bluuebunny/crossref_metadata_2025 huggingface dataset:
Splash Droplet Production by Waterdrop Impact
Authors: Mutchler Calvin K.
Published: February 2008

Splash droplets produced by waterdrop impact were described by the normal distribution parameters derived on a volume basis. The major splash variables of surface water depth d and waterdrop diameter D were examined by using the distribution parameters: D50, the droplet diameter when 50% of the splash volume consists of larger droplets; σ, the standard deviation; and N, the number of droplets produced by one waterdrop impact. For a waterdrop diameter of 0.4 cm, D50 was about 0.04 cm near zero depth, reached a maximum size of 0.15 cm at d/D = 0.5, and then decreased to a constant size of less than 0.13 cm for d/D > 3. Larger waterdrops produced larger splash droplets.
Hydrologic Effects of Deforesting Two Mountain Watersheds in West Virginia
Authors: Patric James H. , Reinhart Kenneth G.
Published: February 2008

The upper half of one watershed and the lower half of another were deforested and maintained barren from 1965 to 1967. Forest on the remaining halves was cut in 1968. Water yield increases from both watersheds averaged almost 6 inches during the half deforested stage and rose to over 10 inches after complete deforestation. The duration of the flows greatly increased on both watersheds. Other hydrologic effects (instantaneous peak flows, stream temperature, specific conductance, and turbidity) were greater on the lower half deforested watershed. These results show again that forest cutting causes substantial increases in streamflow, but, more important, they provide some landmark values on hydrologic effects of complete deforestation.
Cis and Trans Links in Natural Channel Networks
Authors: Smart J. S. , Wallis J. R.
Published: February 2008

An explanation of the excess of trans links over cis links in natural channel networks is proposed. The basic assumptions are (1) channel networks develop by headward growth, (2) tributaries are generated independently on the two sides of the main channel, and (3) once a tributary has been established, the probability of other tributaries developing further downstream on the same side is greatly diminished. Computer simulations of a simplified version of this model produce networks with about 58% trans links.
A Chance‐Constrained Approach to the Conjunctive Use of Surface Waters and Groundwaters
Authors: Nieswand G. H. , Granstrom M. L.
Published: February 2008

A set of chance‐constrained linear programing models for the conjunctive use of surface waters and groundwaters was developed for the Mullica River basin in New Jersey. A zero order decision rule was used to obtain deterministic equivalents for the chance‐constrained models. The resulting linear programing models were solved for a variety of constraint situations. The results indicated the maximum total withdrawals that could be expected from the basin for the assumed conjunctive use operation. The satisfaction of specified target outputs for the basin by alternative feasible combinations of surface water and groundwater withdrawals was also demonstrated.
Hymo, A problem‐oriented computer language for building hydrologic models
Authors: Williams Jimmy R. , Hann Roy W.
Published: February 2008

Hydrologists unfamiliar with computer programing methods can use Hymo to great advantage in watershed modeling. This problem‐oriented computer language provides twelve commands, commonly used in hydrology, to transform rainfall into runoff hydrographs and to route these hydrographs through streams and valleys or reservoirs. These functions make Hymo quite useful in the design and evaluation of flood control structures, flood forecasting, and research studies. The procedures used in Hymo were selected because of their accuracy, simplicity, and practicality. The input data required for Hymo are normally available for most watersheds. Hymo is quite flexible in that hydrologists familiar with Fortran 4 programing can easily add new commands or modify the present commands.
Watershed management: A systems approach
Authors: Eisel L. M.
Published: February 2008

A systems approach to land use management decision making in wildland areas is developed and demonstrated by using a hypothetical example. A major component of this systems approach is a chance‐constrained programing model for investigating the effects of risk and uncertainty on land use management decisions. The solution of the chance‐constrained model indicates the most efficient set of land use management activities for reaching specified goals subject to certain requirements and regulations. In addition to indicating the type and extent of land use management activities for a specific area, the systems approach provides additional results and conclusions concerning more general aspects of land use management decision making. The development and solution of the chance‐constrained model indicate that the risk and uncertainty associated with the system physical and economic parameters can significantly affect the design of land use management activities. The model results further suggest that future outdoor recreational demand and benefits are important factors in the design of land use management activities. The solution of the chance‐constrained model indicates that forest management practices to increase stream‐flows may have only a minimal effect on the design and operation of downstream reservoirs.
Use of naturally occurring phenomena to study hydraulic diffusivities of aquitards
Authors: Davis Richard W.
Published: February 2008

Measurement of the response of an artesian aquifer system to naturally occurring stress fields can be used to determine aquitard properties. One method proposed here uses the response of an artesian aquifer to a short‐term rise of water levels by approximating a step function in the unconfined aquifer above it. An analysis of the corresponding change in artesian water levels gives a value for α/m2, the aquitard hydraulic diffusivity divided by the square of the aquitard thickness. The application of this method is demonstrated by using data from a well field in Pasco County, Florida. A second method uses the fact that the response of an artesian system to barometric or tidal stresses is frequency dependent. As an incidental consequence, it is necessary to restrict Jacob's definition of barometric and tidal efficiencies to aquifer responses to instantaneous stress changes. The methods described are easily applied and serve to check the values of a boundary condition that is assumed to be homogeneous in other analytical approaches.
Economic optimization of a single‐cell aquifer
Authors: Brown Gardner , Deacon Robert
Published: February 2008

Optimal economic use of an aquifer over time is analyzed under conditions of economic growth, inequality of groundwater withdrawal and consumption, and availability of surface water and artificial recharge. The value of an aquifer as a natural water quality treatment facility is derived.
Best combination of waste treatment and spatially distributed discharge of effluent
Authors: Mendiratta A. K. , Davidson Burton
Published: February 2008

The optimal control theory based on Pontryagin's minimum principle has been applied to the problem of specifying the best combination of minimum percent BOD waste treatment and effluent distribution policies for a single plant on a specified polluted river segment. The analysis features a new dual water quality stream standard consisting of a minimum allowable DO concentration at every point in the river segment combined with a maximum allowable BOD concentration at a specified downstream point. The optimal BOD effluent distribution policies are compared with choice suboptimal effluent discharge patterns associated with best single point, best uniform, and best bang‐bang injection policies. The inequality constraints, the nonlinearities in the system model, and the synthesis of the optimal controls were handled in a direct manner by using the Pontryagin control theory principle combined with gradient search and penalty function techniques. The results of the study very definitely established certain guidelines for increasing the assimilative capacity of a given river segment through judicious combinations of minimum percent BOD waste treatment and continuous BOD effluent distribution or dumping patterns associated with single plant effluents. The systems analysis was made tractable by incorporating a no short‐circuit constraint into the dumping policies.
Chemistry and occurrence of cadmium and zinc in surface water and groundwater
Authors: Hem John D.
Published: February 2008

The median concentration of zinc in 726 filtered samples of water taken from rivers and lakes of the United States in November 1971 was close to 20 μg/l, and the median concentration of cadmium was a little below 1 μg/l. The concentrations of both elements tended to be consistently higher in water from northeastern and southeastern states. Chemical thermodynamic calculations summarized by solubility graphs suggest that the carbonate and hydroxide solubilities of these elements are higher than the concentrations commonly found, but for 24 of 80 analyses for which chemical equilibrium computations could be made, saturation with respect to one or both of the metals was closely approached. Zinc solubility may also be controlled by silicate in some waters. Biological factors and Sorption by stream sediments may also be significant controls. Concentrations of cadmium above 10 μg/l may be stable in water having low total solute concentrations and pH and can be difficult to remove by conventional water treatment processes.
Use of subjective information in estimation of aquifer parameters
Authors: Lovell R. E. , Duckstein L. , Kisiel C. C.
Published: February 2008

In the calibration of aquifer models, the desire for an automated adjustment process is sometimes in conflict with the need for subjective intervention during the calibration process. Working from the established concept of modeling for unconfined aquifers with rectangular nodes, this paper describes a method of obtaining subjective information in addition to that customarily used in model calibration. Such information is assembled and quantified at the same time as the usual data are gathered for initial estimation of parameters. This information is then introduced into an automatic adjustment process in such a way that the calibration process can proceed without interruption until the desired level of relative accuracy is reached, or until it is shown that the desired level cannot be reached within the constraints assigned. A decoupling technique that permits (under restricted conditions) simultaneous adjustment of all parameters is also described. A digital computer model of the Tucson basin aquifer is used to illustrate the concepts and demonstrate the adjustment method.
Systems analysis of the Panama Canal water supply
Authors: Lewis David C. , Beard Leo R.
Published: February 2008

An objective function employing the economic evaluation of the simulated operation of the Panama Canal was used to evaluate the existing and potential supplemental water supplies at ever increasing levels of shipping. The simulated operation of the canal was based on the assumption of a repeat of historical runoff to determine the ‘optimal’ operation (to obtain the maximum revenue minus the costs of supplemental water) for existing and deeper channels through Gaillard Cut. The computer model of canal operation and the use of reservoir rule curves to provide operational criteria are presented. The use of simulated runoff to investigate canal operation under other synthetic chronological streamflow traces with the same statistical characteristics as those of the historical sequence are discussed.
Modeling problems and problem avoidance in water resource management
Authors: Hass Jerome E.
Published: February 2008

We first define basic forms of modeling and discuss classes of problems facing the modeler. We then discuss ways of avoiding problems by creating artificial marketplaces to allocate the assimilative capacities of the receiving water more efficiently. Finally, we examine the extent to which other problems could be avoided if the government were to create and sell discharge rights that would then be freely traded in a ‘rights market.’
Streamflow Simulation: 1. A new look at Markovian Models, fractional Gaussian noise, and Crossing Theory
Authors: Rodriguez‐Iturbe Ignacio , Mejia Jose M. , Dawdy David R.
Published: February 2008

A broken line process is presented as a potential hydrologic simulation model. The process is composed of the sum across a series of broken lines. By proper choice of the number of broken lines considered and of their parameters, various statistical characteristics may be modeled. These include an arbitrary monotonic correlation structure and memory. In addition, the second derivative of the correlation function at the origin may be preserved. This preservation of the second derivative is an important property in crossing theory.
Streamflow simulation: 2. The broken line process as a potential model for hydrologic simulation
Authors: Mejia Jose M. , Rodriguez‐Iturbe Ignacio , Dawdy David R.
Published: February 2008

This paper deals with the theory of the broken line process and its applications in the simulation of stochastic sequences.
Long memory monthly streamflow simulation by a broken line model
Authors: Garcia Luis E. , Dawdy David R. , Mejia Jose M.
Published: February 2008

The Chixoy River in northern Guatemala exhibits a long‐term dependence of monthly streamflows. A broken line model is developed to simulate the long‐term dependence for the Chixoy River. The method for the determination of parameters for simulation is computationally easy. In addition, an algorithm is developed for preserving the memory of the historical streamflow record, which is operationally useful because if simulations of future streamflow are to be used for purposes of planning and design, such simulations should preserve a memory of the past, if long‐term persistence is assumed to exist. The broken line model is shown to be a useful operational alternative to an autoregressive model.
Broken line process derived as an approximation to fractional noise
Authors: Mandelbrot Benoit B.
Published: February 2008

The broken line process has been advanced recently as a possible replacement for fractional noise as a model representing long‐run persistence in hydrology and turbulence. It is shown that in fact one can rederive the broken line process as an approximation to fractional noise and that efforts to preserve the value of ρ″(0;) may well be misplaced.
Integration of the agricultural demand function for water and the hydrologic model of the Pecos Basin
Authors: Gisser Micha , Mercado Abraham
Published: February 2008

The result of integrating the agricultural sector with the aquifer of the Pecos basin is given. In particular, steady state solutions to hydrologic and economic equations are given in which imported water is artificially recharged to the aquifer and its cost is added to the cost of pumping. A two‐cell model for the Pecos basin aquifer is developed. One cell is for the confined aquifer, and the other is for the shallow aquifer. The hydrologic solution of the model yields two linear steady state functions that relate the water table in the two cells to other hydrologic variables, such as recharge, discharge, and irrigation. The cost of pumping water is also estimated. The agricultural demand function for irrigation water is empirically estimated by applying the technique of parametric linear programing. The demand function for water is linked to the water table hydrologic equations. Solutions are found for a range of expected prices of imported water.
Stomatal resistance during senescence of hardwood leaves
Authors: Gee G. W. , Federer C. A.
Published: February 2008

Leaf resistance to vapor flow was measured with a diffusion porometer on hardwood trees in central New Hampshire during autumn senescence and was compared with leaf color and chlorophyll content. Daytime diffusion resistance remained at the low values found in summer (1–10 sec/cm) as long as the leaves remained green. Resistances ranged from 5 to > 35 sec/cm when chlorophyll content was below 0.4 mg/g of fresh weight and leaf color was yellow green or yellow. Autumn transpiration evidently continues unabated in green leaves but declines to small values when leaves turn color.
Linear decision rule in reservoir management and design: 3. Direct capacity determination and intraseasonal constraints
Authors: Eastman John , ReVelle Charles
Published: February 2008

A chance‐constrained model for multipurpose reservoir operation is reviewed and extended. The model minimizes required capacity subject to chance constraints for water supply, recreation, and flood control. A linear decision rule is used to make commitments based on existing storage. A study of the structure of this linear programing formulation reveals a direct solution in the special case when as much water as possible is reliably committed, a reasonable case for water supply. The structure of the model requires an adequate degree of continuity. This requirement generally restricts the usefulness of the model to multipurpose reservoirs. Using an execution rule to specify when within a decision period water will be released, we can extend the model to include constraints on storage within a decision period. Increasing the length of a decision period is seen to produce a large increase in reservoir capacity due to the making of commitments for a longer future of uncertain inflows. Numerical examples are provided that demonstrate the increased capacity required in a seasonal model over that required in a monthly model and the effect of using intraseasonal constraints.
Waterway transportation simulation models: Development and application
Authors: Carroll Joseph L. , Bronzini Michael S.
Published: February 2008

A computer simulation model developed for studying the operating characteristics of alternative inland waterway transportation systems is described. The first part of the model (Towgen) processes information concerning commodity flows and waterway fleet characteristics to derive a list of tows that will move on the waterway under study. The second part of the model (Watsim) simulates the movement of these tows through the ports, locks, pools, and channel delay areas comprising the waterway system. Results of applying the model to a 10‐lock subsystem on the Illinois waterway and upper Mississippi River are given.
Functional coefficients in the analysis of groundwater flow
Authors: Pinder George F. , Frind Emil O. , Papadopulos Stavros S.
Published: February 2008

Although hydrologists applying finite element techniques in groundwater flow analyses have generally assumed constant aquifer parameters over each element, variable properties can be handled easily by using isoparametric quadrilateral elements in conjunction with approximating equations generated by using Galerkin's technique. A steady state radial flow problem in which transmissivity varies as a linear function of the radius from the well indicates that the accuracy of the numerical scheme may be improved considerably through the use of functional aquifer coefficients.
Identification of multiple reach channel parameters
Authors: Becker Leonard , Yeh William W‐G.
Published: February 2008

The previously developed influence coefficient algorithm for the solution of the parameter identification problem is extended to multiple reach channel flows, and the stage hydrograph and velocity data and observation station location requirements for an effective determination of the parameters are discussed. The specific application chosen here involves the identification of the individual reach friction parameters, which are not physically measurable and which have to be determined from the mathematical model by the use of concurrent input and output measurements. The influence coefficient algorithm is incorporated with numerical solutions of the unsteady equations of flow through explicit finite difference formulations of these equations. The explicit formulations simplify the computer program but necessitate special precautions to avoid computational instabilities. The stability criteria, which must be observed, are indicated.
A possible explanation for Nordin, McQuivey, and Mejia's Observation of the Hurst Phenomenon in turbulence
Authors: Fischer Hugo B.
Published: February 2008

Nordin et al. [1972] have analyzed a number of records of turbulent velocity fluctuations in several open channels and have concluded that within the range of their observations the rescaled range of the velocity deviation increases faster than the square root of time. This implies that turbulent fluctuations have a longer memory, or correlation time, than the period of the observations. This letter suggests a possible explanation.

When the writer was beginning his Ph.D. dissertation experiments [Fischer, 1966], he made some visual experiments in which a line source of a small quantity of intense blue dye was dropped onto the surface of a uniform flow. The flow was approximately 6 cm deep in a rectangular, smooth‐bottomed channel 110 cm wide. The dye was dropped onto the water surface to form an initially straight line perpendicular to the flow direction. Invariably, the line did not remain straight. Soon after hitting the water surface some of the dye was carried forward of the line in the shape of a series of tongues. Between the tongues some of the dye lagged behind the line and formed a series of tails. Figure 1a is a sketch of the appearance of the line shortly after entering the water. The striking observation was that each time the experiment was repeated the tongues and tails were separated by a distance of approximately twice the depth of flow.
Stochastic reservoir management and system design for irrigation
Authors: Dudley Norman J. , Burt Oscar R.
Published: February 2008

An integrated intraseasonal and interseasonal stochastic dynamic programing model is developed to determine an optimal decision rule with respect to the following three classes of crop irrigation decisions: (1) intertemporal water application rates, (2) whether or not some acreage should be ‘abandoned’ from further irrigations for the remainder of the season, and (3) the optimal acreage to plant for potential irrigation at the beginning of the season. Solutions of the problem are shown to be a basis for optimizing the levels of three design variables, namely, developed irrigation acreage, reservoir capacity, and distribution system capacity. A method is presented for incorporating variance, as well as expected value, of net benefits into the decision criterion for optimal developed acreage. An application is made to a simplified real situation in which optimal acreage to develop is the only design variable. State variable transition probabilities are calculated by a simulation model. A significant trade off was found between expected net benefits and their variability in determination of the optimal developed acreage for irrigation.
Cost‐effectiveness methodologies for data acquisition in water quality management
Authors: Ward Robert C. , Vanderholm Dale H.
Published: February 2008

Current water quality regulatory procedures are established in such a manner that they require sound data as a basis for action. In establishing the regulatory procedures, much emphasis has been placed on the water criteria, whereas little emphasis has been placed on developing the ways and means to provide meaningful data to enforce the criteria. The object of the study is to develop methodologies that permit the rational evaluation and design of data acquisition systems for water quality management. This must necessarily include an evaluation of the cost of a data acquisition system and its effectiveness. The evaluation and design procedure of the water quality data acquisition system is based on two major points. First, the strategy used by the managing agency must be related to a specific type or form of data. Second, the character of the streams to be managed must be carefully delineated. To relate these two points to some measure of system effectiveness, a data acquisition system model is developed. This model relates grab‐sampling frequency to the detection of pollution events. By then determining the cost of various sampling frequencies, cost‐effectiveness relationships can be developed. The procedure is applied to Colorado.
Progressive taxation as a policy for water quality management
Authors: Ferrar Terry A.
Published: February 2008

The recent literature on water resource management has argued for the allocative efficiency associated with effluent charge environmental controls. In this work we demonstrate that the operational characteristics of such techniques tend to render them impotent as standard maintenance measures. We then define a new effluent taxation structure that alleviates this significant operational weakness by incorporating a progressive taxation schedule that is tied to the water quality standards.
Disaggregation processes in stochastic hydrology
Authors: R. Darío Valencia , Schakke John C.
Published: February 2008

The need to preserve both long‐term and short‐term variance and covariance properties of hydrologic processes has led to the development of numerous stochastic models during the past few years; Among these are the models first proposed by Mandelbrot and Wallis for preserving the Hurst phenomenon. All these models use sequential generation schemes, and some require the process to be stationary without seasonal variations. The model presented herein preserves seasonal variations and does not necessarily generate data sequentially, although the autoregressive models of any order are special cases of this model. If an annual series has been generated by this or any other model, this model may be used to generate a parallel series of seasonal events from the given series of annual events. It may further be used to generate monthly, weekly, daily, and hourly events.
Interactive multiobjective programing in water resources: A case study
Authors: Monarchi David E. , Kisiel Chester C. , Duckstein Lucien
Published: February 2008

Multiple‐objective problems are ubiquitous in human affairs and are commonly attacked in a subjective way. Semops, a sequential multiobjective problem solving technique, allows the decision maker to trade off one objective versus another in an interactive manner. Semops cyclically uses a surrogate objective function based on goals and the decision maker's aspirations about achieving these goals. The algorithm, applied to a synthetic case study of regional water quality management, demonstrates that (1) a complex situation can be handled, (2) the individuality of the decision maker's preference structure is preserved, (3) the feasible alternatives do not need to be specified a priori, (4) the concept of a satisfactory solution rather than an optimum solution is more realistic in situations involving conflicting goals.
A numerical and similarity analysis of infiltration into crusted soils
Authors: Ahuja L. R.
Published: February 2008

One‐dimensional, vertical infiltration of water through a crust of constant nonzero hydraulic resistance is theoretically examined in two ways, a numerical solution and a similarity reduction of the problem for early to intermediate times. The soil‐water content at the crust‐soil interface increases with time to approach a predictable final steady water content asymptotically. A greater proportion of the flow takes place at intermediate to low water contents, and without an appreciable effect of gravity, as the crust resistance increases. For the water content at the crust‐soil interface, the cumulative infiltration, and the wet front progress, simple expressions arise from the similarity reduction analysis, which is based on specific functional forms of the soil‐water diffusivity and suction head, and a relatively small initial soil‐water content. For early to intermediate times of flow, the similarity analysis describes adequately the calculated numerical solution flow data for Yolo soil. For intermediate to large times, a Green and Ampt type solution is linked to the similarity expression for cumulative infiltration with fair success.
Cesium 137 in a mountain stream channel
Authors: Hubbard John E. , Striffler W. D.
Published: February 2008

Concentration of the radionuclide 137Cs in water, sediment, and channel vegetation was determined in a Colorado mountain watershed in 1967. No measurable 137Cs was found in stream water. Specific 137Cs activity in sediment decreased exponentially with distance from the headwaters. Its concentration was 124 pc/g at the headwaters, where a snowfield has existed continuously since the atmospheric testing of nuclear weapons, to 4 pc/g 5600 meters downstream. Stream vegetation samples also indicated a similar decrease in specific 137Cs activity with site location downstream.
A stream length study
Authors: Blyth K. , Rodda J. C.
Published: February 2008

The length of flowing channel in a small clay basin in southeast England was observed once per week over a period of 1 year. The main controls of the total length of flowing channel were found to be the effective rainfall during the previous week and the length of stream flowing at the time of the previous week's observation. Variations in the lengths of streams of different orders were studied, first‐order streams being found to vary most.
Use of censored data in the estimation of Gumbel distribution parameters for annual maximum flood series
Authors: Leese Morven N.
Published: February 2008

Maximum likelihood equations for the estimation of Gumbel distribution parameters from censored samples are derived; expressions for their large‐sample standard errors are also given. Censored samples arising in annual maximum flood series are described, and it is shown that a set of historic floodmarks may, under certain assumptions, be combined with recent noncensored data, to form what is essentially a censored sample. Maximum likelihood methods are applied to such a sample, and the resulting estimates are compared with those obtained from the recent data alone. The estimates agree closely, and the use of the extra information contained in the historic floodmarks is shown to lead to a reduction in the large‐sample standard errors of the estimates.
Hydrodynamics of laminar flow over a porous bed
Authors: Lin Wender , Gary Don M. , Norum D. I.
Published: February 2008

Equations defining overland flow over a porous bed under different time‐variable infiltration conditions are presented. Experimental data for nonrainfall events were obtained from a specially constructed laminar model that used horizontal capillary tubes to synthesize the infiltration process. Tests were conducted at different discharges and slopes. The results from these tests were found to be in close agreement with those obtained from numerical solutions of the theoretical hydrodynamic equations.
On Estimators Obtained From a Sample Augmented by Multiple Regression
Authors: Moran M. A.
Published: February 2008

A sample of N observations is taken from a p + 1 variate normal distribution. The first N observations include values on all p + 1 variates, whereas the remaining N‐n observations include values for p of the variates only. This paper reviews the properties of the estimators that use the N complete observations on the p variates to improve estimation of the mean and variance of the variate with only n observations. In particular, the relationship of suggested estimators to maximum likelihood estimators, corrected for bias, is given. The general advantages and limitations of such estimators are discussed.
Soluble Phosphate Output of an Agricultural Watershed in Pennsylvania
Authors: Gburek William J. , Heald Walter R.
Published: February 2008

Soluble phosphate data from the stream draining a 7.7‐km2 Pennsylvania agricultural watershed are reported. Yearly watershed soluble phosphate output and monthly and within‐month phosphate concentration variations are interpreted. The stream approaches constant and low phosphate concentrations of 10‐ppb or less PO4‐P during continuing base flow recession. Concentrations vary seasonally, 10‐ to 15‐ppb PO4‐P commonly occurring in the winter and 20‐ to 30‐ppb occurring in the summer. Implications of the between‐sample variation of phosphate concentrations as related to the partial area hydrologic concept are also discussed.
Earthquake damage costs in the design of water resource systems
Authors: Jacobsen S. E. , Torabi M. , Bansal P. P.
Published: February 2008

A renewal theoretic cost model is developed for the purpose of evaluating expected future damage costs due to earthquakes for a segment of a water distribution system located in a large seismic region. These costs depend upon the intensity that the structure is designed to withstand. A probabilistic model for the occurrences of earthquakes during a planning period in a region with several faults is used to obtain expected future damage costs as a function of design intensity. A numerical example is included to indicate the usefulness of the methodology, and we show how the optimal design intensity for a structure at a given location can easily be computed. The difficulties that arise in network systems problems are discussed.
The estimation of ρ in the first‐order autoregressive model: A Bayesian Approach
Authors: Lenton Roberto L. , Rodriguez‐Iturbe Ignacio , Schaake John C.
Published: February 2008

Three general approaches to derive marginal posterior probability density functions for the autocorrelation coefficient of the first‐order normal autoregressive model are presented, from which Bayes estimators can be obtained for a given loss function. The different approaches are based on varying assumptions about the incidental parameters of the model and are shown numerically to be approximately equivalent with respect to their mean and variance. A comparison is made between the Bayes estimator and some classical estimators on the basis of the risk function and the expected risk. The risk functions are determined by Monte Carlo methods for quadratic, symmetric linear, and various asymmetric linear loss functions. The Bayes estimators are shown to be considerably advantageous, especially when the sample size is small. The Bayes estimators are also shown to be extremely robust under changes of the loss function.
Snow accumulation and snowmelt as influenced by a small clearing in a lodgepole pine forest
Authors: Gary Howard L.
Published: February 2008

Snow accumulation was observed under a thinned lodgepole pine stand about 35 feet tall and 80 years old for two winter seasons before and two seasons after cutting a clearing 1 tree height wide and 5 tree heights long. The clearing was on a gently sloping plateau 9000 feet above msl and was oriented perpendicularly to the prevailing southwest wind. The maximum snowpack water equivalent the first year after clearing averaged 13.1 inches in the upwind forest, 16.2 inches in the clearing, and 12.2 inches in the downwind forest zone. The snow accumulation pattern was similar the second year. The increased snow catch in the clearing was offset by the snow deficit in the downwind forest. The clearing affected the distribution of snow over the area but not the total amount of snow water equivalent. Melt rates in the clearing were about twice those in the interior forest zones. Near the middle of the melt season the clearing as a whole contained 12% less snow water equivalent than the interior forest.
A mixing cell model for longitudinal dispersion in open channels
Authors: Banks Robert B.
Published: February 2008

A steady uniform flow occurs in an open channel that consists, it is imagined, of a series of cells arrayed in a longitudinal direction. At time zero a step function change in concentration is imposed at the origin, and it is assumed that complete mixing then occurs in each of the cells. The main result is that the longitudinal dispersion coefficient is essentially equal to the product of the flow velocity and the cell length. Relating this result to the well‐known form K = a0Du*, a definition is obtained for the length of a dispersion unit.
A solution of the inorganic carbon mass balance equation and its relation to algal growth rates
Authors: Kelly Mahlon G. , Church M. Robbins , Hornberger George M.
Published: February 2008

The mass balance equation describing the dissolved inorganic carbon content of river water is solved for varying conditions of net community productivity, alkalinity, temperature, atmospheric exchange, and accrual of groundwater carbon to give CO2 concentration throughout the day. Without accrual of groundwater the CO2 concentration must lie in the range where it will influence growth rate of some plant species, but groundwater input prevents this situation in most rivers. In lakes, groundwater input and exchange with the aphotic zone may prevent the influence of CO2 on algal growth rates. In waters with little groundwater input or little vertical mixing the CO2 concentration may influence relative growth rates of species and thus the community composition but probably not the total plant biomass produced.
Effects of high‐magnitude floods on channel form: A case study in Maryland Piedmont
Authors: Gupta Avijit , Fox H.
Published: February 2008

Four major floods occurred in the Patuxent River basin in the Maryland piedmont during the summers of 1971–1972. High flows of August 3–4 and September 11–12, 1971, caused by thunderstorms were of 50‐year and over 100‐year recurrence intervals, respectively. On August 27, 1971, a nearby storm brought bank‐full flooding and tropical storm Agnes again produced floods well over the 100‐year level on June 21–22, 1972. Record discharges on the Patuxent and its tributary, the Little Patuxent, were recorded on September 11, 1971, and June 22, 1972, respectively. Among the more striking effects were destruction of floodplain vegetation, widening of stream channels, and clearing of the channels of all but very coarse materials. Low and medium flows succeeding each flood reduced enlarged channel widths by building up bar remnants with fines and forming new bars along channel margins, tending to destroy the evidence of such floods. Channels preserve flood‐originated forms when high‐magnitude floods occur with sufficient regularity.
Reverse flow routing by the implicit method
Authors: Eli R. N. , Wiggert J. M. , Contractor D. N.
Published: February 2008

The concept of ‘reverse’ flow routing in rivers is proposed, in which upstream flow hydrographs are specified from a downstream flow requirement. An example is given of reverse flow routing by the implicit method of solution of the equations of momentum and continuity. Reverse flow routing is further described in the context of the x‐t plane, and then the point is made that solutions were not found in all possible directions of computation in the x‐t plane. Solutions were found only in the directions of increasing time and decreasing distance (upstream).
A data acquisition system for transient porous media experiments in a sector tank
Authors: Orhun Akin , Luthin J. N.
Published: February 2008

A data acquisition system was constructed to measure and record soil water pressures and flow rate of groundwater flow problems under transient conditions.
Multilevel optimization for conjunctive use of groundwater and surface water
Authors: Yu Wanyoung , Haimes Yacov Y.
Published: February 2008

This study aims at developing a general systems analysis approach, other than straight simulation methods, for handling the complex problem of optimal conjunctive use of groundwater and surface water resources. A two‐dimensional asymmetrical grid network model is chosen to represent the aquifer system. A water resource management problem is considered for a hypothetical region that is composed of several adjoining subregions over a common aquifer basin. It is suggested that the regional water authority regulate optimally the intersubregional aquifer boundary conditions and impose a pumping tax on the local water agencies of the subregions. The pumping tax will provide the revenue for the regional authority to recharge the aquifer basin. The solution is implemented by a completely decentralized decision‐making structure of a two‐level hierarchy.
Sources and trends in waste water loadings to the San Francisco Bay Region
Authors: Breslaw Jon A.
Published: February 2008

This study uses data obtained from the U.S. Army Corps of Engineers Permit Program and self‐monitoring data from the regional water quality control board in an analysis of waste discharges to water‐courses in the San Francisco Bay region. The analysis shows that the majority of these discharge loads can be attributed to a few sources. Trend analysis showed that the BOD load has declined in relation to the quantities discharged in the early 1960's. Nutrients, however, have increased at an annual rate of about 4% since the early 1960's.
Evaluating multireservoir operating rules
Authors: Mejía José M. , Egli Paul , Leclerc André
Published: February 2008

Different decision rules for operating a multireservoir system are examined. The system analyzed serves recreation as well as flow augmentation purposes. The operation rules range from the so‐called conventional policy to a policy that uses flow forecasting and mathematical programing for the optimization. Historical data are used to simulate the operation of the system under the different rules, and an assessment of the policies is made on the basis of multiobjective criteria.
CRE: A method for solving probability problems related to hydrologic time series
Authors: Torelli Latino
Published: February 2008

When the probability structure of a time series is known, a number of probability problems related to the series remain to be answered. In the present contribution a method (CRE, event realization counter) for solving such problems is proposed. It consists of approximating the original series with continuous distribution by a suitable series with discrete distribution. For the latter, exact solutions of the problems in consideration can be derived. The validity of the approximation is checked, the algorithms used described, and a few applications of the method shown.
The use of stereo, horizontal, and ground level orifice gages to determine a rainfall‐elevation relationship
Authors: Sevruk Boris
Published: February 2008

In the range of altitude from 1100 to 1850 m above sea level the mean rainfall totals over a 10‐year period from June to September as measured by means of 22 storage gages with horizontal orifices and wind shields generally decreased with increasing elevation in the upper part (6.8 km2) of the prealpine watershed of Baye de Montreux. The substitution of a stereo orifice for the horizontal one on the nine gages located on the slopes open to rain‐bearing winds resulted in a slightly increasing mean rainfall catch with increasing elevation (r=0.430). After 23 ground level stereo gages were set up in the watershed, a visible improvement in the rainfall‐elevation relationship was registered (r=0.710).
Simulation of storm velocity effects on flow from distributed channel networks
Authors: Surkan A. J.
Published: February 2008

Programs have been designed to perform computer simulation experiments on the effects of storms traveling over drainage networks. The system of programs makes it possible to simulate the response of any channel network to storms with boundaries that are numerically specified by line segments. The excess runoff response function of discrete approximations of spatially distributed networks may be simulated for storms with any velocity and initial position. Storms are modeled as polygons surrounding areas of uniform intensity. An average flow velocity for each segment of the network can be specified independently by an input vector of transit times associated with network nodes. The computer time taken for each simulation of storm travel depends on the number of calculations performed in determining which network segments are overlapped by the storm. Results include hydrographs simulated for both actual fixed storms and for moving test storms that travel with specified speeds and directions over a binary tree model of a natural watershed with an assumed constant average internal flow rate.
The shape of the interface in steady flow in a stratified aquifer
Authors: Mualem Y. , Bear J.
Published: February 2008

The present work deals with the shape of the interface in a coastal aquifer in which a thin horizontal semipervious layer is present. Field observations and laboratory experiments have shown that under these conditions a discontinuity in the shape of the interface occurs such that a freshwater region exists under the semipervious layer while immediately above it, saline (or mixed) water is present in the aquifer. The paper presents an approximate solution for the shape of the interface below the semipervious layer and for the extent of the freshwater region above it under steady state conditions. The solution is based on the Dupuit assumption and on a linearization of part of the flow equations. Laboratory experiments on a Hele‐Shaw model have shown a good agreement between the forecasted interface profiles and those actually observed in the model. From the results of the experiments it follows that the separation of the interface into two parts, below and above the semipervious layer, decreases as the length of landward seawater intrusion increases. The proposed solution can readily be applied to the case of a phreatic surface under an artificial recharge basin, when the aquifer is separated into subaquifers by a sequence of semipervious layers.
The National Water Commission Report: A review
Authors: Ingram Helen M. , Roefs Theodore G. , Allee David J.
Published: February 2008

The National Water Commission Report has serious limitations as a professional document judged by analytical criteria including explicit assumptions, conceptual frameworks, and coherent and consistent recommendations. The report is structured by certain value positions rather than analytical concepts. These include rationality, efficiency, equity, faith in dollar measurements, new federalism, and the separation of policy and administration. The report falls short of a blueprint for change of present water policy because it lacks a comprehensive framework and is too discursive over too many unrelated topics.
A programing model for the design of multireservoir flood control systems
Authors: Windsor James S.
Published: February 2008

A methodology is presented that employs mixed integer programing as the optimization tool for the planning and design of multireservoir flood control systems. Temporal and spatial flood variability is accounted for in the analysis by using representative sets of recorded or synthetically derived flood hydrographs for each subarea in the basin. The probable maximum flood is also included as part of the model input data to ensure that floods are controlled even under the most adverse conditions.
Estimating infiltration for erratic rainfall
Authors: Reeves Mark , Miller Edward E.
Published: February 2008

To estimate cheaply the infiltration/runoff of typically unsteady rainfall events for purposes of watershed modeling, a method known as ‘time compression’ has been tested against hysteretic Darcy computations. This method assumes that for a given soil the maximum infiltration rate is simply a function of the cumulative infiltration, regardless of the rainfall versus time history. Hysteretic characteristics from soils measured by Topp (1971) were employed in the Darcian calculations. The appraisal proved generally encouraging for application of this approximation to watershed modeling. The maximum infiltration rate was uniformly underestimated to a moderate degree in the early minutes of a downpour commencing late in an unsteady event.