bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of mass transport with uncertain physical parameters
Authors: Tang D. H. , Pinder G. F.
Published: February 2008

The coefficients of the mass transport equation are often characterized by considerable uncertainty. Where the functional form of this uncertainty is known the transport equation can be solved to yield a solution also characterized by uncertainty. The spatial and temporal dependencies of this uncertainty are dependent upon the variance of the velocity and dispersivity, the magnitude of the dispersivity, the functional form of the probability distribution function, and the number of uncertain parameters considered in the analysis. In general the uncertainty, as measured by the coefficient of variation, is considerably smaller for the solution than for the input parameters. While any finite variance theoretically can be accommodated by the method employed for solution of the stochastic partial differential equations, it is nevertheless essential to select numerical parameters (Δx and Δt) such that certain constraints on the form of the coefficient matrix are not violated.
An evaluation of marginal waters as a natural resource in Israel
Authors: Buras N. , Darr P.
Published: February 2008

The scarcity of water in Israel and its possible effect on the socioeconomic development of the country have evinced considerable interest in the utilization of marginal waters. A nonlinear mathematical model was formulated, whose dual solution has shown that urban waste water and brackish water have substantial values ranging up to 65% of the cost of imported freshwater. The nonlinear production function in the mathematical model permitted the detailed analysis of the impact of the economies of scale on the primal and dual solutions. The optimal allocation of water for the Central Negev in 1992 calls for 40% of the forecast total water demand to be supplied by 26 million m3 of treated urban waste water and brackish water.
Effects of clearcutting on soil water depletion in an Engelmann spruce stand
Authors: Hart George E. , Lomas David A.
Published: February 2008

Soil water depletion was monitored for five growing seasons on 0.4 hectare plots in a mature stand of Engelmann spruce in northern Utah. Three plots were then clearcut and in the first season soil water depletion was 20 to 25 cm less than on an uncut plot. This change, which represents a savings of water previously lost to evapotranspiration, is considerably greater than reported for comparable studies in aspen and lodgepole pine. The effects of clearcutting on soil water depletion are expected to persist for as many as 50 years. In the first winter after cutting, peak snow water equivalent in the clearcut plots averaged 91 cm, or 31 cm greater than for the uncut control plots.
A note on diffusion from a continuous line source in a time varying flow
Authors: Wilson Robert E.
Published: February 2008

This note describes approximate techniques for calculating the transient concentration field resulting from horizontal diffusion from a continuous source in a time varying flow. Using these techniques, calculations could be performed either by hand or very economically by machine. The analyses are based on a model for two‐dimensional horizontal diffusion in which the field for a continuous source is represented as the superposition of the fields for instantaneous patches; the spread of an instantaneous patch is characterized by a diffusion velocity. The specific case considered is an oscillating flow characteristic of a tidal estuary, but the techniques should be of practical value in the description of concentration fields of passive quantities introduced into a variety of time varying flows.
Stabilized sand surfaces for overland flow studies
Authors: Podmore T. H. , Burney J. R.
Published: February 2008

A method was developed to produce stable durable sand surfaces for use in overland flow studies. Hydraulic and physical characteristics of the surfaces produced could be quantified repetitively without deterioration.
Some basic considerations in the design of hydrologic data networks
Authors: Moss Marshall E.
Published: February 2008

Two preeminent considerations of data network design are the random nature of the hydrologic phenomena and the uses that will be made of the data. Information distilled from the data is usually measured in a parametric statistical sense, although the data user is more concerned with the integrated measure of information—what impact does the lack of perfect hydrologic information have on the ensuing decisions? Two facets of the network, the efficiency of the data collection and the effectiveness of the resulting information, must be integrated to achieve a complete network design.
Development of hydrometric networks in British Columbia
Authors: Kreuder W. L.
Published: February 2008

The growth and purposes of the Water Survey of Canada's British Columbia network are described from a practical point of view, tracing the progress toward a rational data gathering system. The network consists of several subnetworks of which three, the regional, the major stream and the national inventory, are described in detail. As the major stream and national networks are reasonably simple in purpose and operation, the major part of the discussion is concerned with the regional network whose main purpose is the transfer of information. To meet this purpose and to analyze the performance of the network, certain procedures for the organization of data have been employed. These procedures included data banks for both hydrologic quantities and grid square extracted physiographic characteristics and regression analysis for relating the quantities in these data banks. The discussion outlines the British Columbia experience of sampling and transferring data in a diverse and primarily mountainous terrain.
Termination of hydrologic data collection (a case study)
Authors: Lane Leonard J. , Davis Donald R. , Nnaji Soronadi
Published: February 2008

Research objectives for the Southwest Watershed Research Center (SWRC), as determined by the U.S. Department of Agriculture‐Science Education Administration (USDA‐SEA), require a broad data base. The operation of seven experimental watersheds near Albuquerque, New Mexico and Safford, Arizona, which only obtain data on precipitation and runoff, was examined to determine (1) if their operation should continue as is, (2) if their data collection abilities should be expanded, or (3) if their operation should be discontinued. The decision‐making procedure is modeled in terms of the theory of ‘bounded rationality’ rather than classical optimization theory.

The choice of alternatives was subject to three constraints: that the resources for data collection activities at SWRC would not be increased, that it be administratively feasible, and that no research program be seriously impaired, A problem‐data matrix that showed the data needs for several research objectives was constructed. Based on this matrix and an estimate of the value of the research to the agricultural community, the three alternatives for the operation of seven watersheds were evaluated.

Considering the constraint of no additional resources and of administrative feasibility, the alternative of closing the seven watersheds was the best. To check that the third constraint was not violated, regional studies were made to compare precipitation and runoff characteristics of the Safford and Albuquerque watersheds with other experimental watersheds. A Bayesian decision analysis on the worth of future data was made. The regional analysis and the Bayesian study showed that closure of the watersheds would be detrimental to the precipitation and runoff data base, but not to the extent of impairing research objectives. The Albuquerque and Safford watersheds were closed in June 1976.
On the statistical characteristics of drought events
Authors: Dracup John A. , Lee Kil Seong , Paulson Edwin G.
Published: February 2008

Several statistical tests are performed on streamflow series for purposes of analyzing multiyear drought events. These statistical tests on both high‐flow and drought event parameters include (1) stationarity in terms of their linear trend; (2) randomness in terms of lag‐l serial correlation; (3) correlation and cross correlation between these parameters (duration, magnitude and severity). The test results and their implications are discussed in relation with the characterization of high‐flow and drought event series. Two types of envelopes for drought duration and severity are presented which use Tschebycheff's inequality. These envelopes give an excellent indication of the maximum response of a watershed in terms of drought duration and severity during the period of record.
Runoff calculation on semi‐arid watersheds using a Rotadisk Rainulator
Authors: Morin Joseph , Cluff C. Brent
Published: February 2008

A method of determining runoff from ungaged semi‐arid unit watersheds is presented. The method consists of using the realistic rotating disk rainfall simulator (Rotadisk Rainulator) to measure the infiltration rate combined with data from recording raingages. The infiltration rate is expressed mathematically as a function of rainfall volume and soil parameters by a modified Horton‐type equation. A runoff depth for the unit area is then calculated using a computer program which essentially subtracts the infiltration and surface storage from the rainfall as measured by existing recording rainfall records. The method was tested using four 1‐ac gaged watersheds on the Atterbury Experimental Watershed on the valley floor east of Tucson, Arizona. In general, the measured and calculated runoff were in good correlation, while the standard deviation of the differences between them was between 1 and 3 mm over a 3‐year period for the four unit watersheds tested.
Methods of confining oil in unlined caverns in aquifers: Water table maintenance by well recharge
Authors: Thunvik Roger , Braester Carol
Published: February 2008

One of the methods of petroleum storage is using unlined caverns located below the water table of an aquifer. The water pressure will exceed the oil pressure in the cavern, water will penetrate the cavern, and the oil will be confined. In order to prevent excessive lowering of the water table and to maintain a prescribed constant water level it is necessary, in most cases, to inject water into the aquifer. The influence of rock properties and of flow geometry on the rates of water flow into the cavern and on the shape of the phreatic surface were studied. The equations of flow were solved by a numerical method, and the results were presented in a dimensionless form.
Water quality, energy, and socioeconomics: Path analyses for studies of causality
Authors: Kaplan E. , Thode H. C.
Published: February 2008

Water quality data for 65 variables were obtained for the period 1955–1977 and aggregated on a county basis. Measurements were taken primarily for streams in New England, the Middle Atlantic States, and Ohio. When a subset of 138 counties with complete data was used, it was found that county aggregation statistical procedures resulted in data which describe known chemical characteristics of natural waters. Energy and socioeconomic data were merged with water quality data for these 138 counties. A path diagram was proposed to provide insight into possible causal relations between energy production and consumption activities and water quality. Direct and indirect pathways from energy production and use were traced to three factors characterizing water quality: specific conductance, hardness, and dissolved metallic ions. This analysis explained 25–40% of the variance in three water quality factors and indicated the applicability of this technique to regional assessments of water quality impacts due to a range of human activities.
Improved linear trial function finite element model of soil moisture transport
Authors: Hromadka T. V. , Guymon G. L.
Published: February 2008

Two methods of modeling a higher‐order approximation function of soil moisture transport by an improved linear trial function approximation are presented. The first approach considered is based upon use of the alternation theorem and a finite element capacitance matrix that incorporates the Galerkin finite element, subdomain, finite difference, and proposed nodal domain integration methods. The second approach extends the first approach by developing a temporal relationship for element matrices such that a higher‐order approximation function can be modeled by a linear approximation function. Comparison of model results produced from a nodal domain integration model incorporating these improved linear trial function approximations to the finite element, subdomain, and finite difference methods indicates that this approach may lead to a generalized modeling method for soil moisture transport problems.
Determination of horizontal‐to‐vertical hydraulic conductivity ratios from seepage measurements on lake beds
Authors: Barwell V. K. , Lee David Robert
Published: February 2008

This paper describes a new method of determining the anisotropy of aquifers contiguous with lakes. The method is based on the observed rate of decline of seepage flux with distance offshore and on the thickness of the aquifer. Deviations from an exponential decline in seepage rate with distance offshore give a measure of aquifer heterogeneity and, consequently, an estimate of the reliability of the anisotropy determination. A simple formula, derived as an analytical solution of a steady state two‐dimensional groundwater flow equation, makes it relatively easy to calculate anisotropy ratios from field measurements of seepage flux through lake beds and a small number of boreholes. The importance of the anisotropy ratio in controlling the offshore distribution of groundwater and solute movement into lakes is discussed.
Estimating the costs in lost power of alternative Snake‐Columbia Basin management policies
Authors: Hanson R. J. , Millham C. B.
Published: February 2008

This work, in part, describes a 51 dam, 56 time period long‐range simulation model of the hydropower system in the Snake‐Columbia basin, including projects on those two rivers and on major tributaries thereof. The model is then applied to study a series of alternative basin management scenarios, and the consequences in lost power of these scenarios are evaluated economically. With 56 time periods and 51 projects (some having as many as five data sets), computational efficiency in a restricted computing environment is important. Efficiency in this model was achieved via use of ‘French Curve’ cubic spline data fits, together with fast pointers to carefully defined data structures. In addition, care was taken to couch the model in a setting making it accessible to use by nonprogramers, in a quasiconversational mode. Some technical detail on the implementation of the model is included in the paper. Mention is also made of another model developed during this effort, called PASO (Peaking Alternatives System Operation), a heuristic look ahead model now operational and available to interested users. Discussion of the validation procedures for both models is involved. The ‘firm power’ capability of the hydropower system in the Pacific Northwest is that maximal (monthly or biweekly) energy production which the system could produce during a 44½‐month ‘critical period’ of extremely low historical flows. In years of higher, more normal flows, the hydropower system can generate power substantially in excess of the firm capability. This ‘secondary’ power ebbs and flows annually as a function of many things, and it therefore seemed most relevant to focus studies of alternative basin management schemes on firm power production. Accordingly, the work assumed the historical flows of the period July 1, 1928‐June 30, 1932, a period of time including the critical period. The model and flow data was applied to the series of alternative basin management schemes, each selected for its environmental and/or political interest. The impact of each management scheme was then evaluated in terms of lost or foregone power against a ‘base regulation’ in which the objective was to generate as much power as possible over the critical period. Lost power was conservatively evaluated at 35 mills per lost kilowatt‐hour for baseload, with much higher costs possible for lost peaking.
Alternative indices of resilience
Authors: Fiering Myron B
Published: February 2008

The concept of resilience of a water resource system is explored, and a few definitions are suggested and compared. These are based on the time required to pass from one system state to another and involve the passage to or from a state defined as failure. Some of the definitions involve probability of recovery from failure to some acceptable state within a specified time interval; thus the system's dynamics and standards are explicitly included.
Estimating resilience by canonical analysis
Authors: Fiering Myron B
Published: February 2008

Canonical correlation analysis is used to formulate linear estimates of independent or orthogonal (incremental) information on the performance of water resource systems. Simple economic and resilience indicators are compared, and for the particular configurations chosen in this paper the replicated and independent information sets are explained in terms of the connectivity of the various reservoirs. The canonical correlations are relatively high, indicating that there is significant replication of information; a taxonomy is developed which suggests those basin and structural characteristics which would indicate less replication and consequently improved description of system performance. The procedure is based on simulation studies reported in an earlier paper in this series.
Numerical treatment of leaky aquifers in the short time range
Authors: Chen Benito , Herrera Ismael
Published: February 2008

The numerical treatment of leaky aquifers in the short time range is complicated because it requires the use of very refined meshes. This range of time includes not only pumping tests but also many regional studies because the definition of short time range depends on the thickness and diffusivity of the aquitard. The groundwater system of Mexico City is an example in which the short time range extends well beyond the whole life span of the pumping wells. In this paper a procedure which permits the avoidance, to a large extent, of these difficulties is explained; it is based on the integrodifferential equations approach. In addition a method that can be applied to control the error is presented.
Tracer movement in a single fissure in granitic rock: Some experimental results and their interpretation
Authors: Neretnieks Ivars , Eriksen Tryggve , Tähtinen Päivi
Published: February 2008

Radionuclide migration was studied in a natural fissure in a granite core. The fissure was oriented parallel to the axis in a cylindrical core 30 cm long and 20 cm in diameter. The traced solution was injected at one end of the core and collected at the other. Breakthrough curves were obtained for the nonsorbing tracers, tritiated water, and a large‐molecular‐weight lignosulphonate molecule and for the sorbing tracers, cesium and strontium. From the breakthrough curves for the nonsorbing tracers it could be concluded that channeling occurs in the single fissure. A ‘dispersion’ model based on channeling is presented. The results from the sorbing tracers indicate that there is substantial diffusion into and sorption in the rock matrix. Sorption on the surface of the fissure also accounts for a part of the retardation effect of the sorbing species. A model which includes the mechanisms of channeling, surface sorption, matrix diffusion, and matrix sorption is presented. The experimental breakthrough curves can be fitted fairly well by this model by use of independently obtained data on diffusivities and matrix sorption.
Incremental dynamic programing may yield nonoptimal solutions
Authors: Turgeon André
Published: February 2008

It is shown in this paper, with two examples, that incremental dynamic programing may converge to a nonoptimal solution if the same state increment is used for every stage. Then it is shown how to adjust the increment sizes in each stage to obtain the desired results.
Real time adaptive closed loop control of reservoirs with the High Aswan Dam as a case study
Authors: Bras R. L. , Buchanan R. , Curry K. C.
Published: February 2008

An algorithm is presented to introduce real time streamflow forecasts in reservoir operation. The adaptive control technique can handle situations where stream flow transition probabilities and system objectives are continuously updated and changing over finite transient periods before achieving steady state conditions. As a case study, streamflow forecasting and adaptive control are used in the High Aswan Dam, Egypt, to minimize losses due to irrigation deficits, power production deficits, and flood damages. Results are extensively compared to those obtained using a traditional steady state stochastic dynamic programing approach and those obtained using the heuristic operational policy of High Aswan Dam.
Unsaturated flow in spatially variable fields: 2. Application of water flow models to various fields
Authors: Bresler Eshel , Dagan Gedeon
Published: February 2008

The method of modeling water flow during infiltration and redistribution formulated in part 1 of this study has been applied to compute expectations and variances of a few water flow variables and of effective hydraulic properties. Two spatially variable soils with different degrees of variation have been investigated. The expectations and variances are obtained by using the statistical averaging procedure and probability density function (pdf) of saturated hydraulic conductivity Ks. The stationarity hypotheses and the requirement that the integral scale of Ks is much smaller than the length scale characterizing the field in the x, y plane have been adopted. An approximate solution which assumes the concept of a wetting front and uniform water content is used for the statistical averaging procedure. A comparison of these results with data computed by a more accurate numerical solution to Richard's equation shows that the approximate simplified models lead to a quite accurate value of the expectations and variances of the flow variables when the field is sufficiently heterogeneous. It is suggested that in spatially variable fields, stochastic modeling represents the actual flow phenomena more realistically and provides the main statistical moments (mean, variances) by using simplified flow models which can be used with confidence in applications. The field effective hydraulic properties have been defined and derived by using approximate models. It is shown that effective properties may be meaningful only under very restricted and special conditions, such as steady gravitational flow. They do not exist in the general case of infiltration‐redistribution. It is concluded that the traditional deterministic approach for solving the flow equations cannot be justified for solving flow problems in spatially variable fields.
Analytical solution of a partially penetrating well in a two‐layer aquifer
Authors: Javandel Iraj , Witherspoon Paul A.
Published: February 2008

The behavior of a two‐layer aquifer pumped by a partially penetrating well is a matter of considerable interest. Analytical solutions are developed for drawdowns in either layer and are evaluated numerically to illustrate some typical cases. The validity of the solutions is demonstrated by comparison with the limiting single‐layer case and with results from finite element calculations. Asymptotic solutions for small and large values of time are developed to show that (1) at early times with partial penetration the behavior of the pumped layer is exactly the same as that of a single layer and (2) at large values of time a semilog plot of drawdown versus time yields a straight line whose slope is only a function of the sum of the two transmissivities. A method is proposed for the interpretation of pump test data.
A geostatistical approach to the trickle irrigation design in heterogeneous soil: 1. Theory
Authors: Russo David
Published: February 2008

A geostatistical approach was used to investigate the spatial variability of two measured soil hydraulic parameters, the saturated hydraulic conductivity Ks and α = d[log K(h)]/[d(h)], where K is the hydraulic conductivity and h is the soil water pressure head. Using a linearized solution to steady infiltration from a circular shallow pond, the spatial distribution of the midway soil water pressure head between emitters, hc (for a given trickle discharge rate Q and spacing between emitters, d), was calculated using the spatially variable soil parameters Ks and α. The spatial distribution of the crop yield Y was calculated from the spatially variable hc by using a quadratic expression for the Y(hc) relationships. It was found that the spatial variability of each of the measured input parameters (Ks and α) or the calculated output variables (hc and Y) is expressed through the variogram γ and can be characterized in terms of the coefficient of variation CV and the integral scale J. In the case of log Ks, for which the sill is reached at relatively small range, two different γ were tested. Results showed that the kriged values of log Ks as well as the resultant values of hc = hc(Ks α; d, Q) were relatively insensitive to the selected γ. The spatial variability of hc reduced the average (over the field) crop yield that would have been obtained when hc was uniform throughout the field. The spatially variable soil parameters Ks and α were used to calculate the spatial distribution of the spacing between emitters (d) required to achieve (for a given trickle discharge) a prespecified value of hc, uniform throughout the field. It was found that the use of a spatially variable d increased the field crop yield by 3% relative to the yield that was obtained when a single‐valued d uniform throughout the field was used. The spatial distribution of d was combined with hydraulic principles to derive the spatial distribution of lateral diameter and length for engineering design requirements.
Calcite supersaturation and precipitation kinetics in the Lower Colorado River, All‐American Canal and East Highline Canal
Authors: Suarez D. L.
Published: February 2008

In situ pH determinations and analysis of major ions in solution indicated that the lower Colorado River is supersaturated with respect to calcite throughout the entire daily cycle, in both winter and summer. Although the ion activity product was 4 to 6 times greater than the calcite solubility product, there was no detectable precipitation. Chemical analyses of water samples taken along 350 km of the river and canals from Parker Dam to the Salton Sea also revealed no evidence of calcium carbonate precipitation despite the inflow of saline and highly supersaturated irrigation return flows. Laboratory kinetic studies indicated that calcite crystal growth rates with Colorado River water are about 30% of the rate for pure Ca‐HCO3 waters and about 70% of that for synthetic Colorado River water. Calcite precipitation by crystal growth in the river is limited by the combination of short residence times and unavailability of reactive calcite. Critical supersaturation levels necessary for heterogeneous nucleation do not occur; a high suspended load limits algal photosynthesis and thus prevents large decreases in daytime H2CO3 levels.
Timing and duration of high rainfall rates in the southwestern United States
Authors: Osborn Herbert B.
Published: February 2008

High‐intensity rains of short duration and limited areal extent are important in the southwestern United States to engineers, hydrologists, meteorologists, and others concerned with the frequency, magnitude, duration, and distribution of thunderstorm rainfall. In this paper, data from two dense raingage networks, one in southeastern Arizona and the other in eastern New Mexico, were used to establish expected occurrences of high rainfall rates (50 mm/h and greater) and diurnal and seasonal variability in such occurrences. Expected occurrences and durations above various thresholds were determined for both point and area for each location.
Modeling Rapidly Varied Flow in Tailwaters
Authors: Ferrick Michael G. , Bilmes Jonathan , Long Sam E.
Published: February 2008

An understanding of the downstream propagation of sharp‐fronted, large‐amplitude waves of relatively short period is important for describing rapidly varying flows in tailwaters of hydroelectric plants and following the breach of a dam. We developed a numerical model of these waves by first identifying the primary physical processes and then performing an analysis of the solution. A linear analysis of the dynamic open channel flow equations provides relationships describing flow wave advection, diffusion, and dispersion in rivers. A one‐dimensional diffusion wave model modified for application to tailwaters simulates the important physical processes and is straightforward to apply. The “modified equation” and von Neumann analyses provide insight into the effects of numerical parameters θ, Δx, and Δt upon stability and dissipative and dispersive behavior of the solution, but the Hirt analysis is found to yield incorrect phase relationships. The capability and accuracy of the model are enhanced when physical diffusion of a river wave is balanced by numerical diffusion in the model. Field studies were conducted in two greatly different tailwaters to assess our understanding of large‐scale, rapidly varying flow waves. The accurate simulation of waves having wide‐ranging amplitudes, shapes, periods, and base flows attests to the soundness of both the physical basis of the model and the numerical solution technique. These studies reveal that diffusion of short‐period waves in natural, free‐flowing rivers is significant and that inertia is negligible.
A Model for Constrained Optimum Water Pricing and Capacity Expansion
Authors: Dandy G. C. , McBean E. A. , Hutchinson B. G.
Published: February 2008

Previous studies of optimum water pricing and capacity expansion have ignored the political and administrative factors which limit the range of feasible decisions. A general model is presented for identifying the water price horizon so as to maximize the present value of net benefits. Constraints on the range of water price, the rate of price change, and financial cost recovery are included in the model. The model is applied to a hypothetical case study of an urban water supply system. The results indicate that optimum water pricing and capacity expansion policies are likely to achieve some increase in economic benefits when compared with average cost pricing. Administrative and political constraints tend to reduce these benefits but result in more acceptable pricing policies.
Aspects of Quasilinear Infiltration from Surface Sources, Especially the Case α = 0
Authors: Philip J. R.
Published: February 2008

Three recent papers on steady two‐dimensional infiltration from spatially variable surface sources may lead to confusion about the quasilinear analysis. The papers assert that putting α = 0 in quasilinear solutions for the stream function gives solutions for saturated flows. In fact, putting α = 0 yields the precisely opposite case of purely capillary‐driven unsaturated flows. The argument of the papers is that for α = 0 the quasilinear equation for the stream function is reduced to Laplace's equation, which is obeyed by the stream function for saturated flows. The kinematics of all two‐dimensional solenoidal irrotational flows is, however, such that their stream functions obey Laplace's equation, and the physical meaning, and indeed the physical existence, of any flow can be determined only from supplementary dynamic information about the velocity potential.
Kinematic Models for Soil Moisture and Solute Transport
Authors: Charbeneau Randall J.
Published: February 2008

The kinematic theory of soil moisture and solute transport in the vertical direction for unsaturated groundwater recharge is considered. The general theory of kinematic models is reviewed and applied for an isolated wetting event wherein the soil starts at and eventually drains to field capacity. Analytical expressions are developed for the water content and moisture flux as a function of depth and time. The approach is extended for an arbitrary sequence of surface flux or water content boundary conditions. The transport of a solute with a general nonlinear sorption isotherm is also considered. It is shown that for the general isotherm the vertical displacement of a solute isochore during an arbitrary wetting sequence depends only on the total depth of water infiltrated and not on how the infiltration rate varies with time.
Real Time Irrigation Scheduling via “Reaching” Dynamic Programming
Authors: Pleban Shlomo , Heermann Dale F. , Labadie John W. , Duke Harold R.
Published: February 2008

A dynamic programming model is formulated for determining surface irrigation schedules over the short term that minimize irrigation labor costs while meeting crop requirements under a limited water supply. This is a relevant problem for a large number of farm operations on the High Plains served by wells tapping the Ogallala Aquifer. The model is capable of solving high‐dimensional problems by a “reaching” forward algorithm that defines a surrogate state space by using binary decision policies rather than by discretization of the actual state variables. Real time use of the short‐term model was simulated for two irrigation seasons, using data from the Northern Colorado Research Demonstration Center near Greeley, Colorado. The model optimized the scheduling of nine field groups divided into a total of 24 fields. An 8% savings in irrigation costs resulted for both years, as compared with conventional scheduling, while maintaining acceptable soil moisture levels.
A Geostatistical Approach to Solute Transport in Heterogeneous Fields and Its Applications to Salinity Management
Authors: Russo David
Published: February 2008

In heterogeneous fields in which the soil water properties and the initial salinity vary under a deter‐ ministic water application rate uniform throughout the field, the salinity during leaching might also differ from place to place. A geostatistical approach was used to investigate the spatial variability of three soil properties: the saturated hydraulic conductivity Ks, the soil characteristic α = d log (K)/d(ψ) (K being the soil hydraulic conductivity and ψ being the pressure potential), and the dispersivity λ, as well as the initial salinity EC0, by using actual measured field data. These properties were used as input parameters of a simplified water and salt flow model, which in turn was coupled with the conditional simulation method to analyze the salinity profile and its spatial distribution during leaching in a 187‐ha plot of land. Analysis of the results showed that 107 hours of continuous leaching (6527 m3 ha−1) were required to obtain an average salinity of EC* = 5 dS/m for the field layer between the soil surface and the 40‐cm depth. By considering the leaching of the different sites in the field, rather than that of the entire field, it was shown that, theoretically, the amount of water for leaching required to obtain EC* = 5 dS/m uniformly throughout the field can be reduced to 4038 m3 ha−1 (a reduction of 38%). Practically, since the field had to be subdivided into small subplots and because of engineering design requirements for the water supply system, the amount of water for leaching required to obtain the above‐mentioned value of EC* for the entire field (5193 m3/ha) could be reduced by only 20%.
Bed Load Transport in a River Meander
Authors: Dietrich William E. , Smith J. Dungan
Published: February 2008

Bed load transport in Muddy Creek, Wyoming, a sand‐bedded meandering river with equilibrium bottom topography, was found to consist of a zone of maximum sediment flux that shifted across the channel from near the inside bank in the upstream part of the bend toward the pool at the minimum radius of curvature. Significant net cross‐stream transport continued even through the crossings between the bends. The downstream bed load transport field for the bend which was studied in greatest detail was the same as that computed from bed form migration measurements and can be predicted from appropriate boundary shear stress data and the Yalin bed load equation. The zone of maximum bed load transport followed an outward‐shifting region of maximum boundary shear stress, although in the downstream end of the bend the sediment transport maximum tended to stay closer to the centerline than the boundary shear stress maximum due to particle size influences. Net cross‐stream transport varied with particle size and was effected by three major processes: topographically‐induced, near‐bed, cross‐stream flow; trough wise flow along obliquely oriented bed forms; and rolling or avalanching of particles on bed form lee faces plus rolling or mass sliding on a steep cross‐stream point bar side slope. Coarse particles were carried outward over the top of the point bar by a near‐bed cross‐stream flow that was induced by downstream shoaling. These particles then rolled and slid on the point bar side slope and eventually were carried toward the outer bank by troughwise transport along oblique dunes. In the upstream part of the bend, fine particles were carried inward by the channel curvature‐induced, near‐bed flow and by troughwise transport along lee faces of oblique bed forms. Fine particles and coarse particles crossed paths on top of the point bar, where weak troughwise flow moved just the finer particles toward the convex bank, and on the point bar face, where coarse particles rolled against the secondary circu‐ lation that was carrying the finer particles. Net cross‐stream bed load transport was toward the pool and was on average about 10% of the downstream bed load transport. The Engelund equation predicts reasonably well the general pattern of net cross‐stream transport through the meander, but it does not account for the substantial troughwise transport caused by oblique bedforms at several locations in the bend. Our observations suggest that equilibrium bed topography occurs when there is net outward transport into the outward shifting zone of maximum boundary shear stress.
Stochastic dynamic programming models for reservoir operation optimization
Authors: Stedinger Jery R. , Sule Bola F. , Loucks Daniel P.
Published: February 2008

Most applications of stochastic dynamic programming have derived stationary policies which use the previous period's inflow as a hydrologic state variable. This paper develops a stochastic dynamic programming model which employs the best forecast of the current period's inflow to define a reservoir release policy and to calculate the expected benefits from future operations. Use of the best inflow forecast as a hydrologic state variable, instead of the preceding period's inflow, resulted in substantial improvements in simulated reservoir operations with derived stationary reservoir operating policies. While these results are for a dam at Aswan in the Nile River Basin, operators of other reservoir systems also have available to them information other than the preceding period's inflow which can be used to develop improved inflow forecasts.
Sufficient conditions for river meandering: A simulation approach
Authors: Howard Alan D. , Knutson Thomas R.
Published: February 2008

A digital simulation model produces realistic meandering patterns starting from an initially straight channel with small random perturbations. The model assumes that nominal migration rates increase as channel curvature increases but reach a maximum when bend radius divided by channel width is about 3, with decreasing rates for sharper bends, in accord with observations of Nanson and Hickin (1983) and others. However, it is also necessary to assume that local migration rates are a weighted average of local and upstream nominal rates, with the weighting decreasing upstream. The model includes provisions for neck cutoffs and may be used to forecast future patterns of channel migration in meandering streams.
Ex post evaluation of flood control investments: A case study in North Dakota
Authors: Palanisami K. , Easter K. William
Published: February 2008

Ex post estimates of a flood control project in North Dakota are compared with the U.S. Army Corps of Engineers ex ante estimates. Ninety‐two percent of the ex ante benefits were suppose to come from water supply and 8% from flood control. Ex post estimates found zero water supply benefits and flood control 37 times higher than ex ante estimates. These added flood control benefits were enough to make up for all the lost water supply benefits. Still the ex post analysis shows that the ex ante estimates were based on inadequate information and did not include commerical fishing and recreation benefits which accounted for 28% of the ex post benefits.
Stochastic models of subsurface flow: Log linearized Gaussian models are “exact” for covariances
Authors: Gutjahr Allan
Published: February 2008

Stochastic solutions for steady state infinite domain flow models are studied under the assumptions that log conductivity and head are second‐order stationary jointly Gaussian processes. It is shown that the covariance relationships previously derived are exact solutions for the nonlinearized equations no matter how large the input variance is.
Groundwater Chemistry Change due to Tidal Fluctuations in the Stonehouse Brewery Well, Plymouth, England
Authors: Roxburgh I. S.
Published: February 2008

The Stonehouse Brewery Well is sunk 24 m into the well‐cemented, fissure‐dominated Plymouth Limestone. Groundwater within the well can be shown to be in hydraulic continuity with the marine waters of Plymouth Sound. Groundwater was discharged from the well for 28 hours at approximately 13,500 L/h and samples taken hourly were subsequently analyzed for pH, conductivity, magnesium, potassium, sodium, chloride, calcium, and nitrate. The results of these analyses are reported and briefly discussed in particular the apparent tidally influenced cyclicity of certain data sets and the apparent influence of the upcoming of saline water beneath the pumped well upon the chemistry of the discharged well water.
Validity of the Local Equilibrium Assumption for Modeling Sorbing Solute Transport Through Homogeneous Soils
Authors: Valocchi Albert J.
Published: February 2008

Sorption processes that occur during reactive solute movement through porous media can be modeled using either an equilibrium or kinetic approach. Because of the resulting conceptual and mathematical simplification, many transport models assume local chemical equilibrium is valid for describing sorption reactions. This paper presents quantitative criteria to assess the validity of the local equilibrium assumption for one‐dimensional, steady flow through homogeneous soils. A method is described whereby formulas for solute breakthrough curve time moments can be determined without knowledge of the nalytical solution to the mass transport model. This method is applied to several commonly used nonequilibrium formulations as well as the standard linear equilibrium model. The formulations considered include both the physical nonequilibrium models where the sorption rate is controlled by diffusive solute transfer between mobile and stagnant fluid zones and the chemical nonequilibrium models where the overall sorption rate is governed by the rate of reaction at the soil‐solution interfaces. Criteria for local equilibrium to be valid are derived by comparing the time moment formulas for the nonequilibrium and equilibrium models. These criteria explicitly show that basic system parameters (e.g., seepage velocity, dispersion coefficient, distribution coefficient, sorption rate, boundary conditions) have a significant influence on the attainment of local equilibrium.
Stochastic Dynamics of Precipitation: An Example
Authors: Cho Han‐Ru
Published: February 2008

An example is developed to illustrate how atmospheric dynamics may naturally lead to stochastic behavior in precipitation. Due to a process in the atmosphere known as scale contraction, large fluctuations in precipitation may be induced by small mesoscale inhomogeneities in the initial temperature field. If the initial states of the participating air masses of a mid‐latitude cyclone are not well defined at the mesoscale, precipitation may be considered as a dynamic process subject to random initial conditions.
Water‐Limited Equilibrium of Savanna Vegetation Systems
Authors: Eagleson Peter S. , Segarra Rafael I.
Published: February 2008

The average annual water balance of savanna vegetation systems is modeled as an interactive competition between trees and grass for water and energy. Ecological optimality hypotheses are introduced which allow specification of the woodland canopy density, the grass canopy density, and the plant (water use) coefficients of both tree and grass under conditions of natural equilibrium. Only one tree‐grass equilibrium state is found and is shown to agree well with the observed state of savanna in Sudan and the Transvaal. This state is stable with respect to perturbations of vegetation canopy density, but is metastable with respect to shifts in climate. Two other equilibrium states exist as vegetation monocultures, i.e., grassland and forest, but both are shown to be unstable with respect to perturbations of vegetation density.
A Distinct Policy Which Forms a Market Within the California State Water Project
Authors: Curie Madalene Mary
Published: February 2008

There are recurring suggestions that California water rights markets ought to be formed in order to capture estimated economic losses. Such markets would have to be created from the existing nonmarket water institution. This paper exemplifies a process of examining a particular water project, the California State Water Project, within an economic framework in order to construct a distinct proposal for market formation. Surprisingly, the law need not be changed in this case. The sufficient condition for market formation is the codification of the project's water transfer policy.
Alternatives and Uncertainties in Interstate Groundwater Law
Authors: Utton Albert E.
Published: February 2008

The courts are at a beginning stage in the development of interstate groundwater law, and two conflicting legal approaches are contending for use by the courts in deciding interstate groundwater disputes. The Supreme Court has, over the years, developed the doctrine of equitable apportionment to settle disputes on interstate streams and recently used the commerce clause of the Constitution to decide an interstate groundwater case. Equitable apportionment requires the consideration of equitable factors by a third‐party decision maker in allocating the uses of interstate waters. Commerce clause analysis requires that the market place shall allocate the use of interstate waters. Equitable apportionment recognizes the equality of states under the concepts of federalism; commerce clause analysis largely erases statelines. An integrated interstate water law is preferable to having one law for interstate surface waters and another for groundwaters. If the integrating principle is that of equitable apportionment, it has the advantage of allowing states and regions to plan, conserve, and manage waters over time, while at the same time preventing any one state from taking more than an equitable share.
Regression Approximations for Transport Model Constraint Sets in Combined Aquifer Simulation‐Optimization Studies
Authors: Alley William M.
Published: February 2008

Problems involving the combined use of contaminant transport models and nonlinear optimization schemes can be very expensive to solve. This paper explores the use of transport models with ordinary regression and regression on ranks to develop approximate response functions of concentrations at critical locations as a function of pumping and recharge at decision wells. These response functions combined with other constraints can often be solved very easily and may suggest reasonable starting points for combined simulation‐management modeling or even relatively efficient operating schemes in themselves.