bluuebunny/crossref_metadata_2025 huggingface dataset:
A parameter‐efficient hydrologic infiltration model
Authors: Smith R. E. , Parlange J.‐Y.
Published: February 2008

By adopting two extreme assumptions concerning the behavior of unsaturated soil hydraulic conductivity K near saturation, we derived a two‐branched model for ponding time and infiltration rate decay for arbitrary rainfall rates. One assumption was that K varies slowly near saturation and leads to an expression for ponding time and infiltration decay. For initially ponded conditions, ponding time is zero, and with rainfall rate r → ∞, the familiar Green and Ampt (1911) expression results. The other, rather opposite assumption was that K varies rapidly, e.g., exponentially, near saturation. This model also holds for both rainfall and ponded surface conditions, and for ponded conditions the expression is identical to that of Parlange (1971). Each model uses only two parameters, saturated soil conductivity Ks and a parameter that is roughly related to sorptivity and responds nearly linearly to variations in initial saturation. Both parameters are physically related to measurable soil properties. Methods are presented to estimate parameters of either model from infiltrometer tests. The two models are compared with a precise numerical solution of the unsaturated soil water diffusion equations for three soils that represent a range of soil behaviors near saturation. Our results show that either assumption would be an excellent model for most hydrologic purposes, and the relative goodness of fit of each model is generally consistent with the appropriate behavior of K(θ → θS).
Finite element method for subsurface hydrology using a mixed explicit‐implicit scheme
Authors: Narasimhan T. N. , Neuman S. P. , Witherspoon P. A.
Published: February 2008

The mixed explicit‐implicit Galerkin finite element method developed previously by the authors is shown to be ideally suited for a wide class of problems arising in subsurface hydrology. These problems include confined saturated flow, unconfined flow under free surface conditions subject to the Dupuit assumption, flow in aquifers which are partly confined and partly unconfined, axisymmetric flow to a well with storage, and flow in saturated‐unsaturated soils. A single computer program, entitled Flump, can now handle all of these problems. The mixed explicit‐implicit solution strategy employed in the program insures a high level of accuracy and computation efficiency in most cases. It eliminates many of the difficulties that groundwater hydrologists have been encountering in trying to simulate extensive aquifer systems by finite elements. Some of the outstanding features of this solution strategy include an automatic control of time step size, reclassification of nodes from explicit to implicit during execution, automatic adjustment of the implicit time‐weighting factor, and the treatment of boundary conditions and source terms as arbitrary functions of time of the state of the system. Five examples are presented to demonstrate the versatility and power of this new approach. A purely physical derivation of the finite element equations which does not rely on the Galerkin formalism is also included in one of the appendices.
The carbon isotope geochemistry of a small groundwater system in northeastern Ontario
Authors: Fritz P. , Reardon E. J. , Barker J. , Brown R. M. , Cherry J. A. , Killey R. W. D. , McNaughton D.
Published: February 2008

The carbon isotopic composition (13C and 14C) of the inorganic carbon dissolved in the waters of a small, largely unconfined aquifer in unconsolidated sediments on the Canadian Shield has been investigated. Three principal carbon sources are recognized: soil CO2, rock carbonate, and biogenic CO2. The average δ13C value of the soil CO2 is close to −21.0 ± 1.5%, and present‐day 14C activities of the soil CO2 vary between 130 and 162% modern 14C. Very minor amounts (< 1.0%) of carbonate minerals (δ13C = −0.6‰) are present within the aquifer and react with this soil CO2 to produce a dissolved inorganic carbon (DIC) with 14C activities which are as much as 50% below the initial activities of the soil CO2. The third carbon source, a biogenic CO2, could be detected only indirectly, and its presence is primarily deduced from the occurrence of methane in the deeper parts of these aquifers. The large isotope fractionation which occurs during bacterial coproduction of CO2 with this methane results, however, in a 13C‐rich CO2 and thus a DIC with high δ13C values. Values of δ13C as high as +11‰ have been measured in groundwaters on the Canadian Shield. Since the origin of the destroyed organic matter is not yet known, no assessment of the importance of this CO2 for the 14C contents of the DIC is possible.
Initial effects of clearcut logging on size and timing of peak flows in a small watershed in western Oregon
Authors: Harr R. Dennis , McCorison F. Michael
Published: February 2008

Size of annual peak flow in a small watershed in western Oregon was reduced 32%, and average delay of all peak flows was nearly 9 hours following clearcut logging. Size of annual peak flows caused by rain with snowmelt was reduced 36%, and peak flows resulting from rain with snowmelt were delayed an average of nearly 12 hours following logging. Changes are attributed mainly to differences in short‐term accumulation and melting of snow. No significant changes were detected in size or timing of peak flows that resulted from rainfall alone.
Instantaneous unit hydrograph with negative ordinates—possible?
Authors: Boneh A. , Golan A.
Published: February 2008

The answer to the question posed in the title of this paper is yes, provided that some restrictions are imposed on the rainfall excess which is the input to the surface runoff system. Obviously, impulsive inputs are not admissible when the instantaneous unit hydrograph (IUH) has negative ordinates, since the IUH is the direct surface runoff response (known as the ‘Output’) to an instantaneous rainfall burst of unit volume and such runoff, by definition, cannot be negative. Is an instantaneous unit hydrograph with negative ordinates (IUHWNO) desirable? Now the answer is no, because of the restrictions that have to be imposed on the input. The purpose of this paper is not to justify the assumption of linearity, an assumption which is open to serious doubts, but rather to point out that IUHWNO can be of value if and when linearity of surface runoff systems is assumed. Two problems are considered: (1) The first is the ability of an IUHWNO to represent a real‐world surface runoff system. A ‘degenerate IUH’ does not have this ability, and hence the term ‘nondegenerate IUH’ is carefully defined in the paper. Several conditions are derived in the paper which enable decision as to the degeneracy of a given IUHWNO. (2) The second problem is the determination of the class of admissible inputs in a surface runoff system which is represented by a given nondegenerate IUHWNO. These two problems are relevant to whether or not one should explicitly introduce nonnegativity sign constraints into the IUH ordinates in the identification of a surface runoff system from input‐output records. Possible extensions to nonlinear and time‐varying systems are considered in the paper for continuous or discrete‐time systems.
The effect of intercepted rainfall on the water balance of a hardwood forest
Authors: Singh B. , Szeicz G.
Published: February 2008

Evaporation from a large hardwood forest is estimated from measurements of the required meteorological variables and from measured stomatal resistances. A correction factor is derived to overcome the incorrect assumption that evaporative demand remains the same during wet and dry periods. The factor is based on the ratio of the isothermal resistances during the wet and subsequent dry periods. The stomatal measurements were converted to canopy resistances by dividing by the leaf area index and were used to obtain the water balance for the entire season. The results are analyzed to show that evaporation from a wet canopy is often 2–3 times greater than transpiration from the same surface. Rates of interceptional loss, calculated from the wet and dry evaporation rates, were verified by direct measurements of throughfall and stemflow. Net interceptional loss, equal to the excess evaporation from a wet canopy over a dry one, depended on rainfall duration and character and was on the average about 60–80% of total interception, In the overall summer water balance of 442 mm of precipitation and 52‐mm depletion of soil storage, transpiration via the trees accounted for 261 mm; evaporation from the wetted leaves and branches for 111 mm, and runoff for 131 mm, giving an error of closure in the water balance of only 9 mm. If transpiration only had been used instead of interception when the canopy was wet, the error in the water balance would have been 100 mm.
Cost allocation for a regional wastewater treatment system
Authors: Loehman E. , Orlando J. , Tschirhart J. , Whinston A.
Published: February 2008

There are economies of scale in the construction of regional wastewater treatment systems. Effluent dischargers have the option of participating in a regional system or constructing separate smaller systems. In order to encourage participation in a regional system so that the economies are realized, the cost allocation method employed must offer economic incentives. The cost allocation problem is viewed in game theoretic terms, and the Shapley value (a game theory solution) is suggested as an allocation method. The method is applied to the Meramec River Basin in Missouri where eight dischargers are identified. The problems of application are discussed and the reactions of the eight dischargers are cited.
Water trade‐off between electric energy and agriculture in the four corners area
Authors: Gisser Micha , Lansford Robert R. , Gorman William D. , Creel Bobby J. , Evans Mark
Published: February 2008

The results of estimating the economic impact of the growing electric generating sector on agriculture are given. A linear programing (LP) model was designed to represent agriculture in three subregions and the Navajo Indian Irrigation Project. The assumption was made that the electric generating sector will purchase water from farmers. The impact of shifting water from agriculture to the electric generating sector was evaluated by reducing the water allocation for agriculture at discrete steps, and after each reduction the LP model was run. Changes in the shadow prices of water, farm income, and employment were calculated after each linear programing run. Regional multipliers (at the county level) were applied to gauge the impact on the regional economy. It was concluded that commercial farms would be able to sell water to the energy sector by switching from flood irrigation to sprinklers. Part‐time farmers would reduce their cultivated acreage. Farmers would need relatively large funds to invest in sprinklers. For the utilities the cost of the water would be relatively insignificant.
The significance of the storage parameter in saturated‐unsaturated groundwater flow
Authors: Narasimhan T. N.
Published: February 2008

An essential feature of transient groundwater movement is the phenomenon of change in groundwater storage. Storage change is governed by three fundamental processes: change in void volume of the skeleton, change in fluid saturation, and change in fluid density. Since the expansivity of water is very small, the phenomenon of change in storage in fully saturated media is dominated by matrix deformation. When the soil is partially saturated it is customarily assumed that the matrix is essentially rigid and desaturation is the only process governing change in storage. While this assumption may be reasonable at relatively low saturations, it may not be valid at high saturations or in the transition zone between the saturated and unsaturated regimes. The key to the understanding of this lies in a proper appreciation of the constitutive relationships that exist between mechanical stresses on the one hand and moisture suction on the other. This paper examines the theoretical as well as the practical consequences of the role of soil deformation in saturated‐unsaturated groundwater flow.
Irrigation planning: 1. Cropping pattern
Authors: Matanga George B. , Mariño Miguel A.
Published: February 2008

Irrigation programs, specified in terms of dates and depths of irrigation, are developed for corn, grain sorghum and pinto beans. The information contained in the irrigation programs for each crop is applied in an area‐allocation model to determine a cropping pattern for the three crops. The area‐allocation model is a linear optimization model which maximizes gross margin from yields of crops under consideration subject to total water supply, maximum amount of water that can be delivered for irrigation purposes on any date of irrigation, and irrigation labor. The land area to be allocated to each crop for planting is the decision variable. Results from the area‐allocation model include cropping pattern, gross margin, total irrigation depth on each date of irrigation, total irrigation labor, and crop yield. Sensitivity analysis is performed to study the effect of changes in crop prices on the optimal results.
Drainage network power
Authors: Gregory K. J.
Published: February 2008

Although many indices of drainage basin characteristics have been devised and employed in previous studies, there is still a need to identify those indices which have an easily interpreted physical significance to be of use in explanatory models. Whereas stream power has been used in hydraulic studies of river channels, a comparable expression can be developed to denote the potential energy available in the stream network of a drainage basin. An index of drainage network power is obtained as the volume of the channel network divided by the basin relief and this index expresses the potential energy of the network of channels in the basin and it may be directly related to flood potential. The index is used in a study of 14 basins in Britain and it correlates well with mean annual flood obtained from a partial duration series.
A Chance Constrained Optimization Model for reservoir design and operation
Authors: Houck Mark H.
Published: February 2008

A chance constrained linear programing model which employs multiple linear decision rules is developed. The model incorporates explicitly the stochastic nature of the streamflow process, can be used in design and/or management situations, does not significantly restrict the operating policy prior to solution, and is economically and computationally feasible. A portion of the Yakima River system is modeled to demonstrate the use of the multiple linear decision rules.
Induced groundwater recharge in the Ganges Basin
Authors: Chaturvedi M. C. , Srivastava V. K.
Published: February 2008

The Ganges basin in India has a serious problem of water availability. The basin area, which is only one twelfth that of the United States, has a population greater than the total U.S. population, and it is increasing at a rate of 2.5% per annum. About 77% of the population is engaged in agriculture which is totally dependent on irrigation, as almost 85% of rainfall takes places in 2–3 monsoon months. Surface storage possibility is extremely limited, but groundwater recharge appears feasible, since sedimentary alluvial formations extend to depths of thousands of meters. Three alternative schemes of groundwater recharge have been proposed. One involves pumping heavily along perennial rivers prior to monsoons so as to lower groundwaters to promote induced groundwater recharge. The second proposes a similar approach along nonperennial rivers. The third involves irrigation during monsoons with groundwater lowered adequately in the nonmonsoon period so that enough induced groundwater recharge takes place to provide adequate supplies for nonmonsoon months. A simulation‐optimization model has been developed to study the surface flow‐groundwater interaction and has been applied to study comparative cost effectiveness of the three alternate approaches. Sensitivity analysis has also been carried out. It is shown that the third scheme is the most attractive.
A planning model for the management of groundwater quality
Authors: Willis Robert
Published: February 2008

A dynamic planning model is presented for the optimal management of groundwater quality in regional aquifer systems. The groundwater system is conjunctively managed as a water supply resource and as a storage reservoir for waste water residuals. The waste waters are discharged to the groundwater basin through injection wells. Within the groundwater system, constituents are assumed to follow first‐order chemical or biochemical reactions and linear equilibrium adsorption. The Galerkin finite element method is used to transform the flow and mass transport equations of the aquifer system into systems of ordinary differential equations which are imbedded as constraint equations in the planning model. The mathematical model, which is structured as a nonconvex programing problem, allows the planner or resource manager to determine (1) the optimal pumping and injection schedules (rates and locations) required to satisfy an exogenous water target and waste load demand and (2) the maximum injection concentrations that can be discharged to the basin without degrading the quality of the aquifer. Operational policies are developed for a 480‐day operational cycle for a hypothetical groundwater basin, where it is assumed that groundwater extraction represents the principal resource of the aquifer system. Linear programing is used to identify the optimal planning policies. The important parameters affecting the optimal decisions are discussed.
Effect of infiltration rate on biological clogging and water quality changes during artificial recharge
Authors: Okubo T. , Matsumoto J.
Published: February 2008

The effect of infiltration rate on biological clogging and water quality changes is investigated experimentally using a sand column. The concentration of soluble COD in the effluent is stable during 3 months of infiltration, and the lower the initial infiltration rate is, the higher the average percentage of the reduction of soluble COD becomes. The soluble COD is primarily removed in the surface layer. The hydraulic conductivity in the bottom layer decreases at the highest infiltration rate. The variation of infiltration rate is divided into four stages. In addition, the biological‐clogging model is proposed, and the mechanism of biological clogging is discussed.
Dimensionality problems in water quality network design
Authors: Lettenmaier Dennis P.
Published: February 2008

Dimensionality problems in design of water quality networks arise from the multiple variables measured, which may be generated by different physical, chemical, and biological processes, and from the multiple spatial and temporal dimensions of the processes generating the measurements. The problem is further complicated by the range of objectives which a network may be required to meet. The designer is almost inevitably constrained by budget considerations to employ the same network to measure an array of variables, often for more than one objective. These considerations serve to pose serious difficulties in arriving at an analytical formulation of the problem, far less to solve it, with the result that almost all existing water quality networks have been designed on an ad hoc basis. Although no one approach is likely to be universally applicable, several techniques have been employed in particular situations. Included are state estimation, time series analysis, probability theory, and the theory of regionalized variables. Several promising applications of these techniques to water quality network design are reviewed, and suggestions for future research directions are advanced.
A frequency distribution for annual floods
Authors: Boughton Walter C.
Published: February 2008

A distribution for frequency analysis of the logarithms of annual floods has been derived from data from 78 catchments in eastern Australia. The statistics of data from these catchments demonstrate the need for three‐parameter distributions instead of two‐parameter distributions for analysis of annual floods. A nonlinear relationship between frequency factor and In In [T/[T − 1)] function of recurrence interval is demonstrated, and this relationship is used as the basis for the distribution. Methods of fitting the distribution to data sets, including sets which contain zero values, are described. A comparison is made of results from the new distribution, the log Pearson type 3, the log normal, the log Gumbel, and the Gumbel distributions.
Linear system models for regional aquifer evaluation studies
Authors: Bathala Chenchayya T. , Rao A. Ramachandra , Spooner J. A.
Published: February 2008

A generalized linear system model is formulated to analyze several types of groundwater flow problems. An iterative procedure is developed to predict aquifer response due to pumping demand by considering the analytical relationships governing the groundwater flow. Historical pumping rates, groundwater levels, stream stages, and estimated storage coefficients are used as inputs to the model. The model outputs are the aquifer transmissivities and the predicted groundwater levels. The sensitivity of the model to variations in the estimated storage coefficients is investigated. The technique is illustrated by considering a realistic but hypothetical regional aquifer system, and the results are demonstrated to be satisfactory. The technique is insensitive even to large errors in the estimated storage coefficients. The number of simultaneous equations to be solved and hence the computational time required are much smaller than those encountered in the conventional numerical models of aquifer systems. Aquifer transmissivity and storage coefficient values are computed as a part of this procedure. Therefore expensive pumping tests that are usually required to estimate these aquifer parameters are not necessary in this technique.
Multiobjective statistical method for interior drainage systems
Authors: Haimes Y. Y. , Loparo K. A. , Olenik S. C. , Nanda S. K.
Published: February 2008

In this paper the design of a levee drainage system is formulated as a multiobjective optimization problem in a probabilistic framework. The statistical nature of the problem is reflected by the probabilistic behavior of rainfall and river stage events in any given month. The multiobjective approach allows for the incorporation of noncommensurable objectives such as aesthetics, economics, and social issues into the optimization problem, providing a more realistic quantification of the impact of a flood or high water situation in an interior basin. A new method referred to as the multiobjective statistical method, which integrates statistical attributes with multiobjective optimization methodologies such as the surrogate worth trade‐off method, is developed in this paper. A case study using data from the Moline area in Illinois suggests the use of the procedure.
Methods for water supply forecasting
Authors: Young G. K. , Bondelid T. R. , Daley S. A.
Published: February 2008

A cost effective method for generating extended streamflow predictions (ESP) is presented. ESP methods provide probabilistic streamflows during any designated time period. The method presented is based on a sensitivity analysis of the rainfall inputs and resulting streamflow of calibrated rainfall/runoff (R/R) models. The sensitivity approach assumes that knowledge of the variances and sensitivities (partial derivatives) of R/R model input parameters allows one to determine the variance of the output. Monthly rainfall is assumed Markovian. This assumption is used in selection of the input rainfall. The sensitivity approach is applied to the Occoquan watershed in northern Virginia for a period of severe drought. The streamflow variance is within 12% of the value obtained by the current National Weather Service (NWS) technique and required less than 10% of the computer effort required by the NWS technique.
The potential of remotely sensed thermal infrared data to infer surface soil moisture and evaporation
Authors: Price John C.
Published: February 2008

Recently launched satellites provide high‐quality thermal infrared data suitable for estimating hydrologic parameters at the earth's surface. Analytical expressions are derived that relate mean evaporation rate and a quantity dependent on soil moisture (diurnal heat capacity) to surface temperature of bare soil areas. These expressions are corrected for micrometeorological effects through use of a numerical model which simulates the diurnal cycle of surface temperature under realistic air temperature, humidity, and wind speed conditions. Results illustrate the sensitivity of 24‐hour mean temperature to mean evaporation rate, and of the day‐night temperature range to near‐surface soil moisture. This suggests the potential of remotely sensed thermal data for assessing the surface moisture budget.
Numerical model describing groundwater treatment by recharge of oxygenated water
Authors: Boochs P. W. , Barovic G.
Published: February 2008

In aquifers containing iron and manganese rich groundwater, groundwater quality can be improved by injecting an oxidizing agent into the aquifer to promote precipitation of iron and manganese. In this study, oxygen rich water was recharged by an injection well. Concentration measurements were carried out around the well at different locations to find out the demand for oxygen to oxidize iron (II) within the aquifer. Evaluation and interpretation of the field experiments were made by comparison with a mathematical model. The experiments and in particular the model calculations show that the method is practicable and economic.
The infiltration‐soil water storage relationship at a point in watershed modeling
Authors: Bloomfield P. H. I'a. , Pilgrim D. H. , Watson K. K.
Published: February 2008

In most deterministic watershed models developed for synthesizing runoff from rainfall on a continuous basis, a single‐valued relationship between infiltration capacity and soil water storage is used. This type of relationship is examined using results from a numerical solution of the partial differential equation governing flow in unsaturated soil for a profile of uniform initial water content under ponded conditions. The fact that a nonunique relationship exists between infiltration capacity and soil water storage is demonstrated, suggesting that models employing a single‐valued relationship contain a serious conceptual and practical error. The nonunique relationship, which can also be derived from the Philip equation, can be represented by simple empirical infiltration equations for practical application in deterministic watershed modeling. However, the parameters of these equations depend on the initial soil water content, the time interval used in calculations, and the soil store capacity. The nonunique relationship between infiltration and soil water storage is also shown to be applicable to modeling infiltration under rainfall conditions.
Analysis of national water pollution control policies: 1. A national network model
Authors: Gianessi Leonard P. , Peskin Henry M. , Young G. K.
Published: February 2008

In order to study the national implications of federal water pollution control policies, the authors developed a water pollution network model. This model links both point and nonpoint sources of pollution at the county level of detail with a national network of major rivers, lakes, reservoirs, and bays. While the geographical scope of the model and existing data availability required making many simplifying assumptions, the model permits comprehensive analyses that are not possible with existing techniques.
Performance evaluation of a stochastic optimization model for reservoir design and management with explicit reliability criteria
Authors: Houck Mark H. , Datta Bithin
Published: February 2008

A seasonal, chance‐constrained linear programing model, which facilitates the development of reservoir system designs and operation policies and which incorporates multiple linear decision rules (LDR) conditioned upon the streamflows in other seasons, is evaluated with variations in the numbers of seasons per year and decision rules per season. The performance is also compared with the original, single‐LDR model. The motivations for the expected results and the numerical solutions obtained for the examples considered are presented. The multiple‐LDR model is shown to be superior to the single‐LDR model: for equivalent restrictions on the reservoir operation and performance the multiple‐LDR model gives a smaller capacity reservoir than the single‐LDR model. Furthermore, as the number of LDR's per season is increased, the required capacity decreases. And when the operating rules defined by the models are tested in a simulation of actual reservoir operation, the multiple LDR's perform more closely to the specifications prescribed in the linear program than the single LDR.
The statistical mechanical theory of groundwater flow
Authors: Sposito Garrison , Chu Shu‐Yuan
Published: February 2008

The macroscopic differential equations of mass, linear momentum, and energy balance for groundwater are derived from first principles by using the methods of statistical mechanics. The resulting macroscopic equations agree with those derived recently on the basis of fluid mechanics and local volume averaging, except in the case of energy balance. The balance equations for total and internal energy in groundwater are analyzed in detail. It is shown that the groundwater internal energy is actually a partial specific internal energy and that its time development is affected by a gravitational field, whereas the time development of the total energy of groundwater is not. Finally, it is shown that the standard equation of groundwater flow is a special case of the macroscopic equation of internal energy balance. An appeal to the macroscopic equation of mass balance is not required in order to derive the flow equation.
Effect of grain size and snowpack water equivalence on visible and near‐infrared satellite observations of snow
Authors: Dozier Jeff , Schneider Stanley R. , McGinnis David F.
Published: February 2008

Satellite observations of snow in the near‐infrared wavelengths can be used to roughly estimate snow grain size. When the grain size is large, it is possible to use measurements in the visible wavelengths to estimate snow water equivalence below some threshold value of around 100 mm. While sufficient data to fully evaluate these possibilities are not available, model calculations, selected satellite observations, and limited ground truth are in qualitative agreement. Complications arise because the effect of contamination by atmospheric aerosols is similar to that of finite depth, and because the near‐infrared channel on the NOAA TIROS‐N series satellites is not in the wavelength region where snow reflectance is most sensitive to grain size.
Multiobjective analysis of irrigation planning in river basin development
Authors: Vedula S. , Rogers Peter P.
Published: February 2008

A river basin that is extensively developed in the downstream reaches and that has a high potential for development in the upper reaches is considered for irrigation planning. A four‐reservoir system is modeled on a monthly basis by using a mathematical programing (LP) formulation to find optimum cropping patterns, subject to land, water, and downstream release constraints. The model is applied to a fiver basin in India. Two objectives, maximizing net economic benefits and maximizing irrigated cropped area, considered in the model are analyzed in the context of multiobjective planning, and the tradeoffs are discussed.
Modeling double aquifer flow using a comprehensive potential and distributed singularities: 1. Solution for homogeneous permeability
Authors: Strack O. D. L. , Haitjema H. M.
Published: February 2008

A technique is presented for modeling two‐dimensional horizontal flow in a system of two infinite aquifers. The aquifers are separated by a thin impermeable layer and are hydraulically connected through openings in the separating bed. The upper aquifer is unconfined, and the flow in the lower aquifer is confined in some regions and unconfined in others. The model includes cross flow, inflow from rainfall, and flow toward creeks, canals, lake boundaries, and wells. Line sinks are used for incorporation of the creeks, canals, and lake boundaries. The method is validated against various exact solutions, and some examples of applications of the method are discussed.
A growing season water balance model applied to two Douglas fir stands
Authors: Spittlehouse D. L. , Black T. A.
Published: February 2008

The forest water balance model presented requires only daily solar radiation, maximum and minimum air temperature, and rainfall as the input weather data. Site parameters are root zone depth, soil water retention and drainage characteristics, estimated canopy leaf area index, and the coefficients of the evapotranspiration and rainfall interception submodels. The evapotranspiration submodel calculates the forest evapotranspiration rate as the lesser of energy‐limited and soil‐limited rates. The former is calculated from the 24‐hour net radiation and the latter from the fraction of extractable water in the root zone. Solar radiation and air temperature are used to calculate net radiation. Interception is calculated from the daily rainfall. The root zone is treated as a single layer with drainage calculated as a function of the root zone water content. Water deficits and the matric potential of the root zone are used to indicate tree Water stress. The model was tested on two Douglas fir stands of different stand density and leaf area index. The coefficients used in the evapotranspiration submodel were found to be the same for both stands. It was also found that over 20% of the growing season rainfall was lost through interception.
Project evaluation during inflation, revisited: A solution to Turvey's relative price change problem
Authors: Hanke Steve H. , Wentworth Roland W.
Published: February 2008

Recent literature on benefit‐cost analysis has dealt with the general problem of project evaluation during inflation. This report extends an earlier analysis in order to illustrate the correct manner for dealing with cases in which relative prices change during the life of a project. A problem posed by Ralph Turvey illustrates the nature of the difficulties which can arise if one fails to account properly for relative price changes. These difficulties can be overcome if one gives explicit attention to the choice of the numeraire to be used in conducting the benefit‐cost analysis. Also, unlike cases in which all prices change in the same proportion, correct analyses in the presence of relative price changes require a forecast of general price inflation.
Sensible energy storage in aquifers: 2. Field experiments and comparison with theoretical results
Authors: Sauty J. P. , Gringarten A. C. , Fabris H. , Thiery D. , Menjoz A. , Landel P. A.
Published: February 2008

Ten successive in situ experimental investigations of hot water storage by a single well and a pair of wells (doublet) were conducted in 1976–1977 at Bonnaud, Jura, in a confined aquifer 2.5 m thick. The injected volumes ranged from 500–1700 m3. Temperature profiles were measured daily in 12 boreholes distributed along two perpendicular axes within 13 m of the injection well. Individual temperatures were measured by ten thermistors placed in the caprock. The results are discussed and used to calibrate two mathematical models. An axisymmetric model allows the calibration of average values of the parameters, while a three‐dimensional model is used to determine their spatial variation in the horizontal plane. The latter model leads to the identification of a nonhomogeneous transmissibility field which fully accounts for both hydraulic and thermal contour curves. The models, which were matched against particular experiments, proved accurate when simulating other periods. Evidence is given of the importance to the recovery ratio of thermal dispersion in the aquifer and of the water content of the caprock. In a final section, experimental results of single well storage at Bonnaud, Campuget, and Auburn are compared with general type curves derived in the companion paper. They prove to yield adequate predictions of water temperature during the production phases.
Evaporation from the surface of the Arctic Tundra on Axel Heiberg Island
Authors: Ohmura Atsumu
Published: February 2008

Hourly and daily evaporation rates were measured at the base camp (79°25′N, 90°45′W, 200 m above mean sea level) as part of the energy balance program during the Axel Heibergy Island Expedition in spring and summer of 1969, 1970, and 1972. The study period covered about 50 days of the dry snow period, 15 days of the melt period, and 2 months of the postmelt period in each year. The measuring and analysis methods are described, in that the aerodynamic profile method is examined, objective criteria are developed to accept or reject the profile data for the Bowen ratio energy balance method, and the problems of the snow lysimeter and the ordinary weighing lysimeter are described. Systematic differences among these methods are presented, and the causes for the differences are examined. Seasonal and diurnal variations of the evaporation rate are discussed. A unique effect of the föhn on evaporation is found and the cause investigated. Each season, characterized by different surface conditions, is found to possess a rather distinctive evaporation rate and ratio of latent heat flux to net radiation. The annual total evaporation is estimated at 140 mm, which is equivalent to 80% of the annual total precipitation, the remaining 20% being annual total runoff. The runoff occurs mostly during and immediately after the melt of the snow cover.
On the relationship between kriging and state estimation
Authors: Chirlin Gary R. , Wood Eric F.
Published: February 2008

Interpolation of sampled random spatial processes is of interest to hydrologists. The interpolation task requires the determination of an underlying process that may be confounded by both process noise and data measurement error. One approach that has appeared in the hydrologic literature is universal kriging. Universal kriging interpolates a discrete stationary spatial process obtained by polynomial filtering through spatial differencing of the original nonstationary process. The interpolation procedure of kriging is presented within the more general framework of state estimation. The paper analyzes the assumptions and limitations of kriging within state estimation and discusses some of the concerns of practitioners which have arisen in recent papers.
Stability of βMnOOH and manganese oxide deposition from springwater
Authors: Hem J. D. , Roberson C. E. , Fournier Reba B.
Published: February 2008

Beta MnOOH is precipitated preferentially (with respect to Mn3O4) at temperatures near O°C when Mn2+ is oxidized in aerated aqueous solutions. Upon aging in solutions open to the atmosphere a slurry of βMnOOH tends to disproportionate to form MnO2 and Mn2+. In such aged solutions, Mn2+ and H+ activities can be constant, and both the oxidation reaction Mn2++¼O2(aq) + 3/2H2O → βMnOOH (c) + 2H+ and the disproportionate reaction 2βMnOOH (c) + 2H+ → MnO2 (c) + Mn2+ + 2H2O can have positive reaction affinities. It is not possible for both reactions to be in thermodynamic equilibrium in the same system unless oxygen is almost completely absent. A value for ΔGf0 of −129.8±0.6 kcal/mol was obtained for βMnOOH from experimental data by assuming that the reaction affinity for the oxidation reaction is equal to that for the disproportionation. A value for ΔGf0 for βMnOOH of −129.8±0.5 kcal/mol was determined by measuring the redox potentials for the postulated half‐reaction MnO2 (c) + H+ + e− → βMnOOH (c) at 0°, 5°, and 15°C and extrapolating to 25°C. Both these values are consistent with laboratory observations that βMnOOH is less stable than γMnOOH or Mn3O4 at 25°C. Analytical data for manganese‐depositing springwater samples are consistent with a nonequilibrium model involving disproportionation of either βMnOOH or Mn3O4.
Linear kernels for Karst Aquifers
Authors: Dreiss Shirley J.
Published: February 2008

Karst aquifers contain significant water reserves in many parts of the world, but development and management of these reserves is difficult because of the complexity of the aquifers. This paper presents a method of characterizing karst aquifers based on the use of single, linear kernel functions. The kernels are identified with a deconvolution technique proposed by Neuman and de Marsily (1976) by using estimated groundwater recharge during isolated storms as the system input and the rapid storm response of spring flow as the system output. Derived kernels for large springs from data for different storms are similar in shape and time to peak. Average kernels derived from spring flow responses for multiple storms differ in shape for different springs but suggest a regularity in the response of individual springs to precipitation. The derived kernel functions presently cannot be validated because of the use of a scaling factor in the moisture balance for the springs. They can be used, however, to predict the storm response of a spring if the total volume of the rapid spring flow response is known.
Synthetic streamflow generation: 2. Effect of parameter uncertainty
Authors: Stedinger Jery R. , Taylor Marshall R.
Published: February 2008

The parameters of stochastic models of monthly streamflows can be estimated with only limited precision given the finite and often short streamflow records available for planning. This paper illustrates the impact of the uncertainty in the parameters of the distribution of annual flows on estimates of monthly reservoir system reliability. Even with the 50‐year flow record available for the upper Delaware River basin, the impact of the uncertainty in parameters describing the distribution of annual flows on estimated capacity‐reliability relationships is shown to be rather large and as important as the choice between a relatively simple Thomas‐Fiering monthly streamflow model and a Markov model of annual flows coupled with disaggregation to obtain monthly values.
Calculation of pollutant removal during groundwater restoration with adsorption and ion exchange
Authors: Charbeneau Randall J.
Published: February 2008

A technique is presented for calculating pollutant removal rates during groundwater restoration processes. The hydraulic information required by the method is obtained from the conservative tracer breakthrough curve for a flow system. The influence of adsorption and ion exchange chemistry on species transport is included through, application of the method of characteristics. The combined result gives the effluent concentration at a production well as a function of time during a restoration project. The method is applicable for any well pattern and its economy is such that a pencil and paper calculation will suffice for yielding quantitative answers for complex flow problems. The method is applied to calculate ammonium removal rates for site restoration by recirculation with chemical sweeps following in situ leach mining of uranium.
Soil‐ and atmosphere‐induced plant water stress in cotton as inferred from foliage temperatures
Authors: Idso S. B. , Reginato R. J. , Farah S. M.
Published: February 2008

Foliage temperatures of cotton obtained by means of infrared thermometry, along with air wet and dry bulb temperature measurements, were used to investigate certain relationships existing between the water contents of soil and air and the ability of the crop to maintain transpiration at the potential rate. It was found that as soil water content is progressively depleted following an irrigation, departure from potential transpiration begins to occur at smaller and smaller values of air vapor pressure deficit in a regularly predictable fashion. It was also demonstrated that the plant water potential of cotton transpiring at the potential rate is a function of the air vapor pressure deficit and that the difference between this base value and the tension that develops under nonpotential conditions is a unique function of a newly developed plant water stress index. Finally, an example of the application of this foliage temperature‐based index to evaluating the effects of an irrigation event is presented.
Real‐time daily reservoir operation by mathematical programing
Authors: Houck Mark H.
Published: February 2008

The use of mathematical programing models for real‐time reservoir operation is investigated. Two measures of the quality of the operations designated by the math programing models are used: (1) the total value of actual penalties (surrogate for costs and benefits) incurred by the operation and (2) the closeness of the physical operations designated by the models to the physical operations of the theoretically best operations. Of the five different types of objective functions used in the models, two were clearly superior to the others. One of these requires trial and error fitting of a multiparameter objective function; the other does not. The model which does not require trial and error parameter fitting may be used to operate a reservoir system either when correct benefit and loss functions defining the effects of operation are available or when only descriptions (in the form of cumulative distribution functions) of desirable physical operations are available.
Stochastic daily precipitation models: 1. A comparison of occurrence processes
Authors: Rolda´n José , Woolhiser David A.
Published: February 2008

A first‐order Markov chain and an alternating renewal process (ARP) with a truncated geometric distribution of wet day intervals and a truncated negative binomial distribution of dry day intervals are compared as models describing the occurrence of sequences of wet and dry days. Numerical optimization techniques are used to obtain approximate maximum likelihood estimates of the Fourier coefficients which describe the seasonal variation of the two Markov chain parameters and the three parameters in the alternating renewal process. For the four U.S. stations studied, the Markov chain model was superior to the ARP using the minimum Akaike information criterion.
Effects of aggradation and degradation on riffle‐pool morphology in natural gravel channels, northwestern California
Authors: Lisle Thomas E.
Published: February 2008

After the flood of December 1964, 12 gaging sections in northern California widened as much as 100% and aggraded as much as 4 m, and then degraded to stable levels during a period of 5 years or more. As channels aggraded, bed material became finer, and low to moderate flow through gaging sections in pools became shallower, faster, and steeper. Comparisons of longitudinal profiles also show the diminishment of pools as well as a decrease in bar relief accompanying the excessive sediment load. As gaging sections degraded, hydraulic geometries recovered to a limited degree; full recovery probably depends on channel narrowing and further depletion of sediment supply. The hydraulic changes with aggradation indicate an increase in the effectiveness of moderate discharges (less than 1‐ to 2‐year recurrence interval, annual flood series) to transport bed load and shape the bed. Bars become smaller, pools preferentially fill, and riffles armored with relatively small gravel tend to erode headward during falling stages and form a gentler gradient. Excess sediment can thus be more readily transported out of channels when additional contributions from watersheds are usuall slight.