bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of characteristic values for physical and chemical lake sediment parameters
Authors: Håkanson Lars
Published: February 2008

The aim of this work is to discuss how characteristic values can be determined for physical and chemical sediment parameters in lakes. It is shown that various physical sediment parameters, e.g., water content, bulk density, organic content, grain size, degree of compaction, and sediment depth, may be related to each other and especially to the water content of the sediments, which may be considered as a key parameter in this context. It is demonstrated that the areal distribution of these physical parameters may be described by the following general formula: Ph0–1 = PhK − KL, [(100 − Dp)/(Dp + KL Kph)] where Ph0–1 is the given physical sediment parameter from the 0 –1 cm, PhK is the characteristic content of the parameter in the given lake/basin, KL is an empirical lake constant, Kph is a parameter constant, and Dp is the relative water depth (Dp = 100% for the maximum depth). The validity of this relationship is illustrated for five Swedish lakes (Hjälmaren, Vänern, northern Vättern, western Mälaren and Ekoln). The relationship is important since it provides a means for prognosis and determination of physically relevant, characteristic values and not just traditional statistical values, such as various types of means. It is demonstrated: (1) that the distribution of physical sediment parameters depends on the water depth (the relative water depth), (2) that the spread (standard deviation) around the mean is large in shallow waters, where erosion, transportation as well as accumulation of fine sediments may appear, (3) that the spread decreases with increasing water depth, and (4) that the spread is relatively small at all water depths within the zone of accumulation. This allows the determination of a characteristic value at Dp = 100% (=Dmax). This argument will only be valid in lakes with areas of accumulation. The ‘critical’ water content (WT−A) separating areas of accumulation from zones of transportation may be estimated from the relationship WT−A = WK – 10, where WK is the characteristic water content. Characteristic values may be determined in a similar manner for chemical parameters showing a high correlation with the water content, i.e., essentially noncontaminating parameters. For contaminating substances, which are distributed in a typical way in lake sediments in the form of distinct tongues with decreasing concentrations with distance from the polluting source, characteristic values cannot be determined with the mentioned method. However, for contaminating substances, like mercury in the investigated lakes, characteristic values may be determined from the map illustrating the areal distribution pattern as the areal median value.
Estimates of resilience indices by simulation
Authors: Fiering Myron B
Published: February 2008

A few of the resilience indices described in an earlier paper in this series are calculated for several reservoir configurations which constitute a set of sample plans for a river basin. Basin characteristics are introduced to estimate proposed surrogates of system resilience without the necessity of performing long and expensive simulation studies; these simulations are necessary to develop resilience indices for the sample basins and to compare them to a few conventional ranking functions. The objective is to determine if conventional indices replicate information contained in resilience indices and the extent to which either or both of these can be estimated from basin geometry. While imperfect, the results are encouraging and suggest areas for continuing work in the mapping of basin characteristics and configuration into performance indices.
Optimal water pricing and storage: The effect of discounting
Authors: Manning R. , Gallagher D.
Published: February 2008

Optimizing the use of an exhaustible resource is a special case of the problem of storing a resource available as a periodic function of time. An extension of Hotelling's rule describes optimal storage policies: When water is in storage, its price should rise at the rate of interest, except that with contents at capacity the price must go up faster than the rate of interest. When contents are exhausted the price rises no more quickly than the rate of interest, and it must fall at some time. A rule is given for optimal storage capacity, and a version of Hotelling's rule is found for approximately optimal policies.
Atmospheric moisture transport and the water balance of the Mediterranean Sea
Authors: Peixoto José P. , De Almeida Mario , Rosen Richard D. , Salstein David A.
Published: February 2008

Previous studies of the water balance of the Mediterranean have relied on estimating evaporation (E) and precipitation (P) rates separately over the basin. An independent approach is to obtain the net difference between these rates by evaluating the divergence of the atmospheric flux of water vapor over the region. We apply this aerological approach to compute the annual mean value of E‐P over the Sea using upper air data collected during the 5‐year period 1968–1973. Our result is in general agreement with those obtained by the more classical methods. In addition we present maps of the two‐dimensional fields of precipitable water, of the vertically integrated water vapor flux vector, and of the divergence of water vapor over the region. These analyses are discussed in light of various climatological and hydrological considerations.
Stream‐aquifer influence coefficients as tools for simulation and management
Authors: Illangasekare Tissa , Morel‐Seytoux Hubert J.
Published: February 2008

Explicit relationships between the controllable decision variables and known initial conditions and the resulting states of combined stream‐aquifer systems are established through a set of coefficients referred to as influence coefficients. The discrete kernel approach for an isolated aquifer is combined with the discrete kernel approach for an isolated stream to derive the influence coefficients for a combined stream‐aquifer system. The isolated aquifer and the stream are coupled using a linear relationship for the stream‐aquifer interaction. The explicit nature of the relationships defining the state variables is well suited for the formulation of optimization type management problems as mathematical programing problems.
Steady state perched groundwater mounds on thick sublayers
Authors: Brock Richard R.
Published: February 2008

Perched mounds that develop beneath a strip recharge basin are considered using the potential theory for a saturated flow. The mounds are assumed to develop upon an aquitard or sublayer whose thickness is large enough so that the vertical velocity at the base of the mound does not vary with distance from the centerline of the basin. A finite difference technique was used to solve the potential theory, and 20 mound profiles were determined for K/KL = 10, 50, 100, 500 and R/K = 0.2, 0.35, 0.50, 0.65, 0.80. K/KL is the ratio of the permeabilities, and R is the recharge rate. These profiles are compared to those based on the approximate Dupuit‐Forchheimer (DF) theory, and a criterion for the range of validity of the DF theory for predicting the maximum mount thickness H0 is derived. It is found that for a sufficiently large value of K/KL, which depends on R/K and the desired accuracy, the DF theory is adequate. For smaller values of K/KL the potential theory must be used. Equipotential lines and velocity distributions are presented for a typical case where the potential and DF mound profiles are quite different.
Stochastic trigger model for flood peaks: 2. Application of the model to the flood peaks of Goksu‐Karahacili
Authors: Kavvas M. L.
Published: February 2008

In order to assess the suitability of the stochastic trigger process in modeling flood peak occurrences in the time‐discharge plane, the trigger process is applied to the flood peaks data of the Karahacili gaging station on the Goksu River, Turkey, in each of the flood seasons which are defined in the paper. The flood peak process in each flood season is treated as a transient stochastic process which starts at the beginning of the season and ends at the end of the season. Consequently, time‐discharge nonhomogeneous trigger processes are used to model these seasonal flood peak processes. In each flood season the two‐dimensional nonhomogeneous stochastic trigger (TDNST) model is calibrated by fitting its first theoretical time‐discharge moment and its second theoretical time moment to the corresponding estimated moments of the observed flood peak counts at Goksu‐Karahacili. Then in each flood season the theoretical two‐dimensional probability mass function (pmf) of the variable discharge exceedence level (DEL) is calculated from the calibrated TDNST model for that flood season. The goodness of fit of the theoretical two‐dimensional pmf to the empirical two‐dimensional pmf of the Goksu‐Karahacili flood peak counts in each flood season is tested by the chi‐square goodness‐of‐fit (CSGQF) test. In all of the flood seasons the TDNST model passes the CSGOF test at discharge levels above the 500‐m3/s DEL. This DEL corresponds to a river stage that is 1 m above the river bank stage at Goksu‐Karahacili.
Resource allocation to interrelated projects
Authors: Mehrez Abraham , Sinuany‐Stern Zilla
Published: February 2008

A multiattribute utility function was used to specify the decision‐maker's preferences, along with a zero‐one budget model, to solve the problem of selecting among interrelated multiobjective long‐range projects. Increasing the number of projects increases the complexity of the problem. The advantages of the model for relatively small problems are demonstrated by a case study dealing with a subset of Israeli water development projects for 1981.

Full article is available on microfiche. Order from American Geophysical Union. 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document W81‐002; $1.00. Payment must accompany order.
Methods for apportioning the cost of a water resource project
Authors: Heaney James P. , Dickinson Robert E.
Published: February 2008

Numerous ad hoc methods are used to apportion the costs of a water resource project among participants and/or purposes. Unfortunately these procedures do not always work, i.e., they lead to unfair assignment of costs. Accepted criteria for efficiency/financial analysis used in the water resources field are expressed in axiomatic form. These criteria are compared to accepted axioms of fairness from cooperative n‐person game theory. Similarities between the two approaches are identified. The minimum costs, remaining savings (MCRS) method is proposed as an improved method of financial analysis. The MCRS method can be viewed as a generalization of the presently used separable costs, remaining benefits method.
Real‐time, statistically linearized, adaptive flood routing
Authors: Georgakakos Konstatine P. , Bras Rafael L.
Published: February 2008

The use of nonlinear routing models within real‐time, adaptive, streamflow forecasting has been limited because of the linearity restrictions of the most popular filtering and optimal estimation techniques. This work proposes a linearization methodology suitable for nonlinear multidimensional functions of nearly Gaussian nonstationary processes. Lack of bias and exact preservation of moments are a few of the advantages of the procedure. In order to facilitate computations, simple analytical approximations for the linearization coefficients are offered. A state parameter covariance partitioning algorithm is proposed for real‐time estimation of the states and parameters of the linearized router. An illustrative example of its use, based on data from the Bird Creek basin in Oklahoma, is presented.
Streamflow changes after logging 130‐year‐old Douglas fir in two small watersheds
Authors: Harr R. Dennis , Levno Al , Mersereau Roswell
Published: February 2008

Timber harvest in two small watersheds in western Oregon containing 130‐yr‐old timber increased annual water yield up to 42 cm. For 4 years after logging, yield increases averaged 38 cm at a 13.0‐ha clearcut watershed and 20 cm at a 15.4‐ha watershed where timber was shelterwood cut. Increased summer flows were indicated by much fewer low‐flow days after logging, particularly at the clearcut watershed. During the 1977 drought year, only eight and two low‐flow days occurred at the clearcut and shelterwood cut watersheds, respectively, compared to 143 and 135 low‐flow days predicted by the calibration relationship. Neither the size nor the timing of peak flows changed significantly after logging at either watershed.
A stochastic dynamic programing model for the operation of the Mediterranean‐Dead Sea Project
Authors: Weiner Dan , Ben‐Zvi Arie
Published: February 2008

Construction of the Mediterranean‐Dead Sea Project and exploitation of the elevation differences becomes possible as a result of the reduction in the Dead Sea water levels due to increased withdrawals from its drainage basin over the past 50 years. These withdrawals would be replaced by a controlled inflow of water from the Mediterranean, which would generate hydroelectric power. An optimization of the annual Mediterranean water inflows, taking into account the high variability of the remaining natural inflows to the Dead Sea, is carried out by applying a stochastic dynamic programing algorithm to maximize the discounted expected value of the plant benefits. In addition the algorithm determines the operational level of the Dead Sea with respect to the probability of occurrence of high hydrologic flows.
Plotting positions of annual flood extremes considering extraordinary values
Authors: Zhang Yongping
Published: February 2008

A generalized plotting position formula for estimation of the recurrence interval or its reciprocal, the exceedance probability of hydrologic events in an incomplete data sample containing both extraordinarily large and small historical values, is derived. The derivation is based on order statistics analysis and is independent of the probability distribution of the hydrologic variable. It is shown that the Weibull formula is a special case of the generalized formula.
A geomorphoclimatic theory of the instantaneous unit hydrograph
Authors: Rodríguez‐Iturbe Ignacio , González‐Sanabria Marcelo , Bras Rafael L.
Published: February 2008

The instantaneous unit hydrograph is conceived as a random function of climate and geomorphology varying with the characteristics of the rainfall excess. The probability density functions of the peak and time to peak of the IUH are analytically derived as functions of the rainfall characteristics and the basin geomorphological parameters. The main characteristics of these pdf's are studied, and a new approach to hydrologic similarity is initiated under the concept of the geomorphoclimatic IUH. For a given set of geomorphologic characteristics and a particular intensity and duration of rainfall, the peak and time to peak of the IUH corresponding to those values can be easily estimated.
A modeling scheme for the study of drainage density
Authors: Escobar Luis A. , Rodríguez‐Iturbe Ignacio
Published: February 2008

An analytical approach is taken for the modeling of the drainage density of a basin. A rainfall model, a runoff model, and an erosion model are coupled together to estimate from climatic and geomorphologic characteristics the expected length of no‐erosion in a basin and, through this parameter, the drainage density of the watershed. The convergence of overland flow as an important cause of the growth upslope of the channels is explicitly taken into account in the model, as well as a simple approximation to the evolution in time of the contributing area at the source. The approach is applied to two basins in Puerto Rico, with encouraging results.
Prediction of annual floods generated by mixed processes
Authors: Waylen Peter , Woo Ming‐ko
Published: February 2008

In areas where the annual flood series is generated by more than one distinctive hydrologic process, the Gumbel distribution does not provide a satisfactory fit. Physical evidence is used to identify the flood‐generating processes, which in the Cascade Mountains include snowmelt and rainfall. Individually, the snowmelt and rain generated annual floods are adequately modeled by simple Gumbel distributions. These distributions have to be compounded to provide a good fit to the annual floods which are produced by mixed processes.
Seasonal aspects of the surface and advective heat fluxes of Kootenay Lake, British Columbia
Authors: Wiegand Ronald C. , Carmack Eddy C. , Daley Ralph J. , Gray Colin B. J. , Jasper Steve , Pharo Christopher H.
Published: February 2008

A description is given of the heat and water balances of Kootenay Lake, British Columbia. Although the lake has a moderately high throughflow (781 m3 s−1), the heat budget is more in character with a lake that is little influenced by rivers. The discussion focuses upon the role of rivers in the thermal history of lakes; a contrast is drawn between Kootenay Lake and Kamloops Lake, British Columbia, a strongly riverine lake with a much greater heat budget. It is suggested that the riverine nature of lakes can be characterized using a renewal time that applies to that region of the lake lying above the base of the river plume. Furthermore, the relative roles of advective and surface effects can be qualitatively described using a ratio of surface buoyancy or wind energy to river production of turbulent energy. These parameterizations may prove to be useful descriptors in a lake classification system based upon riverine quality.
Comparison of estimators of standard deviation for hydrologic time series
Authors: Tasker Gary D. , Gilroy Edward J.
Published: February 2008

Unbiasing factors as a function of serial correlation, ρ, and sample size, n for the sample standard deviation of a lag one autoregressive model were generated by random number simulation. Monte Carlo experiments were used to compare the performance of several alternative methods for estimating the standard deviation σ of a lag one autoregressive model in terms of bias, root mean square error, probability of underestimation, and expected opportunity design loss. Three methods provided estimates of σ which were much less biased but had greater mean square errors than the usual estimate of σ: s = (1/(n ‐ 1) ∑ (xi −x¯)2)½. The three methods may be briefly characterized as (1) a method using a maximum likelihood estimate of the unbiasing factor, (2) a method using an empirical Bayes estimate of the unbiasing factor, and (3) a robust nonparametric estimate of σ suggested by Quenouille. Because s tends to underestimate σ, its use as an estimate of a model parameter results in a tendency to underdesign. If underdesign losses are considered more serious than overdesign losses, then the choice of one of the less biased methods may be wise.
Derivation of vertically averaged equations describing multiphase flow in porous media
Authors: Gray William G.
Published: February 2008

An extension of the REV averaging technique, used to derive balance equations for multiphase or porous media flow problems, is presented Theorems which allow a one‐step transformation from three‐dimensional point equations for a single phase to two‐dimensional point equations for multiphase systems are derived. The theorems are then applied to obtain the vertically averaged balance equations of mass, chemical species, momentum, energy, and entropy. The relation between these equations and their unaveraged predecessors is clearer than when the standard two‐step averaging procedure is applied. Furthermore, constitutive relations are more easily hypothesized for the current system of equations than for previously derived forms.
A heuristic solution procedure for a joint reservoir control‐capacity expansion problem
Authors: Sniedovich Moshe , Nielsen Peter A.
Published: February 2008

A joint reservoir control‐capacity expansion problem is considered in which the expansion policy is required to be deterministic. Since this problem is difficult to solve, because the release policy is stochastic, a heuristic procedure is proposed, which utilizes an upper bound to the optimal deterministic solution obtained by solving a modified stochastic problem and a simple averaging heuristic for transforming stochastic policies into deterministic policies. A simple numerical example demonstrates the overall procedure.
Constant velocity kinematic analysis of an infiltrating microcatchment hydrograph
Authors: Zarmi Y. , Ben Asher J. , Greengard T.
Published: February 2008

A watershed of about 200 m2 is used in many arid zones to provide the irrigation needs of a single tree. The objectives of this study were to develop and test a physical model to predict the hydrodynamic processes on a natural microcatchment of this size. A rectangular area of 125 m2 was selected on loessial soil with a fairly uniform grade of approximately 1%. Rainfall was applied uniformly over the catchment at intensities of 60, 40, 20, and 10 mm/h. Inspection of all the hydrographs indicated that the nature of the recession part was very similar for all intensities. Recession appeared as a set of parallel lines which decreased rapidly the moment that the rain stopped. At all intensities the recession lasted about the same time (10.4 ± 2.3 minutes) and was independent of the surface detention. It was then suggested that a good approximation is obtained when velocity of water flow on the surface is assumed to be constant, independent of time or position along the catchment. These qualitative results simplify the analytical solution of the continuity equation and provide a new insight into the problem of flow over an infiltrating surface. In addition, the analytical solution developed for this case is much easier to utilize than large‐scale computer simulations.
A review of distributed parameter groundwater management modeling methods
Authors: Gorelick Steven M.
Published: February 2008

Models which solve the governing groundwater flow or solute transport equations in conjunction with optimization techniques, such as linear and quadratic programing, are powerful aquifer management tools. Groundwater management models fall in two general categories: hydraulics or policy evaluation and water allocation. Groundwater hydraulic management models enable the determination of optimal locations and pumping rates of numerous wells under a variety of restrictions placed upon local drawdown, hydraulic gradients, and water production targets. Groundwater policy evaluation and allocation models can be used to study the influence upon regional groundwater use of institutional policies such as taxes and quotas. Furthermore, fairly complex groundwater‐surface water allocation problems can be handled using system decomposition and multilevel optimization. Experience from the few real world applications of groundwater optimization‐management techniques is summarized. Classified separately are methods for groundwater quality management aimed at optimal waste disposal in the subsurface. This classification is composed of steady state and transient management models that determine disposal patterns in such a way that water quality is protected at supply locations. Classes of research missing from the literature are groundwater quality management models involving nonlinear constraints, models which join groundwater hydraulic and quality simulations with political‐economic management considerations, and management models that include parameter uncertainty.
Unsaturated flow in spatially variable fields: 1. Derivation of models of infiltration and redistribution
Authors: Dagan G. , Bresler E.
Published: February 2008

Models of water flow in the upper soil layer of spatially variable fields are developed. Field variability is assumed to take place in the horizontal plane. The saturated hydraulic conductivity is assumed to be a random variable of lognormal distribution, and head suction and moisture content are related to it by simple analytical relationships. The aim of the study is to derive the expectation and variances of the moisture content, suction heads, hydraulic conductivity, and water flux as functions of depth and time for infiltration and redistribution. Toward this aim a simplified solution of vertical flow in a homogeneous column, based on the concept of moving front, is developed. The statistical procedure for using this solution in a spatially variable field is outlined.
Bar resistance in gravel bed streams at bankfull stage
Authors: Prestegaard Karen L.
Published: February 2008

Total flow resistance in gravel bed streams with high width/depth ratios and low sinuosities is primarily a result of grain and bar roughnesses. The relative importance of these two roughness elements has not been established. The relative importance of grain and bar resistance is examined for 12 straight and divided gravel bed reaches at bankfull stage by using the Keulegan equation to determine a resistance division of energy slope. The remaining slope is assumed to represent the relative importance of bar resistance. Bar resistance accounts for 50 to 75% of the total resistance in these reaches. Calculated values of reach‐averaged bar slope correlate closely with field measurements of bar magnitude.
One‐dimensional bed wave movement in lowland rivers
Authors: Weir G. J.
Published: February 2008

We show that recent measurements in the East Fork River, Wyoming, of annual gravel wave translation, annual bedload transport, and annual variations in riverbed cross‐sectional area can be described to within a factor of 2 by using the Gradowczyk characteristic velocity for bed waves to describe gravel wave translation, the Engelund‐Hansen formula for bedload transport, and a DuBoys‐like formula for changes in cross‐sectional area. No free parameters are needed.
Kinetic analysis of strontium and potassium sorption onto sands and gravels in a natural channel
Authors: Bencala Kenneth E. , Jackman Alan P. , Kennedy Vance C. , Avanzino Ronald J. , Zellweger Gary W.
Published: February 2008

A kinetic, first‐order mass transfer model was used to describe the sorption of strontium onto sand‐ and gravel‐sized streambed sediments. Rate parameters, empirically determined for strontium, allowed for the prediction of potassium sorption with moderate success. The model parameters varied significantly with particle size. The sorption data were collected during an experimental injection of several elements into a small mountain pool‐and‐riffle stream. The sorption process onto sand‐ and gravel‐sized sediment was relatively slow compared to changes in the dissolved concentrations.
Optimum design of small reservoirs (tanks)
Authors: Helweg Otto J. , Sharma Prem N.
Published: February 2008

Small reservoirs, called tanks, are a part of traditional water harvesting methods in the semiarid tropics of India and many other countries. Though considerable investment is being planned to construct more of them, no investigation has taken place to discover the most efficient design of these tanks. This paper proposes a nonlinear optimization model to design these tanks. It is, in a sense, ‘appropriate technology’ because a traditional approach is combined with newer techniques to improve irrigation systems without capital intensive or high technology construction methods.
Economic evaluation of water harvesting in microcatchments
Authors: Oron Gideon , Ben‐Asher Jiftah , Issar Arie , Boers Theo M.
Published: February 2008

A cost‐benefit analysis of the microcatchment water harvesting (MCWH) technique has shown that in highly dry zones (i.e., annual precipitation of less than 150 mm), the predicted income is negative. The introduction of modified technology improved water harvesting and thus increased the predicted net income. These modifications are associated with additional expenses, leaving the additional benefit questionable. A cost‐benefit analysis of MCWH with inserts (perforated vertical drainage pipes) to improve water use efficiency has led to a conclusion that net income is higher than that of MCWH without inserts. However, in a highly dry zone the net income is still negative (although only slightly), while in dry zones (i.e., annual precipitation of 250 mm) it becomes positive.
Distributed parameter modeling of a producing vapor‐dominated geothermal reservoir: Serrazzano, Italy
Authors: Pruess K. , Weres O. , Schroeder R.
Published: February 2008

The simulator SHAFT79 of Lawrence Berkeley Laboratory has been applied to a field‐wide distributed parameter simulation of the vapor‐dominated geothermal reservoir at Serrazzano, Italy. Using a three‐dimensional geologically accurate mesh and detailed flow rate data from 19 producing wells, a period of 15.5 years (from 1959 to 1975) has been simulated. The reservoir model used is based on field measurements of temperatures and pressures, laboratory data for core samples, and available geological and hydrological information. The main parameters determined (adjusted) during development of the simulation are permeabilities and much of the initial conditions. Simulated patterns of pressure decline show semiquantitative agreement with field observations. Field pressures decline overall somewhat more rapidly than predicted in the simulation. It is concluded that (1) the interface between overlying steam cap and deeper boiling aquifer remains stationary during exploitation and (2) the aquifer boils approximately uniformly throughout in response to production. Furthermore, the simulation suggests that some steam flowing to the main well field originates from deep fractures rather than from boiling in the two‐phase zones modeled. Effects of cold recharge, incomplete thermal equilibration between rock and fluid, and different assumptions regarding the depth of the steam/two‐phase interface are investigated. The reservoir model is used to extrapolate (forecast) production rates on a well‐by‐well basis through 1990. Injection of spent condensate is briefly examined, and negligible impact on field performance is predicted. Simulation methodology and ambiguity of parameter determination are discussed.
Category‐unit loss functions for flood forecast‐response system evaluation
Authors: Krzysztofowicz Roman , Davis Donald R.
Published: February 2008

Economic evaluation of the performance of a flood forecast‐response system requires a large amount of information for the estimation of a loss function. This function must encode the cost of protective action undertaken in response to flood warnings and the flood damage sustained. The concept of category‐unit functions is exploited to reduce field survey demands and to circumvent high computation requirements. The loss function consists of a unit damage function, a unit cost function, and a unit reduction function; the degree of response that can be actually implemented is bounded by a decision constraint function. These four functions are estimated from data of various origins for seven categories of structures and three categories of decision makers.
Water quality management with time varying river flow and discharger control
Authors: Herbay Jean‐Pierre , Smeers Yves , Tyteca Daniel
Published: February 2008

An extension of the classical river quality management problem is presented that allows for time varying operation of the treatment plants. The hydrology of the river is represented by a set of steady state flow regimes; a river water quality model is used for each of these regimes to give a constraint set to be imposed on the discharges in order to achieve the stream standards during that regime. The objective function distinguishes between investment costs, fixed operating costs, and variable operating costs. A treatment system is sought that minimizes the sum of these costs, taking account of the possibility of operating the treatment system at various different levels during the year. The model is quantified and tested on an example.
Constitutive theory for vertically averaged equations describing steam‐water flow in porous media
Authors: Gray William G.
Published: February 2008

Constitutive theory based on the Coleman and Noll method of exploitation of the entropy inequality is applied to the vertically averaged equations describing flow of two fluid phases in a porous medium. In the most general case considered the solid phase is assumed to be inert and elastic while each fluid phase is allowed to undergo phase change. For simplicity, the phases are assumed to be ideal in that the thermodynamic state within a phase depends only on the properties of that phase. However, interphase processes depend on the thermodynamics of all phases. The general constitutive forms obtained are ultimately linearized for the slow flow case to obtain equations appropriate for the description of a geothermal reservoir or other slow, two‐phase fluid flow through an elastic medium.
Slug tests in fissured aquifers
Authors: Barker John A. , Black John H.
Published: February 2008

A simple model of a slug test in a fissured aquifer has been studied in order to gain insight into the difficulties of interpreting data from such tests. The model is used to estimate the errors that would result from applying the standard type curve analysis to fissured aquifers. It is found that the derived aquifer transmissivity will always be overestimated, but by a factor which is unlikely to exceed 3. By contrast, the derived storage coefficient can be in error by a factor ranging from 10−6 to 105. The volume of the aquifer influenced by a slug test is investigated, and a simple formula for estimating the range of a test is suggested.
A kinematic model for surface irrigation: Verification by experimental data
Authors: Singh Vijay P. , Ram Rama S.
Published: February 2008

A kinematic model for surface irrigation is verified by experimental data obtained for 31 borders. These borders are of varied characteristics. Calculated values of advance times, water surface profiles when water reaches the end of the border, and recession times are compared with their observations. The prediction error in most cases remains below 20% for the advance time and below 15% for the recession time. The water surface profiles computed by the model agree with observed profiles reasonably well. For the data analyzed here the kinematic wave model is found to be sufficiently accurate for modeling the entire irrigation cycle except for the vertical recession.
Evaluation of irrigation water quality for a spatially variable field
Authors: Bresler Eshel , Yaron D. , Segev Anat
Published: February 2008

A model to predict the optimal salt concentration of irrigation water when various sources of water are available is described and illustrated for citrus. The model employs a stochastic model for soil water and solute movement and a linear programing economic model for best solutions over an extended time period. The model was developed for a Mediterranean‐type climate where an irrigation (salt accumulation) season is followed by a rainfall (salt leaching) period. Soil water flow generated by an irrigation or rainfall is assumed to be steady and vertical. Transient solute transport is assumed to obey the diffusion‐convection equation. The probability of any given average root zone salinity after any cycle of irrigation or rain is calculated for any combination of applied water salinity and initial soil salinity using a probability density function for the saturated hydraulic conductivity. The expectation of the total income from a crop yield having a known response function to soil salinity is maximized by the model subject to a given probability of the average root zone salinity exceeding a prespecified critical concentration. The cost of water is assumed to decrease as the salinity of irrigation water increases. Optimal water management depending on the salt concentration of the irrigation water over 6 years for citrus is illustrated in terms of minimum cost, maximum income, optimum salt concentration of the irrigation water, spatial distribution of average root zone salinity, and the probability of exceeding a prescribed critical soil salinity concentration.
Reliability constrained reservoir control problems: 2. Randomized strategies
Authors: Sniedovich Moshe , Nielsen Peter A.
Published: February 2008

The potential use of randomized strategies in water resources planning is critically examined and difficulties related to the implementation of such strategies are discussed. The overall conclusion is that it does not appear likely that water resources planners will accept these types of strategies because of the frequency‐based approach to probability which is commonly used to interpret probabilistic constructs in the water resources context. On the other hand, it is possible to use randomized strategies to obtain upper bounds for heuristics designed to generate pure strategies.
Channel Networks: A Geomorphological Perspective
Authors: Abrahams Athol D.
Published: February 2008

The study of channel networks has been dominated since 1966 by the random model. However, recent work has shown (1) that although the topological properties of small networks conform to the random model more closely than those of large ones, even small networks exhibit systematic deviations from topological randomness and (2) that the topological and length properties of channel networks are controlled to a large degree by the spatial requirements of subbasins and the need for these subbasins to fit together in space, by the size, sinuosity, and migration rate of valley bends, and by the length and steepness of valley sides. The factors that control the density properties of channel networks vary with the scale of the investigation and the geomorphic processes governing channel initiation. Although progress has been made toward a satisfactory stream junction angle model, further work is needed. The evolution of channel networks has been investigated by a variety of methods, including the development of conceptual and simulation models, the monitoring of small‐scale badland and experimental drainage basins, and the substitution of space for time. The morphology of most channel networks is largely inherited from the past or strongly influenced by inherited forms. Inasmuch as there is no way of ever knowing the origin or complex history of such networks, the use of stochastic models in their study seems unavoidable.
On the Problem of Permissible Covariance and Variogram Models
Authors: Christakos George
Published: February 2008

The covariance and variogram models (ordinary or generalized) are important statistical tools used in various estimation and simulation techniques which have been recently applied to diverse hydrologic problems. For example, the efficacy of kriging, a method for interpolating, filtering, or averaging spatial phenomena, depends, to a large extent, on the covariance or variogram model chosen. The aim of this article is to provide the users of these techniques with convenient criteria that may help them to judge whether a function which arises in a particular problem, and is not included among the known covariance or variogram models, is permissible as such a model. This is done by investigating the properties of the candidate model in both the space and frequency domains. In the present article this investigation covers stationary random functions as well as intrinsic random functions (i.e., nonstationary functions for which increments of some order are stationary). Then, based on the theoretical results obtained, a procedure is outlined and successfully applied to a number of candidate models. In order to give to this procedure a more practical context, we employ “stereological” equations that essentially transfer the investigations to one‐dimensional space, together with approximations in terms of polygonal functions and Fourier‐Bessel series expansions. There are many benefits and applications of such a procedure. Polygonal models can be fit arbitrarily closely to the data. Also, the approximation of a particular model in the frequency domain by a Fourier‐Bessel series expansion can be very effective. This is shown by theory and by example.
Optimal Annual Operation of a Coastal Aquifer
Authors: Shamir U. , Bear J. , Gamliel A.
Published: February 2008

Optimal annual operation of a coastal aquifer is determined by using a multiple objective linear programing model based on a multicell model of the aquifer and a network representation of the hydraulic distribution system. The decision variables are pumping and/or recharge quantities in each cell. Four objective functions are based on (1) a desired ground water surface map, (2) a desired location of the sea water‐fresh water interface toe in each coastal cell, (3) a desired concentration map of a selected conservative contaminant, and (4) minimization of the energy for pumping and recharge. An approximate linearized expression of the location of the interface has been developed to enable the use of linear programing as the optimization method. A trade‐off procedure is employed for identifying the most desirable solution. The model is applied to a segment of the coastal aquifer in Israel (a 44‐km strip along the coast with a width of 7 to 15 km) and results are discussed.
Insolation Topoclimates and Potential Ablation in Alpine Snow Accumulation Basins: Front Range, Colorado
Authors: Olyphant Greg A.
Published: February 2008

Measurements of insolation during the Indian Peaks snowmelt season indicate that the average diurnal trajectory of solar transmission is highly asymmetric with lower values occuring in the afternoon when cloud coverage is maximum. A statistical analysis of simulated insolation suggests that topographic factors interact with prevailing sky conditions to produce a complex pattern of topoclimates within the study area. Differences between insolation topoclimates are not stationary; they depend upon timing and degree of cloud coverage as reflected in the diurnal trends of solar transmission. On an average summer day (clear morning‐cloudy afternoon), simulated insolation to north and south facing basins is roughly equivalent, while east facing basins receive the largest daily totals. These findings are important to snow hydrologists because relative (intramountain) differences in glacier ablation, and therefore potential basin melt, appear to be adjusted to the pattern of radiation that occurs on partly cloudy (not cloudless) days.
Evaluation of Slug Tests in Wells Containing a Finite‐Thickness Skin
Authors: Faust Charles R. , Mercer James W.
Published: February 2008

The effects of a finite‐thickness skin (low‐permeability zone surrounding the well bore face) on the response of slug tests is investigated by using a numerical model and a simple analytical solution. The results show that, for skins of finite thicknesses, estimates of hydraulic conductivity provided by slug tests can be more representative of the skin than of the surrounding formation. When a finite‐thickness skin is present, the slug test response is shifted along the horizontal axis, making estimates of hydraulic conductivity unreliable. This result is different from that obtained by using an analytical solution (Ramey et al., 1975) for a skin of infinitesimal thickness.
A Geostatistical Approach to the Trickle Irrigation Design in a Heterogeneous Soil 2. A Field Test
Authors: Russo David
Published: February 2008

In a heterogeneous field in which the soil water properties vary under a “deterministic” uniform trickle irrigation system, the midway soil‐water pressure head hc and the yield of a crop also differ from place to place. These differences may, in turn, reduce the average (over the field) yield relative to the yield that would be obtained if the soil was uniform throughout the field. A field experiment was conducted to test the hypothesis that this yield reduction may be eliminated by using a spatially variable trickle irrigation system. Twenty‐five plots (200 m2 each) were established on a 30‐m2 grid. Half of each plot was equipped with a standard trickle irrigation system with constant spacing between emitters of d = 50 cm (control plots), and the other half was equipped with a trickle irrigation system for which the spacing between the emitters was selected by using the pertinent hydraulic properties (the saturated hydraulic conductivity Ks and the soil parameter α) according to the procedure of Bresler (1978) as described in paper 1 (Russo, 1983b). Values of hc measured at different times, as well as the total fruit yield Y of bell pepper (Capsicum frutescens var. “Maor”), were used to estimate the seasonal and the spatial distributions of hc and the spatial distribution of Y and their moments. The variograms of hc and Y were calculated and used to estimate their integral scales. It was found that the use of a spatially variable d relative to the use of a uniform d did not change the seasonal behavior of hc but reduced the spatial variability in hc and Y by 35% and 11%, respectively, and increased the integral scale of hc and Y by 30% and 10%, respectively, but increased the average total fruit yield by only 1.9%. The use of a spatially variable d reduced the dependence of Y on hc. This indicates that when the emitters are properly spaced, it is not the water but other factors that most influence yield. When a constant d was used, the dependence of Y of hc decreased with time. This and the relatively good agreement between the values of hc measured at the initial stages of the growing season and those calculated in paper 1 demonstrate that the concept of hc is important in the early stages of the plant's growth, when the root system is not fully developed. Both the theoretical (paper 1) and the experimental results showed that although Ks and α, as well as hc, varied considerably in the field the spatial variability of the crop yield was relatively small. This explains why the use of a spatially variable d essentially was not an improvement over the fixed d. It is suggested that this study will be considered as a methodological one, which can be adapted to solve practical problems associated with field spatial variability.
Price Rigidity and Quantity Rationing Rules Under Stochastic Water Supply
Authors: Fakhraei S. Hamid , Narayanan Rangesan , Hughes Trevor C.
Published: February 2008

When the quantity of water available falls short of “normal” water supply, the typical response of municipalities is to impose some form of rationing. Although economically efficient measures such as raising prices or issuing transferable ration coupons have been advocated, they are seldom implemented. Yet the economic efficiency implications of rationing have not been analyzed in the context of stochastic supplies. In this paper, two forms of quantity rationing are proposed and the long‐run prices which maximize the expected net benefits are derived with only the knowledge of the demand distribution.