bluuebunny/crossref_metadata_2025 huggingface dataset:
Consequences of Historic Rainfall on Western Iowa Farmland
Authors: Spomer R. G. , Heinemann H. G. , Piest R. F.
Published: February 2008

Rainfall on five soil and water conservation research watersheds near Treynor, Iowa, varied from 18 to 22 inches for the period of May 28 to June 27, 1967. This unique series of events has a return period that exceeds 100 years, based on the 97‐year Weather Bureau record at nearby Omaha, Nebraska.

Surface runoff from two corn cropped watersheds planted on an approximate contour approached or exceeded 50% of the storm rainfall during the period. Surface runoff was 8% or less for all rainfall events on a corn cropped, terraced watershed and 17% or less for all but one storm on a grassed watershed.

These rains occurred a few weeks after planting when the corn plants were only 6 inches tall; consequently, little or no erosion protection was provided for the bare, loose soil. Sheet rill erosion rates were 75 to 100 tons per acre on the contoured corn watersheds. By contrast, conservation practices on two other watersheds limited the sheet rill erosion to 2.5 tons per acre.

Gullies on the contoured corn watersheds eroded severely, whereas conservation practices on the other watersheds reduced gully erosion to an insignificant amount.
Evaporative Capacity of Unsaturated Air
Authors: Showalter A. K.
Published: February 2008

Falling water droplets quickly assume surface temperatures equal to the wet‐bulb temperature of the air. Formulas for absolute humidity and Ferrel's psychrometric formula are used to develop a simple relationship for calculating the capacity of air to absorb water droplets evaporated into it. Such data are relevant for determining water losses during sprinkler irrigation, the discrepancy between radar observed liquid water contents and ground observed rainfall and other factors important in the hydrologic balance of the atmosphere. The evaporative capacity E0 in g/m3 of the air is determined to be explicitly defined by an equation involving wet‐bulb temperature Tw in °K, wet‐bulb depression Δtw in °C, and atmospheric pressure ρ in mb E0 = (p·Δtw)/(7Tw)
Flood Wave Modification along a Prismatic River
Authors: Ghosh Somenath
Published: February 2008

The modification of a flood hydrograph in a uniformly wide river reach with no downstream control that takes into account the effect of pseudoviscosity terms has been studied graphically by using the method of characteristics as discussed by Abbott. The routed profiles in the ux, hx, ut, and ht planes indicate the usual reduction in peak height and velocity with distance, and the stage discharge curve shows the familiar loop pattern.
Evaluation of Snow Water Equivalent by Airborne Measurement of Passive Terrestrial Gamma Radiation
Authors: Peck E. L. , Bissell V. C. , Jones E. B. , Burge D. L.
Published: February 2008

Recent research studies have investigated an airborne gamma radiation detection system to determine the water equivalent of snowpacks in nonmountainous areas. Snow attenuates natural gamma emissions from the soil, and the magnitude of attenuation is related to the mass of the water blanket between the soil and the detector. Gamma spectral and total counting rates are collected and recorded by an airborne system using 14 4‐ by 4‐inch sodium iodide (NaI (Tl)) crystals. These data are corrected for soil moisture, background radiation, and effects of air density. Extensive snow depth and density measurements were taken to determine ‘ground truth’ water equivalent under the flight path. Results of the first year of research indicate that gamma spectral data may be expected to give areal measurement of snow water equivalent within at least 0.2–0.5 inch over favorable terrain. The use of total count data is even more promising but requires methodology still under development for eliminating background interference.
Effect of a Freezing Zone of Finite Width on the Thermal Regime of Soils
Authors: Nakano Yoshisuke , Brown Jerry
Published: February 2008

The effect of a freezing zone of finite width on the thermal regime of soils is studied. For soils having a very thin freezing zone, the concept of an artificial freezing zone is introduced for computational simplicity. The computational method based on such a concept is found to be sufficiently accurate for practical applications. The classical method, which assumes the existence of a freezing boundary of infinitesimal width, produces a large error for soils retaining substantial amounts of unfrozen water at sub‐zero temperatures.
Optimal Capacity of Port Loading Facilities
Authors: Case Leland S. , Lave Lester B.
Published: February 2008

Route changes and delays owing to such factors as adverse weather make it difficult to predict the exact arrival of ships or barges in a port. In choosing the capacity of loading facilities in a port, one must consider that there will be many times when the facilities will be unused and many times when cargo vessels must wait a substantial time before they are serviced. The choice of capacity of port facilities when arrival and service times are random is considered here. Queuing theory can be applied to determine the average waiting time for an individual cargo vessel as a function of the arrival and service distributions, the capacity of the terminal facility, and the arrival rate. To save waiting time for a vessel, the terminal capacity must be expanded. The optimal capacity of a loading facility is determined by trading off the additional capital cost of a dock against the value of the vessel time saved. Estimates are made of costs and savings incurred by investing in new facilities. The effects of seasonality in traffic and speeding the service rate are also considered.
Steady State Flow around Wells in Aquifers with Hydraulic Conductivity Varying with Depth
Authors: Youngs E. G.
Published: February 2008

In the two recent studies on the steady state flow around wells in a two‐layered aquifer [Khan et al., 1971] and on the spacing of drainage wells in a layered aquifer [Khan and Kirkham, 1971], the potential and stream functions were obtained in the form of summation series. To obtain these functions, the use of a physical artifice was required. However, some of the more important aspects of these problems, but not the potential and stream functions, may be obtained very simply without recourse to simplifying assumptions by following the method first used by Charnyi [1951] to calculate flows to wells and through vertically sided dams and later developed by Youngs [1965, 1966b] to obtain horizontal seepage rates in aquifers with hydraulic conductivity varying with depth. The use of this general method in seepage studies has been explored further in a number of different situations [Youngs, 1966a, 1967, 1971a, b].
General Analysis of Longitudinal Dispersion in Nonuniform Flow
Authors: Gelhar L. W. , Collins M. A.
Published: February 2008

An analytical method is proposed by which the effects of flow nonuniformity and variable dispersion coefficients can be evaluated for problems involving longitudinal dispersion in porous media. A boundary layer approximation is used to develop general solutions of the one‐dimensional convective‐dispersion equation for steady flow. Several examples are considered by using the analytical method, and the general effect of flow nonuniformity on dispersion is discussed. Comparisons of the analytical solution with numerical solutions of the exact equation indicate that the method will yield accurate results in many applications.
Recurrence relations for first order sequential reactions in natural waters
Authors: Di Toro Dominic M.
Published: February 2008

The kinetics of many biologically and chemically reactive substances in natural waters can be approximated by first order reactions. A recurrence formula is presented that relates the concentrations in the sequence to the concentration distribution of the first reactant in the sequence. This recurrence relation applies to general spatial and temporal regimes. In particular, the recurrence relation immediately extends the known analytical solutions for a single first order reacting substance to any sequentially reacting set of substances for various spatial and temporal settings. This increase in the applicability of known solutions renders problems soluble that had heretofore been difficult to analyze.
Criteria for groundwater level data networks for hydrologic and modeling purposes
Authors: Peters Helen J.
Published: February 2008

Budget and technical considerations require the formulation of specific criteria in designing water level data networks that are to be measured over a long time period. Specific purposes or uses of longtime water levels relate to various intensities of hydrologic studies. Specific criteria in terms of measurement frequency and observation point density for purposes of storage and storage fluctuation for five intensities of hydrologic investigations were developed subjectively and are presented, each related to needed geologic detail. The lead time for data collection varies from 1 to 15 years, depending on the intensity of the study and the resulting decision type. Application of the criteria in California's groundwater basins confirms the utility of the concept, but identifies the need for a definition of accuracies of contour maps constructed from various point densities and other study input, for close control of measurement points, for broad judgment at boundaries, and for specifications of needed accuracy of interpreted information by users.
Measurement of atmospheric and ground level precipitation
Authors: Hamon W. Russell , Cox Lloyd M.
Published: February 2008

Actual atmospheric precipitation is calculated from dual measurements of an unshielded and a shielded gage. The mathematical relationship developed is independent of wind and the form or density of precipitation and contains a single coefficient. This coefficient was evaluated by using data from snow pillows and sunken gages and by using the calculations of actual precipitation obtained from the profile measurements of wind and catch in unshielded gages. Ground level precipitation and snow storage measurements are obtained from a surface precipitation gage consisting of a saucer‐shaped concrete platform 5 feet in diameter with a border and a central collector. Snow on the platform is hydraulically weighed, and snowmelt and rainfall are collected in a tank. Continuous measurements of these quantities are obtained by use of pressure bulbs and metal diaphragms that activate recorder pens on a mechanical strip chart drive.
Groundwater flow in an inhomogeneous aquifer
Authors: Kuiper L. K.
Published: February 2008

An analytic solution is obtained for the groundwater head in a confined inhomogeneous and isotropic aquifer of constant thickness. The vertical z and horizontal y direction components of the groundwater flow are assumed to be zero. The specific storage Ss is assumed to be a constant, but the hydraulic conductivity K is taken to be K =ko [1 − (x/a)], where ko and α are constants. Initial and boundary conditions imposed on the groundwater head h(x, t) are h(x, 0) = 0 for 0 < x ≤ a and h(0, t ≥ 0) = ho, where ho is a constant. The solution for h(x, t) is found for 0 ≤ x ≤ a and t > 0. The solution is compared graphically with the solution for the case where K = ko and an impermeable boundary exists at x = a. The comparison shows that h(x, t) approaches its final value ho more rapidly for K = ko than for K = ko[1 − (x/a)].
Water Resources Systems Symposium: Introduction
Authors: Schwarz Harry E.
Published: February 2008

The Research Committee on Water Resources Systems is the youngest in the family of committees of the Section on Hydrology. Since its organization in 1966, the committee has set itself not only the goal of furthering research in the analysis of water resources systems, but of bringing together researchers and practitioners in a meaningful exchange of ideas.

The symposium presented on April 12, 1971, at the 52nd Annual Meeting of the American Geophysical Union in Washington, D.C., was the first effort of the committee to present a program of invited papers.
Engineering and economic evaluation of the reliability of water supply
Authors: Damelin E. , Shamir U. , Arad N.
Published: February 2008

A simulation model is developed and used for evaluating the reliability of supplying a known demand pattern in a given water supply system in which shortfalls are caused by random failures of the pumping equipment. An economic model is presented that enables one using the reliability model to compute the cost of the marginal water obtained by improving the reliability of the system and to determine the desirability of the improvement from this cost computation. Results are presented from the initial tests of the reliability model, in which the sensitivity of the reliability to various variables was examined. The results of applying the reliability and economic models to an existing water supply system are presented and discussed.
River Dee Research Program: 2. A long‐term control strategy for a multipurpose reservoir
Authors: Wilkinson J. C.
Published: February 2008

The purpose of the long‐term control strategy is to define retention levels for a multipurpose reservoir that permit maximum storage to be available for flood alleviation subject to shortages in its water supply function occurring with a specified tolerable frequency. A recursive relationship is derived to calculate the probability of no shortage occurring within a chosen interval of time for any given set of retention levels. This relationship is used in conjunction with an iterative search procedure that finds the optimal set of minimum retention levels necessary to meet a given demand with a specified acceptable frequency of failure, and thereby as much storage as possible is allowed for flood alleviation.
Turbulent transfer and mixing of submerged heated water jet
Authors: Bourodimos E. L.
Published: February 2008

An attempt has been made to analyze the turbulent diffusion, transfer, and mixing of a warm submerged jet discharged horizontally into a body of water of different temperature in a river or lake. When a jet of heated effluent is discharged into a receiving body of water at some depth below its surface, it rises as a plume to the surface and then spreads laterally and longitudinally at the free surface. The rising of the plume is a combination of both the initial momentum flux and the net buoyant force due to the difference in density between the heated effluent and the surrounding ambient flow water. On the basis of conservation laws for heat, mass, and momentum transfer, numerical solutions have been developed and compared with existing experimental data. The practical objective of this analysis is to find the parameters of turbulent mixing, entrainment, and dilution and thereby to establish theoretical and practical engineering criteria for preventing thermo‐pollution in lakes and rivers from power plant thermal discharges. The results of these numerical model techniques (suitable for high‐speed digital computation) have already been successfully employed in predicting patterns of actual hydrodynamics and thermal behavior of heated jet discharges from power plants along the Hudson Estuary and River in New York.
Jet type model for the three‐dimensional thermal plume in a crosscurrent and under wind
Authors: Stefan H. , Vaidyaraman P.
Published: February 2008

A dynamic three‐dimensional model for predicting water temperatures in a thermal plume has been formulated and tested. The plume that results from the discharge of heated water is described in terms of a buoyant, turbulent half jet. The effects of a crosscurrent and wind can be accommodated by the model. Mixing by turbulence, lateral spread due to buoyancy, heat transfer at the water surface, and deflection of the main trajectory under wind shear stress in a current are accounted for. Although it was necessary to make several broad assumptions, e.g., that all cross‐sectional temperature distributions are similar and that there is no distortion of the cross section by wind, the results show the overall behavior of the plume reasonably well. The model does not account for the effects of solid boundaries; its main features are its simplicity and comprehensiveness, its combination of the several processes having a major effect on plume behavior, and its ability to include possible future experimental or theoretical results without major changes in the program.
Opportunity costs of a transbasin diversion of water: 1. Methodology
Authors: Moncur James E. T.
Published: February 2008

A large‐scale transbasin water diversion project must be justified not only in terms of the direct costs of transporting water but also in terms of the value of services foregone by the exporting region due to the diminution of its water supply. A general model is developed to evaluate these opportunity costs. The procedure adapts the decomposition algorithm for linear programs to optimize operations of the water system with respect to time, multiple complementary and competitive uses, and location, allowances being made for serial as well as parallel configurations of reservoirs. The algorithm solves iteratively for the optimal value of the river's services. Two solutions are needed: one assuming ‘natural’ inflow conditions and, to simulate the situation after a diversion, one assuming depleted inflows. The difference between these optimal values is a measure of the opportunity costs incurred by the water‐exporting region. A subsequent article applies the procedure to the Columbia River basin.
Fitting of distribution functions by nonlinear least squares
Authors: Snyder Willard M.
Published: February 2008

An initial investigation of the use of nonlinear least squares to estimate the parameters of distribution functions produced promising results. All parameters of a distribution and seemingly most common distributions can be fitted by a common technique, and thus special methods adapted to particular distributions are eliminated. Two long‐standing problems, plotting positions and sample outliers, vanish with this method of fitting.
Stream channel enlargement due to urbanization
Authors: Hammer Thomas R.
Published: February 2008

Stream channel enlargement occurs in response to the change in streamflow regimen accompanying urbanization. This empirical study relates the imputed increase in channel cross‐sectional area to detailed land use data and other information for 78 small watersheds near Philadelphia. Important differences between the effects of various types of impervious land use are observed: large channel enlargement effects are found for sewered streets and area of major impervious parcels such as parking lots, and much smaller effects are observed for unsewered streets and impervious area involving detached houses. Relatively low channel enlargement effects are attributed to all types of impervious development less than 4 years old and also to street and house area more than 30 years old. The influence of impervious development on channel size is found to be significantly related to topographic characteristics of the watershed, to the location of impervious development within the watershed, and to man‐made drainage alterations. Although the relative importance of these interactive factors proves difficult to establish, the most critical determinant of the amount of channel enlargement resulting from a given level of urbanization appears to be basin slope.
Modeling infiltration during a steady rain
Authors: Mein Russell G. , Larson Curtis L.
Published: February 2008

Few of the infiltration models in current use are suitable for the situation in which the rainfall intensity is initially less than the infiltration capacity of the soil. In this paper a simple two‐stage model is developed for infiltration under a constant intensity rainfall into a homogeneous soil with uniform initial moisture content. The first stage predicts the volume of infiltration to the moment at which surface ponding begins. The second stage, which is the Green‐Ampt model modified for the infiltration prior to surface saturation, describes the subsequent infiltration behavior. A method for estimating the mean suction of the wetting front is given. Comparison of the model predictions with experimental data and numerical solutions of the Richards equation for several soil types shows excellent agreement.
Spring discharge of an Arctic River determined from salinity measurements beneath sea ice
Authors: Walker H. J.
Published: February 2008

The Colville River drains an area of 60,000 km2 in arctic Alaska. Subice salinity measurements seaward of the Colville delta made possible the calculation of the river's discharge during breakup in 1971. Between May 27 and June 15 the discharge was 5.70 × 109 m3, which is about 58% of the total for 1971.
Rayleigh‐Ritz and Galerkin finite elements for diffusion‐convection problems
Authors: Smith I. M. , Farraday R. V. , O'Connor B. A.
Published: February 2008

Finite element methods are presented for the solution of certain two‐dimensional partial differential equations of interest in water resource problems. Earlier work using Galerkin's method for one‐dimensional problems is shown to be a prototype finite element technique. It is suggested that previous variational (Rayleigh‐Ritz) formulations of finite elements for some problems are misleading and are of limited application when compared with Galerkin's method. The accuracy and stability of the techniques presented are discussed in relation to the well‐known ‘numerical diffusion and dispersion’ phenomena prevalent in popular finite difference methods.
Geomorphology and hydrology of Karst drainage basins and cave channel networks in east central New York
Authors: Baker Victor R.
Published: February 2008

Surface water in the karst drainage basins of east central New York is collected by swallow holes on upland surfaces. Free surface streams, flowing through meandering cave conduits, provide links between the upland surface catchments and large karst springs draining into the major river valleys. Flow through the conduits fluctuates markedly with surface runoff. Mean velocities of 0.5 ft/sec were determined during a period of rapid snowmelt by dye tests. The cave conduits form an integral part of a drainage organization characterized by Horton's hierarchy stream numbers, lengths, and drainage areas. The conduits, the highest‐order streams in the hierarchy, have meandering reaches with wavelengths directly related to up‐stream drainage area and contributed runoff. Both the morphology of the cave channels and the hydrology of the karst drainage basins are strikingly similar to those observed in surface water stream systems.
Geohydrologic study of the gort lowland and adjacent areas of western Ireland using environmental isotopes
Authors: Bowen R. , Williams P. W.
Published: February 2008

Isotopic analyses of precipitation, surface waters, and groundwaters in western Ireland have facilitated the interpretation of general hydrologic relations. They show that the groundwaters fall into a single group isotopically indicative of the good mixing to be expected in a karstic region and that components of modern (i.e., post‐1954) recharge are present, relatively rapid circulation in the groundwater system being suggested. However, it is possible that retardation as a result of ‘covered karst’ mantling occurs.
Optimization model for the operation of flood control systems
Authors: Windsor James S.
Published: February 2008

A methodology employing recursive linear programing as the optimization tool is presented for the analysis of multireservoir flood control systems. By means of dividing the flood period into shorter operational periods it is shown how the system policies may be adjusted to incorporate the latest forecast information and thus ensure maximum flexibility under actual operating conditions. A basic assumption is that decisions regarding the number, location, and size of the individual reservoirs in the system have previously been made.
Analysis of coupled heat‐fluid transport in partially frozen soil
Authors: Harlan R. L.
Published: February 2008

An analogy can be made between the mechanisms of water transport in partially frozen soils and those in unsaturated soils. By use of this analogy a Darcian approach is applied to the analysis of coupled heat‐fluid transport in porous media with freezing and thawing. With the aid of a numerical model, freezing‐affected soil‐water redistribution and infiltration to frozen soil are examined from a phenomenological point of view, and the effects of soil type and initial conditions on the response of a hypothetical soil column are studied. In general, the model shows that the rate of upward redistribution of soil water to a freezing zone at the soil surface decreases from coarse‐textured soils to fine‐textured soils and decreases with increase in depth to the water table. Subsequent redistribution during melting of the frost wedge is shown to occur at a rate less than that associated with freezing. Infiltration to partially frozen soil is also shown to have a significant influence on soil‐water redistribution and the response of the groundwater table.
Agricultural demand for water in the Pecos River Basin: An addendum
Authors: Gisser Micha
Published: February 2008

A study that deals with importing water to the Pecos River basin and using this water without artificial recharging (Gisser, 1970) is compared with another study that deals with the problem of recharging imported water into the aquifer (Gisser and Mercado, 1972). The sensitivity of the demand for water function to changes in salinity constraints is explored, and the possibility of reducing natural discharge of water by lowering the evaporation rate of salt cedars is investigated.
Unsaturated flow properties used to predict outflow and evapotranspiration from a sloping lysimeter
Authors: Scholl David G. , Hibbert Alden R.
Published: February 2008

Field measurements of sou moisture content and pressure potential were used to determine the moisture flux, hydraulic gradients, and dynamic conductivity of a 200‐foot sloping soil lysimeter. These measurements were then used to predict outflow and evapotranspiration. A vertical unsaturated Darcian analysis was used to evaluate conductivity during the first study phase, in which evapotranspiration was eliminated by sealing the model surface with a plastic sheet. The moisture flux term in the Darcy equation was determined by evaluating moisture content change in depth and time. Moisture flux determined in this way agreed with measurements of actual outflow. Conductivities were solved from flux and hydraulic gradients, and corresponding water contents were assigned. Conductivity curves were highly significant and agreed with those obtained when the model was uncovered. Evapotranspiration was solved during the second study phase (cover removed and grass established) by using a water balance based on moisture content and potential, rainfall, and conductivity (from the first study phase). Results at the deepest level in the profile agreed well with those based on actual outflow.
Improved dynamic programing procedures and their practical application to water resource systems
Authors: Mawer P. A. , Thorn D.
Published: February 2008

An optimization algorithm is described that uses value iteration dynamic programing and simulation in conjunction with penalty costs to derive long‐term operating policies for water resource systems. Very efficient value iteration procedures are developed for two types of problems, illustrated by numerical examples. An indication is given of how the methods described can be applied to multireservoir systems by using the concept of an equivalent reservoir.
Optimal control of multiunit interbasin water resource systems
Authors: Takeuchi Kuniyoshi , Moreau David H.
Published: February 2008

A method for finding optimal operating policies for a multiunit water resource system that extends over two river basins and serves multiple demands is presented. The method was developed and tested for one of several systems that have been proposed for further development of the water resource in the urbanizing Piedmont Triad region of North Carolina. Monthly operating decisions are given by solutions of a piecewise linear programing problem, the objective function for which consists of two parts, immediate economic losses within the month and the expected present value of future losses as a function of end‐of‐month storage levels in the reservoirs. The latter function is estimated by imbedding the linear programing problem in a stochastic dynamic programing problem. An approximate solution technique for the larger problem is described, and computational experience is reported.
Point processes of seasonal thunderstorm rainfall: 2. Rainfall depth probabilities
Authors: Smith R. E. , Schreiber H. A.
Published: February 2008

As a sequel to an earlier study of the stochastic properties of daily rainfall occurrence in a summer thunderstorm season, the probabilistic nature of daily rainfall depths is examined. Daily rainfall depths are found to be well described by what may be termed a compound exponential distribution. Some 1600 to over 2000 daily rainfalls from three stations are partitioned in various conceptual ways to evaluate homogeneity with respect to the pattern of occurrence with sequences or seasons as well as the annual variance of population properties. Although some small but statistically significant inhomogeneities are found, the statistical description of depths in arbitrary intervals, such as annual total depths, is shown to be treatable as the sum of a random number of (independent) random variables by using the model for rainy day occurrence. Simulations from this model match well the measured data from the stations treated. The effect of truncation of the rainfall sample on both depth distribution and Markov chain dependence is discussed. It is also indicated how daily depths are functions, in turn, of individual storm occurrence probability (number per day) and storm depth distributions.
Point processes of seasonal thunderstorm rainfall: 3. Relation of point rainfall to storm areal properties
Authors: Smith Roger E.
Published: February 2008

Following a two‐part study of the stochastic nature of thunderstorm occurrence and the probability of daily rainfall depths, the importance of point rainfall information to areal rain distribution is indicated. A probabilistic expression is developed for the relationship between the point depth of rainfall, the local probability distribution of storm cell maximum depth, and the dimensionless expression of storm depth area pattern. In a sample test the expression is successfully used to reproduce point rainfall depth probability from storm maximum depth distribution and depth area data from Tombstone, Arizona.
Stochastic analysis of phreatic aquifers
Authors: Gelhar L. W.
Published: February 2008

Three analytical models are developed to describe the spectral response characteristics of phreatic aquifers subject to time variable accretion and fluctuations in adjacent stream stage, it is found that a linear reservoir model will approximate the behavior of a more complete distributed linear model based on the Dupuit approximation if a single parameter is adjusted appropriately. A linearized two‐dimensional analysis including the effects of vertical flow shows, under conditions of large anisotropy with relatively narrow partially penetrating streams, differences from the Dupuit analysis that may be important under some field conditions. Possible applications of the results in aquifer evaluation are suggested.
Renovated waste water: The question of public acceptance
Authors: Sims John H. , Baumann Duane D.
Published: February 2008

What laymen think and feel about using renovated waste water appears to depend primarily upon what they know about it and their general educational level rather than upon unconscious fears of contamination or general belief and attitudinal systems concerning nature, technology, aesthetics, authority, progress, or destiny.
Integrodifferential equations for systems of leaky aquifers and applications: 2. Error analysis of approximate theories
Authors: Herrera Ismael
Published: February 2008

This paper is the second of a series devoted to developing a method of analysis based on the integrodifferential equations of leaky aquifer systems. In part 1 [Herrera and Rodarte, 1973a] the integrodifferential equations were derived, and an interpretation for some of the approximate theories was given in terms of the memory functions occurring in the equations. The same equations are quite suitable for a systematic analysis of the errors involved, and therefore in this paper they are used to carry it out.
Chloride balance of an urban basin in the Chicago area
Authors: Wulkowicz Gerald M. , Saleem Z. A.
Published: February 2008

During the relatively mild winter of 1972–1973, 20,260 t (metric tons) of NaCl and 40 t of CaCl2 were spread on roads within the Salt Creek basin of the Chicago metropolitan area. Over 600 water samples were collected from 11 creek sites within the basin during the salting season. Chloride concentration in the water varied from 35 to 1530 mg/1 during the sampling period. Road salt chloride content of the water at any time is dependent on (1) temperature and colligative properties of NaCl, (2) duration of precipitation events, and (3) dilution capacity of the stream. Models are presented for three subsections of the basin based on the relationship between chloride concentration and discharge of the creek during nonsalting periods. A fourth subsection could not be modeled because of insufficient data. Monthly chloride budgets for all four subsections from November 1 through April 30 show that between 55 and 72% of the road salt chloride was removed by the creek from the various subsections. Changes in the percentage of chloride removed correlate well with the following indicators of the degree of urbanization: (1) percentage of area as streets, (2) highway density, (3) population density, and (4) road salt application per unit area. Sixty‐two percent of the chloride was removed by the creek from the basin during the first 6 months of the study period. Further sampling after April 30 but before salting commenced in December 1973 indicates that an additional 10% of road salt chloride was removed from the basin by the creek during the second 6‐month period. A portion of the remaining chloride was removed through the groundwater, and the rest was retained in the basin because of lag mechanisms.
Chance‐constrained dynamic programing and the optimization of water resource systems
Authors: Askew Arthur J.
Published: February 2008

In order to limit the probability that a water resource system will fail when it is operated in accordance with its optimum operating policy the latter must be derived subject to relevant chance constraints. When a stochastic dynamic program is used, certain of these constraints can be handled in the same manner as deterministic constraints, whereas others can be applied indirectly by imposing a penalty for failure, the optimum value of which can be found by an iterative search. This search and a precise evaluation of the response of the system may be carried out within the dynamic program by means of minor additions to its basic algorithm. The application of this procedure to four systems demonstrates its power and illustrates the manner in which systems respond to the imposition of constraints on failure.
Patterns of variation in a fluvial system
Authors: Onesti Lawrence J. , Miller Theodore K.
Published: February 2008

Sixteen hydromorphic variables, with observations grouped by stream order, were subjected to principal components analysis to investigate the manner in which variables interact in a downstream direction within a drainage basin. The degree of intercorrelation between variables in a fluvial system is influenced by geology, structure, and variation in the physical characteristics of stream basins. The contention here is that since the degree to which these factors are effective varies downstream in an orderly way, the intensity of interaction between variables should also be so ordered. The results of the analysis support this because the variance accounted for by the first and second principal components increased systematically downstream, whereas that associated with principal components three through six generally decreased. The structure of the data is also examined in the context of varimax rotated components, and the changes that occur between lower‐ and higher‐order stream basins are identified.
Theis equation analysis of residual drawdown data
Authors: Case C. M. , Pidcoe W. W. , Fenske P. R.
Published: February 2008

Equations are developed that allow the transmissivity and storage coefficient of an aquifer to be determined from recovery data taken from an observation well located at an arbitrary distance from the pumped well without the use of antecedent drawdown data. The fundamental result is in the form of a series based on the Theis recovery equation and up to the number of terms given is exact. The assumptions of radial flow in a confined aquifer that is homogeneous, isotropic, and semi‐infinite, which are implicit in the Theis development, are, of course, made in the current work as well. Two numerical examples using actual field data are given.
Predicting reduction in water losses from open channels by phreatophyte control
Authors: Bouwer Herman
Published: February 2008

A procedure is presented for calculating seepage from a stream due to uptake of groundwater by vegetation or evaporation from soil in the floodplain. The calculation requires that the relation between evapotranspiration rate and water table depth be known. If these relations are available for a given floodplain before and after removal of phreatophytes, the reduction in seepage losses from the stream due to phreatophyte removal can be computed. To simplify the calculation process, the curves relating evapotranspiration rate and water table depth, which are generally sigmoid, can be approximated by step functions of the same area. Potential water savings by phreatophyte control are calculated for step functions that are representative of deep‐rooted vegetation, shallow‐rooted vegetation, and bare soil. In addition to the depth from which groundwater can be evaporated before and after phreatophyte removal the water savings are affected by the vertical distance between the water level in the stream and the floodplain.
The effect of roughness strips on transverse mixing in hydraulic models
Authors: Fischer Hugo B. , Hanamura Tetsuya
Published: February 2008

Turbulent transverse mixing is studied in an open channel flow in which the frictional resistance comes primarily from vertical metal strips. Analytically we obtain that the mixing coefficient ϵ = kau, where a is the strip width and u is the mean velocity. The analysis yields k = 0.08 as a minimum. An experiment in a laboratory flume verifies the form of the result and yields as an average k = 0.11.
Well pumping in unconfined aquifers: The influence of the unsaturated zone
Authors: Kroszynski U. I. , Dagan G.
Published: February 2008

An approximate analytical solution describing transient flow toward a partially penetrating well pumped at a constant discharge in a rigid, homogeneous, anisotropic, unconfined aquifer of infinite radial extension and finite depth, considering flow in the unsaturated zone above the free surface, is presented. The proposed solution generalizes Dagan's (1967) one, which is based on saturated flow theory solely. The characteristic hydraulic properties of the unsaturated zone, namely, the retention and hydraulic conductivity curves, are described by analytical expressions that depend on the parameter 1/a', which roughly represents the effective thickness of the unsaturated zone. The problem is solved analytically by replacing the pumping well screen by a line sink distribution of uniform strength, by linearizing the unsaturated flow equation and boundary conditions at the moving free surface, and by transferring the upper boundary to infinity. In order to check the validity of the approximate analytical solution, the problem, free of such approximations, was solved numerically by a finite element scheme for a representative particular case. Comparison between analytical and numerical solutions showed excellent agreement. The influence of the unsaturated zone was found to be negligible for most common cases encountered in application. In the marginal cases of very shallow rigid aquifers and of soils with particularly large unsaturated effective thickness 1/a', the influence of the unsaturated zone upon drawdown was found to be significant at relatively short times, close to the pumping well and close to the free surface.
A theory for local evaporation (or heat transfer) from rough and smooth surfaces at ground level
Authors: Brutsaert Wilfried
Published: February 2008

A model proposed earlier (Brutsaert, 1965) for evaporation as a molecular diffusion process into a turbulent atmosphere is extended by joining it with the similarity models for turbulent transfer in the surface sublayer. The assumed mechanisms were suggested by available flow visualization studies near smooth and rough walls; the theoretical result is in good agreement with available experimental evidence. The important dimensionless parameters governing the phenomenon near the surface are the Dalton (or Stanton) number (i.e., mass transfer coefficient), the drag coefficient (u*2/U2), the roughness Reynolds number (u*z0/v) (except for smooth surfaces), and the Schmidt (or Prandtl) number (v/k). The proposed formulation allows the evaluation of the effects of some parameters, such as surface roughness or molecular diffusivity, that were hitherto not well understood. An important practical result is that in contrast to the drag coefficient, the Dalton number is relatively insensitive to changes in roughness length Z0.
An improved recording gage for blowing snow
Authors: Jairell Robert L.
Published: February 2008

With the experience gained from an earlier gage (Tabler and Jairell, 1971), significant innovations have greatly improved the operation of a simple, inexpensive instrument for recording blowing snow. The most important improvement is the efficient turntable design which allows the precipitation gage to be independent of the snow trap, the result being a high‐quality chart record. Principal advantages include simplicity, inexpensiveness, and suitability for operation in remote areas lacking electrical power. The relationship of snow caught by this gage to snow accumulation behind a snow fence should be studied further as a means of calibration. It appears that the gage can be used to estimate total snow transport during drifting events.
Monitoring agricultural pollution using natural fluorescence
Authors: Lakshman G.
Published: February 2008

Many organic and bio‐organic compounds exhibit natural fluorescence in the visible spectrum. In many cases this is strong enough to be used as a technique to monitor the presence of pollutants from animal wastes on land and in water. A number of soil and runoff samples from feedlot sites have been analyzed for the nature and stability of their natural fluorescence. A strong correlation exists between the fluorescence emission and the water quality parameters such as total carbon (TC), total organic carbon (TOC) and total inorganic carbon (TIC). It can be used in the quantitative measurement of agricultural pollution, and future research should help to exploit the technique for remote sensing applications.
Determination of snow depth and snow extent from NOAA 2 satellite very high resolution radiometer data
Authors: McGinnis David F. , Pritchard John A. , Wiesnet Donald R.
Published: February 2008

The NOAA 2 environmental satellite and subsequent environmental satellites provide daily coverage of the earth in the visible (0.6–0.7 μm) and thermal (10.5–12.5 μm) spectral bands. The ground resolution of the very high resolution radiometer is 1 km at nadir. This improved resolution in the visible spectral band permits more detailed observations of snow features than were possible with the previous operational satellites. A visible band image from February 11, 1973, depicts the heavy snow cover in considerable detail in areas from Alabama to North Carolina. Digitized reflectance data from the study area have been compared with prestorm bare ground digitized reflectance data of February 6, 1973, to examine the relation of snow reflectivity to snow depths. A regression analysis of greatest brightness versus greatest snow depth for 201 data pairs produced a power correlation coefficient of 0.86. Reflectance values from snow deeper than 30 cm tended to be uniformly high; values from snow less than 30 cm tended to increase rapidly as snow depth increased.
Normal mode analysis of the linear equation of groundwater flow
Authors: Nutbrown D. A.
Published: February 2008

The study of groundwater flow, given equations of motion and boundary conditions which are mathematically linear, can be analyzed by using a normal mode approach. For the fully continuous case the simplest example is the familiar double Fourier analysis. Analogous results exist for the semidiscrete case, in which only time is treated as a continuous variable, and a method can be given for computing normal modes whose corresponding recession factors lie within prescribed ranges. One application of this approach suggests an empirical form for the base flow component of a stream hydrograph. The fully discrete case can also be treated and provides a convenient basis for the comparison of the more common approximations to the solution of the transient groundwater flow equation. In particular, it can be shown why the study of model problems does not provide a useful guide to the accuracy of the alternating direction implicit method applied to more general situations.
A new model for predicting the hydraulic conductivity of unsaturated porous media
Authors: Mualem Yechezkel
Published: February 2008

A simple analytic model is proposed which predicts the unsaturated hydraulic conductivity curves by using the moisture content‐capillary head curve and the measured value of the hydraulic conductivity at saturation. It is similar to the Childs and Collis‐George (1950) model but uses a modified assumption concerning the hydraulic conductivity of the pore sequence in order to take into account the effect of the larger pore section. A computational method is derived for the determination of the residual water content and for the extrapolation of the water content‐capillary head curve as measured in a limited range. The proposed model is compared with the existing practical models of Averjanov (1950), Wyllie and Gardner (1958), and Millington and Quirk (1961) on the basis of the measured data of 45 soils. It seems that the new model is in better agreement with observations.
Economic uncertainties in water resources project design
Authors: Szidarovszky Ferenc , Bogárdi István , Duckstein Lucien , Davis Donald
Published: February 2008

Economic uncertainty programing (Ecup) is a method which enables decision makers to analyze economic uncertainties in the design of water resources systems separately from hydrologic uncertainties. Ecup distinguishes between economic and hydrologic variables in the expression of a payoff or objective function. The economic variables, assumed to have been estimated at discrete points only, are treated as random variables. A postulated joint probability distribution of these variables is used to estimate by Monte Carlo simulation the distribution of payoff resulting from a project. The worth of perfect information or expected opportunity loss is calculated. In a case study the problem of choosing among flood protection levees of different heights is examined. The random economic factors considered are the flood losses and construction costs. The sensitivity to various degrees of error correlation and loss uncertainty is analyzed. It is found that a relatively small uncertainty in the economic estimates of the payoff function may cause considerable variance in both the distribution of benefits to be expected from a levee and the height of the optimal levee.