marei S. M. , Towner G. D.
Published: February 2008

The analysis derived from an application of the Dupuit‐Forchheimer approximations by Childs to the problem of flow of groundwater over sloping impermeable beds, in which it is assumed that the streamlines are parallel to the sloping bed rather than horizontal as previously assumed by Pavlovsky, was tested in a Hele‐Shaw analog. Seepage rates and water table positions were measured for a range of slopes up to 30° and with flow both up and down the slope. Considerably better agreement was found, especially at the largest slopes, by using the revised assumption. The theoretical seepage rates calculated from Childs’ analysis also lay between the limits given by an exact analysis due to Youngs, in contrast to values calculated by using Pavlovsky's analysis which fell outside the limits for large flow rates.
The impact of suburbanization on fluvial geomorphology
Authors: Graf William L.
Published: February 2008

Analysis of aerial photography for the period 1950–1971 and field data collected from 1970 to 1974 indicate that in the Denver area suburban development has caused significant changes in fluvial systems. By first introducing large quantities of sediment and later by increasing surface runoff, suburban development leads to an expansion of floodplains followed by downcutting of streams. As areas of suburban development increase, greater percentages of stream lengths are dominated by transportation, and lesser percentages are dominated by erosion and deposition.
A proposed index for comparing hydrographs
Authors: McCuen Richard H. , Snyder Willard M.
Published: February 2008

Existing goodness of fit indices are inadequate for comparing model‐generated hydrographs with measured hydrographs. The Pearson product‐moment correlation coefficient, which is the most frequently used index of regeneration, is inadequate because it is insensitive to differences in the size of the two hydrographs. A better coefficient of regeneration is obtained if Pearson's coefficient is adjusted by using a ratio of the standard deviations of the two hydrographs being compared. The resulting index is numerically the same as the regression of the hydrograph with the smaller variance on the hydrograph having the larger variance. Examples are used to illustrate the superiority of the modified correlation index.
Theory of multiple leaky aquifers: 1. The integrodifferential and differential equations for small and large values of time
Authors: Rodarte Leopoldo
Published: February 2008

The general problem of multiple leaky aquifers is analyzed by using a particular problem as a starting point. Differential and integrodifferential equations for small and large values of time, valid for the analysis of multiple leaky aquifers, are obtained. The proposed equations are appropriate for both the numerical and the analytic treatment of the regional evolution of the piezometric loads.
Fulvic acid and aquatic manganese transport
Authors: Zajicek O. T. , Pojasek R. B.
Published: February 2008

The role of allochthonous organic substances in the solubilization of manganese was investigated. The organic substances used were leachaes of a variety of watershed materials, fulvic acid, and a number of pure model compounds. It was found that manganese concentration and water color were directly proportional, in most cases, and that the organic materials comprising the color are effective in dissolving manganese oxides and stabilizing the dissolved manganese in solution.
A slug test for determining hydraulic conductivity of unconfined aquifers with completely or partially penetrating wells
Authors: Bouwer Herman , Rice R. C.
Published: February 2008

A procedure is presented for calculating the hydraulic conductivity of an aquifer near a well from the rate of rise of the water level in the well after a certain volume of water is suddenly removed. The calculation is based on the Thiem equation of steady state flow to a well. The effective radius Re over which the head difference between the equilibrium water table in the aquifer and the water level in the well is dissipated was evaluated with a resistance network analog for a wide range of system geometries. An empirical equation relating Re to the geometry of the well and aquifer was derived. The technique is applicable to completely or partially penetrating wells in unconfined aquifers. It can also be used for confined aquifers that receive water from the upper confining layer. The method's results are compatible with those obtained by other techniques for overlapping geometries.
Effect of sequence length n on the choice of assumed distribution of floods
Authors: Wallis J. R. , Matalas N. C. , Slack J. R.
Published: February 2008

Although overdesign and underdesign losses vary with the length n of flood sequences, the choice of flood frequency distribution for estimating the design flood is not overly sensitive to n. Bias in the estimate of the design flood does not account for differences in the analytical forms of the underlying and optimal assumed distributions of floods.
Parameter optimization for watershed models
Authors: Johnston P. R. , Pilgrim D. H.
Published: February 2008

A detailed search for the optimum values of the parameters of the Boughton model is described. The Simplex and Davidon optimization methods were used. Rapid initial reductions in the objective function were readily achieved, but the solutions approached several widely different apparent optima. Alternate use of different optimization methods and numerical and algebraic studies enabled considerable further progress to be made in the search. Much information was obtained on various aspects of parameter optimization. These include interdependence and indifference of parameters, the form of the response surface and the occurrence of discontinuities, the required length of the ‘warm‐up’ period for different types of stores, and the effects of using different types of objective functions. As typical stores were analyzed and the only basic assumption involved was that the data contained errors, the findings should apply to most watershed models.
On the stochastic foundations of the theory of water flow through unsaturated soil
Authors: Bhattacharya R. N. , Gupta Vijay K. , Sposito Garrison
Published: February 2008

The parabolic differential equation that describes the isothermal isohaline transport of water through an unsaturated soil is shown to be the mathematically rigorous result of a fundamental stochastic hypothesis: that the trajectory of a water molecule is a nonhomogeneous Markov process characterized by space‐ and time‐dependent coefficients of drift and diffusion. The demonstration is valid in general for heterogeneous anisotropic soils and provides for three principal results in the theory of water flow through unsaturated media: (1) a derivation of the Buckingham‐Darcy flux law that does not rely directly on experiment, (2) a new theoretical interpretation of the soil water diffusivity and the hydraulic conductivity in molecular terms, and (3) a proof that the soil water diffusivity for anisotropic soil is a symmetric tensor of the second rank. A dynamic argument at the molecular level is developed to show that the fundamental Markovian hypothesis is physically reasonable in the case of water movement through an unsaturated soil.
Morphometry and floods in small drainage basins subject to diverse hydrogeomorphic controls
Authors: Patton Peter C. , Baker Victor R.
Published: February 2008

Morphometric parameters such as drainage density, stream magnitude, and relief ratio are practical measures of flood potential in small (<100 mi2) drainage basins. Stereoscopic interpretation of low‐altitude aerial photographs provides the most accurate maps of basins for generating these parameters. Field surveys of a high‐density limestone basin in central Texas show that 1:24,000 scale topographic maps accurately portray the efficient stream channel system but fail to reveal numerous small gullies that may form portions of hillslope hydrologic systems. Flood potential in drainage basins can be defined by a regional index computed as the standard deviations of the logarithms of the annual maximum streamflows. High potential basins tend toward greater relief, greater drainage density, and thus greater ruggedness numbers than low–flash flood potential watersheds. For a given number of first‐order channels (basin magnitude), flash flood regions have greater ruggedness numbers, indicating higher drainage densities combined with steep hillslopes and stream channel gradients. Transient controls on flood response, such as differences between local rainstorm intensities, appear to be the major influences on hydrographs in areas of moderate dissection and relief. Morphometric parameters for low‐potential flash flood regions )Indiana and the Appalachian Plateau( are better estimators of frequent low‐magnitude runoff events (mean annual flood), while the same parameters correlate better with the maximum flood of record in high‐flood potential regions (central Texas, southern California, and north central Utah).
Detection of trends in water quality data from records with dependent observations
Authors: Lettenmaier Dennis P.
Published: February 2008

Classical statistical tests for trend, both parametric and nonparametric, assume independence of observations, a condition rarely encountered in time series obtained by using moderate to high sample frequencies. A method is developed for summarizing the power of the parametricttests and the nonparametric Spearman's rho test and Mann‐Whitney's test against step and linear trends in a dimensionless ‘trend number’ which is a function of trend magnitude, standard deviation of the time series, and sample size. For the case of dependent observations, use of an equivalent independent sample size rather than the actual sample size is shown to enable use of the same trend number developed for the independent case. An important related result is the existence of an upper limit on power (trend detectability) over a fixed time horizon, regardless of the number of samples taken, for a lag 1 Markov process.
Network design for the estimation of areal mean of rainfall events
Authors: Bras Rafael L. , Rodríguez‐Iturbe Ignacio
Published: February 2008

This work recognizes rainfall as a multidimensional stochastic process. By using the knowledge of such processes and of multivariate estimation theory a procedure for designing an optimal network to obtain the areal mean precipitation of an event over a fixed area is developed. The methodology used in this problem allows consideration of the following aspects of network design: (1) spatial uncertainty and correlation of process, (2) errors in measurement techniques and their correlation, and (3) non‐homogeneous sampling costs. Optimal networks are given in terms of the number and location of stations together with the resulting cost and mean square error of rainfall estimation.
Hysteretical models for prediction of the hydraulic conductivity of unsaturated porous media
Authors: Mualem Yechezkel
Published: February 2008

A theory which permits a quantitative prediction of the actual phenomena of considerable hysteresis characterizing the hydraulic conductivity‐capillary head relationships, and the less significant hydraulic conductivity‐moisture content hysteresis, is proposed. The models used to represent capillary hysteresis are extended to permit the prediction of the hydraulic conductivity of unsaturated porous media for any continuous process of imbibition and drainage. The generalized models require the same amount of experimental data as the previous models with the addition of a measured value of the hydraulic conductivity at a definite point. For an incomplete measured θ(ψ) loop the knowledge of K at the minimum measured value of ψ can be used to improve prediction. The dependent domain model suggested by Mualem and Dagan (1975) is generalized by adding two functions KL(ψ) and KH(ψ). All K(ψ) scanning curves are expressed with the aid of KL(ψ) and KH (ψ) by convenient compact formulation similar to that used to describe the θ(ψ) curves. The theory is verified by comparison with the detailed experimental data presented by Topp and Miller (1966). Very good agreement between theory and observations is found. The predicted K(ψ) hysteresis has all the experimentally observed features. The predicted K(θ) hysteretical loop almost shrinks to a unique curve, though the ψ(θ) loop, used as data, is of considerable extent.
Multistation, multiyear synthesis of hydrologic time series by disaggregation
Authors: Tao P. C. , Delleur J. W.
Published: February 2008

A model is presented which is designed for multivariate (multistation, multiyear) data syntheses such as the simulation of several rainfall series over a region, of tributaries and mainstream runoff series, and of rainfall and concurrent runoff series in watersheds. The model is an application of the disaggregation scheme proposed by Valencia and Schaake. If a time series of higher‐level (e.g., annual) events for each station has been generated by some scheme which preserves the long‐term properties, then the disaggregation model can be used to generate parallel time series of lower‐level (e.g., monthly, weekly) events for each corresponding station. The aggregation of the generated lower‐level sequences can preserve the long‐term properties of the original higher‐level series. The seasonal variations, the means, the variances, the autocovariances, and the cross‐covariances, properties of the original lower‐level time series, are also conserved. The lower‐level generated series also preserves the correlations between stations. The generation of multivariate normal random numbers makes use of either the Crout factorization or the principal component analysis depending on whether the covariance matrix of the lower‐level series is positive definite or positive semidefinite, respectively. A technique for modeling nonnormal residual components is discussed. The model has been applied to 36 rainfall, runoff, and rainfall‐runoff sequences in the lower Ohio and upper Mississippi River basins located in Indiana, Illinois, Ohio, and Kentucky. The properties of the generated data series show excellent agreement with those of the historical observed data series.
An evaluation of some fluorescent dyes for water tracing
Authors: Smart P. L. , Laidlaw I. M. S.
Published: February 2008

Eight fluorescent dyes (amino G acid, photine CU, fluorescein, lissamine FF, pyranine, rhodamine B, rhodamine WT, and sulpho rhodamine B) were compared in laboratory and field experiments to assess their utility in quantitative tracing work. The properties considered included sensitivity and minimum detectability, the effect of water chemistry on dye fluorescence, photochemical and biological decay rates, adsorption losses on equipment and sediments, toxicity to man and aquatic organisms, and cost. The orange fluorescent dyes are more useful than the blue and green because of the lower background fluorescence at the orange wave band, which permits higher sensitivities to be obtained. Pyranine fluorescence is strongly affected by pH over the range encountered in natural waters, which precludes its simple use in quantitative work. Amino G acid, photine CU, pyranine, and fluorescein all have high photochemical decay rates. Pyranine, lissamine FF, and amino G acid are the dyes most resistant to adsorption, but rhodamine WT, fluorescein, and sulpho rhodamine B also have moderately high resistance. Rhodamine B is readily adorbed by most materials. Rhodamine WT (orange), lissamine FF (green), and amino G acid (blue) are the three tracer dyes recommended; they may be used simultaneously to trace three injection sites with the filter combinations suggested.
The economic basis of resource information systems: The case of streamflow data network design
Authors: Attanasi E. D. , Karlinger M. R.
Published: February 2008

A general method for the economic design of natural resource information systems is presented for a certain class of natural phenomena. The system design is determined by the interaction of the technical input‐output relationship, i.e., the production function, the set of resource constraints, and an economic loss function defined in terms of parameter uncertainty. An application of the proposed method to streamflow network design is presented. Results of this analysis indicate that the method is fairly robust with respect to the assumptions. Observations are made which suggest extensions to flood measurement networks, long‐term precipitation networks, and seismic observation network design.
Bed load transport by natural rivers
Authors: Bagnold R. A.
Published: February 2008

Since stream power ω and sediment transport rate i are different values of the same physical quantity, namely, the time rate of energy supply and dissipation, it is rational to relate one to the other. The experimental relation has been difficult to interpret because of the spurious curvature of log‐log plots in which a constant threshold stream power of zero is involved. The substitution of an excess power ω − ω0 removes this curvature, and existing data on laboratory bed load transport rate measurements ib suggest a general empirical relation: ib ∝ (ω − ω0)[(ω − ω0);0]½. Existing laboratory data have also shown clearly that at any given value of ω − ω0 the bedload transport rate ib decreases as an inverse function of the ratio flow depth to grain size Y/D. The East Fork River (Wyoming) project has recently enabled bed load sampling devices to be calibrated, so reasonably reliable measurements can be made in natural rivers. The uncertainties in the measurement of the corresponding river power are discussed, and a simple data reliability test is suggested. Data covering three seasons collected from both Snake and Clearwater rivers appear to be reliable. Though there is much scatter due to day variations in the river conditions, these data, together with data on an imtermediate scale from East Fork River and on a small laboratory scale, conform with startling consistency to the following general empirical relation: ib/(ω − ω0) ≈ [(ω − ω0)/ω0]½(Y/D)−⅔ over a 2 million‐fold range of stream discharge. The degree of consistency of the above empirical relation with the theoretical relation deduced previously (Bagnold, 1973) is discussed, as are also some morphological implications of the dependence of ib on the depth to grain size ratio Y/D.
A method of estimating parameters and assessing reliability for models of steady state groundwater flow: 1. Theory and numerical properties
Authors: Cooley Richard L.
Published: February 2008

A new nonlinear least squares solution for the Hydrogeologic parameters, sources and sinks, and boundary fluxes contained in the equations approximately governing two‐dimensional or radial steady state groundwater motion was developed through use of a linearization and iteration procedure applied to the finite element discretization of the problem. Techniques involving (1) use of an iteration parameter to interpolate or extrapolate the changes in computed parameters and head distribution at each iteration and (2) conditioning of the least squares coefficient matrix through use of ridge regression techniques were proven to induce convergence of the procedure for virtually all problems. Because of the regression nature of the solution for the parameter estimation problem, classical methods of regression analysis are promising as an aid to establishing approximate reliability of computed parameters and predicted values of hydraulic head. Care must be taken not to compute so many parameters that the stability of the estimates is destroyed. Reduction of the error variance by adding parameters is desirable provided that the number of degrees of freedom for error remains large.
Assessing the accuracy of suspended sediment rating curves for a small basin
Authors: Walling D. E.
Published: February 2008

Sediment rating curves are often used to estimate suspended sediment loads where the sampling program is insufficient to define the continuous record of sediment concentration. Use of this technique will involve errors in the values of sediment load produced, and comparison with measured daily values has been employed by several workers to assess the magnitude of these errors. Comparisons are more difficult for small‐ and medium‐sized catchments because of the general lack of direct measurements of loads. Recording turbidity meters could be employed to provide a continuous record of sediment concentration which can be used to calculate sediment loads. Results are presented for the river Creedy in which the values of sediment load calculated from the continuous concentration record have been compared with estimates derived from rating curves. The rating‐curve data have been grouped according to season and stage tendency to provide various rating relationships. Values of annual sediment load estimated by using a rating curve could involve errors of up to +280%, whereas the errors for monthly loads could range between +900% and −90%. Careful consideration should be given to possible error terms before rating‐curve estimates of sediment load are used in statistical and other analyses.
Influence of soil properties, leaching fraction, and plant water uptake on solute concentration distribution
Authors: Jury W. A. , Fluhler H. , Stolzy L. H.
Published: February 2008

Studies of salt movement through 24 cropped lysimeters receiving high‐salinity irrigation are reported. A great deal of variability was found between depth–equivalent salinity sensor readings during the experiment, both between different lysimeters receiving the same water and salt inputs and among lateral replicates within each lysimeter. A computer simulation of the first 75 days of the experiment, using the measured soil properties and external inputs, alternately varied the hydraulic conductivity–water content relation, the irrigation flux, and the water uptake distribution by an amount consistent with the uncertainty in their measurement to see the effect on solute concentrations. It was found that large variations in the conductivity–water content relations and 10% uncertainty in the input flux had little effect on solute concentrations but that variations in the water uptake patterns within the top 60 cm created a large distribution of concentrations at a given depth and time.
Modeling soil water hydrology under a post oak (Quercus stellata Wangenh.)– shortleaf pine (Pinus echinata Mill.) stand in east Texas
Authors: England C. B.
Published: February 2008

A digital model of watershed hydrology successfully computed daily soil water contents of the two upper layers in a Boswell soil (Vertic Paleudalf) under an east Texas post oak (Quercus stellata Wangenh.)–shortleaf pine (Pinus echinata Mill.) stand throughout 4 years (1957–1960). This experiment demonstrated the fidelity of the model components to the prototype system elements. In addition, it provided parameters useful in applying the model for elucidating the hydrology of watersheds containing oak‐pine forests.
Integrodifferential equations for systems of leaky aquifers and applications 3. A numerical method of unlimited applicability
Authors: Herrera Ismael , Yates Robert
Published: February 2008

The integrodifferential equation formulation of leaky aquifer mechanics is used to develop a numerical method of unlimited applicability based on the finite element technique. This approach reduces the dimensionality of the problem and effectively uncouples the equations corresponding to each of the aquifers. Thus the number of nodes required and the bandwidth of the matrices involved are significantly reduced. Consequently, storage and computer time are decreased by a factor greater than 30 in axially symmetric problems and by a considerably greater factor in the absence of such symmetry.
Influence of the hysteresis effect on transient flows in saturated‐unsaturated porous media
Authors: Hoa N. T. , Gaudu R. , Thirriot C.
Published: February 2008

In the following report the authors experimentally and numerically study one‐ and two‐dimensional transient flows where the hysteresis of the relationship of suction‐water content clearly appears. In the numerical simulation of these flows, by using a finite element method, the hysteresis effect is taken into account by considering both its primary and secondary scanning curves; when the seepage surface occurs, it too is taken into account. The comparison with experimental results shows that in the concerned problems a numerical simulation in which this hysteresis effect is ignored may involve important errors.
A method for parameter sensitivity analysis in differential equation models
Authors: Kohberger Robert C. , Scavia Donald , Wilkinson John W.
Published: February 2008

A numeric method for analyzing global parameter sensitivity about a fixed point in parameter space for differential equation models is presented. The method is suitable for large‐scale, multiresponse systems which may not be in steady state. By using a quadratic model, the relationship between several global response characteristics and parameter perturbations is examined. Sensitivity relationships are defined with both backward elimination regression model selection procedures and eigenvalue‐eigenvector analyses. An example of the method is given using an ecosystem model consisting of 14 coupled differential equations.
Nonstructural floodplain planning
Authors: Bialas Wayne F. , Loucks Daniel P.
Published: February 2008

Recent years have been witness to increased annual flood damages in flood‐prone regions despite increased flood protection expenditures. To reduce flood damage, more attention is being focused on nonstructural flood damage control measures, such as land use restrictions in regions of high flood risk, vis‐à‐vis structural measures such as dams and levees. Some mathematical optimization techniques are proposed to assist in the preliminary selection of economically efficient and politically feasible floodplain zoning plans.
Nonstationarity of the mean and the hurst Phenomenon
Authors: Boes Duane C. , Salas Jose D.
Published: February 2008

Hurst (1957), Klemeš (1974, 1975), and Potter (1975, 1976a, 1976b) show that nonstationarity of the mean provides a possible explanation of the so‐called Hurst phenomenon; O'Connell (1971) and Wallis and O'Connell (1973 )show that this phenomenon can also be explained with a mixed autoregressive‐ moving average (Arma) process. These two alternate explanations can be quite similar; in fact, both Hurst's (1957) model and a model suggested by Klemeš (1974) and Potter (1975) have correlation structure identical to an Arma (1,1) process. A mixture model for shifting levels is proposed, and it is shown that the models of Hurst and Klemeš and Potter are special cases.
Integrating ecological and social considerations into urban flood control programs
Authors: James L. Douglas , Benke Arthur C. , Ragsdale Harvey L.
Published: February 2008

A well‐planned flood control program requires integration of diverse sets of information to develop alternative remedial measures for public discussion and selection. Although procedures for the required hydrologic studies, engineering designs, and economic analyses are readily available, procedures for assessing effects on the natural environment and on social aspects are still being developed. This paper illustrates one approach to integrating all this information in comparing alternatives, using the Proctor Creek watershed in Atlanta, Georgia, as an example. The illustration begins with a program such as might be formulated by available planning methodology from hydrologic, economic, and engineering data. The illustration continues with suggestions on how to collect meaningful social suitability data from a questionnaire designed to document public perceptions and preferences, ecological data from natural areas in the floodplain, and data relating the effects of the floodplain land use to the well‐being of the community. A procedure for integrating these considerations with the established analyses into alternatives presented for public discussion and decision making is then illustrated. Suggestions are also made on how the selected flood control program can be most successfully implemented.
Hydraulic conductivity of unsaturated porous media: Generalized macroscopic approach
Authors: Mualem Yechezkel
Published: February 2008

The macroscopic approach which yields the power function relationship between the relative permeability and the effective saturation, Kr = Sen, is generalized to allow n to vary with the soil type. Theoretical analysis shows that n may receive values lower than 3.0 for granular porous media and higher than 3.0 for soils of fine texture. These findings are verified by using experimental data of 50 soils. The lower limit of n is found to be 2.5, while high values (up to n= 24.5) are found for the fine‐textured soils. Statistical analysis of the measured data of the 50 soil samples shows a significant correlation between n and w which indicates the amount of work per unit volume of soil required to drain a saturated soil to the wilting point. By using the soil characteristics ψ − Θ an empirical formula is derived which relates n to w by n = 0.015w + 3.0. This proposed model is compared with the two previous versions of Averjanov (1950) and Irmay (1954) on the basis of the experimental data of the 50 soils. A very good agreement is found between the measured Kr − Θ curves and the theoretical ones, derived by the new model, for granular soils as well as for soils of fine texture where the other models very often fail. The accuracy of the new model is competitive with the best of the statistical models analyzed by Mualem (1976a). By this study the power function model gains a high degree of accuracy, which, compounded by its simplicity, produces an efficient tool for prediction of the hydraulic conductivity of unsaturated soils.
Stochastic models of floods
Authors: Todorovic P.
Published: February 2008

There are essentially two different approaches to the problem of flood analysis. One corresponds to the streamflow annual flood series (AFS); and the other to the streamflow partial duration series (PDS). Here we discuss characteristics of these approaches. Three stochastic models of floods presented in this paper are based on the streamflow PDS. Each model depends on certain assumptions concerning properties of exceedances of a base levelx0. The second and third models represent improvement vis‐á‐vis the first one in the sense that they are based on less restrictive assumptions. The time when the largest exceedance occurs is also studied, and the distribution of this time is determined. Each exceedance is characterized, roughly speaking, by its duration and its volume. Here a method is proposed for determining the distribution of this volume. The distribution function of the largest volume in an interval of time [0,t] is also given. Good agreement between theoretical and observed distributions shows that the assumptions concerning the exceedances are not unduly restrictive.
Evaluating the environmental consequences of groundwater contamination: 2. Obtaining location/arrival time and location/outflow quantity distributions for steady flow systems
Authors: Nelson R. William
Published: February 2008

A steady two‐dimensional flow system is used to demonstrate the application of location/arrival time and location/outflow quantity curves in determining the environmental consequences of groundwater contamination. The subsurface geologic and hydrologie evaluations needed to obtain the arrival results involve a sequence of four phases: system identification, new potential determination, flow system kinematics, and contaminant transport analysis. Once these phases are completed, they are effectively summarized and easily used to evaluate environmental consequences through the arrival distributions.
Preservation of the rescaled adjusted range: 1. A reassessment of the Hurst Phenomenon
Authors: McLeod Angus Ian , Hipel Keith William
Published: February 2008

Previous research related to the controversial Hurst phenomenon is reviewed and evaluated. Because of the inherent statistical properties of the rescaled adjusted range (RAR) statistic it is suggested that research primarily be devoted to this statistic rather than to the various definitions of the Hurst coefficient. Simulation studies reveal that for independently distributed random variables the RAR does not significantly depend on the underlying distribution of the random variables but is a function of the sample size. For modeling correlated data the statistical attributes of a discrete fractional Gaussian noise (FGN) process are studied and also improved. An efficient maximum likelihood estimation technique is developed for the FGN model, and it is shown how the residuals of the fitted model can be calculated and then subjected to diagnostic checks. An exact simulation procedure is developed for simulating FGN in such a way that synthetic traces from the model lie outside the Brownian domain. The Akaike information criterion (AIC) is suggested as a method for choosing between a FGN and a Box‐Jenkins model. For the six annual river flow series that are considered the AIC selects the best Box‐Jenkins model in preference to the FGN process for each data set. Because Box‐Jenkins models can be shown to preserve the historical RAR, in many practical applications it may be advantageous to use a Box‐Jenkins model instead of a FGN process.