bluuebunny/crossref_metadata_2025 huggingface dataset:
A discrete kernel generator for stream‐aquifer studies
Authors: Morel‐Seytoux H. J. , Daly C. J.
Published: February 2008

A finite difference model of the behavior of an aquifer without stream interaction was developed as a first‐stage component of a management model of a stream‐aquifer system. The model is not built as a usual simulator but as a discrete impulse response generator. Once the basic response coefficients have been generated, the finite difference model is no longer necessary to simulate the behavior of the aquifer. Any aquifer response (e.g., return flow to a given reach for a given week) is expressed as an explicit function of the pumping rates. A complete description of the ‘discrete kernel generator’ is provided including the basic equations, truncation error propagation, accuracy, and run costs.
Field channels: A key to better Indian irrigation
Authors: Easter K. William
Published: February 2008

Two different programs which attempted to improve water use and management were evaluated in eastern India. The improvement was through the installation of field channels in existing flood irrigation projects. The channels gave farmers better control over water on each field. The analysis highlights the importance of technically trained people and low‐cost project designs in making projects viable. Annual net returns of 300–350 rupees per acre were obtained in the Sambalpur villages with investment costs of only 34 rupees per acre. The contrasting pilot project in Raipur had a much lower profit potential due to high investment costs. The analysis adds support to the proposition that India should spend more public funds on modest improvements in existing flood irrigation systems and much less on large new irrigation projects.
Methods of pollution control and the rate of change in pollution abatement technology
Authors: Wenders John T.
Published: February 2008

This paper analyzes the impact of an improvement in pollution abatement technology on the costs of a firm producing under three alternative methods of pollution control: tax, subsidy, and emission standards. It is shown that the cost reduction to the firm will be greatest if the firm is operating under the pollutant tax method of pollution control, and therefore it is concluded that the incentive to improve pollution abatement technology will be greater if pollutant taxes are used to control pollution. In addition, it is shown that firms operating under emission standards or subsidy may have no economic inducement to produce some innovations in pollution abatement.
Effect of wind waves and wind tides on the optimum control of large lakes
Authors: Metler W. , Bogárdi I. , Duckstein L.
Published: February 2008

The optimal release policy for a large and shallow lake subject to the double uncertainty of average monthly hydrologic input and instantaneous wind‐induced water rise is calculated. The case of Lake Balaton in Hungary is used to illustrate the methodology. Loss functions are obtained for each lakeshore section; losses due to unfavorable (high or low) water level are given on a monthly basis, and dynamic losses due to waves and wind tides are calculated by using an event‐based model. A stochastic dynamic programing formulation yields an optimum release policy whose sensitivity to loss functions and discount factor is examined.
A Bayesian framework for the use of regional information in hydrology
Authors: Vicens Guillermo J. , Rodriguez‐Iturbe Ignacio , Schaake John C.
Published: February 2008

Water resource designs are perfect examples of decision making under uncertainty. In fact, three types of uncertainties may exist in any design problem: natural, parameter, and model uncertainties. The last two may be considered as informational uncertainties that are due to the lack of perfect information about the streamflow processes. The use of regional information has been suggested as a technique for reducing parameter uncertainties. The use of Bayesian methodology provides a framework for combining regional information with at‐site historical records. Moreover, Bayesian methods allow the hydrologist to consider the parameter uncertainties as well as the natural uncertainties within the decision‐making process. Because of these two advantages the Bayesian approach is a more complete and realistic approach to problems of uncertainty in hydrology and water resource planning than presently used methodologies.
A simple and inexpensive technique for determining colored light intensity underwater
Authors: Marcus Bernard A.
Published: February 2008

A technique for underwater determination of colored light intensity, relative to the surface, is presented. The technique involves using gelatin filters which are less expensive and more easily cut to fit meters than glass.
Meandering of supraglacial melt streams
Authors: Parker Gary
Published: February 2008

During periods of glacial ablation, excess water often concentrates in supraglacial melt streams, which typically exhibit meandering. Herein a stability analysis of straight supraglacial streams is carried out to determine the nature of meandering tendencies. Instability leading to meandering in the flow results from a combination of hydrodynamic and differential heating effects. The heat involved is apparently largely frictional. The analysis indicates that instability occurs only for supercritical flow and that the meander pattern does not migrate downstream. Meander wavelength is determined by channel width, depth, and Froude number. The results agree with field observations.

Summary and entire article are available on microfiche. Order from American Geophysical Union, 1909 K Street, N.W., Washington, D.C. 20006. Document W‐75‐002; $1.00. Payment must accompany order.
Reservoir management models
Authors: Sobel Matthew J.
Published: February 2008

The optimal policies for several discrete time control models of reservoir storage are characterized. Each characterization is exploited to simplify the numerical solution of heretofore formidable problems. Some of the results exploit analogies between multi‐item inventory theory and systems of multiple reservoirs. In particular, it is observed that the ‘linear decision rule’ label in the water resource literature ordinarily arises in contexts where either (1) a myopic policy is optimal, or (2) a multiple‐reservoir optimal release policy, as a function of the vector of reservoir contents, possesses a Jacobian matrix whose values are between zero and one. Either (1) or (2) impressively reduces the computational burden that would otherwise be carried.
The impact of large temporary rate changes on residential water use
Authors: Hogarty Thomas F. , Mackay Robert J.
Published: February 2008

Previous studies have shown that water meters for residences promote elimination of waste and increases in water rates will curtail external uses (e.g., sprinkling) of water by residences. The present study shows that large increases in water rates, even if temporary, will induce substantial, immediate, and quasi‐permanent reductions in domestic (internal) water use by residences. These reductions are effected in various ways, among them, repair of leaks and more efficient use of water‐using appliances.
Stochastic reservoir models: Relative computational effort
Authors: Roefs T. G. , Guitron R. A.
Published: February 2008

Linear programing formulations, dynamic programing formulations, and policy iteration models have all been used to solve for optimal operating rules for a single stochastic reservoir. In this paper, quantitative guidelines which discriminate between dynamic programing models and policy iteration models are developed. A judgment that stochastic dynamic programing models should be the preferred algorithm is reached.
Development and field testing of a basin hydrology simulator
Authors: Knapp Roy M. , Green Don W. , Pogge Ernest C. , Stanford Clarke
Published: February 2008

A computer model consisting of both surface water and groundwater phases and their interaction has been developed to simulate the hydrology of a stream basin. Input to the model includes precipitation, climatic conditions, boundary and initial conditions, and basin constants. Provision has been made for modeling withdrawals from both groundwater and surface water for consumptive use. The computer output includes streamflow hydrographs at selected points, groundwater levels, and groundwater recharge and discharge from the basin. The model is designed to be general in nature so that it will be applicable to different basins with similar geographic and geological conditions. Its structure is such that the basin is divided vertically into four layers and a stream network. The four vertical layers are, in order from top to bottom, a surface layer, an upper soil zone, a lower soil zone, and a groundwater layer (aquifer). Provision is also made to subdivide each layer horizontally into blocks, or subbasins, which are determined by considering topography, soil types, and climatic data. The model is described in detail in this paper, and its application to the Little Arkansas River basin of south central Kansas is made. A 25‐year period of history in this basin is simulated, and comparisons are made between calculated behavior and measured hydrologie behavior in the basin.
Water flow through a multilayer stratified hillside
Authors: Selim H. M.
Published: February 2008

The objective of this study is to present a mathematical analysis for steady state saturated flow through multilayer stratified hillsides of semi‐infinite depth. Two soil surface shapes were considered: a constant soil surface slope and a surface of arbitrary shape. Potential and stream functions were obtained for one‐, two‐, and three‐layered hillsides. The method of solution was based on the Gram‐Schmidt orthonormalization method. For two‐layered hillsides the hydraulic conductivities considered were K1:K2= 1:10 and 10:1. For three‐layered hillsides the hydraulic conductivities were K1:K2:K3 = 1:10:1 and 10:1:10. Flow nets, seepage velocities, and flow rates are presented. These results are useful particularly with regard to subsurface flow, runoff, erosion, and solute movement through sloping soils.
A reconsideration of the ‘requirement approach’ to residential water use forecasting
Authors: Darr Peretz , Feldman Stephen L. , Kamen Charles S.
Published: February 2008

The ‘requirement approach’ in which only population parameters and average consumption figures are used for forecasting water use has been refuted by a number of authors. In the extremely arid environment of the Israeli desert town of Eilat, variations in the socioeconomic characteristics which were predictors of residential water use for major urban areas of Israel were not associated with variations in residential water consumption. Only technical water‐using appliance specifications were found to be correlates. It can be surmised that the tool more apt to be of aid in forecasting water use in such an extreme environment is the requirement approach.
Longshore currents and sediment transport in west shore of Lake Michigan
Authors: Lee Kwang K.
Published: February 2008

Longshore sediment transport presents an important problem at the shores along the Great Lakes. Direct field measurements were made on the parameters related to waves, beaches, longshore currents, and sediment transport. By using the field data from Lake Michigan, the longshore currents are found to be linearly related to the longshore momentum flux of incident waves at the breaker line, and also the longshore sediment immersed weight transport rate is found in terms of the longshore wave energy flux per unit length of beach.
A three‐dimensional Galerkin Finite Element Solution of flow through multiaquifers in Sutter Basin, California
Authors: Gupta S. K. , Tanji K. K.
Published: February 2008

A three‐dimensional finite element solution was obtained for the simultaneous consideration of multiaquifers coupled through semiconfining layers, and the model was applied to a groundwater regime in Sutter Basin, California. The use of a disk/tape in data handling and computation has reduced the core storage and processor time and increased the capability of a given computer system to simulate basins larger than are presently possible with the use of only core storage. This economy is achieved by storing on a disk/tape all the intermediate results which are needed repeatedly. On the Burroughs B6700 each steady state solution of 123 three‐dimensional elements and 232 nodes is obtained with 20 kbit of memory and 1.49 min of processor time.
Evaluation of mean square error involved in approximating the areal average of a rainfall event by a discrete summation
Authors: Bras Rafael L. , Rodríguez‐Iturbe Ignacio
Published: February 2008

Two‐dimensional areal processes are commonly evaluated in hydrology through a discretization in space over the region in which the process is being studied. Such a discretization involves an error in going from the continuous process to the discrete one. This error is studied theoretically, and graphs are presented for its evaluation as function of the size of the area, the functional form of the correlation equation in space, and the level of discretization or size of the sample. Correlation structures of the Bessel type and of the single and double exponential kind are considered, and their different implications are discussed.
Disaggregation models in hydrology revisited
Authors: Mejia José M. , Rousselle Jean
Published: February 2008

The disaggregation model proposed by Schaake et al. (1972) is revised to include linkages with the past at the different levels of aggregation. This modification produces a more realistic hydrologic model.
Isotopic hydrology in the Amazonia: 2. Relative discharges of the Negro and Solimões rivers through 18O concentrations
Authors: Matsui E. , Salati F. , Friedman I. , Brinkman W. L. F.
Published: February 2008

Measurements of 18O were made on samples of water collected during a 2‐year period on the Amazon below the confluence of the Negro and Solimões rivers. The measurements show that the Amazon is not completely mixed 120 km below the confluence. Estimates of relative flows were based on the 18O concentrations and show that the relative contribution of the Negro varied from 19% in February 1973 to 68% in July 1973.
Water transport in the soil‐root system: Transient analysis
Authors: Molz F. J.
Published: February 2008

Equations are developed which describe the transient flow of water in a cylindrical soil‐root system. The main objective is to calculate water potential distributions in the root cortex as well as in the surrounding soil. Numerical results indicate that there will be small water potential gradients in the soil relative to those in the root in the upper 90% of the water availability range. Contrary to past experiments, theory predicts that appreciable amounts of water should flow from roots to soil when roots well supplied with water are in contact with dry soil. An important implication of the study is that models designed to predict the pattern in which roots extract water from soil will have to consider the rate‐limiting aspect of the root tissue.
Optimal design of multilevel branching sewer systems
Authors: Mays Larry W. , Wenzel Harry G.
Published: February 2008

The problem of determining a minimum cost design of a multilevel branching storm sewer system is formulated by using a serial approach to describing the system and proceeding through the computational algorithm. Discrete differential dynamic programing (DDDP) is the basic search technique employed. Results for an example using the serial approach are compared to those achieved by using an earlier nonserial DDDP approach. The several advantages of the serial approach become increasingly important as the size and level of branching of the system increase. These advantages are outlined and discussed, the superiority of the serial over the nonserial approach being demonstrated.
Model uncertainty in flood frequency analysis and frequency‐based design
Authors: Bodo Byron , Unny T. E.
Published: February 2008

Constrained by computational feasibility, attempts to describe random natural phenomena of complex origin analytically can lead to a multiplicity of simplistic potentially representative model forms, as has occurred in the case of flood frequency analysis. Classical statistical methods inadequately confront this model uncertainty. Likelihood and Bayesian methods are presented and shown to permit inference concerning the relative goodness of several potential model candidates with respect to a given set of flood events. The Bayesian inferences are further combined within a decision theoretic structure for examination of the anticipated economic consequences of model uncertainty regarding decisions concerning flood protection levels. Results show that Bayesian methods supply more precise information but require greater effort. Since a model world of simplistic forms may never be defined absolutely, both decision and inference remain subject to the astute judgment of the analyst.
The asymptotic distribution of the range and other functions of partial sums of stationary processes
Authors: Siddiqui M. M.
Published: February 2008

Let ℰn, n = 1, 2, ⋯ , be the net input in a reservoir during the nth period of time, and set S0 = 0, Sn = ℰ1 + … + ℰ n, = 1, 2, ⋯ . Many quantities of interest, such as range, first‐passage times, and duration of deficit period, are functions of the partial sums Sn. In this paper it is pointed out that the functional central limit theorem, which has been previously used to obtain asymptotic results for independent and identically distributed ℰn, can be applied to a class of stationary sequences as well. To this class belong m‐dependent, Markov, autoregressive, and autoregressive‐moving average types of stationary processes.
Bayesian generation of synthetic streamflows: 2. The multivariate case
Authors: Valdés Juan B. , Rodríguez‐Iturbe Ignacio , Vicens Guillermo J.
Published: February 2008

A Bayesian framework for the synthetic generation of annual Streamflows from a multivariate first‐ order autoregressive model is presented. This framework allows the user to include directly the effects of the parameter uncertainties in the evaluation of proposed projects through simulation with the synthetically generated records. The model produces synthetic traces with higher variances than those in the historical records when the records are too short to estimate reliably the ‘time’ values of the parameters of the process. This multivariate model is a natural extension of the model presented by Vicens et al. (1975).
Shape of a streamline water table near inflow and outflow boundaries
Authors: Boast Charles W.
Published: February 2008

A streamline water table is usually pictured to leave an inflow boundary perpendicular to the surface and to approach an outflow boundary tangential to the surface for vertical surfaces or for inclined surfaces with the porous medium ‘below’ the surface. The hodograph solution for the problem of flow through a vertical walled dam proves that theoretically, the water table streamline leaves the inflow boundary horizontally and approaches the outflow boundary vertically but shows that at a practical scale the water table meets the boundaries at finite nonzero slopes. The actual water table shape deviates considerably from the usual way that the water table is sketched. The cause of the difference lies in an intuitive but incorrect assumption that the slope of the water table does not change dramatically near the endpoints of the water table.

Supplement is available with entire article on microfiche. Order from American Geophysical Union, 1909 K Street, N.W., Washington, D. C. 20006. Document W77‐002; $1.00. Payment must accompany order.
Minimizing costs in well field design in relation to aquifer models
Authors: Bostock C. A. , Simpson E. S. , Roefs T. G.
Published: February 2008

For a given production rate from a proposed well field, well construction and replacement costs decrease with fewer and larger wells spaced farther apart, while pumping lift costs increase. A method for minimizing the sum of these two costs uses a two‐dimensional uniform grid of wells to select a combination of well spacing and well capacity that minimizes costs for a given demand. Uncertainty in field permeability at future well sites is treated by averaging the possible outcomes over all wells in accord with a probability density function for permeability values. The method assumes an annual cycle whereby the water table declines owing to pumping in a dry season and is recharged to its initial state during a wet season.
Water and ice potentials in frozen soils
Authors: Groenevelt Pieter H. , Kay B. D.
Published: February 2008

The envelope pressure potentials of the liquid water and ice in a frozen soil are defined. The envelope pressure potential of liquid water is a generalization of the definition of the envelope pressure potential (overburden potential) of the water in an unfrozen swelling soil. In order to express these envelope pressure potentials in terms of volume ratios, use is made of the void ratio, the moisture ratio equivalent, and the ice ratio equivalent. A new development is initiated by the formulation and derivation of the frost potential of both the liquid water and the ice. These frost potentials are expressed in terms of the ice ratio, the moisture ratio, the ice ratio equivalent, and the moisture ratio equivalent. The relations between these variables are intrinsic properties of the porous medium which have to be determined experimentally.
Mathematical modeling of natural groundwater recharge
Authors: Krishnamurthi N. , Sunada D. K. , Longenbaugh R. A.
Published: February 2008

A mathematical model is presented to determine natural groundwater recharge by using transient soil moisture data measured as a function of vertical position. The model is based upon the finite difference form of the Richards equation. The assumption is made that moisture content varied in the linear range of pressure‐moisture and conductivity‐moisture relations to obtain a solution to a particular field problem. The parameters of the model, estimated by a linear model of the moisture data, characterize the hydraulic properties of soil and their spatial variability. The finite difference form of the mathematical model is solved by iteration using the Newtonlike method, ensuring computational speed and accuracy. The model and the computer program are verified by using the first‐order approximate one‐dimensional solution of the infiltration equation for homogeneous soil. Application of the model to the High Plains of Colorado provides monthly recharge rates which correlate adequately with the time series data of water table elevations and events of precipitation and ephemeral streamflow.
The small sample estimation of h
Authors: Şen Zekâi
Published: February 2008

In this paper a general analytical procedure has been presented for evaluating the expected value of the Hurst coefficient h in small samples. In particular, the expectation of h has been derived analytically in an explicit form for the lag 1 Markov process, and then the validity of this analytical expression has been checked against the results obtained by Monte Carlo simulation techniques. To this end a large number of synthetic sequences have been generated for various values of sample sizes n and the lag 1 serial correlation coefficient ρ with the assumption that the underlying random variables are normally distributed. Furthermore, it has been shown that the bias in ρ for small samples is accentuated in the expected value of n which is a function of both n and ρ only.
Ohio River power curve regression equations
Authors: Lee Larry J. , Henson Bob L.
Published: February 2008

By the use of a statistical computer program, power curve regression equations and correlation coefficients were developed for as many river parameters as could be accurately quantified for the Ohio River. This was done with the expectation that these equations would be useful in sorting from the many river parameters those variables that are strongly related and would aid in predicting changes that the river might undergo as a result of the manipulative behavior of man. Results indicate that the equations developed may be useful for both purposes.
Competence of Hope River, Jamaica: A reappraisal of R as a function of D
Authors: Wood Peter A.
Published: February 2008

Shear stress and competence determinations for the Hope River, Jamaica, indicate that widely different values are obtained with different equations. The data suggest that for multichannel streams, R can be approximated by D/2, so that г = γ(D/2)S.
A nonlinear analysis of the relationship between rainfall and runoff for extreme floods
Authors: Liu Clark Chen‐Kun , Brutsaert Wilfried
Published: February 2008

The watershed response to heavy rainfall was considered as a hereditary process. A nonlinear system model was developed in terms of a Volterra integral series of the first kind, which satisfies the principle of dissipation of hereditary action as well as the requirement of time invariance. A workable and practical method was developed to compute optimal response functions or kernels of the two‐term truncated Volterra series. A Galerkin‐type method was used, whereby the kernels were approximated by an orthogonal function expansion in terms of Chebyshev polynomials. The kernels evaluated from historical data for the Cowanesque watershed in the Chemung River basin were tested by reconstituting the hydrograph of an unrelated and unusual flood event caused by tropical storm Agnes of June 1972. It was found that the nonlinear watershed model yields a better prediction of the hydrograph of an exceptional flood than the linear model. The performance of both nonlinear and linear models is sensitive to the assumed value of the rainfall loss rate.
The effect of salt precipitation and high sodium concentrations on soil hydraulic conductivity and water retention
Authors: Frenkel H. , Hadas A. , Jury W. A.
Published: February 2008

Controlled irrigation management of moderate to poor quality water must assure sufficient movement of solution through the root zone to maintain a salinity regime which a crop can tolerate while at the same time minimizing the deterioration of groundwater or river quality. One proposal for accomplishing this objective is a policy of high‐frequency irrigation and minimum leaching, which encourages precipitation of calcium salts from solution and hence decreases the salt flux below the root zone. However, the concentration and fraction of sodium in the remaining solution are increased by such a policy and could be harmful to soil or plant properties. The work reported here analyzes the major plant‐soil‐salinity interactions resulting from irrigation with saline water at controlled leaching fractions. Simulations are run for leaching fractions of 0.30, 0.05, and 0.01 and three different water uptake patterns for two high‐sulfate waters with different salinity levels: 2.1 and 6.6 mmho/cm. Results suggest that soil hydraulic conductivity and water retention should not be adversely affected by high sodium levels or cumulative salt precipitation even at very low leaching fractions. However, it is probable that plant activity will be impaired by the lower leaching fractions because of high osmotic pressure within the root zone and that root proliferation could be reduced by soil structure cementation resulting from salt precipitation.
An efficient numerical method of two‐dimensional steady groundwater problems
Authors: Liu Philip L.‐F. , Liggett James A.
Published: February 2008

The boundary integral equation method (BIEM) is shown to be an efficient and accurate numerical technique for solving problems of Darcy flow in porous media. The BIEM is combined with conformal transformation to the complex potential plane to solve free surface problems without iteration and with relatively few nodal points. Since the BIEM reduces the effective dimensions of the problem by one, the computer time varies approximately as the inverse square of the point spacing, whereas in finite element or finite difference methods the time varies approximately as the inverse of the fourth power of the point spacing. Two examples of the BIEM are presented herein. They are flow through an underdrained dam and a seawater intrusion problem.
Evaluating the environmental consequences of groundwater contamination: 4. Obtaining arid utilizing contaminant arrival distributions in transient flow systems
Authors: Nelson R. William
Published: February 2008

The versatility of the new contaminant arrival distributions for determining environmental consequences of subsurface pollution problems is demonstrated through application to a transient flow system. Though some of the four phases of the hydrologic evaluations are more complicated because of the time dependence of the flow and input contaminant concentrations, the arrival distributions still effectively summarize the data required to determine the environmental implications. These arrival distributions yield two graphs or tabular sets of data giving the consequences of the subsurface pollution problems in a simple and direct form. Accordingly, the public control authorities would be able to use these results to choose alternatives or to initiate corrective actions, depending on the indicated environmental consequences.
Some properties of the geometric mean and its use in water quality standards
Authors: Landwehr Jurate Maciunas
Published: February 2008

The geometric mean is often used to express acceptable levels of fecal coliform counts in federal and state water quality criteria or standards. The expected value of the geometric mean is shown to be a function of the sample size and to be very sensitive to the skew as well as to the form of the underlying distribution function. Implications of these findings are discussed with regard to standards. In particular, it is noted that great care must be taken in specifying the minimal sample size to be used.
The statistical mechanical theory of water transport through unsaturated soil: 1. The conservation laws
Authors: Sposito Garrison
Published: February 2008

The macroscopic differential equations of mass and momentum balance for water in a rigid unsaturated soil are derived from first principles by using the methods of statistical mechanics. The derivation begins with the development, at the molecular level, of expressions for the mass and linear momentum densities of water in a soil. The derivatives of these expressions with respect to the time then provide for local balance equations that are ensemble averaged and local volume averaged in order to produce the macroscopic balance equations. The resulting macroscopic equations agree with those derived for mass and linear momentum transport in a soil on the basis of the continuum theory of mixtures. The unified insight into mass transport processes afforded by a statistical mechanical theory as compared to one evolved from a solely macroscopic view is discussed.
Derivation of equations for variable rainfall infiltration
Authors: Morel‐Seytoux Hubert J.
Published: February 2008

Formulae were derived for prediction of ponding time and cumulative infiltration following ponding under a condition of piecewise variable and even intermittent rainfall. The derivations do not assume immediate saturation at the surface or a piston displacement of air by water; they include the viscous flow of air. The results were compared with experimental data of James and Larson for two conditions: constant rainfall and intermittent rainfall. The proposed formulae are simple to use, requiring no complex solution of a partial or even an ordinary differential equation. The numerical calculations presented in the paper were performed with a small pocket calculator. The agreement with experimental data is good.
Chemistry of snow meltwater: Changes in concentration during melting
Authors: Johannessen M. , Henriksen A.
Published: February 2008

Over much of Norway a large portion of the yearly precipitation falls as snow, and the pollutants contained in precipitation accumulate in the snowpack to be released during a short period in spring. Atmospheric fallout of sulfur compounds has been estimated to be about 30% of the total deposition in Norway, but fallout on the snow cover is probably considerably smaller. During winters with little or no snowmelt before spring, most of the pollutant load is retained in the snowpack. Laboratory and field lysimeter experiments indicate that 50–80% of the pollutant load is released with the first 30% of the meltwater. The average concentration of pollutants in this fraction is 2–2.5 times the concentration in the snowpack itself. The very first fractions may contain more than 5 times the snowpack concentrations. These high concentrations may be due to a freeze‐concentration process during snow recrystallization and melting in which contaminants accumulate preferentially at the surfaces of ice particles. The resulting increase in the acid concentration of low‐buffered water courses occasionally leads to severe physiological stress to fish and other aquatic organisms and even to massive fish kills. This process occurs at a time which is critical to the hatching stage of salmonid fish species.
Physical measurements of river ice jams
Authors: Calkins Darryl J.
Published: February 2008

River ice jam measurements have always been relatively difficult to obtain because of the uncertain stability of the floating ice mass. But recently two ice jams resolidified for about 3 weeks, allowing the ice thickness to be measured at several cross sections along their longitudinal profiles. The size distribution of surface ice floes in one of the jams was also evaluated from low‐level aerial photography. The ice jams were found to be thickest at the downstream end, of the order of 4–5 times the thickness of the ice cover before breakup, and decreased almost linearly in thickness upstream. The largest surface ice floes measured in one ice jam ranged from 0.27 to 0.05 of the river's average width (∼45 m). The largest floes were at the downstream end, and floe size decreased progressively with distance upstream.
Analysis of differences in municipal treatment levels
Authors: Yance Joseph V.
Published: February 2008

Effluent charges are often proposed as the best way to insure that environmental costs will be internalized by the discharger. However, even in the absence of such charges, municipal treatment plants have been constructed for many years, an indication that to a significant degree, states and communities have internalized the pollution costs of waste water discharges. The motivation for such investment varies widely, however, since before secondary treatment became a Federal requirement the percentage of the sewered population in a state receiving such treatment ranged from 9 in New Hampshire to 100 in New Mexico. Using regression techniques, this analysis explains 40–45% of the variation in treatment levels among states in 1968 in terms of factors such as the availability of assimilative capacity relative to waste loads and the recency of urban development. The results of state and local programs appear to have been rational, broadly speaking, more extensive treatment being applied where pollution impacts would be greater. Some of the economic implications of the construction grant program, which provides an added incentive for treatment plant investment, are discussed in the light of these results.
Galerkin Finite Element Procedure for analyzing flow through random media
Authors: Sagar Budhi
Published: February 2008

A method is presented for analyzing flow through a porous medium whose parameters are random functions. Such a medium is conceptualized as an ensemble of media with an associated probability mass function. The flow problem in each member of this ensemble is deterministic in the usual sense. All the solutions belong to a particular Hilbert space, and hence they can be written in terms of linear combinations of its basis functions. This is similar to the Galerkin formulation except that the coefficients in the linear combination are no longer deterministic quantities but random functions. The finite element method in conjunction with a Taylor series expansion is used to get the first two moments of the solution approximately. The method does not require specification of full probability mass functions of the parameters but only their first two moments, and spatial correlations can be easily accounted for. However, it is assumed that the probability mass functions are peaked at the expected value and are smooth in its vicinity. A sample problem is solved to illustrate the procedure. It is observed that the result is sensitive to the element size in the numerical scheme and the variances and spatial correlations of parameters. The expected value of the hydraulic head is found to differ significantly from the results that would have been obtained if the problem had been solved deterministically.
Drainage density and streamflow: A closer look
Authors: Dingman S. Lawrence
Published: February 2008

Drainage density D was defined by Horton as D ≡ L/A, where L is the total length of stream thalwegs in an area of size A. Because the average distance from watershed divide to channel is approximately 1/2D, many authors have used D as a measure of drainage efficiency and hence as an independent variable for predicting a wide variety of streamflow characteristics in ungaged watersheds. However, ‘effective drainage density’ DE≡ Lv/A, where Lv is the total length of stream valleys, is a better characterization of divide‐to‐channel distance than D. Furthermore, in Hortonian overland flow, DE (or, approximately, D) is only one of several factors affecting drainage efficiency, and its influence can be readily overridden. In saturation overland flow, neither DE nor D is fundamentally related to drainage efficiency, though they may proxy for more fundamental parameters. In groundwater flow, drainage efficiency is proportional to DE; thus higher flow variability will tend to be correlated with higher DE. The proportions of groundwater runoff and storm runoff from a watershed are not fundamentally related to D or DE regardless of mode of flow. These theoretical conclusions are supported by close examination of previous studies relating drainage density to hydrologic variables and indicate that DE (or D).is of much more limited value as an independent variable for predicting hydrologic characteristics than has been widely assumed in the literature.
An objective criterion for the selection of representative basins
Authors: Ebisemiju Fola S.
Published: February 2008

The existence of a hydrologically uniform area is questionable. Therefore it is unlikely that a drainage basin can truly represent the diverse environmental and terrain conditions in any given area. The widely documented strong association between basin morphometry and hydrological responses indicates the possibility of identifying hydrologically similar basins on the basis of similarity of their gross morphology. By using a multidimensional morphological classification of drainage basins, a rational basis for the selection of representative basins is developed. The procedures for this classification and selection are outlined and illustrated with an example from southeastern Nigeria.
A note on estimating finite difference interblock hydraulic conductivity values for transient unsaturated flow problems
Authors: Haverkamp R. , Vauclin M.
Published: February 2008

Nine different methods of weighting interblock hydraulic conductivity values used for modeling one‐dimensional water transfer in homogeneous unsaturated soil are tested for their influence upon the accuracy of the finite difference solution. On the basis of these results the most suitable weighting relation is selected. In a first stage the numerical results obtained by the models using the various conductivity weighting formulas are compared with the quasi‐analytical solution developed by Philip for a clay soil. In a second stage the models are used to simulate a laboratory experiment carried out on a sandy soil. In both cases, rather drastic boundary conditions are applied. It appears clearly from these tests that the weighting errors are of critical influence on the accuracy of solution. As proposed in this note, the geometric mean taken over two adjacent hydraulic conductivity values is the only weighting method that generates little weighting error. The latter weighting relation is found to be preferable in terms of flexibility, precision, and feasibility.
Annual precipitation in the northeast United States: Long memory, short memory, or no memory?
Authors: Potter Kenneth W.
Published: February 2008

Regional filtering and intervention analysis of nineteen 100‐year precipitation series from the northeast United States indicate that eight of these series are of doubtful homogeneity. Statistics of these series are generally distorted. Of particular significance is the inflation of the short‐lag autocorrelation function and Hurst coefficient. For the precipitation series which appear to be homogeneous the estimated autocorrelation functions and Hurst coefficients are remarkably consistent with a lag l autoregressive process, indicating that annual precipitation in the northeast United States is a short‐memory process. Based on these results, it is recommended that before long‐term memory is inferred from analyses of hydrologic series, the homogeneity of these series should be clearly established.
Universal constants for scaling the exponential soil water diffusivity?
Authors: Brutsaert Wilfried
Published: February 2008

The exponential form of the soil water diffusivity can be scaled either with the wetting front parameter Φf = xf/t½ or with the sorptivity A0 = F/t½; these variables, which arise in the problem of sorption in a dry soil, are xf the distance to the wetting front, t the time, and F the infiltrated water volume. It is shown that the three constants used in this scaling are not independent and that only one constant is needed.
Calculation of evaporation during the three stages of soil drying
Authors: Idso S. B. , Reginato R. J. , Jackson R. D.
Published: February 2008

A single equation is developed to calculate daily evaporation rates during all three stages of soil drying. The only required input data are daily incoming and reflected solar radiation and maximum and minimum air and soil surface temperatures. Experiments demonstrating the validity of the equation were conducted on an Avondale loam soil at Phoenix, Arizona, under a wide range of climatic conditions. It is shown that the effects of many important meteorological parameters are automatically accounted for by the direct measurement of the soil surface temperature.
Field test of solution flow models in a heterogeneous irrigated cropped soil
Authors: Bresler E. , Bielorai H. , Laufer A.
Published: February 2008

Data obtained from a controlled irrigation experiment in a citrus grove are compared with results obtained from simultaneous water and salt flow models considering water uptake by the trees. In the models, spatial variability in soil hydraulic properties has been taken into account by using a single dimensionless scaling parameter which allows the range of the soil water retentivity h(θ) and hydraulic conductivity K(θ) functions to be approximated with a probability of about 0.95. Measured data of water content profiles were obtained with the aid of the neutron probe method. Saturated paste extracts of disturbed soil samples were used for the measured salt profile data. Variability in the water and salt content observations is expressed in terms of the 95% confidence limits (CL) of the measurements made in six replications at each of the three experimental treatments. An irrigation period of 7 months was simulated and compared each year. The comparisons between models and experiments are based on average values, on ranges of CL of field data, and on simulated results computed with highly probable ranges of soil hydraulic properties. The results suggest that for estimating field values of water content (θ) and salt distribution profiles with approximate ranges of K(θ) and h(θ) at a given probability, the models have been sufficiently developed.
Variation of rain chemistry during storms at two sites in northern California
Authors: Kennedy Vance C. , Zellweger Gray W. , Avanzino Ronald J.
Published: February 2008

The chemical composition of rainfall at Menlo Park, on San Francisco Bay, is compared with rainfall at Petrolia, which is near the coast about 500 km north of San Francisco. Sequential samples representing 1.35 to 5.4 mm of rain were collected from November 1971 to January 1972. At rural Petrolia the Cl:Na ratio was that of seawater for Cl concentrations ranging from 0.02 to 38 mg/l. In metropolitan Menlo Park the Cl:Na ratio in rain closely approximated that in seawater above about 0.5 mg/l Cl, but at lower Cl concentrations the ratio exceeded that in seawater, a fact attributed to the presence of anthropogenic Cl. Other constituents dissolved in Menlo Park rain (along with their concentration ranges in milligrams per liter), and believed to be derived in part from anthropogenic sources, were Ca (0.01–1.07), Mg (<0.01–1.08), Pb (0.003–0.035), Zn (0.002–0.013), Mn (0.0001–0.0057), Cu (0.0008–0.0024), NO3‐N (0.02–0.54), and Br (<0.01–0.12). The range of pH values was smaller in the rural than in the metropolitan areas; average H+ activity corresponded to a pH of 5.1 to 5.2 in both areas. At Petrolia, pH decreased with increased dissolved salts in rainfall, but no relation between pH and dissolved salts was evident at Menlo Park.
Multiobjective risks in reservoir operation
Authors: Croley Thomas E. , Raja Rao Kuchibotla N.
Published: February 2008

Reservoir operation objectives are considered by maximizing an objective function while maintaining various minimum values of a second objective in an optimization constraint. This is often referred to as the ϵ‐constraint approach; a priori estimates of objective worth are thereby eliminated. The constrained optimizations are repeated for many synthetic sequences of inputs to evaluate the risk associated with attainment of one objective for a given value of another objective. A trade‐off level for design of the reservoir operation rule is then subjectively selected based upon consideration of objective trade‐offs and their risks. An operation rule is estimated from the optimum decision set associated with the selected trade‐off level, by using Implicit Stochastic Optimization methods already available. These techniques are applied to the practical problem of the Coralville reservoir, near Iowa City, Iowa, for flood control and recreation operating purposes and resulting operation rules are compared to the existing operation rule.
An initial value problem for the horizontal infiltration of water
Authors: Babu D. K. , Th. van Genuchten M.
Published: February 2008

An initial value problem for the horizontal infiltration of water is solved by means of a perturbation technique. The diffusivity is assumed to vary as a positive power of the normalized water content. Evolution of the profile is supposed to be taking place in two stages. In the first stage, moisture content at the origin increases steadily as some arbitrary power of dimensionless time until the maximum normalized value of unity is attained; thereafter, in the second stage, moisture content at the origin remains at the constant value of unity. The moisture distribution at the end of the first stage defines the initial values of moisture for the problem in the second stage. This paper derives the flow details for the second stage, and constructs moisture profiles as they evolve for times greater than unity.