bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical tests of Leopold's System for quantifying aesthetic factors among rivers
Authors: Hamill Louis
Published: February 2008

Leopold has published a set of techniques for comparing aesthetic factors among rivers, which include uniqueness ratios and graphic derivations of scale of river character and scale of valley character. The usual practice in evaluating recreational and scenic resources is to use a consistent rating scheme and to derive summary measures of attractiveness by adding evaluation numbers or ratings. The latter procedures were used to test Leopold's methods by using the Spearman rank correlation coefficient to compare rankings by the two methods. There was poor correlation between evaluation numbers and uniqueness ratios for physical and water quality factors. Correlation was better for human use and scenic factors. The meaning of additive evaluation numbers is more comprehensible than the meaning of additive uniqueness ratios; the additive uniqueness ratios were concluded to be less efficient. The graphic procedures were found to introduce unexpected anomalies in combining two or more sets of factors, and the addition of evaluation numbers was concluded to be more reliable. The addition of evaluation numbers requires less time and effort than the procedures advocated by Leopold and is less subject to errors.
Effect of skewness in three stochastic Pentad river flow models on crossing properties of synthesized data
Authors: Kottegoda N. T.
Published: February 2008

Large samples are synthesized through autoregressive, fast fractional noise, and broken line models, based on a practically significant pentad time unit, for four stations in the British Wye catchment. Hydrologic characteristics such as the numbers, durations, and magnitudes of droughts and floods are assessed by means of the crossing properties at critical levels in the time series. If a Gaussian distribution is applied to the stochastic component, crossing properties other than surplus run lengths are unrealistic. Compatibility with historical properties is achieved by the incorporation of approximately twice the coefficient of skewness estimated from the original data through a transformation to a gamma function. Also there is agreement in serial correlograms and coefficients of skewness. In this way neither negative numbers nor outliers are generated through autoregressive models, but run lengths at extreme levels in data from all models need adjustment, and a closer fitting distribution function is desirable.
Extension of Israel's National Water System as a function of artificial rainfall prospects
Authors: Kally Elisha
Published: February 2008

Positive results obtained from an artificial rain experiment in Israel are the major motive for the proposed extension of the Israel National Water System. Should the system be extended while the artificially induced rain increment, though highly probable, is not definitely proven? The decision maker is confronted with the choice between two alternative policies: to extend the system or not to extend it. Either policy will yield a certain expected value that is determined by the probability of increasing the water yield of Lake Kinneret by cloud seeding. The probability of ‘no increase’ that would give equal justification to both policies seems considerably higher than the no‐increase probability indicated by the findings of the artificial rain experiments, and thus the policy of ‘extension’ appears to be preferable.
The biochemical oxygen demand of finely divided logging debris in stream water
Authors: Ponce Stanley L.
Published: February 2008

The impact of Douglas fir needles and twigs, western hemlock needles, and red alder leaves on dissolved oxygen and thus on the quality of mountain stream water was examined. The mean COD, 90‐day BOD, and BOD rate coefficients were, respectively, 454 mg O2/g, 110 mg O2/g, and 0.125 for Douglas fir needles, 947 mg O2/g, 110 mg O2/g, and 0.056 for Douglas fir twigs, 570 mg O2/g, 200 mg O2/g, and 0.049 for western hemlock needles, and 882 mg O2/g, 286 mg O2/g, and 0.047 for red alder leaves. The 90‐day values of BOD and K1 for the leaf material could be estimated accurately by tests of 20, 20, and 60 days, respectively, for Douglas fir needles, western hemlock needles, and red alder leaves. The BOD of leaf material exposed to fluctuating temperature exerted a 5‐day BOD 4.0, 2.4, and 4.2 times greater than the standard temperature BOD5 for Douglas fir needles, western hemlock needles, and red alder leaves, respectively. Toxicity of a leachate extracted from each species was determined on guppies and steelhead trout fry. The concentration of material needed to produce toxic effects was very high, so high, in fact, that oxygen depletion probably would be responsible for death long before the leachate effect. Data on oxygen depletion obtained in this study will be useful in developing a predictive model for water quality management on forested lands.
Total sediment discharge sampling over sills
Authors: Hansen Edward A.
Published: February 2008

Easily installed wooden sills permit collection of bed load sediment normally missed in the ‘unsampled zone.’ Sills also (1) provide a rigid unchanging control at which to sample, (2) reduce the chance of sample bias from sediment stirred up by the wader, and (3) permit control of the sampling interval because the sample points can be marked directly on the sill. Field data indicated that the ‘sill samples’ probably provided better measurements of total sediment discharge than traditional ‘stream samples’ do. Nonuniformity of bed load discharge in cross sections of the sampled streams complicated the problem of getting unbiased samples. Lateral nonuniformity of sand bed load discharges was greatest in coarse (gravel and cobble) bedded channels having small sand loads. Sampling modifications are proposed to compensate for this nonuniformity.
A nonlinear time variant rainfall‐runoff model for augmenting monthly data
Authors: Tuffuor Samuel , Labadie John W.
Published: February 2008

Deficiency of data is a serious obstacle to river basin management in developing countries. A lumped, nonlinear, seasonally time variant rainfall‐runoff model is applied to the problem of augmenting limited monthly runoff data for the Todzie River basin, Ghana. When the trade‐off between model realism (and therefore complexity) and its practical usability for a developing nation is considered, a proper balance may have been achieved in the model presented here. Though the model is nonlinear, it is simple and easily calibrated or identified by gradient search procedures. The model produced estimates of seasonal evapotranspiration (assuming four distinct seasons per year) that were extremely close to available historical data. It also gave a good fit to available runoff records for the more important wet seasonal flows.
A stochastic model of dispersion in a porous medium
Authors: Todorovic P.
Published: February 2008

A set of tagged particles released in a flow through a porous medium is subject to random dispersion. For a statistically homogeneous and isotropic porous medium a stochastic model of longitudinal dispersion is determined, provided the fluid flow is steady and no mass transfer occurs between the solid phase and the fluid. This paper is a continuation of a previous one on the problem of longitudinal dispersion. Here a stochastic model is presented to describe longitudinal dispersion of a set of tagged particles released continuously (but not necessarily at uniform rate) in a flow through a porous structure. The model depends on two constant parameters λ1 and λ2, which in turn depend on the properties of the porous medium and hydraulic conditions. Finally, it should be emphasized that the model presented here is kinematic in the sense that it treats only the statistical properties of the law of motion of a tagged particle in a flow through a porous medium and does not go into particulars of dynamic conditions. Consequently, it does not explicitly contain parameters of the hydraulic forces leading to this motion.
Wind effects on chemical films for evaporation suppression at Lake Hefner
Authors: Crow F. R. , Mitchell A. L.
Published: February 2008

Chemical films applied to lake surfaces for evaporation suppression are greatly affected by the local wind speed and direction. An evaporation suppression research project was conducted at Lake Hefner where water‐based slurries of hexadecanol and octadecanol were applied at the upwind side of the lake by an offshore sprinkler system. The distribution system was designed for maximum film cover under south winds. The chemical was applied at a variable rate adjusted to the demand created by local wind speed and direction. The application rate required to replace film removed by the wind, in terms of pounds per hour per foot of distribution line perpendicular to the wind, averaged 6.5–8 times greater than for an experimental pond with a similar application system. The upper wind speed limit for successful film application was 13 mi/h. Distribution studies were made to determine the percent of time that wind speeds and directions were favorable to the application of film, i.e., with speeds less than 13 mi/h and direction between 135° and 225° azimuth.
A thermodynamic integral equation for the equilibrium moisture profile in swelling soil
Authors: Sposito Garrison
Published: February 2008

The methods of thermodynamics are employed to develop a nonlinear integral equation for the equilibrium moisture profile in a swelling soil which is assumed to be uniform in the distribution of dissolved substances. The equation is shown to be identical with an expression suggested (but not derived) by Philip in response to criticism of his discussion of the hydrostatics of swelling porous media.
An integrated power process model of water use and waste water treatment in chlor‐alkali production
Authors: Singleton F. D. , Calloway James A. , Thompson Russell G.
Published: February 2008

An economic evaluation was made of the effects of increasingly restrictive waste water effluent standards and higher costs of water withdrawals on resource use, waste discharges, and costs of producing chlorine and caustic. Both mercury cell and diaphragm cell methods of production were studied for large modern plants at the design stage. Zero discharges of total solids in diaphragm cell plants increased production costs 5.6%; zero discharges of total solids in mercury cell plants increased production costs 12.1%. Zero‐discharge restrictions of mercury may only be accomplished by use of diaphragm cells. Similar results were obtained for assumed Houston and Saginaw locations.
Some observations concerning preparation and storage of stream samples for dissolved inorganic phosphate analysis
Authors: Johnson Arthur H. , Bouldin David R. , Hergert Gary W.
Published: February 2008

The influence of storage conditions and duration of storage was studied by using about 100 stream samples from Fall Creek collected near Ithaca, New York. Freezing and refrigerated storage were found to be unsatisfactory, since changes in measured concentrations were usually observed after relatively short periods of time (24 hours). An isobutanol extraction procedure is described which minimizes storage problems and is useful for routine analysis of water samples for dissolved inorganic phosphate.
An evaluation of some linear decision rules in chance‐Constrained models for reservoir planning and operation
Authors: Loucks Daniel P. , Dorfman Philp J.
Published: February 2008

Several linear decision rules used in chance‐constrained models for estimating efficient reservoir capacities and operating policies are compared and evaluated. A chance‐constrained model that includes known or unknown reservoir release targets, or storage volume targets, permits this comparison, since regardless of the linear decision rule chosen, release or storage volume commitments can be made, and their maximum probabilities of failure estimated, well in advance of any period in which they apply. Optimization and simulation techniques are used to evaluate the performance of each decision rule.
Bayesian generation of synthetic streamflows
Authors: Vicens Guillermo J. , Rodríguez‐Iturbe Ignacio , Schaake John C.
Published: February 2008

Generation of synthetic streamflow traces has proven to be an extremely useful technique for the evaluation of water resource planning and management alternatives. But existing models do not account for the uncertainty in the streamflow parameters. Past research efforts have focused on obtaining ‘best’ estimates of these parameters which are then used as the ‘true’ values of the process. Bayesian methods are here used to overcome this shortcoming. By incorporating the parameter uncertainties into the generation scheme, alternatives may be evaluated under both the natural and the parameter uncertainties. This is accomplished by integrating over the probability distribution of the parameters to obtain the Bayesian, predictive, or unconditional probability distribution function (pdf) of the streamflows. Use of the Bayesian pdf for synthetic generation is shown to lead, on the average, to better designs under uncertainty conditions.
A stochastic model of dispersion of sediment particles released from a continuous source
Authors: Todorovic P.
Published: February 2008

Recent interest in bed sediment as a pollutant and as a carrier of various pollutants has emphasized the need for better understanding the dispersion process of bed sediment. Unfortunately, the existing mathematical models were constructed to describe longitudinal dispersion of a set of bed sediment particles simultaneously released in a flow from a line or a point source. In this paper, stochastic models are proposed for description of the longitudinal dispersion of a set of bed sediment particles released in a flow over a certain interval of time at a given rate α(u). Two particular cases are considered separately. First, the release occurs during a finite time interval, say, [0, t]. Second, the release occurs during [0, ∞). provided that certain regularity conditions hold, it is shown that both dispersion models are obtained by means of a simple integral transformation of the model for instantaneous release.
The effect of climate on the chemistry of carbonate groundwater
Authors: Drake John J. , Wigley T. M. L.
Published: February 2008

The temperature coefficient of the log Pco2‐temperature relationship for springwater from carbonate terrains in North America is approximately 0.07/°C. Consideration of a simple model of soil air behavior and various published data suggests that the temperature coefficient of the same relationship for soil air is of the order of 0.04/°C. A model where the soil zone is the source of carbon dioxide for water entering a groundwater system and where the subsequent chemical evolution of the water occurs under closed system conditions is consistent with these relationships.
Coupled saturated‐unsaturated transient flow in porous media: Experimental and numeric model
Authors: Luthin James N. , Orhun Akin , Taylor Geroge S.
Published: February 2008

Experimental data were obtained from a sector tank for the transient flow toward a well. The data included both the saturated and the unsaturated flow region. The data were used to verify the accuracy of a computer solution using an implicit numerical procedure. Agreement between the two sets of data was good. The computer solution can be adapted to a wide variety of groundwater flow problems.
Forecasting water levels in aquifers by numerical and semihybrid methods
Authors: Hafez E. , Shamir U. , Bear J.
Published: February 2008

Two methods which employ a cell model for forecasting water levels in aquifers are compared: the (noniterative) alternating direction implicit (ADI) finite difference method and a semihybrid iterative method, in which a resistor network is the analog part. By using simulation of the semihybrid method it is concluded that this method requires a larger computational effort than the ADI method.
Decision perspectives on urban storm water pollution
Authors: Young G. K.
Published: February 2008

The objectives of this study are to develop and use a novel and simple method of analysis of the urban combined sewer and overflow problem. An aggregated method is presented which relates a few significant variables to produce a scalar that describes the severity of pollution for an urban area. Typical values of the variables are assigned, and sensitivity analysis of urban storm‐induced pollution to various control measures is demonstrated. Digital computers are not necessary. The method takes a macroanalytic perspective which should produce comparisons adaptable to decision rules for funding priorities. Work on specific cities is necessary to refine the approach and rank alternatives. The method should be able to screen out poor candidates for funds early in the decision‐making process and concentrate feasibility studies and analysis upon needy sites and viable alternatives. The method as applied to typical values leads to the following conclusions: (1) the method has utility for first‐level screening of alternatives at the national or state decision‐making level; (2) the hydrologie variables, formerly thought to be very complicated factors in studies of this problem, with the exception of receiving water streamflow at the start of a storm, do not enter into the assessment of the maximum pollutional impacts of storms; (3) a relatively small set of variables, several relating to water use and the sewer treatment system and the others defining the quality of receiving waters, storm wash and raw sewage, are used to conduct the analysis using the simplified method; and (4) the maximum storm‐induced water quality is several times the water quality associated with the dry weather engineering design limits of sewage treatment performance.
Urban watershed management using activity indicators to predict water quality
Authors: Darby William P. , McMichael Francis Clay , Dunlap Robert W.
Published: February 2008

The first step in the management of small watersheds by local regulatory agencies is the establishment of priorities for implementing the dictates of the 1972 Federal Water Pollution Control Act amendments. Although data requirements for establishing priorities are extensive, typically, very little water quality and streamflow data exist for small urban watersheds. Local regulatory agencies do not possess the resources to generate these data. To solve this problem, the use of indirect indicators is developed to describe watershed activity, predict water quality, and forecast the status of several individual water quality parameters. Stream quality is then predicted for watersheds for which no previous direct measurements had been made. The methodology is applied to Allegheny County in Pennsylvania, a region composed of 52 small urban watersheds. Indicators of watershed activity are used here to determine which streams should be sampled to provide a representative measure of water quality conditions existing throughout the county. The information from the monitoring program is currently being used by the Allegheny County Health Department to define implementation priorities for the small urban streams in the region.
On the joint distribution of the largest flood and its time of occurrence
Authors: Gupta Vijay K. , Duckstein L. , Peebles R. W.
Published: February 2008

In a partial duration series the total number of exceedances as well as the exceedance flows is formalized as a random sequence of random variables. This formalism along with some physically reasonable assumptions leads to a rigorous expression for the joint distribution function of the largest exceedance and its time of occurrence. The deviation provides one way to consider the temporal changes in the occurrence and the magnitudes of individual exceedances due to ‘seasonal’ influences. This approach is general enough to be applied to any time interval of interest; furthermore, the derived expressions are exact (nonasymptotic). It may thus represent an improvement over an application of Gumbel's classical extreme value theory to flood phenomena, which is based on the premise that a large number of exceedances are available over time intervals of interest and which provides only asymptotic expressions.
An automatic release instrument with underwater buoy for marking of field equipment
Authors: Håkanson Lars , Edlund Leif , Uhrberg Roland
Published: February 2008

In practical fieldwork one often encounters the problem of marking registration instruments placed below the water surface. Marking buoys can for various reasons disappear if they are placed visibly, valuable equipment and data thus being lost. In this paper a new technique and a new instrument for marking field equipment are introduced. The instrument, which in principle consists of an anchor, a buoy, an electronic circuit with a clock, and a release mechanism, is to be placed on the bottom. After a predetermined time span the clock triggers the release mechanism, and the buoy and the instrument float to the surface, where they can be collected with good accuracy in time.
A linear programing model for use in guiding urban floodplain management
Authors: Day John C. , Weisz Reuben N.
Published: February 2008

Modern planning seeks better solutions to urban flood problems through floodplain management practices involving coordinated land use and engineering approaches. Land use control can be integrated with dams, levees, channel works, etc., but the physical and economic interrelationships must be taken into account. Trade‐offs require quantification of the economic impacts of dissimilar alternatives. A computational technique employing linear programing to determine the optimum combination of flood control works and land development policies is applied to the Tucson situation and found to yield information helpful for floodplain management.
Hydrodynamics of groundwater flow in a fractured formation
Authors: Streltsova T. D.
Published: February 2008

Hydrodynamical aspects of groundwater flow in fractured formations and the basic hydraulic properties controlling the flow are the subject of the present consideration. A brief literature survey on studying the physical characteristics of the fractured rocks and on developing an understanding of the mechanism of fluid flow in fractured formations constitutes an introductory section. Basic definitions, relations, and assumptions given for subsequent interpretation of the flow behavior in a fissured rock then follow. Concepts of fractured, homogeneous, and heterogeneous water‐bearing formations and their response mechanism to a pressure change are considered. The general differential equations for a flow in a fractured and in a heterogeneous formation of uniform anisotropy are derived. Two types of the flow behavior, fissure flow and pore flow, are distinguished. Two drawdown equations, respectively, for a flow in a fissure space, whether void or infilled with a fine material, and for a flow in a porous space to a well discharging at a constant rate in a fractured aquifer, are given. A fractured reservoir response to a pressure change due to pumping is illustrated by the field drawdown and recovery data. A particular case of a heterogeneous formation, an aquifer‐aquitard system, is discussed, and the drawdown distribution in both aquifer and aquitard is given when account is taken of their elastic properties.
The use of linear programing techniques for estimating the benefits from increased accuracy of water supply forecasts
Authors: Moore John L. , Armstrong John M.
Published: February 2008

Probabilistic linear programing techniques and Bayesian statistics are combined in this paper by utilizing an example from the area of irrigated agriculture and water supply forecasts to assess the value of increased forecast accuracy to decision units. The case studied was confined to a two‐period analysis involving (1) a crop planting period and (2) a growing and harvesting period. The model is developed in terms of Bayesian analysis and demonstrates how linear programing can be applied to rather complex decision making problems involving uncertainty. Testing of the model involved the use of an IBM computer program available at the University of Michigan. For various assumptions as to supplemental water supply the model showed a net benefit to irrigators of about $6/acre for a reduction in uncertainty of 33% resulting from the introduction and improvement of water supply forecasts.
Operation of a reservoir collecting water from a small watershed
Authors: Buras Nathan , Diskin M. H. , Zamir S.
Published: February 2008

Best operation policies, linear and nonlinear, were developed for a small reservoir in which storm runoff water might be augmented by pumping water from another source. These policies were aimed at a full reservoir at the beginning of the yearly irrigation season and, indirectly, utilized more efficiently the existing neighboring pumping installations, which are usually idle in winter. The operating policies are expressed as time‐dependent functions indicating the level of the reservoir which would ensure its being full at the end of the rainy season with a given probability. When these policies were tested with a synthetic hydrologic series of 45 years, it appeared that the cost of operating the reservoir was inversely proportional to the daily amount of water pumped into it from external sources.
Criteria for the use of vertical averaging in environmental dispersion models
Authors: Galloway F. M.
Published: February 2008

Vertical averaging, or averaging in a plane perpendicular to the mean flow, in environmental dispersion problems is desirable from the standpoint of the efficiency of computer solution. This paper presents a method based on computer solution of a model transport problem for estimating when cross‐plane averaging is appropriate. The method is applied to four examples representing typical lakes, rivers, estuaries, and the atmosphere, respectively. The results are correlated in terms of a characteristic length, velocity and turbulent diffusivity, and two dimensionless parameters that depend on the velocity and vertical diffusivity profiles. It is shown that these parameters vary over a relatively small range for the variety of examples that are considered.

The appendix is available with entire article on microfiche. Order from American Geophysical Union, 1909 K Street, N.W., Washington, D.C. 20006. Document W76‐003; $1.00. Payment must accompany order.
Lake Erie terrestrial radiation
Authors: Derecki Jan A.
Published: February 2008

Terrestrial or long‐wave radiation over a body of water consists of the atmospheric radiation, with incident and reflected components, and the radiation emitted by the water body. These three radiation components produce a net back radiation, an energy loss from the water to the atmosphere. Basic required data (air temperature, humidity, solar radiation, and water surface temperature) were derived, and long‐term (17 years) average monthly radiation values were calculated for the Lake Erie incident and reflected atmospheric radiation and the radiation emitted by the water body. The net result or the effective net back radiation averaged 100 Ly/d from 1952 to 1968.
Aerial spraying of phreatophytes with antitranspirant
Authors: Davenport D. C. , Martin P. E. , Hagan R. M.
Published: February 2008

An antitranspirant (AT) can retard excessive groundwater consumption by phreatophytes without eradicating them. To determine whether aerial spraying (the only realistic application method for most sites) of a 6% (vol/vol) wax‐based AT emulsion would provide adequate spray coverage and reduce transpiration, multiple passes were made with (1) a fixed wing plane on salt cedar, cottonwood, and willow and (2) a helicopter on salt cedar. Spray coverage on the ground was 30–100% in the open (depending on the number of passes and wind drift) and 10–90% under the canopies (depending on vegetation density). Average coverage on tags ranged from 13% in the lower canopy to 75% in the upper (depending on species and application rate) after spraying by the fixed wing plane and 47 to 98% after spraying by the helicopter. Coverage in the center of dense bushes was 0–20%, but transpiration is only minimal there. Scanning electron microscope photomicrographs showed considerable AT on foliage in the upper canopy and lesser amounts in the lower; the film was detected even 24 days after spraying. Aerially applied AT increased resistance to leaf water vapor diffusion by 150% during the first few days and by 80% thereafter. Transpiration of outer foliage of salt cedar was reduced 50% initially and 20% after two weeks without phytotoxicity.
Effects of NEPA's Review and comment process on water resources planning: Results of a survey of planners in the Corps of Engineers and Soil Conservation Service
Authors: Hill William W. , Ortolano Leonard
Published: February 2008

The guidelines of the Council on Environmental Quality for implementing the National Environmental Policy Act require that environmental statements be circulated to other agencies and publics for review and comment. Effects of the ‘review and comment’ (R&C) process spawned by this requirement are assessed in the context of water resources planning in the U.S. Army Corps of Engineers (Corps) and the Soil Conservation Service (SCS). The assessment, which relies on data from questionnaires administered to personnel in all Corps districts and SCS state offices in 1974, concerns the extent to which increased coordination and information transfer brought about by the R&C process have influenced decision making. Obstacles serving to impede the functioning of an effective R&C process are also noted.
Optimization of crop irrigation strategy under a stochastic weather regime: A simulation study
Authors: Ahmed J. , van Bavel C. H. M. , Hiler E. A.
Published: February 2008

A dynamic simulation model of the soil‐water‐atmosphere‐plant system is developed as a tool for optimal irrigation decision making under a stochastic weather regime and when water supplies are limited. Crop yield, foliage development, plant water deficits, and irrigation decisions have been treated as interdependent processes. Yield susceptibility of the crop to water deficit is a function of crop growth stage. The stomatal regulation of transpiration by the crop has been taken into account also. The model is a closed loop dynamic system, in which past irrigation decisions and weather conditions affect the current as well as the future response of the crop system and, consequently, the future irrigation decisions and the overall water use efficiency. The specific illustration in this paper pertains to grain sorghum grown under weather conditions typical for south central Texas.
Some statistical properties of wind waves in La Cygne Lake
Authors: Yu Yun‐Sheng , Ozawa Kenneth S.
Published: February 2008

Wind‐generated waves in La Cygne Lake, Kansas, were measured at six different stations in the lake with wind speeds ranging from 1.2 m/s to 7.8 m/s. Statistical analysis of 50 wave records shows that the measured values of H1/3/Hm and Hmax/Hm agree well with the predicted values based on the Rayleigh probability law. Normalized wave spectra are similar and follow approximately the power law. On the high‐frequency side the 5th power law is a good fit, while on the low‐frequency side the normalized spectral value increases with the 4th power of the normalized frequency.
On solving the infiltration equation—Comparison of perturbation and iterative techniques
Authors: Parlange J.‐Y. , Babu D. K.
Published: February 2008

A recent solution obtained by Babu following a perturbation method is compared with an earlier iterative method. It is shown that after improvement, Babu's perturbation solution becomes identical to the iterative solution using Cisler's correction. A simpler solution based on an optimal scheme is also presented.
Reservoir operation under conflicting objectives
Authors: Fronza G. , Karlin A. , Rinaldi S.
Published: February 2008

The problem of determining the optimal operation of a montly regulated two‐purpose reservoir is discussed in this paper. A basic assumption is made about the decision‐making structure of the system in the sense that the operation is not assumed to result from a supervisor's choice but from the users' trade‐off. The solution of the problem is found by means of a game theory approach in both the noncooperative and the cooperative situations.
Flow characteristics during infiltration into a horizontal sand column
Authors: Poulovassilis A.
Published: February 2008

Experimental water content profiles established during infiltration into a horizontal sand column were compared with theoretical ones calculated from the soil‐water diffusivity, which was determined independently of the infiltration process. Discrepancies between the theoretical and experimental profiles were found. In particular, the experimental profiles for small times showed a retardation of the penetration which became more pronounced as the water content increased, and no unique relationship between the water content and the variable λ = x/(t)½ (x being the distance and t the time) was found. Thus the experimental profiles gave incorrect and varying soil‐water diffusivities. The comparison of the actual flow rate q with the rate q′ given by the product of the hydraulic conductivity and the observed potential gradient showed that q = q′, where 0 < α ≤ 1, a varying with the water content and the potential gradient. The effect of the ‘less than proportional’ flow on the profile development is discussed. It is argued that the infiltration process at relatively late times was conditioned by the profile development during the very early stages. Previous experimental infiltration work is discussed, and it is argued that two mechanisms able to produce non‐Darcian behavior may be responsible for the various reported infiltration patterns. Finally, the results of the present work are discussed in terms of a critical Reynolds number where the flow becomes non‐Darcian.
Hyperoxygen concentrations in the hypolimnion produced by injection of liquid oxygen
Authors: Fast Arlo W. , Overholtz William J. , Tubb Richard A.
Published: February 2008

The hypolimnion of a quarry pond at Ottoville, Ohio, was oxygenated during the summers of 1973 and 1974. The highest hypolimnetic oxygen concentrations attained were 8.0 mg/1 in 1973 and 21.5 mg/1 in 1974; thermal stratification was maintained both years. The 21.5‐mg/l oxygen concentration is the highest value yet reported for a hypolimnion and constitutes an upper limit controlled by pressure, temperature, and oxygen demand. Degassing was observed as the high value was reached. Hypolimnion concentrations (of N2) were calculated for different injected mixtures of O2 and N2 gases.
The thermal structure of small lakes: The influence of a modified wind speed
Authors: Henderson‐Sellers Brian
Published: February 2008

The thermal structure of a lake is determined primarily by the wind shear, which induces turbulence in the lake. In the case of a lake of small areal extent, numerical models employing observed or climatological functions for the wind speed give unacceptable results. It is shown that if the wind speed is modified by a function of the lake surface area, then the annual stratification of a small lake can be realistically described. This technique is illustrated for the case of Farmoor Reservoir in England.
A least squares method for computing statistical tolerance limits
Authors: Wallace J. R. , Grant J. L.
Published: February 2008

Statistical analysis often requires the fitting of a probability density function to sample data in order to estimate either the population parameters or a particular percentile point of the population. In either case the exact determination of the population values cannot be expected because a sample generally does not completely describe the population. The theories of statistical confidence regions and tolerance limits allow inferences to be drawn regarding relationships between the estimates and the corresponding unknown population values. A least squares procedure has been devised which allows the construction of confidence regions and tolerance limits for arbitrary distribution functions. The class errors, ei, are defined as the difference between the sample histogram and the expected frequency based upon the density function. The confidence region is defined by the relation Rα = {θ : [R1(e)/R2(e)] < [m/(N − m)]F(α, m, N − m)}, where θ represents the m‐dimensional parameter vector of the distribution function, R1(e) and R2(e) represent decompositions of
of ranks m and N − m, respectively, and F is Snedecor's F statistic. The η tolerance limit of the γ percentile point is found from the relation
.
A study of heat transfer processes above a cooling pond
Authors: Hicks B. B. , Wesely M. L. , Sheih C. M.
Published: February 2008

Rapid‐response instrumentation mounted on a fixed tower located centrally in a strongly heated cooling pond at a nuclear power facility has enabled evaluation of the turbulent fluxes of momentum, moisture, and sensible heat. The results agree well with evaluations based on stability‐corrected bulk aerodynamic formulations, provided all atmospheric measurements are made close to the water surface and in a location with adequate upwind fetch. The bulk formulae are those that have been verified recently over more extensive water surfaces, with a minor modification based on the finding that the surface of the cooling pond appears to be significantly smoother than that of open ocean.
A note on the Hurst Phenomenon in turbulent flows
Authors: Van Atta C. W. , Helland K. N.
Published: February 2008

Experimental observation of a long‐established theoretical result for the behavior of the rescaled range is reported. Suitable dimensional scaling is found to collapse all available geophysical and laboratory data for the rescaled range in turbulent flows.
Some properties of variance reduction techniques where hydrological extremes are estimated by Monte Carlo Simulation
Authors: Moore R. J. , Clarke R. T.
Published: February 2008

An estimate
of a water resource system's performance, when it is derived by simulation using synthetic streamflow sequences, is subject to at least three errors: first, model errors, arising from the approximation to the ‘true’ streamflow mechanism which the model represents; second, sampling errors in the model parameters θ when they are calculated from the historic records; and third, errors introduced by the Monte Carlo calculation from which
is derived. This paper presents some observations on the effects of the first two types of error on the estimate
but concentrates on the application of variance reduction techniques to the derivation of Monte Carlo estimates
for given θ. These techniques are, first, the use of control variates and, second, the use of antithetic variates, and their application is illustrated by using some hypothetical examples of the calculation of probabilities of extreme hydrological events and of the calculation of reliability measures for a much oversimplified storage system. Considerable reduction in the variance of
resulted from the application of the control variate method; the reduction in Var
resulting from the use of antithetic variates was much less but still probably worth the small additional programing effort required. It is concluded that the promise of the control variate method suggests that it should be applied to assist in the efficient simulation of more realistic water resource systems than the trivial ones considered in this paper.
Casing depths and solute travel times to wells
Authors: Kirkham Don , Sotres M. Olga
Published: February 2008

Travel times are computed for a solute moving by assumed piston flow in a steady state along streamlines in a phreatic (water table) aquifer in which a tube well is located to determine the influence of unscreened casing depth on travel time. Flow nets are first computed by potential theory and then travel times along sets of streamlines for 18 geometries. Parameters varied are unscreened casing depth, well radius, and thickness of aquifer, all for a fixed radius of influence. For a well radius of 10 ft (3.05 m), a radius of influence of 500 ft (152 m), an aquifer thickness of 100 ft (30.5 m), a depth of the unscreened (impervious) casing below the water table of 25 ft (7.62 m), a hydraulic conductivity of 100 ft/d (30.5 m/d), a head difference across the system of 5 ft (1.52 m), and an aquifer porosity of 0.25 the longest travel time for a solute entering at the water table is 89.3 yr, and the shortest, which is for flow along the well casing, 0.500 day. Corresponding travel times for the same geometry, except that the unscreened depth of casing is doubled from 25 ft (7.62 m) to 50 ft (15.24 m), are 106.4 yr and 2.38 days. Other times may be determined conveniently from charts that give dimensionless times t′ that are to be multiplied by a factor [ƒ/(KH)]b2, where ƒ is aquifer porosity, K is hydraulic conductivity, H is pumping drawdown depth, and b is radius of influence. The computed travel times should be useful in well design and protection from solutes, such as nitrates and acids originating from agriculture, industry, strip mines, sanitary landfills, or other groundwater pollution sources near wells.

Supplementary appendix (computer program) is available with entire article in microfiche. Order from American Geophysical Union, 1909 K Street, N.W., Washington, D.C. 20006. Document W78‐001; $1.00. Payment must accompany order.
Stochastic analysis of spatial variability in subsurface flows: 1. Comparison of one‐ and three‐dimensional flows
Authors: Bakr Adel A. , Gelhar Lynn W. , Gutjahr Allan L. , MacMillan John R.
Published: February 2008

The complex variation of hydraulic conductivity in natural aquifer materials is represented in a continuum sense as a spatial stochastic process which is characterized by a covariance function. Assuming statistical homogeneity, the theory of spectral analysis is used to solve perturbed forms of the stochastic differential equation describing flow through porous media with randomly varying hydraulic conductivity. From analyses of unidirectional mean flows which are perturbed by one‐and three‐dimensional variations of the logarithm of the hydraulic conductivity, local relationships between the head variance and the log conductivity variance are obtained. The results show that the head variance produced by three‐dimensional statistical isotropic conductivity perturbations is only 5% of that in the corresponding one‐dimensional case. The head variance is also strongly dependent on the correlation distance of the log conductivity covariance function. These results emphasize the importance of including spatial correlation structure and multidimensional effects in stochastic simulation of groundwater flow.
A feature prediction model in synthetic hydrology based on concepts of pattern recognition
Authors: Panu Umed Singh , Unny T. E. , Ragade R. K.
Published: February 2008

It is reasonable to consider that sequences of hydrologic data corresponding to daily, weekly, or monthly measurements occur in well‐defined groups. These groups possess collective properties of the data forming them. Such a collection of properties can be called a hydrologic pattern. A pattern is a description of an object, and the objects of concern in this paper are groups of data on hydrologic phenomena observed at regular time intervals. Hydrologic patterns describing each of these groups are expressed by n appropriate properties. Further, the dimensionality, n in number, can be reduced by considering only those characteristic properties, m in number (m≤n), that are common in all hydrologic patterns of the same category. These m characteristic properties are called features. A procedure is presented to extract information present within patterns and among patterns of the pertinent hydrologic data. In addition, on the basis of the above information, a zero‐order Markov feature prediction model is postulated. The basic assumptions of the model and their implications are presented. The model is applied to South Saskatchewan River flow data in an effort to demonstrate its usefulness in real situations.
Steady phreatic flow over a sloping semipervious layer
Authors: Mualem Y. , Bear J.
Published: February 2008

The present work deals with steady phreatic flow above a thin semipervious sloping layer located at some distance below ground surface and above the water table of an underlying phreatic aquifer. Cases of both upsloping and downsloping semipervious layers are studied. A uniform recharge of constant rate and a semipervious layer of finite length are considered, either with length of flow shorter than the semipervious layer or with flow bypassing its edge. For each case, linearization is applied to the nonlinear continuity equation which governs the flow. Analytical solutions are then derived for the shape of the phreatic flow wedge, the length of the wedge, and the discharge rate. These results are compared with experimental ones obtained in a Hele‐Shaw analog. A good agreement is generally found between computed and observed results. Because of the analogy which exists between a phreatic surface and an interface in a coastal aquifer, the same results can also be applied to the steady freshwater flow above an interface in an aquifer divided into two subaquifers by a sloping semipervious layer.
Percolation rates with surface layers of gravel or clay flocs on soil fed clear and turbid waters
Authors: Lehman O. R.
Published: February 2008

Suspended solids in water can plug the surfaces of aquifer recharge basins, and they are often chemically flocculated and removed in costly separate floc‐settling basins. This work evaluated floc and gravel filters on recharge surfaces as substitutes for settling basins. Disturbed soil in permeameters was treated with layers of small gravel and constant feedwater heads of either clear tapwater, untreated turbid runoff water, or turbid runoff water treated to form and retain flocs. Untreated turbid water reduced percolation rates more than the other feedwaters, and gravel layers markedly reduced percolation of all feedwaters. The percolation rate of water with flocs was only slightly less than that of tapwater. These results suggested that untreated turbid water or gravel layers are unacceptable for recharge surfaces. However, combinations of soil, gravel, and clay may have considerable potential for reducing percolation in water retention basins. Flocculation and settling seldom remove all fine particles from turbid water; thus a filter layer of flocs may extend the effective life of a recharge surface and eliminate costly separate floc‐settling basins.