bluuebunny/crossref_metadata_2025 huggingface dataset:
Gains from joint operation of multiple reservoir systems
Authors: Hirsch Robert M. , Cohon Jared L. , ReVelle Charles S.
Published: February 2008

Synergistic gains are defined as the gains in benefits due to joint operation of a system of reservoirs in excess of the benefits from optimal individual operation. These gains are a result of both the deterministic (regional) and the stochastic diversity of flows into each of the reservoirs. They are captured by the use of flexible reservoir operating rules which base release decisions for a given reservoir on the state of the entire system, not just on the state of that reservoir. One possible operating rule is formulated and is demonstrated to be highly effective in capturing synergistic gains. A hypothetical design problem of sizing three water supply reservoirs in parallel is solved by three methods. The first method assumes that no synergistic gains are achievable. The second and third methods recognize the existence of such gains. The method recommended here incorporates the operating rule into the design process and makes use of the observation that the system yield is a function of system capacity.
Augmenting summer streamflow by use of a silicone antitranspirant
Authors: Belt G. H. , King J. G. , Haupt H. F.
Published: February 2008

A 65‐ac (26.3‐ha) cedar‐hemlock catchment in northern Idaho was sprayed with a 5% aqueous emulsion of silicone oil to reduce transpiration. The antitranspirant, Dow Corning XEF‐4‐3561, was applied by helicopter at the rate of 40 gal./ac (375 1/ha). From June 1 to September 15, 1974, streamflow, soil water, and leaf water potential were monitored on the 65‐ac (26.3‐ha) treated watershed and an adjacent 50‐ac (20.2‐ha) control watershed. By using the paired watershed method with regression equations based on 6 years of pretreatment data, predicted and observed streamflow were obtained for the period June 1 to September 15. Differences between predicted and observed streamflow were compared by using the paired ‘t’ test and found significant at the 97.5% confidence level. During a 63‐day period a 12% increase in streamflow resulted from the antitranspirant application. During this same period, soil water storage was greater on the treated watershed than on the control watershed; however, the difference was not statistically significant. Seasonal leaf water potential in cedar indicated that stress was greater on the control watershed than on the treated watershed. Systematic differences in leaf water potential for hemlock did not occur.
Transient analysis of phreatic aquifers lying between two open channels
Authors: Singh Sita Ram , Jacob C. M.
Published: February 2008

The unsteady state flow of water through an unconfined aquifer can be represented by the Boussinesq equation. The nonlinear term involving the highest derivative in this equation was approximated by a linear term, and the resulting approximate Bossinesq equation was linearized to a Fokker‐Planck equation by the method of functional transformation. Solutions to the problem of groundwater flow through phreatic aquifers lying between (1) constant water level boundaries and (2) variable water level boundaries were obtained from the general solution of the Fokker‐Planck equation for constant and variable rates of recharge and withdrawal. Variable rates of recharge and withdrawal were approximated by periodic step functions which represented two different rates, one each for both rainy and dry seasons. Variable water levels in the open channels were approximated by step functions, and the initial condition was represented by straight line segments. An analytical solution of the approximate Boussinesq equation was compared with the finite difference solution of the original Boussinesq equation. The difference between the two solutions was almost negligible, and therefore the applicability of the analytical solutions to groundwater resource management was established. The effect of variable water level boundaries on groundwater dynamics was studied by performing a sample calculation.
A multicriteria analysis for water resource and land use development
Authors: Nijkamp P. , Vos J. B.
Published: February 2008

A new variant of the concordance analysis is developed and discussed in this paper. The concordance procedure in general is a multicriteria evaluation method for alternative projects. It is based on a pairwise comparison of (weighted) project outcomes, and it can be used both as an elimination method for less desirable projects and as a selection method of good projects. The new variant introduced in this paper is based on the idea of satisficing (or norm) project outcomes, which may serve as a frame of reference for the evaluation techniques. Such satisficing outcomes are also important in attacking the dimensional problems of a multicriteria analysis. The new concordance variant is illustrated by means of an empirical application to the selection of the most desirable plan out of a series of alternatives for the development of the Markerwaard area in the Netherlands. It is concluded that the concordance analysis is a useful tool in taking account of intangibles in water resource and land use design.
A multidimensional model for the synthesis of processes of areal rainfall averages
Authors: Lenton Roberto L. , Rodríguez‐Iturbe Ignacio
Published: February 2008

The synthesis of processes of areal rainfall is treated by proposing an extension to a previous model of point rainfall synthesis. The proposed model generates sample functions of a random process of areal rainfall that preserves its areal covariance structure but uses as input not the areal covariance itself but the point covariance of the corresponding point rainfall process. A numerical application of the model is presented, and the practical implications of preserving areal covariance rather than point covariance when rainfall models are used in conjunction with distributed rainfall‐runoff models are discussed.
Distributed numerical model for estimating runoff and sediment discharge of ungaged rivers 2. Model development
Authors: Solomon S. I. , Gupta S. K.
Published: February 2008

This is the second of a series of three papers describing the methodology of development of a distributed model for estimating runoff and sediment discharge of ungaged rivers. This paper presents the design of the model which permits its application to watersheds of any size and the obtaining of runoff and sediment time series at any point of the river basin which is being modeled. The model requires inputs which are usually available for most areas and/or can easily be synthesized from secondary sources or by transposition. The model was designed with the aim of keeping the number of model parameters at a minimum. It permits the simulation of the nonlinear response of the watershed elements to the meteorological input. The model calibration and validation were carried out by using data available in a river basin in southern Ontario. A more detailed analysis of the calibration‐validation results is presented in the third paper of the series.
Bayes design of a reservoir under random sediment yield
Authors: Duckstein Lucien , Szidarovszky Ferenc , Yakowitz Sidney
Published: February 2008

The design of a reservoir subject to long‐range sediment accumulation stemming from the sum of a random number of random sedimentation events is investigated. The event‐based simulation method, which is applied to a case study in southern Arizona, involves generating synthetic sequences of Poisson inputs into the modified universal soil loss equation. The stochastic inputs result from a fitted bivariate distribution of runoff‐producing precipitation events (representing the amount and duration of such precipitation) and an independent fitted exponential distribution of interarrival time between events. The simulated sequences of sediment yield events thus obtained are used to calculate accumulated sediment yield and cost of a given design for each sequence. The optimum design and corresponding Bayes risk are evaluated in four cases: (1) under natural uncertainty, (2) under natural uncertainty and uncertainty in the bivariate rainfall distribution parameters, (3) under natural uncertainty and uncertainty in the Poisson counting distribution parameter, and (4) under all three types of uncertainty. The effect of rainfall record length is ascertained by further computer experiments, but only a partial Bayesian analysis is provided because of the complexity created by a three‐dimensional parameter uncertainty. The optimum reservoir capacity and corresponding Bayes risk are shown to increase substantially (up to 20 and 90%, respectively) as more uncertainties are incorporated into the model.
Classification of the hydrologic settings of lakes in the north central United States
Authors: Winter Thomas C.
Published: February 2008

The hydrologic settings of 150 lakes in the north central United States were investigated by principal component analysis as a first attempt to develop a general classification of the hydrologic settings of lakes. Precipitation‐evaporation balance and the water quality variables have high loadings on the first principal component. Highest loadings on component 2 are for streamflow in and out of the lakes. Components 3 and 4 are characterized by geologic and groundwater flow variables. The drainage basin area/lake area ratio, the overland runoff variable, has the highest loading on component 5. The stability of the principal components was tested by randomly splitting the data and comparing a principal component analysis of each subsample. This showed the first two principal components to be the most stable. The components described by the groundwater variables are less stable, but there is justification for using them with caution. Of the variables examined in this study the distribution of dissolved solids of groundwater is most closely related to the distribution of lake types as determined by other limnological typologies in the north central United States. The study indicates that the following are the most important variables to be considered in classifying the hydrologic settings of lakes: dissolved solids concentration of groundwater, precipitation‐evaporation balance, streamflow inlet and outlet, the ratio of drainage basin area to lake area, and lake depth. Of the groundwater variables, local relief and regional slope are more important than is regional position. Texture of the drift and bedrock, which is related to hydraulic conductivity of the rocks, is very important.
Value of information in reservoir optimization
Authors: Klemeš V.
Published: February 2008

Numerical experiments with operation policy optimization for a reservoir fed with a random log normal input demonstrated a negligible sensitivity of results to the assumed form of input distribution, a near optimality of the policy ‘draft equals input mean’ for any reservoir size and any size of input sample used for the policy development, and a similarity between the effects of hydrologic and economic uncertainties. In particular, it was shown that the so‐called standard policy, ‘draft equals target,’ arises from any optimal policy as either hydrologic or economic uncertainties grow beyond limits. While there was a clear hierarchy of optimal policies governed by the amount of information underlying the optimization if operation results were assessed vis‐à‐vis expected values and the true imput population, the hierarchy was highly distorted when it was judged from the performance of individual policies on a 10‐year sample from the true input population, representing an actual future operation period. It was also found that the degree of optimality of a given policy did not depend on the degree to which the underlying input model and its parameters agreed with the true input population, but rather on the similarity of the features of the ‘historic’ sample underlying a given policy and the ‘future’ 10‐year sample on which the policy performance was tested.
The small sample expectation of population and adjusted ranges
Authors: Şen Zekâi
Published: February 2008

The general form of small sample expectations for population and adjusted ranges is derived by employing a methodology based on the Brownian motion. An application of the methodology to any normal and stationary process used in hydrology has been performed. Moreover, the asymptotic ideal reservoir sizes for dependent processes have been derived.
Parameter estimation of the Green and Ampt Infiltration Equation
Authors: Brakensiek D. L. , Onstad C. A.
Published: February 2008

Infiltrometer data are utilized to test a fitting procedure for the Green and Ampt infiltration equation parameters. The spatial variation of the estimated parameters is averaged to give lumped parameter values for watershed modeling. An appropriate scale for parameter averaging is discussed, which transforms parameter values to normal deviates. A sensitivity analysis for the equation parameters is performed for both infiltration estimates and runoff hydrograph volume and peak rates. The capillary pressure parameter shows least sensitivity; however, variation in the fillable porosity and effective conductivity parameters has a major influence on infiltration and runoff amounts and rates.
A stochastic model of the operation of a stream‐aquifer system
Authors: Flores W. E. L. , Gutjahr A. L. , Gelhar L. W.
Published: February 2008

A simple lumped parameter stochastic model for optimal water management in a stream‐connected aquifer system is examined. The physical system is represented by a linear reservoir model, and a conditional probability approach is used to estimate the effect of parameter variability. A drawdown correction is used to incorporate the local drawdown of the wells and is a crucial part of the model. A management analysis is carried out by using a linear decision rule to minimize the expected value of the discounted costs with appropriate chance constraints, and the resulting nonlinear optimization problem is solved iteratively by using a standard linear programing package. In order to evaluate the limitations of the lumped parameter model in a management context, the results of the management technique are compared with results from Maddock (1974) who used a distributed representation of the aquifer. The conclusions of this analysis indicate that stochastic effects are not very important in arriving at an operating policy but are important in determining the expected cost.
Study of the relative efficiency of finite difference and Galerkin techniques for modeling soil‐water transfer
Authors: Hayhoe H. N.
Published: February 2008

Horizontal infiltration of water into a dry soil is used to study the efficiency of finite difference and Galerkin procedures in accurately locating the steep wetting front. The location of the wetting front is determined by a quasi‐analytic solution to Richards' equation. The Galerkin technique is evaluated by using linear, Hermite cubic, and Lagrange quintic elements. These schemes are compared with the performances of the Crank‐Nicolson central difference method where a standard and a modified averaging procedure for soil‐water diffusivity on grid subintervals is utilized. The comparisons are made on the basis of error as a function of spatial grid refinement and the relative efficiency in achieving a practical level of accuracy. The results lead to the conclusion that the Galerkin scheme wih linear elements or the finite differencing scheme with the modified averaging procedure is preferable to the other techniques.
The economic value of the Panama Canal
Authors: Gibbs Stephen R.
Published: February 2008

The net present economic value of the Panama Canal, based on an alternative cost measure of willingness to pay for services, is estimated. In order to obtain the estimate the likely shift in marine transportation patterns, should the canal become unavailable, is described. The net present economic value of the canal to the world is estimated to be of the order of $6 billion, and the value to the United States is approximately $1.6 billion. Values in this range may well be judged by the Congress and President to be less significant than potential effects in other important objective dimensions stemming from a new Panama Canal treaty.
Use of bounding wells to counteract the effects of preexisting groundwater movement
Authors: Whitehead W. R. , Langhetee E. J.
Published: February 2008

The deleterious effects of preexisting groundwater movement on the cyclic storage of freshwater in salaquifers can be negated by placing bounding wells around these proposed storage areas and operating them at predetermined rates. Some of these wells would produce water; others would be used to inject water. The computational procedure for determining the well rates produces a balanced system (sum of production rates equals sum of injection rates); hence the environmental impact of a bounding well system will be minimal. In many field applications as few as six bounding wells will be sufficient to counteract the effects of preexisting groundwater movement.

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Theory of flow in unconfined aquifers by integrodifferential equations
Authors: Herrera Ismael , Minzoni Antonmaria , Flores Emigdio Z.
Published: February 2008

It is shown that when the diffusion of the deviation of the drawdown from its average value can be neglected, the unsteady flow in unconfined aquifers is governed by an Integrodifferential equation. For incompressible flow this equation reduces to Boulton's delayed yield equation with ε = 3. When the flow is compressible, the kernel can be approximated by Boulton's delayed factor in a range of times whose lower limit approaches zero with the compressibility.
Hydrologic impact of grazing on infiltration: A critical review
Authors: Gifford Gerald F. , Hawkins Richard H.
Published: February 2008

The hydrologic importance of grazing is receiving increased attention on rangelands in the United States. The literature on this topic is fragmented. This paper explores the available literature for information useful in understanding the hydrologic impacts of grazing intensity as related primarily to infiltration and runoff. Generally, data relative to range condition are not adequate for evaluating hydrologic impacts. Data relating grazing intensity to infiltration rates are available, yet distinct limitations are evident. These limitations are discussed in terms of identifying future research needs. The greatest need appears to be a detailed definition of the long‐term effects of grazing (by year and season) on infiltration rates as a function of site, range condition, and grazing intensity. Once obtained, infiltration rates must be coupled with an appropriate method for generating runoff volumes, storm hydrographs, and long‐term water yields.
Moisture profiles during steady vertical flows in swelling soils
Authors: Giráldez J. V. , Sposito Garrison
Published: February 2008

Practical working equations for describing numerically soil moisture profiles in homogeneous swelling soils during steady vertical flows were developed. These equations were solved on a computer with soil water and swelling curve data appropriate to Rideau clay loam, which was taken as a typical example of a swelling soil. Unsaturated swelling soils were shown to exhibit either xeric or hydric profiles for downward flows, whereas for upward flows they exhibit only a xeric profile, just as rigid soils do. On the other hand, saturated swelling soils were shown to have hydric profiles in the downward flow situation and either hydric or xeric profiles during upward flows. The overburden or ‘envelope pressure’ potential was shown to exert a great influence, in almost all circumstances, in reducing the maximum evaporative flow from a shallow water table in a swelling soil as compared to the equivalent nonswelling case.
Evaluating the environmental consequences of groundwater contamination: 1. An overview of contaminant arrival distributions as general evaluation requirements
Authors: Nelson R. William
Published: February 2008

The environmental consequences of subsurface contamination problems can be evaluated completely and effectively by fulfilling the following five requirements: (1) determining each present or future outflow boundary of contaminated groundwater, (2) providing the location/arrival time distributions, (3) providing the location/outflow quantity distributions, (4) providing these distributions for each individual chemical or biological constituent of environmental importance, and (5) using the arrival distributions to determine the quantity and concentration of each contaminant that will interface with the environment as time passes. The arrival distributions on which these requirements are based provide a reference point for communication among scientists and public decision makers by enabling complicated scientific analyses to be presented as simple summary relationships.
Identification and separation of major base flow components from a stream hydrograph
Authors: Birtles A. B.
Published: February 2008

A method is given for the separation of the major base flow components in a river hydrograph using simple models. Simplifying assumptions are made which enable the models to be used without rainfall data if necessary, suitable information being deduced from the river hydrograph. Lumped parameter hydrological models are used for the calculations of actual transpiration, soil moisture deficit, and aquifer recharge rates. The base flow components are each identified in terms of a recession time constant, an initial value, and an infiltration contribution. The techniques are applied to the River Severn, for which flow components are separated and then used to illustrate applications to a study of the behavior of conservative water quality determinants.
The dependence of the parameters in the Green and Ampt Infiltration Equation on the initial water content in draining and wetting states
Authors: Aggelides S. , Youngs E. G.
Published: February 2008

The parameters in the Green and Ampt infiltration equation were determined from infiltration experiments in a sand column at various uniform initial water contents in both draining and wetting states and were compared with various estimates obtained from the soil water properties measured on the same experimental column. The estimates of the soil water pressure head at the wetting front were generally more negative than the values obtained from the directly measured parameters. It was found that the calculated cumulative infiltration as a function of time was fitted better by using Bouwer's crude ‘water entry’ estimate than values deduced by approximating Richards' flow equation.
Long‐term patterns of sediment production following road construction and logging in the Oregon Coast Range
Authors: Beschta Robert L.
Published: February 2008

Suspended sediment production after road construction, logging, and slash disposal was significantly increased (P = 0.95) on two watersheds in Oregon's Coast Range. A 25% patch‐cut watershed showed increases during 3 of 8 posttreatment years. These increases were caused primarily by mass soil erosion from roads. Monthly sediment concentrations before the occurrence of the annual peak flow were increased more than those following the annual peak. Surface erosion from a severe slash burn was the primary cause of increased sediment yields for 5 posttreatment years on a watershed that was 82% clear‐cut. Monthly sediment concentrations were generally increased throughout the winter runoff period on this watershed. The flushing of suspended sediment in Oregon Coast Range watersheds is apparent from seasonal changes of suspended sediment rating curves.
The impact of broadly applied effluent phosphorus standards on eutrophication control
Authors: Gakstatter Jack H. , Bartsch A. F. , Callahan Clarence A.
Published: February 2008

The potential trophic benefits to lakes and reservoirs of a 1‐mg/l and zero‐discharge; total phosphorus effluent standard for municipal sewage treatment plants were examined by using two phosphorus mass balance models. The analysis included 255 lakes and reservoirs receiving municipal sewage treatment plant effluents and located in the eastern half of the United States. These water bodies, their significant tributaries, and contributing effluents were sampled during the U.S. Environmental Protection Agency's National Eutrophication Survey. Improvement in trophic condition is defined as a predicted decrease of at least 25% in external phosphorus supply, which would cause the predicted in‐lake total phosphorus concentration to (1) decrease from greater to less than 40 μg/1 but remain above 20 μg/1, (2) decrease from above 20 μg/1 to less than 20 μg/1, or (3) decrease from less than 20 μg/1 to a lower concentration. The definition stated above being used, the two models indicate that 18–22% of the water bodies would benefit from a 1‐mg/l effluent standard. If the requirement were zero phosphorus, 28% of the water bodies would benefit.
Dissolved iron—An indicator of the groundwater component of small streams draining a granite terrain, South Carolina
Authors: Kheoruenromne I. , Gardner L. R.
Published: February 2008

The flow and dissolved iron content of two small streams draining a woodland basin and a recently deforested basin on a granite pluton in Kershaw County, South Carolina, were measured biweekly from September 1974 through August 1975. During spring and summer the flow of the stream draining the deforested basin was reduced relative to that of the woodland basin because of the higher transpiration associated with rapid biomass accumulation by the newly established vegetation in the deforested basin. The observed relative reduction in flow was accompanied by a relative increase in iron concentration in the flow from the deforested basin. Analysis of the data also indicates that the rate of export of dissolved iron from both basins is independent of stream discharge. These observations suggest that the dissolved iron content of these streams is controlled by the dilution of iron‐rich groundwater by essentially iron‐free surface runoff and shallow interflow. A simple mixing model based on this hypothesis has been developed and found to fit the data.
Derivation of the probability density function of certain biased samples of coarse riverbed material
Authors: Potter Kenneth W.
Published: February 2008

Several commonly used procedures for sampling coarse riverbed material result in samples that are biased toward the larger particles. Kellerhals and Bray (1971) recommend correcting the bias by scaling the sample frequency of each frequency interval by the inverse of the appropriate power of the mean grain size of the interval. If, however, grain size is assumed to be log normally distributed, it is possible to determine the distribution of the biased sample. This provides explicit bias factors for the sample moments.
Chemical characteristics of small streams near Haney in southwestern British Columbia
Authors: Feller M. C. , Kimmins J. P.
Published: February 2008

The hydrological, thermal, and chemical characteristics of two small streams flowing through relatively undisturbed, low‐elevation mountain watersheds in southwestern British Columbia were investigated. All observations and chemical analyses of ecosystems were consistent with the hypothesis that stormflow originated mainly from flow of water through soil macrochannels to groundwater and thence to streams. Water budgets indicated unmeasured groundwater losses. The streams exhibited annual chemical cycles for most parameters, with maximum values in late summer and early autumn and minimum values in winter and early spring. Nitrate concentrations displayed no consistent seasonal variation, whereas potassium and sulphate concentrations were relatively uniform throughout the year. Most chemical parameters decreased with increasing discharge, whereas dissolved oxygen concentrations increased. Potassium concentrations exhibited some increases and some decreases, and chloride, nitrate, and sulphate concentrations were generally not significantly related to discharge. Concentration‐discharge relationships were used to infer the origin of stormflow water. Differences in the chemistry of the two very similar streams have important ramifications for the design of watershed nutrient studies. Nutrient budgets were very similar to those of other watersheds in humid temperate regions, with net losses of calcium, sodium, magnesium, potassium, chloride, and sulphur. Nitrogen and phosphorus exports in dissolved or particulate organic form were not measured. Based on dissolved inorganic measurements, nitrogen was accumulated, while any gains or losses of phosphorus were extremely small.
Groundwater contour mapping in Venice by stochastic interpolators: 2. Results
Authors: Volpi Giampiero , Gambolati Giuseppe , Carbognin Laura , Gatto Paolo , Mozzi Giuseppe
Published: February 2008

Reliable and flexible tools are required to keep under control the subsurface flow field of the Venetian lagoon and the related land subsidence. One such tool is given by the stochastic interpolator developed in paper 1 (Gambolati and Volpi, 1979) and used to map the 1973 and 1977 piezometry of three major Venetian aquifers. A fairly small number of test holes unevenly scattered across the mainland, Venice, and the littorals provide the input data. The output is the reconstructed hydraulic head together with an assessment of its reliability. The 1973 results show the existence of a pronounced cone of depression centered upon the industrial area of Porto Marghera, which turns out to be by far the major pumping site in the whole area. Local withdrawals produce a minor cone in Venice, but they do not account for the overall head decline recorded there. The 1977 contour maps show a substantial recovery of the flow field in the upper 250 m of the groundwater basin, thus providing documentary evidence for the recently observed rebound of the land surface (Carbognin et al., 1976). Significant residual withdrawals still occur in the lowest unit (∼280 m) of the aquifer system.
Urban storm water management: Distribution of flood volumes
Authors: Chan Siu‐On , Bras Rafael L.
Published: February 2008

The frequency distribution of the volume of water above a given threshold discharge is developed. This is done using basic and accessible information like the joint probability density function of rainfall intensity and duration together with expressions, to be derived, relating the volume of interest to rainfall intensity and duration. The resulting distribution function is in a closed analytical form containing only a few climatological and physical parameters of a catchment. This distribution function will be of great value in the design of storage devices, flood control systems, and storm water treatment facilities in urban areas.
Junction losses in open channel flows
Authors: Lin J. D. , Soong H. K.
Published: February 2008

The energy balance of spatially varied flows at the junction of a rectangular open channel and a side channel is investigated by a one‐dimensional flow analysis of experimental data obtained from a laboratory channel system. By means of a large control volume enclosing the neighborhood of the junction and having the control surface located at the cross sections where the flow is unidirectional, the energy loss can be evaluated. The energy loss is then divided into two components: the boundary friction loss and the turbulent mixing loss. The turbulent mixing loss is found to be of the same order of magnitude as the boundary friction loss evaluated by Manning's formula. The loss coefficient is derived as a function of the ratio of lateral to total flow rate. An energy transfer process from the main channel flow to the lateral inflow or vice versa, which is implicit in the one‐dimensional flow analysis, can be analyzed by means of the turbulent mixing loss coefficients. The result may be applied to the calculation of energy losses in the junction or in spatially varied flows with lateral inflow in an open channel flow analysis.
Effect of surface meltwater accumulation on the dissipation of lake ice
Authors: Wake Akio , Rumer Ralph R.
Published: February 2008

The rate of ice melt with and without water accumulation on the ice surface has been computed based on the interfacial heat exchange processes, the thermal diffusion of heat through the accumulated water, and the internal absorption of solar radiation. Although the accumulated water does increase the net absorbed solar radiation due to reduced albedo, the resulting air‐water interface temperature is found to be considerably greater than 0°C, thereby decreasing the net long‐wave, sensible, and evaporative heat inputs. The findings indicate that the overall effect of accumulated water on ice melt may not be quite as large as expected from albedo differences alone.
A stochastic kinematic study of subsynoptic space‐time rainfall
Authors: Gupta Vijay K. , Waymire Edward C.
Published: February 2008

A kinematic stochastic approach to quantify the ground rainfall intensity field due to the passage of a large mesoscale area (LMSA) is presented. The theoretical developments are based on four postulates on the components of an LMSA which incorporate the spatial clustering that the rainfall cells have been observed to exhibit. These postulates lead to a representation of the rainfall field as a stochastic integral. An analysis of the structure of this integral reveals two auxiliary stochastic fields embedded within it. Not only do each of these admit an independent physical interpretation, but their analysis is a precursor to the analysis of the space‐time rainfall field. Some results on the space‐time dependence structure of the auxiliary fields are presented. As an application of these results, expressions are derived for the mean, variance, and the one‐dimensional characteristic function of rainfall intensity. A part of the mathematical construct also provides algorithms which can be used for simulating space‐time rainfall.
Irrigation planning: 2. Water allocation for leaching and irrigation purposes
Authors: Matanga George B. , Mariño Miguel A.
Published: February 2008

For a finite or infinite planning horizon, an interseasonal model is employed to determine an irrigation policy in terms of leaching and seasonal irrigation depths. The interseasonal model employs stochastic dynamic programming and simulation to maximize gross margin over the planning horizon. Solutions to the model are obtained by value iteration and policy iteration methods for a finite and infinite planning horizons, respectively, with researched crop characteristics and measured climatic parameters from Davis, California. Salinity in the root zone of plants is defined as the state variable. A stage is a year commencing at the end of the rainy season. Seasonal rainfall is treated as a stochastic variable. The information provided by the interseasonal model is used in an area‐allocation model that allocates acreage available for planting among the crops for unlimited and limited water supplies.
Unsteady flow in confined aquifers: A comparison of two boundary integral methods
Authors: Liggett James A. , Liu Philip L.‐F.
Published: February 2008

The boundary integral equation method )BIEM( is used for the solution of unsteady flow in confined aquifers. Such flows are described by a diffusion equation. Two approaches are presented. The first method removes the time derivatives with a Laplace transform first and solves an associated equation with the BIEM for several values of the transform parameter. A numerical transform inversion is then used to express the results in physical terms. The second method solves the differential equation directly with the BIEM. Both of these techniques are compared to the exact solutions of two simple problems. The Laplace transform method is found to be superior for general use, although the direct method is simpler and requires less judgment on the part of the analyst.
Real‐time predictor versus synthetic hydrology for sequential reservoir management
Authors: Ambrosino G. , Fronza G. , Guariso G.
Published: February 2008

The aim of the paper is to describe a sequential procedure for reservoir management and to compare it with an existing method, the alternate stochastic optimization (ASO). Following the ASO approach, at each time step the decision on the release is based upon present storage, present and future target releases, and a number of ‘possible’ future inflows given by synthetic generation. In the approach described here the decision is also based on present storage and present and future targets, but the hydrological input is represented by the ‘most likely’ future inflow series, namely, by that inflow series forecast by a real time predictor (in the sense of Box and Jenkins). The management performance of the two methods is substantially the same, but the present procedure allows a very conspicuous computational saving. As a matter of fact, the optimization model (a dynamic program which gives the best decision) is run only once at each time step while it is run 20 or 30 times (depending upon the number of synthetic series used) in the ASO approach.
Boundary integral equation solution to axisymmetric potential flows: 1. Basic formulation
Authors: Lennon Gerard P. , Liu Philip L.‐F. , Liggett James A.
Published: February 2008

In this paper the two‐dimensional boundary integral equation method (BIEM) is extended to problems of axisymmetric flow governed by Laplace's equation. An ‘axisymmetric’ Green's function is defined which leads to a calculation procedure that parallels the two‐dimensional theory. The result is a numerical method which is efficient and accurate for a variety of axisymmetric potential flow problems.
The use of naturally occurring helium to estimate groundwater velocities for studies of geologic storage of radioactive waste
Authors: Marine I. W.
Published: February 2008

Most Hydrogeologic tests to determine suitable geologic sites for disposal of radioactive waste are of short duration when compared to the time span required in the assessment of the safety of the facility. Geochemical studies of fluid and rock offer an opportunity to examine natural processes that have been going on for a period of time comparable to that required for safe retention of radioactive waste. In a study assessing the potential for storing radioactive waste in metamorphic rock at the Savannah River Plant near Aiken, South Carolina, the rate of water movement was determined to be about 0.06 m/yr by analyzing gas dissolved in the water. The gas contained up to 6% helium, which originated from the radioactive decay of natural uranium and thorium in the crystalline rock. The residence time of the water in the rock was calculated to be 840,000 years from the quantity of uranium and thorium in the rock, its rate of radioactive decay, and the quantity of helium dissolved in the water. From this residence time and a flow path of 51 km the average velocity of water through the rock was estimated. This water velocity, which is an average over a broad region (51 km) and a long time period (840,000 years), is more applicable to the assessment of a geologic site for storage of radioactive waste than are velocities estimated from packer tests, pumping tests, or artificial tracer tests, all of which require extensive time and space extrapolations.
On the generalized kinematic routing method
Authors: Beven Keith
Published: February 2008

Field measurements suggest that the relationship between velocity and discharge in steep rough upland channels may be nonlinear at low‐flow stages but approximately linear at high‐flow stages. This paper describes a generalized kinematic channel network routing model which can allow a flow relationship that describes both high‐ and low‐flow characteristics. The model is applied to the channel network of the Institute of Hydrology's River Severn experimental catchment and, for this specific application, proves to be equivalent to a linear model based on a constant kinematic flow velocity. A strategy for choosing and applying a flow routing model for use in small catchments is suggested.
Residential response to urban drought in central California
Authors: Bruvold William H.
Published: February 2008

One hundred residential consumers were interviewed in each of nine selected San Francisco Bay area water districts during the summer of 1977. Results showed that the water conservation and rationing programs mounted by these water districts were generally judged quite fair and effective by consumers. Fairness concerns focused upon allotments based upon people, and effectiveness concerns centered upon clarity and communication of the conservation plan. Data on water use showed the rationing programs to be very effective. A belief that the drought was a harbinger of the need for long‐term residential water conservation was most highly related to actual consumption. A majority of residents favored local rather than regional water conservation programs.
Estimating the effect of water quality improvement on public swimming
Authors: Moore John L. , Perin Dan E. , Maiden Ben G.
Published: February 2008

Water quality is an important factor in determining the attractiveness and usability of swimming areas. In order to estimate the gains in outdoor swimming that may result from water quality improvement, a 38‐state survey of present water‐quality‐related losses in usable beach capacity was conducted. Estimates of potential recreation gains were derived using capacity data in conjunction with a recreation simulation model. The model uses previously estimated recreation participation equations to estimate regional trip generation for outdoor swimming under alternate supply conditions. A probabilistic gravity model is employed to simulate the distribution of recreational activity under various increases in usable beach capacity. Extrapolation from three case studies suggests that an estimated 3.4–7.4% increase in present usable capacity could result in a 1.2–2.7% annual increase in swimming activity days, given the present rate of participation on a national basis. Results of the study also indicate that the increase in usable capacity could produce a 6–25% relocation of present swimming activity to improved beaches.
A rainfall‐runoff analysis of the geomorphologic IUH
Authors: Valdés Juan B. , Fiallo Yolanda , Rodríguez‐Iturbe Ignacio
Published: February 2008

The instantaneous unit hydrograph (IUH) derived from the geomorphologic characteristics of a basin and a timing component, the velocity of the discharge, was presented by Rodríguez‐Iturbe and Valdés (1979). To analyze this geomorphologic IUH in real world basins, a study was carried out on several basins in Venezuela and Puerto Rico. The gemorphologic IUH for each basin was compared with the IUH's derived from the discharge hydrograph produced by a physically based rainfall‐runoff model of the same basins. The effects that the nonlinearities of the rainfall‐runoff model have on the derivation of the IUH are analyzed, and further, controlled experiments are carried out in which the IUH is derived under constant velocity conditions. The geomorphologic IUH's and the ones obtained in the experiments are remarkably similar in all the basins analyzed.
Characterization of the water quality in the Saint Lawrence River: Determination of homogeneous zones by correspondence analysis
Authors: Lachance Marius , Bobee Bernard , Gouin Denyse
Published: February 2008

The application of correspondence analysis to data for turbidity, inorganic nitrogen, and inorganic phosphorus gathered at 112 stations located in the Cornwall‐Quebec reach of the Saint Lawrence River allows the behavior of these three parameters to be detailed. A cluster analysis applied to the results of correspondence analysis leads to the definition of homogeneous zones which are characterized by values of the three parameters considered. The results obtained enter into the design processes of quality network for the Saint Lawrence River by allowing for the elimination of a certain number of stations.
Synthetic hydrology and water supply reliability
Authors: Hirsch Robert M.
Published: February 2008

Synthetic hydrology is a tool that may be used in evaluating the consequences of water supply management decisions. Given that there are many proposed generating methods for synthetic hydrology, it is necessary to evaluate the performance of various synthetic streamflow generators (SSG's). Six different single‐site, monthly generators are considered here. The comparison demonstrates that preservation of statistical moments (mean, standard deviation, and lag correlation coefficients) may be a misleading criterion for judging the ability of an SSG to provide plausible estimates of water supply system performance. It is shown that it is operationally superior to base the specification of marginal distributions of monthly streamflows on transformed values of historical streamflow data rather than on the data itself. Two transformations are considered, the log transform and a newly developed normalizing transform. A new type of autoregressive‐moving average model is shown to be operationally superior to an autoregressive model.
The linear reservoir with Markovian inflows
Authors: Anis A. A. , Lloyd E. H. , Saleem S. D.
Published: February 2008

The purpose of the work reported here is to derive the outflow distribution from a linear reservoir fed by a discrete‐time gamma‐distributed Markovian inflow. A satisfactory continuous time solution is available for the linear reservoir when the inflow distribution has independent increments. For the case of nonindependent increments discussed in the paper the treatment is in terms of a gamma‐distributed Markov chain inflow process in discrete time, for which the Laplace transform of the outflow rate distribution is derived. This is inverted, numerically, for a set of typical parameter values.
A note on error analysis for a phosphorus retention model
Authors: Reckhow Kenneth H. , Chapra Steven C.
Published: February 2008

A statistical technique proposed for the estimation of the uncertainty in the prediction of phosphorus concentration in lakes using the Dillon‐Rigler‐Kirchner model can increase the practical value of this and similar models. The usefulness of this technique can be seen in its application to Lake Charlevoix, Michigan. But there are limitations on the use of this procedure, such as those that relate to model and data uncertainty.
Statistical considerations in network design
Authors: Switzer Paul
Published: February 2008

Following some general remarks on the importance and unimportance of optimization in spatial network design, we take up, in modest detail, how one might exploit spatial autocorrelations and covariateinformation. We point out that spatial autocorrelations themselves require care in their estimation andthen proceed with two illustrations to show how probabilistic error calculations are made for mappingproblems using network station data. One illustration uses a quantitative mapping variable, and the otheruses a qualitative mapping variable.
The worth of hydrologic data
Authors: Dawdy David R.
Published: February 2008

Optimal design of data networks requires a measure of the worth of data. Worth is use specific and difficult to measure. Surrogates to worth, usually some measure of accuracy, have been developed. These surrogates and attempts to translate them to economic measures are discussed. Advances toward realism make solutions more difficult. Simplicity of solution and ease of understanding are required if methods developed are to have any impact on decision makers.