bluuebunny/crossref_metadata_2025 huggingface dataset:
New topologic relationship as an indicator of drainage network evolution
Authors: Coffman D. M. , Keller E. A. , Melhorn W. N.
Published: February 2008

The relationship between the number of links and the number of segments of natural drainage networks is restricted to a narrow envelope. Theoretically, within this envelope a family of curves with the general form y = 2x ‐ (2n ‐ 1) is defined, where y is the number of links, x is the number of segments, and n is the Strahler stream order defined for n = 2, 3, 4, or 5. A comparison of these curves with >100 natural drainage networks indicates that these curves delineate threshold and hypothetical boundary conditions that can be used to predict stream order. Although a number of Strahler orders are possible for a network composed of a fixed set of links and segments, the data suggest that only one most probable order appears in nature. As drainage networks develop from simple to complex, the range of bifurcation ratios fluctuates until a nearly constant value is reached. For any network of given order, the bifurcation ratio increases to an improbable value. When this value is reached, branching increases the order of the network, and thus the bifurcation ratio is decreased.
Absorption of water by a soil from a circular cylindrical source
Authors: Singh Rameshwar
Published: February 2008

The disposal of waste water into a confined stratum of the earth's crust through recharge wells is gaining increasing popularity. Underground burying of radioactive liquid and solid wastes has been practiced for years at Hanford, Oakridge, and other places. These highly dangerous wastes can diffuse out in lateral directions if the containers crack due to earthquakes and internal pressures in relatively thin confined stratum. These situations are often characterized as the absorption of moisture by the partially saturated soil surrounding the disposal site. This phenomenon is governed by a nonlinear partial differential equation, subject to initial and boundary conditions. A method of weighted residuals is applied to extract an explicit solution, which is simple for applications. The solution is valid for any form of the diffusivity function and can be used with any value of initial moisture content. The problem with the initial soil moisture at the threshold level (the minimum moisture content at which the permeability exists) has been investigated by Philip, and the corresponding results of the present paper compare very well with the results obtained by Philip.
Programing model for evaluating economic and financial feasibility of irrigation projects with extended development periods
Authors: Dean Gerald W. , Carter Harold O. , Isyar Yuskel , Moore Charles V.
Published: February 2008

A multiperiod linear programing model of regional irrigation development is formulated and how the solution generates components required for project evaluation of economic and financial feasibility is shown. The model is particularly useful where the time path of development is critical; for example, in large projects where market restrictions for the products produced may permit only a gradual approach to full development over a long period of time. Applications of the model to a large‐scale component of the California water plan show some deficiencies in past current planning procedures that may lead to difficulties in project repayment and create unforeseen negative welfare effects on nonproject producers.
Chloride balance of some farmed and forested catchments in southwestern Australia
Authors: Peck A. J. , Hurle D. H.
Published: February 2008

Loss of chloride in streamflow (salt flow) from forested catchments in southwestern Australia is only slightly greater than the total annual input (salt fall) from rain and dust. However, salt flow from catchments in which a significant area of the forest vegetation has been cleared for farming is much larger and exceeds salt fall by up to 690 kg/ha yr, or a factor 21. The net loss of Cl is interpreted to result from decreased storage in catchment soil water. Removal of the forest vegetation is estimated to have increased groundwater discharge of whole catchments by amounts ranging from about 1 to 13 cm3/cm2yr. From present rates of groundwater discharge, characteristic times for equilibration of Cl input and loss on farmed catchments are estimated to range from 30 to 400 years. In equilibrium the salty streams draining farmed catchments would yield water with Cl concentrations acceptable for drinking.
Mathematical simulation of the subsidence of Venice: 1. Theory
Authors: Gambolati G. , Freeze R. Allan
Published: February 2008

A review of land subsidence theory and an outline of the justification for our choice of a model to simulate the subsidence at Venice are provided. The review is essentially a search for a mathematical model that can be used to link realistically the occurrence of land subsidence to the groundwater withdrawals that are its cause. The Biot system of equations for three‐dimensional consolidation offers the best approach at the theoretical level, but the large number of required parameters precludes application of the approach in practice. Approaches based on the independent solution of the diffusion equation provide a practical alternative, as long as the conditions underlying the development of the equation are recognized, and, if necessary, monitored. At Venice, we have chosen a two‐step procedure to analyze the subsidence in the complex aquifer‐aquitard system that exists there. First, the regional hydraulic head drawdowns are calculated in a two‐dimensional vertical cross section in radial coordinates, using an idealized 10‐layer representation of the geology. The computations are carried out with a model based on the diffusion equation and solved with a numerical finite element technique. The calculated head values in the aquifers are then used as time dependent boundary conditions in a set of one‐dimensional vertical consolidation models solved with a finite difference technkme and applied to a more refined representation of each aquitard. This approach appears to offer the best trade off between theoretical elegance, data availability, and computer limitation. Its main disadvantage lies in the limitations imposed by the requirements of radial symmetry.
Conventional and unconventional alternatives for water supply management
Authors: Davis Robert K. , Hanke Steve H.
Published: February 2008

A computer simulation of the Potomac River basin system run under conditions projected for the year 2010 has been used to test the performance of three water supply systems proposed for the Washington, D.C., metropolitan area. Two of the systems offered additional storage capacity on the Potomac River. These systems were found to meet average daily water withdrawal requirements. A third system, the minimum storage plan, offered no new storage capacity but was found feasible if used in conjunction with pumping from the Potomac River estuary and/or accepting drought adjustment. The minimum storage plan was the least costly system in real terms. However, the most costly reservoir systems are favored by local water planners, because most of the reservoir costs would be shared by the federal government. Although the real costs of the minimum storage plan are less than those of the reservoir plans, it is not favored, because none of the costs are borne by the federal government. This study illustrates the inefficiencies that can be generated by current cost‐sharing policies.
Hydrochemical environments of carbonate terrains
Authors: Drake John J. , Harmon Russell S.
Published: February 2008

Waters within a carbonate aquifer have often been classified on a hydrologie basis. The significance of such grouping to the understanding of the geochemical processes acting in the aquifer is dependent on the classes having a distinctive chemistry. One hundred sixty‐six reliable chemical analyses of carbonate waters from Pennsylvania were grouped on a hydrologic basis, and the groupings were tested by a stepwise linear discriminant function analysis. Two parameters (degree of calcite saturation and equilibrium carbon dioxide partial pressure) are sufficient to distinguish the groups at the 0.005 confidence level and provide a reliable way to examine the geochemical evolution of the waters in the carbonate drainage basin.
Effect of accretion on dynamics of groundwater between two channels
Authors: El Nimr Ahmed
Published: February 2008

A mathematical study investigates the effect of infiltration or evaporation on groundwater level and on the amount of seepage to or from channels that bound an unconfined aquifer. In the analyses the actual free‐surface boundary conditions as well as the exact differential equation were used to obtain the general solution. Three particular cases were studied in detail. In the first, the accretion is considered to be constant, whereas, in the second, it is taken to be varying linearly with time. In the third, the accretion occurs only on a part of the aquifer but does not occur on the other parts. For the three cases, the rate of seepage was given in mathematical forms as well as in dimensionless curves. The free‐surface profile was also drawn for several cases. A comparison with the solutions based on the Boussinesq equation was presented. These approximate solutions were found to give satisfactory results for shallow aquifers but to fail to give reasonably adequate results for relatively thick aquifers. The comparison also indicates that the results of these approximate methods deviate greatly from the exact solutions for small values of time.
Note on the infiltration advance front from border irrigation
Authors: Parlange Jean‐Yves
Published: February 2008

The spreading of a water layer of constant thickness over a near horizontal soil surface is considered. An analytic solution is obtained and compared with an earlier solution. The present solution is applied consistently for short times and estimates gravity effects properly by taking into account the pressure head of the water layer. An infiltration law valid for all times is also suggested to obtain numerical solutions in practical cases.
Water consumption in small communities of northeast Thailand
Authors: Frankel R. J. , Shouvanavirakul P.
Published: February 2008

Water consumption in 14 rural communities of northeast Thailand was studied to determine water needs and to delineate the factors that affect water use. For 13 of these communities, average daily water consumption ranged from 10 to 90 1/cap/day (liters per capita per day). In one village with free wafer distributed through house connections 24 hr/day, water usage ranged from 115 to 160 1/cap/day. Water consumption was significantly influenced by the season of year, limited hours of availability of water through the distribution system, type of water service connection, and price of water for metered house connections only. Design criteria for maximum daily and maximum hourly water demands were found to be 1.5 and 4 times the average daily water consumption, respectively. The data collected reflect initial water use values in villages where water systems are only a few years old.
Algorithm for solving a class of linear programing problems related to reservoir management and design
Authors: Alemany Ricardo , Fernandez Pedro , De Pousa Aurora G.
Published: February 2008

A detailed description is given of an algorithm for easily solving (merely by hand computation) a class of linear programing problems related to the use of the ‘linear decision rule’ in reservoir design and management. Moreover, the method clarifies some theoretical aspects of the practical problem. Then a concrete application is given.
Dispersion during flow in porous media with bilinear adsorption
Authors: Gupta Surendra P. , Greenkorn Robert A.
Published: February 2008

Major sources of the pollution in underground water are various compounds that may come from the runoff of cattle feedlots, from the runoff of fertilizers, pesticides, and herbicides from the cultivated lands, and from domestic and industrial wastes. The equations for the dispersion and adsorption of various chemicals in porous media are formulated to calculate pollution movement. If a bilinear rate of adsorption is assumed, two coupled nonlinear parabolic partial differential equations result. The equations can be solved by the Crank‐Nicolson method, which is a stable, two‐step method. Solutions for the range of variables involved in the movement of pollutants in porous media are obtained for a one‐dimensional model.
Experimental and mathematical modeling of liquid‐liquid miscible displacement in porous media
Authors: Chhatwal Surjit S. , Cox Ronald L. , Green Don W. , Ghandi Bharat
Published: February 2008

When one liquid in a porous medium displaces a second miscible liquid of different density, both gravity effects and dispersion are present at the liquid‐liquid interface. Equations describing this process have been solved numerically. The method of characteristics numerical solution and a new technique, the centered in distance, centered in time method, have been studied. The methods are evaluated by a direct comparison and by checking against an analytical solution for the case of one‐dimensional flow. The solutions were used to simulate saltwater displacement experiments in a two‐dimensional laboratory model as a further test.
Analytical solutions to the one‐dimensional nonlinear diffusion equation for flow through porous media
Authors: Moench Allen F.
Published: February 2008

The one‐dimensional nonlinear diffusion equation is solved approximately by an extension of the Neumann method for a step input to a semi‐infinite medium. The method of solution requires that the region under consideration be divided into an arbitrary number of zones, each zone having known constant diffusivities. The boundaries between zones move at rates that are initially unknown. Two problems are considered: (1) horizontal flow in an aquifer in which the transmissivity and storage coefficients are functions of hydraulic head and (2) horizontal absorption in an unsaturated soil for which the diffusivity is a function of moisture content. Computational results compare well with finite difference and other numerical solutions to the same problems. The technique has application to other nonlinear problems of the same type.
A Useful Theorem in the Dynamic Programing Solution of Sequencing and Scheduling Problems Occurring in Capital Expenditure Planning
Authors: Morin Thomas L. , Esogbue Augustine M. O.
Published: February 2008

The dimensionality of certain sequencing and scheduling problems can be reduced by exploiting their special structures. An example of this type of reduction of dimensionality is presented in the form of a theorem. The use of the theorem in the dynamic programing solution of a previous example is discussed. Sufficient conditions for the optimality of a myopic decision rule are also shown to be a special case of the theorem.
Verification of Water Temperature Forecasts for Deep, Stratified Reservoirs
Authors: Burt Wayne V.
Published: February 2008

Systems for forecasting downstream water temperatures for water passing through man‐made impoundments are discussed. Two forecasts that were made for deep, stratified reservoirs in the Northwest with low outlets are verified. The forecasts were made before the dams forming them had been constructed. Water temperature observations made below the dams after they were constructed are compared with the original forecasts. In both cases the forecasts agreed very well with the observations. A forecast for a high dam and a reservoir with near‐surface outlets is also compared with observed temperatures, but this agreement is not as good as that for the reservoirs with low outlets.
Algebraic boundedness of sample statistics
Authors: Kirby W.
Published: February 2008

Some puzzling results from a computer simulation study are explained by showing that the sample skew coefficient has population‐independent bounds depending only on the sample size. Similar results are obtained for the coefficient of variation of positive data, the maximum standardized deviate, and the standardized range. The upper bounds of these statistics are (n − 2)/(n − 1)1/2, (n − 1)1/2, (n − 1)1/2, and (2n)1/2.
Simulation of alluvial fan deposition by a random walk model
Authors: Price William E.
Published: February 2008

The results of this study suggest that a, digital model based on a random walk may be used to simulate alluvial fan deposition. The model is in three dimensions, is dynamic in time and space, and employs two independent stochastic events: an uplift of the mountain basin contributing sediments and a storm large enough to result in fan deposition. A random walk, each step governed by the gradient and momentum of flow, determines the pattern of deposition. Results of the simulation are printed as geologic maps and sections. The general form of the simulated deposits is that of an alluvial fan, the pattern of simulated flows resembles that of real flows, and fan facies show a concentration of debris flows near the apex and a particle size decrease in water flow deposits downfan. The model could aid in the development of data collection systems, the estimation of aquifer parameters in undeveloped areas, better interpretation of aquifer tests, and improvement in the accuracy of test‐hole correlations.
Drawdown distribution due to well fields in coupled leaky aquifers: 2. Finite aquifer system
Authors: Saleem Z. A. , Jacob C. E.
Published: February 2008

Solutions for the drawdown distribution due to the operation of well fields in coupled leaky aquifers of infinite areal extent are available. This paper is concerned with the drawdown distribution caused by the pumping of well fields in coupled leaky aquifers of finite areal extent. A transform to solve the flow problem is obtained by the modification of the zero‐order Hankel transform. Two cases of the problem are analyzed. Case 1 concerns the upper aquifer when it is confined or unconfined and the drawdown in it is very small compared with its saturated thickness. Case 2 concerns the upper unconfined aquifer when the drawdown in it can be significant in relation to its saturated thickness. Approximate solutions and solutions for special cases are obtained in addition to the exact solutions. The solutions are in the form of series that can readily be evaluated.
Problems in modeling urban watersheds
Authors: McPherson Murray B. , Schneider William J.
Published: February 2008

Modeling of urban watersheds is complicated by the complexities of the hydrologic system brought about by urbanization, model scale, and client diffusion. Modeling objectives vary widely, from storm sewer design to management of local runoff to river basin planning. Each objective requires a different approach to modeling. Current difficulties in modeling involve inherent nonlinearities in most methods of processing inputs for linear models, problems of storm definition, interconnection of urban catchment areas, and shortage of detailed rainfall‐runoff water quality data for calibration. Despite handicaps, progress has been made in modeling urban watersheds and will continue to be made.
A partial area model for storm flow synthesis
Authors: Engman Edwin T. , Rogowski Andrew S.
Published: February 2008

The storm Hydrograph model described is based on the partial contributing area concept. It utilizes a physically based infiltration capacity distribution for computation of rainfall excess, and it incorporates two stages of kinematic routing. In the first stage the rainfall excess is routed over a flow plane to become the lateral inflow hydrograph for the second or channel phase. The overland flow plane expands upslope as the infiltration capacity is exceeded, the size of contributing area and the length of the flow plane being calculated from infiltration curves. The model attempts to account for the natural watershed variability in terms of necessary input data and boundary and initial conditions. The data requirements are three: they include two Manning's n values, one for the channel and one for the overland flow plane, and the initial soil water content.
Regional flood mapping from space
Authors: Rango Albert , Salomonson Vincent V.
Published: February 2008

The Earth Resources Technology Satellite (ERTS 1), launched on July 23, 1972, has been used to monitor the extent of inundation of regional floods with varying recurrence intervals. The inundated areas exhibit sharply reduced near‐infrared reflectances caused by standing surface water, excessive soil moisture, and stressed vegetation, which persist up to 10–12 days after the flood peak. The amount of area affected by flooding over regions encompassing many thousands of square kilometers can be mapped definitively at 1:250,000 scale from ERTS 1 imagery in times much shorter than those required by ground‐based or aircraft surveys. The ERTS 1 imagery also permits easy extension of flood mapping to areas not normally covered by more familiar survey methods. In addition to the detection of flood events, ERTS 1 can be used to map flood susceptibility indicators on the floodplain for purposes of delineating flood‐prone areas.
Derivation of an equation of infiltration
Authors: Morel‐Seytoux H. J. , Khanji J.
Published: February 2008

Since the publication of the article of Green and Ampt (1911) the two constants appearing in their ‘equation of infiltration’ have been considered to be empirical constants. In fact, they can be deduced simply from the soil characteristics, and they have a very precise physical meaning. However, the assumption of an abrupt front separating a saturated zone from the zone at the initial water content can lead to prediction errors of the order of 10–70%. Derived formulas display explicitly the functional dependence of the effective (or flowing) capillary head and of the viscous correction factor as a function of the initial water content. These formulas are both simple and accurate and of practical value to the hydrologist.
Combined conduction‐radiation energy transfer in stagnant water
Authors: Snider D. M. , Viskanta R.
Published: February 2008

The transient heating by radiation of a stagnant layer of water is studied both analytically and experimentally. Solar radiation (insolation) was simulated by tungsten filament lamps in parabolic reflectors of known spectral characteristics. The volumetric rate of internal absorption of radiation was predicted by considering spectral absorption, scattering, and multiple forward scattering by the water according to the model of Viskanta and Toor (1972). The transient temperature distribution was predicted by solving the one‐dimensional energy equation analytically in closed form after first linearizing the boundary condition at the air‐water interface. The analytical model was verified on the basis of laboratory experimental data obtained from transient temperature measurements made in pure water contained in a glass wall test cell using a Mach‐Zehnder interferometer. Comparison of experimental data with the predicted temperature distributions showed good agreement, thus verifying the radiation and total energy models. It was determined that the surface boundary condition and internal radiant heating rate of water must be correctly specified in order to model thermal stratification of stagnant water by radiation properly.
A note on cost‐effectiveness in data acquisition in water quality management
Authors: Nielsen Knud Strange , Friborg Niels , Bundgaard‐Nielsen M.
Published: February 2008

An iterative procedure for sampling in water quality management is presented. The procedure establishes a relationship between cost of sampling and relative uncertainty in total discharge into the water system and at the same time provides an optimal frequency matrix for sampling. The frequency of sampling at each discharge is treated as an independent variable.
Quantitative prediction of seasonal rating curve shifts
Authors: Barrett Curtis B.
Published: February 2008

Application of linear multiple regression techniques to discharge measurement and water temperature data collected for selected Missouri River forecast points resulted in development of a successful quantitative technique for prediction of seasonal rating curve shifts. By utilizing 20 yr of discharge measurement and water temperature data for Omaha, Nebraska, and St. Joseph and Kansas City, Missouri, it was found that the addition of the independent variable water temperature (degrees Fahrenheit) to the stage‐discharge relationship increased multiple correlation coefficients significantly. In all cases studied, increased temperature reflected an increase in stage for a constant flow. The maximum effect of water temperature is indicated for low flows. Water temperature is thought to cause the alterations of bed form configuration resulting in seasonal rating curve shifts.
Water reuse: A flexible and efficient management alternative for municipal water supply
Authors: Dworkin Daniel M.
Published: February 2008

A comparison between the fixed schedule of planned expansion of water supply sources and an alternative expansion program based on a short‐term decision from monitoring reservoir levels, water use, and streamflows and employing water reuse capacity and new source development is simulated for the Colorado Springs, Colorado, municipal water system. For this complex, fast growing system with supply based on streamflows and some current reuse capacity the alternative plan postpones major new development an average of 14 years at a cost at present value of half the original planned expansion.
Time series analysis of a watershed response variable
Authors: Adamowski K. , Oosterveld M.
Published: February 2008

Daily discharge flows are transformed by a recession equation into a dimensionless time series which reflects the storage characteristics of a watershed and also indicates the direct response of a watershed to precipitation. Spectral techniques of time series analysis are employed as an exploratory tool for suggesting different models describing a watershed's response.
The Weibull Probability Assignment Technique: An application to benefit‐cost analysis
Authors: Mercer Lloyd J. , Morgan W . Douglas
Published: February 2008

The flexibility of the Weibull distribution and the information gain made possible by its use to deal with the problem of uncertainty in benefit‐cost analysis are illustrated by application to a benefit‐cost study of water importation for Santa Barbara County, California. The Weibull distribution requires few estimated variables and a minimum of information, is relatively simple to work with mathematically, and can approximate the whole variety of distributions which may characterize input variables in benefit‐cost analysis. Use of the Weibull distribution provides the standard deviation and central tendency measures of the output (net benefit, benefit‐cost ratio, etc.) distribution in benefit‐cost analysis as well as the probability of outcomes indicating a project is not economically feasible. The application reported shows that the use of the Weibull distribution is superior to the usual point estimates and sensitivity tests in benefit‐cost analysis.
Economic assessment of an activity analysis model for water supply planning
Authors: Bishop A. Bruce , Jensen Bartell C. , Narayanan Rangesan
Published: February 2008

A mathematical model for assessing the water supply alternatives with the reuse option is described, and its potential to yield results useful for economic analysis and policy making is explored. The results of the model for Salt Lake County, Utah, used as a case study area are shown. The relative marginal values reflecting quality and accessibility of various sources can aid in planning future water resource development. The supply curves derived from the model are useful for pricing policies. The relative locational advantages of water and waste water treatment plants enter importantly into capacity expansion decisions. The least cost solution indicates the necessity of a facility to recycle waste water for municipal use under increased demand conditions.
Socioeconomic factors affecting domestic water demand in Israel
Authors: Darr Peretz , Feldman Stephen L. , Kamen Charles S.
Published: February 2008

Income, or its surrogate, has been an important predictor of residential water use. In the case of Israel, other socioeconomic variables not collinear with income have been found to be valid predictors and increase the sensitivity of residential forecasting models. For a sample of 1892 residences in Israel, aside from income those variables found to explain a significant portion of the variation in residential water use were number of persons per family, cultural origin, education and age of the head of the household, and number of rooms per household.
An integrated power process model for ethylene production
Authors: Stone John C. , Schwartz Andrew K. , Klein Robert A. , Singleton F. D. , Calloway James A. , Thompson Russell G.
Published: February 2008

This study develops an economic model of a newly designed ethylene plant to evaluate the effects of increasingly restrictive waste water treatment requirements on the costs of producing ethylene, feedstock choice, and the marginal costs of treating major pollutants. Zero discharge of pollutants to the water is attained in the model plant at a production cost increase of 6.9%. Secondary treatment of organic pollutants increases production costs 0.79% with once‐through cooling and 5.15% with recycle cooling. The controlling organic pollutants at each treatment level are identified, and estimates are made of the potential savings in waste treatment from redesign of the production facilities to reduce the raw waste loads of each pollutant.
Use of risk premiums in chance‐constrained dynamic programing
Authors: Askew Arthur J.
Published: February 2008

Stochastic dynamic programing offers a powerful means of deriving optimum operating policies for water resource systems. In order to limit the probability of system failure associated with such policies it is necessary to amend the standard algorithm and use some form of chance‐constrained dynamic programing. This technique may involve an iterative search based on variations in such parameters as the penalty for failure or the discount rate. Use of the latter parameter is found to be quite feasible and is analogous to the imposition of risk premiums when one is investing in less secure ventures: the greater the probability of failure, the greater the premium demanded.
Equations for resistance to flow and sediment transport in alluvial channels
Authors: Maddock Thomas
Published: February 2008

The commonly accepted parameters for sediment transport and resistance to flow of alluvial channels are evaluated and found to be inadequate. A resistance equation B2= [V/(gDS) ½]{[(s−1)12;/(DS)½}·[(s − 1)gd¼/ω²]and a sediment transport equation C = {103[VS/ϕ(d)]− [(k)s−1)g½d)/ϕ)d)D½] [(s−1)gd¼/ω2] channels, where B is a factor that describes the constraints that limit the response of dependent variables to changes in independent variables, V is the mean velocity, D is the mean depth, S is the energy gradient, g is the acceleration of gravity, s is the specific weight of the sediment, d is the median diameter of the sediment discharge, ω is the fall velocity of a characteristic particle size, ϕ(d) has the dimensions and characteristics of a fall velocity with values found by experiment, and k is a dimensionless velocity distribution parameter. Factor C is the concentration by weight in parts per million of the transported sediment. There is no differentiation between forms of transport. Presently used equations are shown to be approximations of combinations of these two equations. The two equations describe channel behavior and sediment transport better than other equations, and they are shown to be particularly effective in describing the effects of changes of temperature on water discharge.
Optimal groundwater quality management: Well injection of waste waters
Authors: Willis Robert
Published: February 2008

A mathematical model for optimal conjunctive utilization of the groundwater quality and quantity resources of unconfined aquifers is presented. The saturated zone of the groundwater system is considered as a component of a regional waste treatment system involving a waste water treatment plant and external sources of dilution water. The model minimizes the cost associated with surface waste treatment while it maintains acceptable water quality levels throughout the aquifer. The results indicate the feasibility of secondary treatment (trickling filter) plus dilution water along with the assimilation capacity of the aquifer for waste water degradation.
The extended Boussinesq Problem
Authors: Collins Michael A.
Published: February 2008

Summary and entire article are available on microfiche. Order from American Geophysical Union, 1909 K Street, N.W., Washington, D.C. 20006. Document W‐76‐001; $1.00. Payment must accompany order.

The original Boussinesq problem of the decline of a groundwater mound between parallel drains is extended to include vertical leakage and recharge and cases of freshwater lenses in confined and unconfined saline aquifers. The solution of appropriate continuity equations with some imposed restrictions by variable separation results in three distinct flow depth configurations, which can be described analytically. Transient behavior in two of these cases is nonlinear but amenable to exact solution and can be delineated in a (2μ + β, σ + μ) plane, where β and σ are leakage and recharge parameters and μ is a separation constant. It is found that similarity solutions, one of which is the original Boussinesq solution, exist for both decreasing and increasing flow depths. Active and passive influences of boundary conditions are distinguished. Solutions are applied to the evaluation of saline water intrusion in some coastal zones of Long Island, New York.
Hydrologic Semantics
Authors: Matalas Nicholas C. , Maddock Thomas
Published: February 2008

There is an aura of mystique that surrounds mathematical modeling of water resources systems. Perhaps some of the mystique is due to the semantics of modeling rather than to the accomplishments of modeling. The literature describes three basic steps in mathematical modeling: (1) identification, (2) calibration, and (3) verification. Identification implies that one has available a set of models that covers all aspects of the physical system of interest and has sufficient information to select the model that applies.
Accuracy of reservoir inflow forecasts based on radar rainfall measurements
Authors: Anderl Bernhard , Attmannspacher Walter , Schultz Gert A.
Published: February 2008

For efficient application of optimum operating procedures to flood protection reservoirs it is essential to forecast on line, i.e., during a storm, the relevant inflow hydrographs. This can be achieved with the aid of a weather radar linked to a computer in which the optimum reservoir operating program is stored as well as a program of a hydrologic rainfall‐runoff model producing the reservoir inflow hydrographs from radar‐measured rainfall data. These inflow hydrographs may be evaluated on the computer during each storm event and can be updated every 5 min, if necessary. The accuracy of these computed hydrographs was tested against the recordings of two river gages installed in catchments close to a weather radar at Hohenpeissenberg in Upper Bavaria. By using a linearly distributed mathematical catchment model it was shown that for the two rivers the synthetic hydrographs computed from radar‐measured rainfall were more accurate than those obtained from continuous measurements of the official point rain gage network of the German Weather Service (one recording gage in 500 km2) and that they were of the same accuracy as those obtained from a special very dense rain gage network (one recording gage in 25 km2) set up for research purposes in the same area.
Weather‐dependent pricing for water resources in the Texas High Plains
Authors: Lane M. N. , Littlechild S. C.
Published: February 2008

This paper examines two alternative schemes for pricing irrigation water. Under the first scheme, price is independent of weather; in the second scheme, price varies with weather so as to generate just enough demand to exhaust reservoir capacity. The second scheme provides savings through the more efficient utilization of available reservoir supplies and through the curtailing of demand so as to allow the construction of smaller reservoirs. The analysis proceeds by means of a linear programing under uncertainty model of a representative farm. The model is applied to the High Plains of Texas. Results suggest that the weather‐dependent pricing scheme would increase farm profits by the order of 10% per annum.
Computation of solar radiation from sky cover
Authors: Thompson Edwin S.
Published: February 2008

A procedure for estimating global solar radiation from sky cover is developed from the records of 47 stations in the United States with long periods of radiation observations during the 10‐year period, March 1961 through February 1971. It fits a general parabolic equation of the form Y = B + (1 − B)(1 − N)p to the observations, where Y is the observed global solar radiation divided by clear sky radiation and N is the sky cover. The variables B (the point at which the parabola crosses the y axis) and P (a variable parameter less than 1.0) are selected to minimize the sum of the errors (Y − Ycalc)2, where Ycalc is the calculated value of Y. The equation Y = B + (1 − B)(1 − N)0.61 is selected as most representative, and the B values in this equation that minimize the sum of the errors squared for the individual stations are shown in Figure 1. The average absolute error of the 5306 data points is 1.18 MJ m−2, or 7% of the average observed radiation. Because of the uncertainties of the observed global solar radiation and observed sky cover, the procedure should be used with caution, particularly for periods of less than 1 month.
Conserving water by antitranspirant treatment of phreatophytes
Authors: Davenport D. C. , Martin P. E. , Roberts E. B. , Hagan R. M.
Published: February 2008

A wax‐based antitranspirant (AT) was sprayed on leaves of three phreatophytes, salt cedar (Tamarix sp.), cottonwood (Populus sp.), and willow (Salix sp.), as an alternative to eradicating them to conserve water. Scanning electron micrographs gave information on the nature of the foliar surfaces and coverage by the AT wax. A 10% solution of AT (vol/vol) reduced the transpiration rates of container‐grown phreatophytes by 35–75% 1 day after spraying and by 17–56% after 4 days. In gas exchange studies with salt cedar in the field, transpiration was reduced 40% by a ‘light’ application of 6% AT and 70% by a ‘heavy’ application. The AT also increased resistance to water vapor diffusion and the water potential of the sprayed leaves. On salt cedar, phytotoxicity occurred at high temperature and solar radiation only if spray applications were very heavy. The AT conserved water much more effectively when it was applied to the outer part of the canopy than when it was applied to the inner shaded foliage, where transpiration was already minimal. These data from sprays applied from the ground provided a basis for trials of AT application by aircraft.
On the income distributional effects of environmental management policies
Authors: Campbell Harry F.
Published: February 2008

The paper analyzes the effects of three environmental policy instruments, effluent charges, effluent standards, and effluent treatment subsidies, in the context of a two‐person two‐firm general equilibrium model in which the distribution of income varies with the choice of policy instrument. It is demonstrated that, under reasonable assumptions about the income distribution process and the nature of consumer preferences, each policy instrument corresponds to a different optimal quantity of effluent and a different set of optimal prices. The implication of this result is that consideration of income distributional effects should play an integral part in the formulation of optimal environmental management policies.
A perturbation solution for a nonlinear diffusion equation
Authors: Liu Philip L.‐F.
Published: February 2008

Nonlinear diffusion problems with a constant boundary condition are investigated. The concept of diffusion front is utilized to develop a perturbation solution. Results are presented for two specific diffusivities which are functions of the concentrations. The present technique is shown to be efficient and accurate.
Autocorrelation characteristics of hydrometeorological data of the United States
Authors: Shahane Ashok N. , Thomas Daniel , Bock Paul
Published: February 2008

Serial correlation coefficients for the 5 years mean monthly time series of precipitation P, runoff R, change in storage ΔS, atmospheric vapor divergence ∇·Q, and evapotranspiration E are computed for 76 small and 10 large combined drainage basins of the United States. An effort is made first to explore the characteristic behavior of these serial correlation numbers and then to compare their geographic distribution with physical factors. The results suggest that the geographic variation of these statistical characteristics shows correspondence with various climatological factors.
Hysteretic steady state soil water profiles
Authors: Poulovassilis A. , El‐Ghamry W. M.
Published: February 2008

The shape of the hysteretic steady state soil water profile is examined theoretically. It is shown that the hysteretic steady state profile which results after wetting acquires usually minimum values of the soil water pressure head, of the hydraulic conductivity, and of the water content, values smaller than the asymptotic values approached at large heights. In contrast, the hysteretic steady state profiles which result after drying do not show such minimum values. Experimental hysteretic steady state profiles established in a vertical sand column confirm the theoretical predictions and are in agreement with those calculated numerically from the flow equation. The importance of the hysteresis for soil water retention and movement is discussed.
Isochrones of travel time and distribution of flood storage from a tracer study on a small watershed
Authors: Pilgrim David H.
Published: February 2008

In the practical application of many methods of flood hydrograph synthesis it is necessary to space isochrones of travel time over the watershed or to allocate the distribution of storage. The available evidence for guiding this procedure is reviewed, but most information applies to large stream systems and to flows lower than the flood discharges of interest. Times of travel data from tracing of flood runoff on a small watershed have been compared with the evidence from large streams. Average velocities were found to increase slightly in a downstream direction through the watershed, despite decreasing slope. This increase conforms with published hydraulic geometry relationships. Five geomorphological parameters have been tested as methods for spacing isochrones. Field inspection to determine mean depths, and possibly roughness, at bank‐full stages should lead to greatest accuracy, but simple parameters based on stream length also gave good results.
Is the soil frozen or not? An algorithm using weather records
Authors: Cary J. W. , Campbell G. S. , Papendick R. I.
Published: February 2008

Frozen soil water is important in hydrologic events because it reduces water infiltration. The presence of soil ice can be predicted reasonably well from detailed knowledge of the soil and microclimatic variables, but this type of information is generally unavailable. Consequently, the purpose of this study was to start with fundamental relations and see how well frozen soil conditions could be identified from daily weather station records of maximum‐minimum temperatures, solar radiation, and snowfall. Two relations were developed, one based on the soil‐atmosphere energy budget and the other on the heat flux across the soil surface layer. Conceptually, the two equations may be used together to give daily snowmelt as well as soil thawing and freezing rates, but in practice, the snowmelt prediction is probably not yet accurate enough for most practical applications. The simpler equation, describing the heat flux in the soil surface, does not require solar radiation input, yet it gave fair predictions of frozen soil on five diverse sites studied in the Palouse region of eastern Washington. Both approaches require only a single constant that accounts for individual site conditions such as slope, aspect, cover, and soil properties.
Evapotranspiration from Douglas fir stands exposed to soil water deficits
Authors: Black T. A.
Published: February 2008

The rate of evapotranspiration from thinned and unthinned stands of Douglas fir was measured using energy and water balance methods. At high values of soil water storage in the root zone the evapotranspiration rate was approximately 80% of the equilibrium evaporation rate. Below a critical value of soil water storage the ratio of the evapotranspiration rate to the equilibrium evaporation rate (E/Eeq) tended to decrease linearly with decreasing soil water storage. The critical values of soil water storage in the root zone were 11.8 and 8.3 cm for the thinned and unthinned stand, respectively. Below these critical storage values, there was approximately 3.5 cm of water remaining in both root zones that was extractable by the trees. The relationship between E/Eeq and the fraction of extractable water in the root zone for both stands was very similar for sunny days. In this relationship, E/Eeq began to decrease when there was approximately 40% of the extractable water remaining in the root zones of both stands.
Determination of the mechanism of recharge in the Los Naranjos Area in Mexico using environmental isotope techniques
Authors: Payne Bryan R. , Ortiz Ignacio Sainz
Published: February 2008

The Río Blanco crosses a coastal plain south of Veracruz in Mexico, and discharge measurements suggested that the river was recharging the groundwater system. The estimated evapotranspiration is very close to the mean annual precipitation, so estimates of effective recharge by infiltration of precipitation are very imprecise. The variations in the stable isotopic composition (D and 18O) of surface and groundwater samples are used to estimate the relative importance of the two sources of recharge to the groundwater system. The data indicate that recharge by infiltration of precipitation is the dominant source of recharge. This conclusion is based upon measurements from individual wells and also on the base flow of rivers originating in the plain, thus providing an estimate integrated over the area drained by the rivers.
Storage mass‐curve analysis in a systems‐analytic perspective
Authors: Klemeš V.
Published: February 2008

During the past decade, the systems approach to storage reservoir problems has been heralded as something of a jump from the stone age of mass‐curve analysis into the modern era of science. In reality, however, no such jump ever occurred. There were a number of small ones but, contrary to the common belief, many of them were confined to the staircase of mass‐curve analysis and not all of them were in the upward direction. This paper attempts to put the mass‐curve technique into a proper perspective by clearing out some undesirable semantic underbrush accumulated over the past decades and by showing an intrinsic identity of some mass‐curve and systems‐analytic formulations. It demonstrates that, for the important special case of convex loss functions, both the dynamic and the linear programming formulations of optimum reservoir operation policies as developed over the past decade still have a long way to go to match a 55‐year old mass‐curve technique in terms of exactness, accuracy, as well as computational efficiency. Last but not least, it shows that the mass‐curve technique provides insights into the problems of storage reservoir operation which are entirely out of reach of the systems‐analytic methods and can significantly enhance the art of reservoir design and operation.