bluuebunny/crossref_metadata_2025 huggingface dataset:
A Galerkin‐finite element simulation of groundwater contamination on Long Island, New York
Authors: Pinder George F.
Published: February 2008

The Galerkin method of approximation in conjunction with the finite element method of analysis may be used to simulate the movement of groundwater contaminants. In solving the groundwater flow and mass transport equations this approach allows a functional representation of the dispersion tensor, transmissivity tensor, and fluid velocity, as well as an accurate representation of boundaries of irregular geometry. A field application of the method to chromium contamination on Long Island, New York, shows that accurate simulations can be obtained by using the Galerkin‐finite element approach.
Drawdown distribution due to well fields in coupled leaky aquifers: 1. Infinite aquifer system
Authors: Saleem Z. A. , Jacob C. E.
Published: February 2008

Solutions for drawdown distribution caused by the pumping of well fields in single aquifers have been obtained for a limited number of cases. However, most of the aquifers in nature are not single isolated aquifers. Consequently, the use of presently available solutions can yield unreasonable results. Equations for the drawdown distribution caused by the pumping of well fields in two coupled leaky aquifers are presented. Two cases of the system are analyzed. Case 1 is about the upper aquifer when it is confined or unconfined and the draw‐down in it is very small in comparison with its saturated thickness; in case 2 the drawdown in the upper unconfined aquifer can be significant. Approximate solutions for relatively short and long times, as well as solutions for special cases, are presented. The solutions involve integrals that can be evaluated by using a digital computer.
Calibrating a water yield model for small ungaged watersheds
Authors: Jarboe Joseph E. , Haan C. T.
Published: February 2008

A four‐parameter water yield model was calibrated on 17 Kentucky watersheds by relating the model parameters to watershed topographic, geologic, and soil characteristics. The relationships were tested by comparing observed and simulated runoff records from six watersheds that were not contained in the original 17 watersheds. The results show that the water yield model can be satisfactorily applied to ungaged basins.
Salt displacement into drain tiles under ponded leaching
Authors: Miyamoto S. , Warrick A. W.
Published: February 2008

Steady state piston‐type displacement into drain tiles is analyzed mathematically when the ground surface is partially covered by an impermeable material or by ponding water away from the drains. By preventing the water from infiltrating directly over the drains a more uniform leaching pattern is attained. The result is to reduce the water required for leaching to the depth of drains by as much as one half. Experimental data obtained from sand tank models support this prediction.
Mathematical simulation of subsurface flow contributions to snowmelt runoff, Reynolds Creek Watershed, Idaho
Authors: Stephenson Gordon R. , Freeze R. Allan
Published: February 2008

A mathematical model of subsurface flow is used to complement a field study of snowmelt runoff in a small upstream source area in the Reynolds Creek Experimental Watershed near Boise, Idaho. Field measurements from an instrumented cross section of this small watershed show that the mechanism of streamflow generation is subsurface delivery of meltwater over limited distances through shallow high‐permeability low‐porosity formations of altered and fractured basalt. The mathematical model provides a two‐dimensional transient saturated‐unsaturated analysis of the subsurface flow at the field site. It proved to be a valuable aid to a unified interpretation of the field measurements. For mathematical models that consist of boundary value problems with boundary conditions that are time and space dependent, the boundary condition sensitivity can thwart the rational calibration‐validation procedure. This, together with the more serious limitations of data availability, funds for data acquisition, and computer capacity, precludes the imminent use of fully deterministic hydrologic response models on a regional scale.
Seasonal effects in flood synthesis
Authors: Brater E. F. , Sangal S. , Sherrill J. D.
Published: February 2008

The effect of urbanization on flood flows is being investigated by analyzing inputs and corresponding flood hydrographs from many watersheds along with corresponding inputs and responses from watershed models. The inputs consist of precipitation plus snowmelt minus infiltration and retention. Because of the large seasonal variation in infiltration rates, accuracy was improved by treating rainfall frequencies seasonally in predicting flood runoff from precipitation and snowmelt. As procedures were developed and improved in accuracy, it became necessary to examine the effect of snowmelt on winter frequencies and the seasonal variation in time‐intensity rainfall patterns more closely. A procedure was developed for including snowmelt with winter rains, and the resulting frequency curves of rain plus snowmelt are presented and compared with conventional rainfall frequency curves. A method of deriving time‐intensity patterns from daily rainfall was developed, and it was shown that a large difference exists between typical winter and summer patterns in southeastern Michigan.
Approximating soil moisture characteristics from limited data: Empirical evidence and tentative model
Authors: McQueen I. S. , Miller R. F.
Published: February 2008

The soil moisture characteristic can be approximated from limited data as a composite of segments that are simple logarithmic relations. From available data, three segments are evident: (1) a capillary segment from saturation to pF 2.5, (2) an adsorbed film segment covering the stress range from about pF 2.5 to about 5.0, and (3) a tightly adsorbed segment that extends from pF 5.0 to 7.0.
Modeling flow and chemical quality changes in an irrigated stream‐aquifer system
Authors: Konikow Leonard F. , Bredehoeft John D.
Published: February 2008

Salinity increases in groundwater and surface water in the Arkansas River valley of southeastern Colorado are primarily related to irrigation practices. A digital computer model was developed to predict changes in dissolved solid concentration in response to spatially and temporally varying hydrologic stresses. The equations that describe the transient flow of groundwater and the transport and dispersion of dissolved chemical constituents were solved numerically. The model simulated flow as well as changes in water quality for both the stream and the aquifer. Detailed field measurements made for a 1‐yr period in an 11‐mi reach of the valley between La Junta and the Bent‐Otero county line were used to verify and calibrate the model. Measured water levels varied by an average of about 3 ft during the study period, and calculated water table elevations in the aquifer were within 1 ft of the observed values approximately 90% of the time. The specific conductances of water samples from five wells in one well field had a standard deviation of about 10% of the mean. Dissolved solid concentrations calculated by the model were within 10% of the observed values for both the aquifer and the stream approximately 80% of the time.
Planning methodology for the design of regional waste water treatment systems
Authors: Joeres Erhard F. , Dressler Joachim , Cho Chien‐Ching , Falkner Charles H.
Published: February 2008

A regional model is developed to consider the trade‐off between economies of scale inherent in waste water treatment plants and added pipe network collection costs. The resulting mixed integer programing model relies on piecewise linear approximations of concave cost curves and incorporates capacity limits dictated by maximum tolerable environmental impact at potential treatment plant sites. Cost savings possible for a region consisting of the central portion of Dane County, Wisconsin, are demonstrated.
The Hurst Phenomenon: A puzzle?
Authors: Klemeš V.
Published: February 2008

It is shown that the Hurst phenomenon is not necessarily an indicator of infinite memory of a process. It can also be caused by nonstationarity in the mean and by random walks with one absorbing barrier, which often arise in natural storage systems. Attention is drawn to the fact that inferences about physical features of a process, based on operational models, can be not only inaccurate but grossly misleading.
Correlation links between normal and log normal processes
Authors: Mejía José M. , Rodríguez‐Iturbe Ignacio
Published: February 2008

The generation of log normal hydrologic variables should be performed so that the characteristics of the historical record are preserved. It is shown that the common scheme used will preserve the first autocorrelation coefficient but will considerably distort the tails of the correlation structure. A new methodology is presented that preserves the tails of the correlation structure, and a simplification of the method is given for the case when the historical data follow a Markovian structure.
Comparison of observed and calculated concentrations of dissolved Al and Fe in stream water
Authors: Jones Blair F. , Kennedy Vance C. , Zellweger Gary W.
Published: February 2008

Measured concentrations of dissolved Al and Fe in streamflow samples treated to avoid particulate contamination can compare favorably with concentrations calculated from data on mineral stability and inorganic complexing. Significant differences are probably related to storm runoff or organic complexing.
Determination of dispersion and nonlinear adsorption parameters for flow in porous media
Authors: Gupta Surendra P. , Greenkorn Robert A.
Published: February 2008

Ottawa washed sand mixed with 0.0–7.5% kaolin clay was used to determine dispersion and nonlinear adsorption parameters during flow through porous media. The ions considered are nitrate as potassium nitrate for the nonadsorbing species and phosphate as monobasic potassium phosphate for the adsorbing species. A one‐dimensional linear model with a longitudinal dispersion coefficient is used, and the dispersion coefficient is determined by the least squares curve fitting method. The dispersion coefficients are correlated with the dispersivity models D=a1Vb1 and D=a2vRb2, where v is kinematic viscosity and R is the Reynolds number based on permeability. The velocity exponent b1 (= b2) is in the range 0.97–1.16 and seems to be independent of clay content. However, parameters a1 and a2 increase approximately linearly with clay content. The static adsorption data for phosphate suggest the Freundlich isotherm F=ksChs. The principle of linear superposition was assumed for dispersion and adsorption in order to estimate the parameters in the dynamic condition. The adsorption parameters are estimated for linear equilibrium (F=k1c) and Freundlich equilibrium (F=k2Cn2) models. The adsorption parameter k1 for the linear model is approximately linear with clay content. The good fit for the linear model is a matter of coincidence for the medium considered. The two adsorption parameters for the nonlinear model are highly correlated and cannot be estimated simultaneously from the dynamic measurements alone. Parameter n2 was estimated by using ks=k2 from the static case. The value of n2 is in the range 0.984–1.155, indicating that the linear model describes the movement of phosphate ions adequately for the medium considered. However, for a natural system in which clay content is high and phosphate ion concentration is low one would expect the generalized Freundlich nonlinear model to give a better fit of data.
Tracing shallow groundwater systems by soil temperatures
Authors: Cartwright Keros
Published: February 2008

Circulating water is known to affect the temperature of the rock through which it flows. Analysis of existing theoretical equations suggests that shallow groundwater flow will also affect the surface soil temperature. Soil temperatures therefore might be used to delineate small, shallow groundwater flow systems; both recharge and discharge zones might be distinguished. Temperature data taken in the field during summer and winter support the theoretical conclusions and agree with the groundwater flow patterns inferred from hydrologic data. In general, winter soil temperature profiles have less data scatter than profiles of summer temperatures. The greater the rate of groundwater flow, the greater the temperature difference between recharge and discharge zones. Temperature variations ranged from 0.75°C in clayey glacial till to 5°C in sand. The effect on soil temperature also decreases with increasing horizontal distance between the recharge and the discharge zone. The effect of horizontal flow in a shallow confined aquifer is also predictable from theoretical models and can be shown by field studies. The amount of heat redistributed depends on the thermal properties of the aquifer and on overburden and the velocity of fluid flow.
Groundwater management and salinity control
Authors: Cummings R. G. , McFarland J. W.
Published: February 2008

A management model is presented that may be useful in analyzing decision rules for the conjunctive management of groundwater reserves for use in irrigation and salinity control. Alternative schemes for decentralized management via taxes and bribes are discussed. Taxes are described that bring about intradistrict efficiency in terms of water use and salinity control when downstream externalities are ignored. When externalities are considered, it is shown that a unique pattern of resource use requires a given institutional structure for the management of bribes.
Coordination of regional water resource supply and demand planning models
Authors: Haimes Yacov Y. , Nainis W. Scott
Published: February 2008

A long‐range capacity expansion planning model is formulated that provides a projection of future water supply availabilities based on economic efficiency. The planning model provides a least‐cost schedule of development projects that also maximizes the net benefits of the outputs of those projects to a regional economy. A dynamic programing algorithm is used to schedule the projects, and a Leontief input‐output linear program is used to model the response to project supplies. Multilevel theory is used to provide a dynamic coordination scheme that seeks the best joint solution of the scheduling problem and the input‐output linear program. A regional planning example is provided.
Appraisal of irrigation projects and related policies and investments
Authors: Bassoco Luz María , Norton Roger D. , Silos José S.
Published: February 2008

Seven examples of analysis with linear programing models are used to illustrate methods of treating interdependence in the appraisal of irrigation projects. The kinds of interdependence analyzed are (1) between investment projects and other policy instruments, (2) among different types of investment projects, and (3) between local and sector‐level decisions on investment outlays. The applications discussed refer to irrigation districts in the central plateau and northwestern littoral of Mexico.
Hydrochemistry of the Athabasca and North Saskatchewan Rivers in the Rocky Mountains of Canada
Authors: Drake John J. , Ford Derek C.
Published: February 2008

The hydrochemical behavior of the Athabasca and North Saskatchewan rivers at their points of departure from the Rocky Mountains during the period May 1967 to February 1970 is shown to be well represented by a model based upon the mixing of two water bodies. These component sources contribute varying proportions of the total discharge through the year. One of them has properties that are in keeping with the theoretically expected and the observed characteristics of surface runoff water in the area and essentially represents snowmelt water. The properties of the other component are similarly in keeping with those expected and observed for groundwater in the rock and glacial aquifers of the area.
A method for maintaining cross and serial correlations and the coefficient of skewness under generation in a linear bivariate regression model
Authors: Kahan Joseph P.
Published: February 2008

This paper is concerned with generating a series of inflows from two different but correlated sources. The parameters of interest, namely, the mean, standard deviation, and coefficient of skewness of the generated values, are chosen to conform with known data. A stepwise process is postulated, whereby unlike the usual multiple‐regression technique an extra variable is added to an otherwise complete model. By using this technique the coefficient of skewness of the inflows can be maintained, a result that circumvents any attempt to calculate the joint moment generating function of gamma random variables, which proved to be the stumbling block of prior analyses.
Mathematical simulation of groundwater abstraction from confined aquifers for river regulation
Authors: Birtles A. B. , Wilkinson W. B.
Published: February 2008

The development of an initially confined aquifer for river regulation is considered. Model investigations cover a range of groundwater abstraction regimes and a number of aquifer systems typical of those found in the United Kingdom. The various factors affecting net gains are discussed. The main conclusions are that high net gains can be sustained only if unconfined storage is developed around the abstraction site. In practice this requires a high density of abstraction wells. Also higher net gains are obtained from those aquifers having a large response time.
Factors affecting adoption of land treatment of municipal waste water
Authors: Carlson Gerald A. , Young C. Edwin
Published: February 2008

A demand curve for land treatment of municipal waste water is derived assuming a profit‐maximizing framework. The outputs of a waste treatment facility are taken to be volume of waste water, degree of waste removal, and potentially marketable by‐product. The demand curve for land treatment technology is estimated by utilizing data collected from 125 U.S. cities. The dependent variable is adoption or non‐adoption of land treatment, and coefficients are estimated by nonlinear regression. The price of by‐products (water), required degree of treatment, price of capital, and local construction cost share all significantly increase adoption. Volume of river flow, rainfall, and volume of effluent flow all have a significant negative effect on adoption. Land prices were insignificant, a factor which is believed to be due to the nonpurchase of land by many land treatment facilities.
On the value of information to flood frequency analysis
Authors: Slack J. R. , Wallis J. R. , Matalas N. C.
Published: February 2008

On the basis of Monte Carlo experiments it was noted that in the absence of information about the distribution of floods and the economic losses associated with the design of flood reduction measures, the use of the normal distribution to represent the distribution of floods is generally better than either the Gumbel, log normal, or Weibull distributions. Nothing is gained in terms of reducing expected opportunity design losses if the underlying distribution F(x) is identified over and above simply using the normal as the assumed distribution. On the other hand, without identifying F(x) but with some detailed specification of the ratio of overdesign to underdesign losses and with a limited specification of the skewness of floods, a considerable reduction in the expected opportunity design losses results.
Diurnal solar flux distribution in a deep water reservoir
Authors: Armaly B. F. , Lepper S. P.
Published: February 2008

The spectral and directional nature of the incident solar radiation is used with spectral properties of the water and the atmosphere to examine the general behavior of the diurnal total solar flux distribution in a deep water reservoir. Simple algebraic expressions that are useful for approximating the behavior of the diurnal total solar flux and its divergence are presented.
A Bayesian approach to analyzing uncertainty among flood frequency models
Authors: Wood Eric F. , Rodríguez‐Iturbe Ignacio
Published: February 2008

The statistical uncertainty resulting from the lack of knowledge of which model represents a given stochastic process is analyzed. This analysis of model uncertainty leads to a composite Bayesian distribution. The composite Bayesian distribution is a linear model of the individual Bayesian probability distributions of the individual models, weighted by the posterior probability that a particular model is the true model. The composite Bayesian probability model accounts for all sources of statistical uncertainty, both parameter uncertainty and model uncertainty. This model is the one that should be used in applied problems of decision analysis, for it best represents the knowledge, or lack of it, to the decision maker about future events of the process.
Urban effects on the distribution of heavy convective rainfall
Authors: Huff F. A.
Published: February 2008

Data from a network of 225 recording rain gages in 5500 km2, operated during the summers of 1971–1973 in the St. Louis area, were used to investigate potential urban effects upon the distribution of heavy rainfalls. The primary purpose was to determine quantitatively the effect of inadvertent weather modification upon the frequency and magnitude of short‐duration, intense rain rates that are pertinent to urban and suburban sewer design and of concern in applications of planned weather modification to alleviate agricultural and municipal water supply shortages. Emphasis was placed upon analysis of (1) rain cells, the basic convective unit responsible for the production of heavy short‐duration rates in thunderstorm‐dominated climates, such as the Midwest, and (2) the distribution of heavy rainstorms producing 25 mm or more of rainfall within the network. Comparison of urban‐affected and rural (nonaffected) rain cells was the primary evaluation tool in evaluating the urban effect. Results showed a substantially greater water yield from the urban‐affected cells compared with that from the rural (control) cells. The excess was greatest in moderate to heavy storms and apparently resulted most often from enhancement of the natural atmospheric rainfall processes in organized weather systems. The 25‐mm rainstorms showed a pronounced maximum of occurrence in a region that frequently lies downwind of two urban‐industrial areas, St. Louis and Alton‐Wood River. It was concluded that the frequency distribution of heavy rainfalls may vary significantly between urban, suburban, and rural areas in large urban‐industrial regions and that this may necessitate reevaluation of sewer design storm parameters in current use.
Factors influencing infiltration and sediment production of semiarid rangelands in Nevada
Authors: Blackburn W. H.
Published: February 2008

Simulated rainfall was used to study infiltration rates and sediment production of 28 plant communities and soils of five watershed areas in central and eastern Nevada. Two antecedent moisture conditions were used: soil initially air dry and initially at field capacity. Infiltration rates and sediment production of the various soils are largely controlled by extent and surface morphology of dune interspace soils. Vesicular horizons are unstable in dune interspace surface soils. These horizons seldom occur in coppice dunes or in well‐aggregated dune interspace soils. Infiltration rate is negatively related, and sediment production positively related to the occurrence and morphology of vesicular horizons. More sediment is produced from soils with antecedent moisture initially at field capacity than from initially dry soil because of the instability of vesicular horizons when the soils were saturated.
Application of a two‐variable Mitscherlich Function in the analysis of yield‐water‐fertilizer relationships for corn
Authors: Hexem Roger W. , Sposito V. A. , Heady Earl O.
Published: February 2008

Variations of models developed by E. A. Mitscherlich in the early part of this century are periodically used for estimating input‐output relationships for plants. Mitscherlich's work focused on a single variable. While these exponential models incorporate features of theoretical appeal, the procedures for quantifying the models are relatively complex when two or more independent variables are included. In fits of Mitscherlich and polynomial forms to yield‐water‐fertilizer data for corn grown under experimental conditions in Colorado and Kansas, test statistics for the polynomial forms are as good as or better than those for the more complex Mitscherlich models.
Calculation of evaporation rates during the transition from energy‐limiting to soil‐limiting phases using albedo data
Authors: Jackson R. D. , Idso S. B. , Reginato R. J.
Published: February 2008

A method is presented that utilizes albedo measurements to partition the fraction of the soil surface area exhibiting energy‐limiting (potential) evaporation and the fraction exhibiting soil‐limiting evaporation to calculate actual evaporation rates during the transition phase (energy limiting to soil limiting). Since albedo is proportional to the surface water content, the change in albedo from day to day is indicative of the fraction of the soil surface that is dry and evaporating at the soil‐limiting rate. By denoting the partitioning factor as β and by using a square root of time relation with a coefficient C for the soil‐ limiting phase the evaporation rate Ec for day n after the soil was wet is

urn:x-wiley:00431397:media:wrcr1885:wrcr1885-math-0001
where Ep is the energy‐limiting rate. The Priestley‐Taylor formula was used to calculate Ep. Calculated evaporation rates were compared with lysimetrically determined rates. It was concluded that this method was reliable for calculating evaporation rates during the transition phase of soil drying.
An integrated finite difference method for analyzing fluid flow in porous media
Authors: Narasimhan T. N. , Witherspoon P. A.
Published: February 2008

The theoretical basis for the integrated finite difference method (IFDM) is presented to describe a powerful numerical technique for solving problems of groundwater flow in porous media. The method combines the advantages of an integral formulation with the simplicity of finite difference gradients and is very convenient for handling multidimensional heterogeneous systems composed of isotropic materials. Three illustrative problems are solved to demonstrate that two‐ and three‐dimensional problems are handled with equal ease. Comparison of IFDM with the well‐known finite element method (FEM) indicates that both are conceptually similar and differ mainly in the procedure adopted for measuring spatial gradients. The IFDM includes a simple criterion for local stability and an efficient explicit‐implicit iterative scheme for marching in the time domain. If such a scheme can be incorporated in a new version of FEM, it should be possible to develop an improved numerical technique that combines the inherent advantages of both methods.
Transient simulation of saltwater intrusion in southeastern Florida
Authors: Segol Genevieve , Pinder George F.
Published: February 2008

The Galerkin‐finite element method can be used to simulate the two‐dimensional movement of the saltwater front in the Cutler area of the Biscayne aquifer near Miami, Florida. The concentration distributions for steady state and transient conditions can be obtained by using pressure head data measured in the field for formulating boundary conditions.
Metagame theory and its applications to water resources
Authors: Hipel Keith W. , Ragade R. K. , Unny T. E.
Published: February 2008

Metagame theory is a positive descriptive approach for the political resolution of water resource conflicts. Various resource problems are formulated, and it is shown by two of the examples that classical game theory, which is based on the theory of rationality, does not work. The concepts of metagame theory are surveyed within a nonquantitative set theoretic framework. The conflicts examined illustrate the potential of metagame theory for analyzing water resource management problems.
One‐dimensional simulation of aquifer system compaction near Pixley, California: 2. Stress‐Dependent Parameters
Authors: Helm Donald C.
Published: February 2008

A major problem facing hydrologists is how to predict land subsidence. A key to this problem is the development of a reliable method for evaluating aquitard parameters. For assumed values of hydraulic conductivity and storage, vertical compaction and expansion of idealized aquitards can be computed (predicted) by an appropriate diffusion equation from known (projected) water level changes in adjacent aquifers. If water levels within the aquifers are observed and the resulting field compaction and expansion are measured, the parameters themselves can be evaluated. Such field measurements are available at a site near Pixley, California, for the composite behavior of a series of 21 doubly draining aquitards. By means of a linear partial differential equation with constant coefficients within one digital model, average hydraulic conductivity for idealized aquitards was evaluated from the field data to be 3 × 10−3 ft yr−1 (2.9 × 10−9 cm s−1), and average nonrecoverable specific storage was evaluated to be 2.3 × 10−4 ft−1 (7.5 × 10−4m−1). A second model allows parameters of nonrecoverable compaction to be stress dependent by assuming for any single material that the product of hydraulic conductivity and an incremental effective stress is a constant and that the product of nonrecoverable specific storage and past maximum effective stress is a constant. The latter assumption is a standard simplification of laboratory consolidation data; the former is introduced in the present paper. This second model improved simulation of observed compaction and expansion severalfold with virtually no increase in computer time. By using a double transformation of applied stress within the second model to linearize the nonlinear partial differential equation, hydraulic conductivity was evaluated to decrease by more than an order of magnitude during 12 years of record from 3.4 × 10−3 ft yr−1 (3.3 × 10−9 cm s−1) near the midplane of an idealized aquitard to 3.0 × 10−4 ft yr−1 (2.9 × 10−10 cm s−1) near the drainage faces of the idealized aquitard. Average nonrecoverable specific storage was evaluated to decrease from 2.3 × 10−4 ft−1 to 1.9 × 10−4 ft−1 (7.6 × 10−4 m−1 to 6.2 × 10−4 −1). In both models the average recoverable specific storage was evaluated to be 4.6 × 10−6 ft−1 (1.5 × 10−5 m−1).
Analysis of aquifer‐aquitard flow
Authors: Streltsova T. D.
Published: February 2008

The general drawdown equation and its particular cases are considered for a partially penetrating well discharging at a constant rate from an aquifer which is overlain by an aquitard containing the water table. An identity is established between the exact solutions, developed in terms of the ρ = μr/h parameter, and those based on the finite difference approximation, developed in terms of the r/B parameter. The relations in the ρ and the r/B parameter are given for a well of complete penetration. The quasi‐steady drawdown equation is developed for a well of partial penetration in an aquifer‐aquitard flow system. The solution is graphically presented, and its use in the distance‐drawdown curve‐matching procedure is described. Determination of the aquifer‐aquitard formation constants is discussed.
Travel times and nonlinearity of flood runoff from tracer measurements on a small watershed
Authors: Pilgrim D. H.
Published: February 2008

Flood runoff has been traced from seven injection points to the outlet of a 96‐acre watershed. Each radioactivity time record at the outlet provides a hydrograph of outflow of the labeled drop of water. The results yield direct information on the flood process of a type and accuracy not possible from conventional analysis of rainfall and runoff records. The relationships of travel time and average velocity with discharge are examined together with the variations of these relationships over the watershed. Average travel times are shown to be similar to the watershed lag. The nature of the nonlinearity of the flood runoff process is demonstrated. Although the process is grossly nonlinear at low flows, linearity is approximated at high flows. Spatial variations of travel time and hydrograph shape are shown to make contributions to nonlinearity that are additional to the lumped dependence on flood magnitude that is normally considered.
A simple method for determining the evaporation from shallow lakes and ponds
Authors: Stewart Robert B. , Rouse Wayne R.
Published: February 2008

This study examines the summertime evaporation from a shallow lake in the Hudson Bay lowlands evaluated by the energy budget (Bowen ratio) and equilibrium model approaches. Energy budget calculations reveal that on the average, 55% of the daily net radiation is utilized in the evaporative process over the lake. Half‐hourly and daily values of evaporation were approximated closely by the Priestley and Taylor (1972) model, where the ratio of actual to equilibrium evaporation equals 1.26. A simple model, expressed in terms of incoming solar radiation and screen height air temperature, is developed from the comparison of actual to equilibrium evaporation. Tests of the model at a different location indicate that the actual evaporation can be determined within 10% over periods of 2 weeks.
Transverse mixing in natural channels
Authors: Yotsukura Nobuhiro , Sayre William W.
Published: February 2008

A mathematical model is presented for predicting the steady state two‐dimensional distribution of solute concentration in a meandering nonuniform natural channel. Two features of the convection‐diffusion (mixing) equation derived herein are that it employs the transverse cumulative discharge as an independent variable replacing the transverse distance and that it is developed in an orthogonal curvilinear (natural) coordinate system which follows the general direction of the channel flow. With the help of the continuity equation of water the transverse convection term which cannot be neglected in a natural channel is eliminated from the mixing equation by a transformation wherein cumulative discharge replaces transverse distance. Introduction of scalar diffusivity coefficients into the mixing equation is found to be more justifiable in the natural coordinate system than in a rectangular Cartesian coordinate system. The transformed mixing equation unifies and generalizes essential concepts of several existing models which have been used successfully for simulating steady state transverse mixing in irregular natural channels. Solution methods, both analytical and numerical, and parameter estimation methods are presented, after which some results of simulation are compared with observed data.
Describing variance with a simple water quality model and hypothetical sampling programs
Authors: Moore S. F. , Dandy G. C. , Delucia R. J.
Published: February 2008

An explicit treatment of the uncertainty in the state of water quality in a body of water can provide a quantitative basis for sampling decisions. Filtering theory, an extension of Bayesian analysis to dynamic systems, is used to obtain an algorithm which describes the time history of variance (uncertainty) in estimates of water quality parameters. Uncertainties arising from measurement errors, incompleteness of data, and random fluctuations exhibited by natural phenomena are taken into account. Sampling design capabilities are illustrated in an evaluation of sampling frequencies for the National Eutrophication Survey. The adequacy of any sampling program is dependent on the available prior data and on the value associated with reductions in uncertainty.
Sensitivity and model variance analysis applied to some evaporation and evapotranspiration models
Authors: Coleman Gerald , DeCoursey Donn G.
Published: February 2008

Variable sensitivity and error variance of six evaporation and evapotranspiration models were calculated. Their sensitivity values were computed by approximating the partial derivatives by finite differences. To compare the models, relative sensitivity ψ was computed by ψi = (100/E1)(ΔE/Δxi), where i = 1, …, n, with sensitivity defined as the percent change in evaporation E per unit change in the input variable xi. A second relative sensitivity ΨR i = [(xi − xio)/E1](ΔE/Δxi) was calculated to compare the relative importance of the different input variables. Error variance was analyzed to find the variance of error due to instrument inaccuracies by E[Var (Z)] = ∑i=1n(ΔE/Δxi)2 Var (xi) where Var (xi) is the instrument variance estimated from the manufacturer's statements. Although no tests were conducted to determine the bias or prediction accuracy of the model, a technique was proposed to show how the instrument error variance could be added to the prediction error variance to determine the overall system variance. In model development the best model will be one whose sum of these two variances is a minimum if there is no prediction bias.
Water temperature forecasting and estimation using Fourier series and communication theory techniques
Authors: Long Leland L.
Published: February 2008

Fourier series and statistical communication theory techniques are utilized in the estimation of river water temperature increases caused by external thermal inputs. An example estimate assuming a constant thermal input is demonstrated. A regression fit of the Fourier series approximation of temperature is then used to forecast daily average water temperatures. Also, a 60‐day prediction of daily average water temperature is made with the aid of the Fourier regression fit by using significant Fourier components.
Critical duration of rainfall for flood estimation
Authors: Meynink William J. C. , Cordery Ian
Published: February 2008

Many methods of estimating design floods from rainfall data involve a trial and error procedure to determine the duration of the design rainfall. An analytical expression for estimating the appropriate duration for use with a particular unit hydrograph is derived. This analytical expression permits the effects of other parameters significant to the estimation of the design flood, such as different storm characteristics, to be evaluated with ease. The analytical approach has considerable flexibility in that the mathematical expression linking unit hydrograph and rainfall characteristics permits the independent adjustment of one of the sets of characteristics. This is particularly advantageous where some form of dimensionless unit hydrograph is available for flood estimation. It means that storm characteristics may be varied from watershed to watershed without any changes being required in the expression for the unit hydrograph. A ‘flexible’ dimensionless unit hydrograph is also developed.
Link length organization and network scale dependencies in the network diameter model
Authors: Jarvis Richard S.
Published: February 2008

Analyses of stream link lengths drawn from drainage networks defined by Strahler order or by magnitude have generally failed to reveal any evidence of organization or covariation between interior and exterior link lengths. Classifying networks by maximum source height or diameter reveals that link length organization is network scale dependent, may not appear significantly for small‐magnitude headwater systems, and is environmentally sensitive to spatial scale threshold constraints. Empirical analyses of networks from two contrasting geomorphic environments reveal that link length organization can be regionally discriminatory and can also differentiate between network states defined by blue lines and valley systems on 1:25,000 topographic sheets. Link lengths were derived by using an automatic digitizer, and these results constitute the largest data set of individual link length measurements reported to date.
A note on an in situ groundwater sampling procedure
Authors: Spalding Roy F. , Exner Mary E. , Gormly James R.
Published: February 2008

A relatively economical procedure for monitoring temporal, spatial, and vertical changes in groundwater quality is presented. In this in situ water sampling technique, large samples (1.1 l) are obtained from a 2‐ft vertical interval of the groundwater column. This procedure permits the quantification of the dynamic nature of groundwater contamination and allows for interpretation of areal sources and the extent of their contamination within the groundwater reservoir.
Changing needs and opportunities in the sediment field
Authors: Wolman M. Gordon
Published: February 2008

Information on the processes of erosion and sedimentation, while sometimes sufficient for gross estimates of yield, remains inadequate for modern environmental management. Little is known about sequential processes involved in the systems of erosion and sedimentation, and practice and theory require attention to unsteady or discontinuous erosion and transportation as sediments move from source through channel systems with intermittent periods of storage. While climatic and hydrologic variations markedly affect yield, transport and deposition thresholds of erosion of cohesive materials and sequences of such effects remain unclear. Impact assessment requires understanding of the highly variable temporal and spatial character of sediment behavior, which is often correlative with pollutant behavior.
A two‐dimensional mathematical model for water quality planning in estuaries
Authors: Zitta V. L. , Shindala A. , Corey M. W.
Published: February 2008

A two‐dimensional vertically well‐mixed steady state intertidal model based upon the law of conservation of mass was developed to describe the distribution of chloride, nitrogen, biochemical oxygen demand, and dissolved oxygen within a geometrically complex estuary having interconnected tributaries and bayous. The model was verified against two sets of independent field data taken under different temperature and flow conditions within the Pascagoula River basin estuary. Application of the model under critical temperature and flow conditions was made to assess present water quality within the estuary and to predict the effect of alternate wastewater management methods on the water quality within the estuary.
Operational assessment of hydrologic models of long‐term persistence
Authors: Lettenmaier Dennis P. , Burges Stephen J.
Published: February 2008

Two annual flow generation models proposed to account for the Hurst phenomenon, fractional Gaussian noise (FGN) and lag 1 autoregressive‐lag 1 moving average (Arma) models, were compared operationally by using the sequent peak algorithm (SPA). The SPA was used to determine empirical probability distributions of storage at a hypothetical single site on the basis of 1000 synthetic annual streamflow traces generated from each model, for constant demands of 0.5, 0.7, and 0.9 of the mean annual flow. The comparisons were made on the basis of population values of the lag 1 correlation coefficient, coefficient of variation, and (for the FGN sequences) Hurst coefficient. For the Arma models, large sample expectations of the Hurst coefficient (O'Connell, 1974)were used in the comparisons. The fast fractional Gaussian noise (FFGN) generator proposed by Mandelbrot (1971) was used to represent FGN. A modification of the Arma model, the annual Arma‐Markov mixture process, was developed and tested. This model has the advantage that the Hurst coefficient is an explicit model parameter. The results of the comparisons showed that at an operating life of 40 years the unskewed (normal) models gave similar storage probability distributions. The small differences between models could be explained in part by differences in equivalent independent sample sizes of the generated time series. For an operating life of 40 years andH= 0.70, tests of skewed (three‐parameter log normal) models gave substantially identical storage probability distributions. For the longer 100‐year operating life, storage distributions for the Arma model differed significantly, apparently owing to the lack of an equivalent populationHvalue for this model. The Arma‐Markov model, however, gave results nearly identical to the FFGN model at the 100‐year operating life and appears to provide a viable low‐cost alternative generation method for the preservation of long‐term persistence in hydrologic time series.
Evapotranspiration of a Douglas fir determined with a weighing lysimeter
Authors: Fritschen Leo J. , Hsia Joe , Doraiswamy Paul
Published: February 2008

The evapotranspiration (ET) of a 28‐m Douglas fir in a weighing lysimeter located on the Cedar River watershed near Seattle, Washington, was determined during the summer and fall of 1972, 1973, and 1974. Average ET rates from the area of the crown projection were 1.8 mm d−1 (55.8 1 d−1 or 14.7 gal. d−1) in 1972, 2.0 mm d−1 in 1973, and 2.5 mm d−1 in 1974. The range for monthly periods was 1.3–3.6 mm d−1. During 1972, ET was 46% of precipitation plus irrigation (P + I), and evaporation of interception (i) was 36% of ET. Comparable values for 1973 were 51% and 37% and for 1974 were 69% and 24%. The lower ET/(P + I) values in 1973 and 1974 were associated with soil moisture depletion studies and longer periods of clear skies. The relatively high i/ET percentages suggest the need for more interception studies. Problems such as irrigation, drainage, listing, wind, rainfall interception, and the translation of data to an area basis that are associated with large plants in lysimeters are discussed.
Soil water regimes near porous cup water samplers
Authors: Warrick A. W. , Amoozegar‐Fard A.
Published: February 2008

Steady soil water regimes near a porous cup water sampler are studied. Results are applicable when one is sampling soil solutions in the field or laboratory and help establish guidelines with respect to the sampling volume and region of influence. The unsaturated hydraulic conductivity is taken as K(h) = K0exp (αh), where K0 and α are constants. The flow net is examined for both point and horizontal line sinks for an infinite medium around the cup. Analytical solutions for the potential and the stream functions are given for the point sink. The maximum radial distance for which flow can be intercepted is the square root of (q/πk0) exp (−αh1), where h1 is the pressure head at large distances and q the extraction rate (units of L3/T). An alternative form is found by expressing q in terms of the cup radius and tension. For the line sink an analytical solution is given for the potential, but the stream function requires a numerical integration. The maximum distance of influence is (q/2K0) exp (−αh1), where q (units of L2/T) is the flow rate per unit length. For both point and line sinks, q increases with A1. Also q at first increases with the suction in the cup (−h0( but approaches a constant value.
A note on plexiglas HS flumes
Authors: Robinson William H. , Wright Malcolm E.
Published: February 2008

H flumes are convenient devices for accurate measurement of open channel flows, especially if trash is present. Several of the HS (smaller) types were constructed of plexiglas and used successfully in a commercial plant to measure effluents from vegetable washers. Lumped data from the calibration of three flumes were fitted to a curve of the form y = axb. The correlation coefficient R2 for observed versus calculated values was 0.998. A 99% confidence band fitted to the prediction curve was very narrow, indicating the high degree of accuracy of the device.