bluuebunny/crossref_metadata_2025 huggingface dataset:
An investigation into the effect of storm type on precipitation in a small mountain watershed
Authors: March William J. , Wallace James R. , Swift Lloyd W.
Published: February 2008

A set of regression equations relating storm rainfall depth to watershed topography and storm type was derived for the high‐density precipitation network at Coweeta Hydrologic Laboratory. The most general equation predicted storm amounts for an independent test group of gages with an average error of 0.38 cm (0.15 inches). The dependent variable was the ratio of the rainfall at each gage site to the rainfall at a base gage. Predictive variables were topographic slope, aspect, ground elevation at the gage site, and smoothed elevation. The smoothed elevation, which is the elevation the gage would assume if it were on a smooth plane representing the general topography of the terrain, appeared in more equations than any other variable. One equation was calculated for each of six identified storm types, and one equation was calculated with all storms considered together. Overall, the equations which considered storm type were not better predictors of site rainfall than the equation which did not consider storm type. Predictions of storm amounts were closest to measured amounts for storms where the low‐pressure center passed east of Coweeta, while the predictions for the air‐mass or thunderstorm type had the greatest errors. The prediction errors of the equations for warm‐, cold‐, and stationary‐front storm types were intermediate. The small number of tropical storms limited development and testing of equations for that type.
Choosing among alternative hydrologic regression models
Authors: Valdés Juan B. , Vicéns Guillermo J. , Rodríguez‐Iturbe Ignacio
Published: February 2008

Bayesian theory provides for the explicit accounting of both parameter and model uncertainties. It is used in this work to derive a procedure for discriminating among alternative hydrologic regression models. In particular, the procedure was used to discriminate among alternative exogenous variables in regression models. Controlled experiments with hydrologic models were designed to test the proposed procedure under different assumptions on model prior probabilities, length of sample, and model subset. These examples showed that besides its theoretical advantages, the use of the Bayesian procedure unambiguously selects the correct model in most of the applications.
An isotopic study of groundwater seepage in the central Kentucky Karst
Authors: Harmon Russell S.
Published: February 2008

Ratios of 18O/16O were determined for meteoric precipitation and vadose seepage at Great Onyx Cave in Mammoth Cave National Park from March through July 1973. Results of this study indicate that (1) the δ18O/dT for precipitation at this site is 0.38‰/°C, (2) short‐term fluctuations in the 18O/16O ratio of seepage water in the vadose zone above the cave do not affect the oxygen isotopic composition of the speleothem calcite precipitated in the cave, and (3) the residence time of seepage water in the vadose zone is about 2 weeks. From spot sampling of base level springs in November 1972 the isotopic composition of the karst groundwater body is estimated to be about δ18O = −5.6‰ and δD = −40‰.
A note on the Poisson assumption in partial duration series models
Authors: Cunnane C.
Published: February 2008

The Poisson process is frequently encountered in probability models of the partial duration series. This paper looks at the necessity for specifying the model in detail by such a process and also examines the validity of the Poisson distribution, in this context, as judged on data from 26 gaging stations on 20 catchments in Great Britain. When all the data are considered jointly the Poisson assumption has to be rejected although it is acceptable in some cases. It is also suggested that if dependence exists in the partial duration series it should be looked for in the point process from which the series arises rather than among successive peak magnitudes.
A survey research evaluation of citizen participation strategies
Authors: Ertel Madge O.
Published: February 2008

The New England River Basins Commission has utilized communication strategies designed to stimulate public involvement in the planning process of three ‘level B’ studies. The effectiveness of these strategies, including agency‐produced printed information, use of the mass media, personal staff contact, and public meetings has been evaluated by means of questionnaires administered to members of the public who attended the final public meetings conducted in each study. The implications of the research findings for more effective functioning of citizen participation programs are discussed.
Composition of Trinidad rainfall
Authors: Dalal R. C.
Published: February 2008

The rainwater collected from daily rainfalls at six rainfall stations in Trinidad over a 1‐year period was analyzed for NH4+, NO3−, urea‐N, Mg2+, Ca2+, Na+, K+, Cl−, and SO42− concentrations. The concentration of these constituents varied from 0.41 to 1.13, 0.41 to 1.24, 0.15 to 0.50, 0.33 to 0.99, 1.88 to 4.52, 1.92 to 2.57, 1.21 to 3.27, 2.10 to 3.93, and 1.89 to 17.75 mg/1 of NH4‐N, NO3‐N, urea‐N, Mg2+, Ca2+, Na+, K+, Cl−, and SO42−, respectively. Considerable amounts of these constituents were added to the soil through rainfall. Major proportions of NH4+ and NO3− and some proportions of SO42− in rainwater may have been derived from gaseous sources, probably originating from soil. Urea‐N seems to have originated as particulate matter from soil organic matter and microbial cell debris. Greater proportions of Ca2+ and K+, and smaller proportions of Mg2+ and SO42− appear to have been derived from terrestrial dust. Sodium, Cl−, Mg2+ and partly Ca2+, K+ and SO42 were derived from marine sources. Thus it appears that the sources of various constituents in the Trinidad rainfall are quite varied.
Investment sequencing and allocation decisions in water resource system design: A note on an alternative algorithm
Authors: Armstrong Ronald D. , Willis Cleve E.
Published: February 2008

Simultaneous consideration of investment sequencing and allocation decisions often gives rise to large‐scale mathematical models. One of the few empirical applications of models of this type was presented in this journal by Rausser and Willis (1976). They formulate a mixed‐integer quadratic program and develop a solution procedure which does not guarantee convergence to an optimal solution. This note presents an alternative algorithm to solve the same problem. The new algorithm requires less computer time and will converge to the optimal solution. References to related decomposition algorithms are given.
Comment on ‘Price elasticity of demand for municipal water: A case study of Tucson, Arizona’ by Robert A. Young
Authors: Colander David Charles , Haltiwanger John C.
Published: February 2008

Results of a time series study of demand for water in Tucson, Arizona, are recalculated, resulting in more inelastic price elasticities than previously estimated. These recalculations support the hypothesis that time series elasticity estimates are likely to be more inelastic than cross‐sectional elasticity estimates.
The worth of streamflow data in water resources planning: Computational results
Authors: Haimes Yacov Y. , Craig Jim A. , Subrahmanian Jayram
Published: February 2008

This paper presents computational results for evaluating the worth of streamflow data in water resources planning. Synthetic streamflow is generated with a synthetic streamflow generator, HEC‐4 simulation model, where the optimal scheduling and capacity expansion of water supply projects are determined with a dynamic programing model. Penalty matrices associated with high‐and low‐yield estimates are then developed, using the results from the HEC‐4 and the dynamic programing models. A multi‐objective optimization problem is then formulated, minimizing the expected monetary penalty (in dollars) and the expected water shortage penalty (in million gallons). The solution of the multiobjective optimization problem (by using the surrogate worth trade‐off (SWT) method) yields a Pareto optimal and preferred data collection policy.
Soil spatial variability and its consequences on simulated water balance
Authors: Sharma M. L. , Luxmoore R. J.
Published: February 2008

Scaling theory, based on the similar media concept, provides a basis for representing soil spatial variability in terms of a single stochastic variable, the scaling factor α, which is related to the microscopic characteristic length of the soil. Based on the measured properties of α (log normally distributed with an arithmetic mean of 1.0 and coefficient of variation of 0.6), the effects of soil spatial variability on the water balance components of a grassland watershed near Chickasha, Oklahoma, were studied by using a simulation model. Monthly simulations of evapotranspiration, surface runoff, deep drainage, and change in soil water storage for the year 1973 were computed for several values of α representing soils with widely ranging hydraulic properties. At any time, vegetation and meteorological parameters were the same for all the soils. Our studies reveal the complexities of soil‐plant‐atmospheric interactions in evaluating the influence of soil variability on water balance and underline the limitations of drawing generalizations. The conclusions are highly dependent on the extent of variability (coefficient of variation of α), the frequency distribution function of the scaling factor, and the soil‐plant‐weather combination.
The application of the gamma neutron method for transport studies in field soils
Authors: Couchat Ph. , Moutonnet P. , Puard M. , Brissaud F.
Published: February 2008

In order to study water movement in the field, deuterated water was monitored by the.gamma neutron method, using 208Tl gamma source and 3He thermal neutron detector. A laboratory device is presented which supplies measurement data on a 5‐ml soil solution. The performance of a gamma neutron probe is evaluated, the background count rate which depends on soil moisture content is related to the neutron emission of 208Tl gamma source, the resolution is found to depend on gamma diffusion and is no more than 15 cm in unsaturated soil, and the calibration is given versus volumetric deuterated water content. The dispersive transport of a D2O pulse on a soil column is studied through a D2O concentration profile and breakthrough curve at the bottom of the column. Then simultaneous measurements of soil water content and D2O concentration by the neutron moisture gauge and the gamma neutron probe enable us to interpret the evolution of the D2O pulses as a function of irrigation during a field experiment.
Water quality sampling: Some statistical considerations
Authors: Liebetrau A. M.
Published: February 2008

Typically, a state, regional, or national water quality (WQ) monitoring system has many objectives. Examples include (1) providing a system‐wide synopsis of WQ; (2) determining whether selected WQ parameters show gradual changes over time; (3a) detecting actual or potential WQ problems, (3b) determining the specific causes of actual problems, and (3c) assessing the effect of any corrective action; and (4) enforcing the law. While these purposes have different data requirements, they are interrelated, and data collected for any one can have value for others; for example, data collected for the listed reasons could be used for future long‐range planning. Each objective makes certain demands of a WQ sampling network, and these in turn have implications concerning sampling design and statistical analysis of resulting data. In a sampling scheme flexible enough to encompass multiple objectives, data sets collected for answering questions arising under points 1–4 need not all have similar characteristics; consequently, a variety of statistical methods are needed. A good sampling design is important for achieving the first two objectives. A working definition of ‘water quality’ is given initially, and this is followed by the definition of a sampling population. The set of all segments of the drainage network serves as the population for several sampling plans. In particular, the use of probability sampling to design a network of synoptic sampling stations is discussed in detail. Finally, sequential statistical procedures are applied to a specific problem of type 3c. In terms of the amount of data required, sequential methods are quite efficient for detecting changes of a specified magnitude in some WQ parameter.
Considerations for the design of a hydrologic data network using multivariate sensors
Authors: Crawford Kenneth C.
Published: February 2008

An experimental design model has been developed to evaluate trade‐offs involved in the optimal sampling of surface rainfall. The model reveals that deployment of statistically adequate sensor arrays depends critically on the storm physics, the sensor engineering aspects, and the procedure chosen for analysis of information from the deployed network. The model is used to examine the effect of sensor density reduction on the ability of a sampling system to detect signal variation. Predictand‐related sensors are shown to be essential to network design. Options in multivariate sensor deployments (spatial and temporal) are explained. Deployment along and across a preferred storm track is related to convective system anisotropy, rain gage density, temporal sampling intervals, availability of radar data, and interrelationships among the multivariate predictor data sets. Any proposed sensor array is shown to represent a balance between the demands of economy and climatology.
Worth of data and natural disaster insurance
Authors: Attanasi E. D. , Karlinger M. R.
Published: February 2008

The Federal Government in the past has provided medical and economic aid to victims of earthquakes and floods. However, regulating the use of hazard‐prone areas would probably be more efficient. One way to implement such land use regulation is through the national flood and earthquake insurance program. Because insurance firms base their premium rates on available information, the benefits from additional data used to improve parameter estimates of the probability distribution (governing actual disaster events) can be computed by computing changes in the premiums as a function of additional data. An insurance firm is assumed to set rates so as to trade off penalties of overestimation and underestimation of expected damages. A Bayesian preposterior analysis is applied to determine the worth of additional data, as measured by changes in consumers’ surplus, by examining the effects of changes in premiums as a function of a longer hydrologic record.
Sampling of interrelated random fields: The rainfall‐runoff case
Authors: Bras Rafael L.
Published: February 2008

The rainfall‐runoff process is the most common vector‐valued random field studied by hydrologists. A historical review of four articles dealing with the sampling of this multivariate problem is presented. Ideas on new formulations to study the sampling needs for rainfall‐runoff modeling are also given.
A case study of rationalization of a rain gage network in southwest England
Authors: O'Connell P. E. , Gurney R. J. , Jones D. A. , Miller J. B. , Nicholass C. A. , Senior M. R.
Published: February 2008

Proposals for the redesign of the Wessex Water Authority daily and monthly rain gage networks in southwest England have been made, based on optimal estimation procedures. Accuracy requirements for point and areal rainfall estimates were assessed from a survey of the use of data from the existing network. Root mean square errors of interpolation were calculated for the existing networks of 333 daily gages and 379 monthly gages using estimates of the spatial autocorrelation of daily and monthly rainfall. Maps of the interpolation accuracy were drawn and compared with the accuracy required by users. The accuracies of areal estimates in certain areas were also assessed. Three network configurations were designed, of 75, 220, and 297 daily gages. The 220‐gage network was found to provide satisfactory accuracies for most users, and has been adopted for implementation.
Intervention analysis with missing data
Authors: Lettenmaier Dennis P.
Published: February 2008

Intervention analysis is a potentially useful tool for modeling time series when the process mean undergoes changes as the result of an external perturbation. The utility of the technique for water resource applications is, however, limited by the requirement that the data be collected uniformly in time. Two approaches for estimating missing data, one of which provides minimum variance estimates when model parameters are known, and a computationally simpler approximation were investigated. The approximation was found to be quite adequate and was incorporated in a practical scheme to estimate missing data and model parameters simultaneously. Subsequently, a method for estimating the parameter variance for use in significance tests on the intervention magnitude was investigated. The adequacy of the approximation was assessed in a series of Monte Carlo tests using three models consisting of step, linear, and impulse decay trends in mean with residual lag 1 Markov noise. Results of the experiments indicated that the suggested method provides adequate estimates of the variance of the intervention magnitude of the step and impulse decay models but that the variance was substantially overestimated for the linear model. However, for the same proportion of missing data the accuracy of the approximation improved as the sample size increased.
Application of recent results in functional analysis to the problem of wetting fronts
Authors: Nakano Yoshisuke
Published: February 2008

Traditionally in hydrology and soil physics, wetting fronts appearing in porous media described by Darey's law have not generally been considered to be singular surfaces. Some recent results from functional analysis are presented as evidence supporting the viewpoint that wetting fronts with a finite propagating speed generally are singular surfaces.
Effect of tail behavior assumptions on flood predictions
Authors: Shen H. W. , Bryson M. C. , Ochoa I. D.
Published: February 2008

Two of the distributions most widely used in flood magnitude modeling are the Gumbel type 1 extreme‐value distribution and the log Pearson type 3. These represent two fundamentally different assumptions about distribution tail behavior in that extreme events from the log Pearson type 3 distribution follow the Gumbel type 2 extremal distribution. This paper compares these two assumptions by comparing flood predictions by the type 1 and type 2 models. For the Gumbel type 1 distribution the ratio of xn1 the magnitude of a flood with a return period n1, to xn2, the magnitude for a shorter return period n2, can be estimated by an upper bound which is In n1/ln n2. It is shown that the ratio of xn1/xn2 from the type 2 distribution is always greater than that from the type 1, approximated by (n1/n2)1/k. An analysis of flow data collected in the United States indicates that in the majority of cases the best fitting type 2 distribution does not have a finite variance and often not even a finite mean. The impact of this on statistical data analysis is discussed.
The effect of soil activity on the chemistry of carbonate groundwaters
Authors: Drake John J.
Published: February 2008

Regional variations in HCO3− concentrations of carbonate groundwaters are explained by the combination of a simple ecological model of soil CO2 production and a consideration of the manner in which soil water, soil air, and carbonate materials interact. Carbonate groundwaters in North America are divided into those which have evolved largely under open system conditions and those which have evolved under closed system conditions. The open system group members (with one exception) all come from high latitudes, and it is suggested that recurrent glaciations have acted to replenish soil zone carbonate materials and maintain the soil zone as an important source of dissolved carbonate minerals.
System model of daily sediment yield
Authors: Sharma T. C. , Dickinson W. T.
Published: February 2008

Input‐output systems concepts have been applied to the modeling of daily runoff‐sediment yield of the Thames River in southern Ontario, Canada. Spectral and correlation techniques have been used to construct a parsimonious model of daily sediment yields. It is shown that a linear discrete dynamic model is possible in terms of the log‐transformed daily runoff and sediment yield sequences. The fluvial system of the Thames River watershed exhibits a weak memory on a daily basis, and the noise component corrupting the watershed fluvial system resembles a white noise process.
Sedimentation of detrital particulate matter in lakes: Influence of currents produced by inflowing rivers
Authors: Wright Richard F. , Nydegger Paul
Published: February 2008

Inflowing rivers can provide a major driving force for water circulation in lakes in which water turn‐over time is short, that is, less than a few years. Such inflow‐induced currents strongly influence the dispersion and sedimentation of allochthonous particulate matter, especially fine‐grained particles that can remain in suspension in lake water for days or weeks. We present data to illustrate the importance of inflow‐induced circulation on sedimentation patterns in Lake Brienz and Lake Biel, two large lakes in northwestern Switzerland, and suggest that such currents should not be disregarded in sedimentological studies of similar lakes elsewhere.
Determination of effective well block radii for numerical reservoir simulations
Authors: Pritchett J. W. , Garg S. K.
Published: February 2008

In the numerical simulation of underground reservoir behavior it is often necessary to employ well blocks (i.e., a grid block containing a well) with dimensions much larger than the well diameter. This paper develops practical procedures for making reasonable estimates of well bore sandface conditions from the well block conditions calculated by numerical reservoir simulations. It is assumed that on a sub‐grid scale, pressures will equilibrate much more rapidly than in the reservoir as a whole; the subgrid flow may therefore be treated as steady flow. The conditions at the sandface may then be deduced from mean well block conditions by assuming that the latter obtain at a definite distance (the ‘effective well block radius’) from the well. The problem is to establish the value of the effective well block radius in terms of the size of the well block and other relevant parameters. Grid pressures obtained in the numerical solution of liquid flow into a single well located in both radial and rectangular grid blocks are examined. It is found that the effective well block radius depends on, among other things, the shape of the grid block (radial or rectangular), the type of mesh (uniform or otherwise) employed, and the character of the spatial discretization scheme.
Comparison of measured and estimated unsaturated hydraulic conductivity
Authors: Parkes M. E. , Waters P. A.
Published: February 2008

Most studies of empirical estimates of unsaturated hydraulic conductivity functions do not account for water which may be relatively immobile under the conditions in which field measurements of conductivity are made. To investigate this, unsaturated hydraulic conductivity data were obtained for three monolith lysimeters, 80 cm in diameter by 135 cm deep, using the instantaneous profile technique. The lysimeters contained well‐structured, freely draining loam soil and moisture measurements were made using a neutron probe. Conductivity estimates were also obtained from laboratory measurements of soil moisture characteristics using the modified Millington and Quirk computational method. Ratios of the calculated to measured conductivities at a matching point near saturation were so large as to suggest that only a minor proportion of the soil pore space was contributing to flow through the whole profile.
An improved technique for spatial sampling of solutes in shallow groundwater systems
Authors: Hansen Edward A. , Harris Alfred Ray
Published: February 2008

The groundwater profile sampler consists of a series of sample probes spaced in sand‐packed compartments in a screened well point. It can be used to collect simultaneously a vertical profile of groundwater samples. The sampler assists in defining the spatial and temporal variation of solutes in shallow groundwater systems.
Analysis of a chance‐constrained reservoir control model
Authors: Sniedovich Moshe
Published: February 2008

A model proposed in the water resources literature for the estimation of the distribution function of reservoir storage levels under a general linear release rule is critically examined. It is shown that the proposed model should not be expected to perform well because it tends to overestimate the tails of the distribution function, and therefore in the context of problems subjected to probabilistic target and spilling constraints it may lead toward unduly conservative design and operation policies. The mean and variance of the proposed distribution function are formally derived, and it is indicated that the variance may possess an inherent positive error because the model ‘allows’ storage levels to take values outside their feasible range determined by the size of the reservoir. Numerical examples supporting these analytical observations are provided.
Numerical stability and accuracy of implicit integration of free surface groundwater equations
Authors: Liu Philip L.‐F. , Liggett James A.
Published: February 2008

In the solution of two‐ or three‐dimensional free surface flow the time‐dependent boundary condition is represented in an implicit finite difference form. The numerical solution may damp or amplify the real solution or contain oscillations, either stable or unstable, about the real solution, depending on the weighting factor θ (which positions the space derivative in time) and the wave number of the solution mode. Zero numerical damping occurs at a value of 0.5 < θ < 0.6; the exact value of θ depends on the wave number and length of the time step. The paper provides a guide for choosing θ and the time step.
Nighttime, wet canopy evaporation rates and the water balance of an evergreen mixed forest
Authors: Pearce A. J. , Rowe L. K. , Stewart J. B.
Published: February 2008

The average nighttime evaporation rate of water intercepted on an evergreen mixed forest canopy is estimated as 0.37 mm/h from a regression of interception loss on gross rainfall for 35 storms occurring between 1900 and 0700 LT. The mean wet canopy evaporation rate estimated by the same method for both daytime and nighttime rainfall in 1975–1976 was also 0.37 mm/h. The similarity of daytime and nighttime evaporation rates indicates that evaporation from the wet canopy is driven by advected energy not by radiation. The diurnal rainfall distribution and nighttime evaporation rate indicate that net interception loss was 81–84% of gross interception, considerably higher than net losses estimated in other studies where nighttime losses were not considered separately from daytime losses. Interception losses at night were 40–50% of total gross interception, 50–60% of the total net interception, and ∽30% of total evaporation.
Seasonal runoff volumes conditioned on forecasted total runoff volume
Authors: Hoshi Kiyoshi , Burges Stephen J.
Published: February 2008

When a single integrated hydrologic forecast is made for a future time, for example, total snowmelt runoff from a snowpack over a period of 6 months, the information can be disaggregated to yield conditional distributions in each of several time intervals within the forecast period. A method that effects forecasted streamflow disaggregation at a single site (it is applicable to any forecast situation) is given. The unconditional distribution of total runoff volumes for the melt season and the unconditional flow in each period (typically 1 month) within the melt season are approximated by three‐parameter log normal (LN3) distributions. Conditional means and skew coefficients as well as conditional covariance between periods (months) and period to total period (1‐ to 6‐month volume) are computed; conditional moments are transformed via LN3 distributions to a multivariate normal domain where conditional distributions are computed by using a principal component technique. The complete conditional distribution of flow in each period results from inverse transformation. Data typical of streamflow from snowmelt in the Cascade Range, Washington, are used to illustrate the approach. The conditional distributions are useful for applications requiring explicit encoding of risk in water resource system operation.
A model of the mean field distribution of a dissolved substance within the riverine layer of a fjord lake
Authors: Hamblin Paul F. , Carmack Eddy C.
Published: February 2008

The time‐averaged distribution of a conservative and passive contaminant in the neighborhood of a junction of two branches of a generalized fjord system is considered. Analytical solutions to the steady advection‐diffusion equations are obtained by the methods of Schwartz‐Christoflel, Boussinesq, and Wiener‐Hopf. A feature of this approach is that it accounts for the anisotropy of the dispersion coefficients in the direction of the streamlines. Solutions are applied to horizontal diffusion in the riverine layer of a fjord lake, and a horizontal dispersion coefficient of 300 m2/s is deduced from matching the predictions to the horizontal distribution of vertically averaged conductivity over the riverine layer. Following Taylor's method, we infer a vertical turbulent diffusivity of 5 × 10−6 m2/s for the riverine layer.
Optimal energy extraction from a hot water geothermal reservoir
Authors: Golabi Kamal , Scherer Charles R. , Tsang Chin Fu , Mozumder Sashi
Published: February 2008

An analytical decision model is presented for determining optimal energy extraction rates from hot water geothermal reservoirs when cooled brine is reinjected into the hot water aquifer. This applied economic management model computes the optimal fluid pumping rate and reinjection temperature and the project (reservoir) life consistent with maximum present worth of the net revenues from sales of energy for space heating. The real value of product energy is assumed to increase with time, as is the cost of energy used in pumping the aquifer. The economic model is implemented by using a hydrothermal model that relates hydraulic pumping rate to the quality (temperature) of remaining heat energy in the aquifer. The results of a numerical application to space heating show that profit‐maximizing extraction rate increases with interest (discount) rate and decreases as the rate of rise of real energy value increases. The economic life of the reservoir generally varies inversely with extraction rate. Results were shown to be sensitive to permeability, initial equilibrium temperature, well cost, and well life.
A stochastic model for the time distribution of hourly rainfall depth
Authors: Nguyen Van‐Thanh‐Van , Rousselle Jean
Published: February 2008

A probabilistic characterization of temporal storm patterns is presented wherein a storm is defined as an uninterrupted sequence of consecutive hourly rainfalls. A stochastic model is proposed to determine the probability distributions of rainfall accumulated at the end of each time unit within a total storm duration. An illustrative application of the model was made by using a 32‐year hourly rainfall record at Dorval Airport on Montreal Island. The hourly rainfall depth was assumed to be an exponentially distributed random variable. The probability of any given number of consecutive rainy hours was determined by first‐ and second‐order Markov chains. Statistical tests were performed to test the fit of the Markov model to the sequence of wet hours. The agreement between the observations and the proposed model is discussed. It is concluded that the methodology in this study is more flexible and more general than those that have been used in previous investigations. By using the stochastic model developed, a storm profile can be characterized in terms of the time of occurrence of a storm, the total storm depth, and the probability estimates of accumulated rainfalls at the end of each time unit within the total storm duration.
Identification of the Wairakei Geothermal System
Authors: Fradkin Larissa Ju.
Published: February 2008

A systematic approach is used to collect information important for identification of the Wairakei geothermal system by conducting numerical experiments with its different models. The identified model is shown to possess some forecasting power. Identification in the presence of linear feedback is discussed.
On identification and validation of some geothermal models
Authors: Fradkin Larissa Ju. , Sorey Michael L. , McNabb Alex
Published: February 2008

Various distributed and lumped parameter models of the Wairakei geothermal reservoir, New Zealand, are discussed within a unifying mathematical framework. The need for proper system identification is emphasized. The best lumped parameter model obtained by system identification techniques is presented and interpreted as a slow drainage model. Validation of different models is conducted by studying their forecasting powers with identified parameter values and by testing these identified values for compatibility with additional data.
Metal ion concentrations associated with late summer sediments of the Ohio River
Authors: Spencer H. T. , Leuthart C. A. , Colyer R. S.
Published: February 2008

The fine late summer sediments of the McAlpine Pool of the Ohio River are described as composed of an average 3% by dry weight volatile solids material. The volatile solids component was found to be associated with virtually all of the COD, hydrogen, sodium, potassium, aluminum, manganese, and lead, as well as a significant portion of the carbon, chromium, iron, copper, and zinc. Magnesium was found to have all of its acid‐soluble component associated with the nonvolatile portion of the sediment. The ambient thorium and uranium concentrations were found to be 11.0 ± 0.8 and 1.4 ± 0.5 μg g−1, respectively. The potential effect of this late summer sediment on aquatic life is suggested.
A stochastic approach for describing convective‐dispersive solute transport in saturated porous media
Authors: Rao P. V. , Portier K. M. , Rao P. S. C.
Published: February 2008

A stochastic approach is used to model convective‐dispersive transport of nonreactive solutes in homogeneous, isotropic, water‐saturated porous media during steady, one‐dimensional water flow at a volumetric rate Q and solute application at a rate of Mh(t). The expected solute concentration C(x, t) is shown to be C(x, t) = (M/Q)∫h(u) ƒ(t − u; x) du, where t is time and ƒ(t; x) is the probability density function (pdf) of the first‐passage time for the solute at position x. This expression yields known solutions for two cases examined (instantaneous release and continuous input) where closed form analytical solutions exist. This stochastic approach leads to statistically valid estimates and confidence intervals for the drift (velocity) and diffusion (dispersion) coefficients under the assumption that ƒ(t; x) is the first passage time pdf for Brownian motion of solute particles with a positive drift.
Secular changes in annual and seasonal Great Lakes precipitation, 1854–1979, and their implications for Great Lakes water resource studies
Authors: Quinn Frank H.
Published: February 2008

An analysis of annual precipitation over the Great Lakes Basin from 1854 to 1979 indicates two distinct precipitation regimes. The first, a relatively dry regime, lasted from the mid‐1880's until the late 1930's. This was followed by a relatively wet regime, which continues to the present. The analysis also indicates that the annual precipitation regime prior to the mid‐1880's was similar to the present regime. The change in precipitation appears to be the result of increased precipitation during spring and summer. A continuation of the present wet regime will present many challenges for water resource managers and planners concerned with lake regulation, water supply forecasting, coastal zone management, and water allocation and uses in the Great Lake Basin.
Convective and pore scale dispersive solute transport in unsaturated heterogeneous fields
Authors: Bresler Eshel , Dagan Gedeon
Published: February 2008

Transport of an inert solute in unsaturated horizontally heterogeneous field soils, which differs from that in laboratory conditions, is investigated. Four solute transport factors and their variabilities have been examined: (1) convection by vertical velocity V, which changes in plane because of variability in soil properties, (2) recharge R, applied on the surface, constant in time but varying in plane, (3) pore scale dispersivity λ, variable in the field, and (4) average dispersivity λ, with field condition value. The variables V, R, λ, and solute concentration C are regarded as random. Closed form equations (requiring a numerical quadrature at most) for the probability distribution of C are derived by using several simplifying assumptions concerning the water flow regime. The mathematical solutions are capable of determining detailed statistical information about solute distribution in the field. Two soils are examined: (1) Panoche soil (150 hectares in area) with low average saturated conductivity and relatively large variance and (2) Bet Dagan soil (0.8 hectare in area) with larger average conductivity and a smaller variance. It is found that for both soils the variability of λ has very little influence and that adopting the value of λ for the entire field is sufficient. The variability of R when it is moderate has a modest effect. The three major factors are the variability in soil hydraulic conductivity, average values of rate of recharge R, and pore scale dispersion λ. It is concluded that (1) average concentration profile in the heterogeneous field cannot be modeled as the solution of convective‐diffusion equation with constant coefficients and (2) if λ is taken at its laboratory‐measured value, its effect upon solute distribution is negligible compared with that of soil variability, but if the large field value is adopted, it has an impact upon solute distribution. The dominant spreading mechanism in Panoche soil is heterogeneity combined with convection. Accounting for both mechanisms is warranted in most cases.
On the relationship between the reliability of parameter estimates and hydrologic time series data used in calibration
Authors: Kuczera George
Published: February 2008

Typically, some of the parameters of conceptual hydrologic models are calibrated using limited hydrologic information, namely, input‐output time series data such as precipitation and streamflow. The first part of this paper examines the sources of stochasticity in these models and then explores the conditions under which parameter estimates are consistent when only input‐output hydrologic time series data are used in calibration. This complements other work done on the stability of parameter estimates. Because the conditions for consistency are stringent, two ways of redressing this situation and also improving the stability of parameter estimates are considered in the second part. Two levels of additional information are considered. The first considers the use of the first two moments of measurement errors to make large sample bias corrections. The second employs time series data corresponding to storage volumes such as groundwater and soil moisture to remove the source of inconsistency due to inferring erroneously unobserved storage volumes and to improve the stability of parameter estimates. Proper use of such information must exploit the interdependence in model equations arising from coupled model structure and correlated disturbances. It is suggested that generalized least squares offers a promising approach for efficiently exploiting all available time series information in model calibration. Finally, a simple hydrologic example is given to illustrate the relationship between estimator reliability and time series data used in calibration.
A low‐cost multichannel recording piezometer system for wetland research
Authors: Hemond Harold F.
Published: February 2008

A low‐cost system for the continuous recording of piezometric head is described. The system uses inexpensive earphones as sonar transducers, while using the narrow stem of the piezometers as an acoustic waveguide. The system overcomes several of the problems commonly encountered in tidal wetland investigations by providing rapid response, freedom from operator disturbance through peat compression, and essentially continuous automatic data recording in a directly machine‐readable medium.
Sensible energy storage in aquifers: 1. Theoretical study
Authors: Sauty J. P. , Gringarten A. C. , Menjoz A. , Landel P. A.
Published: February 2008

This paper presents the results of a theoretical study on the thermal behavior of a hot water storage system in an aquifer using a single well. It is shown that the storage efficiency and temperature are controlled by a limited number of dimensionless groups that depend on the aquifer's physical characteristics and the storage operating parameters. A numerical model is checked against analytical solutions and is then used to evaluate the variation with time of the well temperature during production periods for symmetrical cycles (production volume and flowrate equal to injection volume and flowrate). From these results, type curves are plotted for several sets of dimensionless parameters, covering the range of practical applications. Effects of unequal injection and production periods, standby periods, and other operating conditions are also investigated. Practical recommendations are made for efficient storage projects.
An upstream finite element method for solution of transient transport equation in fractured porous media
Authors: Noorishad Jahan , Mehran Mohsen
Published: February 2008

A finite element method for the solution of two‐dimensional transient dispersive‐convective transport of nonconservative solute species in fractured porous media is presented. A two‐nodal point one‐dimensional transport element for fractures is developed which provides a number of advantages relative to conventional fracture representation by two‐dimensional continuum elements. To eliminate the oscillatory behavior of convective‐dominated transport which is a more likely occurrence in fracture, a very efficient one‐dimensional upstreaming method along with a two‐dimensional method is implemented. Validity of the numerical scheme is established by comparison with existing one‐ and two‐dimensional analytic solutions.
Residential water conservation in a noncrisis setting: Results of a New Jersey Experiment
Authors: Palmini Dennis J. , Shelton Theodore B.
Published: February 2008

East Brunswick Township, New Jersey, conducted a water conservation program in 1980 by distributing to 564 households free packets of water‐saving devices purchased with municipal funds. The program was not a response to a current water supply crisis, and appeals for cooperation were based on the private economic benefits of water conservation. Statistical procedures were developed to measure the proportions of households installing each of the devices distributed, water savings and program costs. Two‐thirds of the households receiving the packets installed at least one device. Average annual water savings per home receiving a packet were estimated at 5010 gallons (18.96 kl). Amortized over ten years at a 10% discount rate, the program cost was approximately 35 cents per 1000 gallons of water saved (9.2 cents per kl). The East Brunswick results compare well to the results obtained from similar conservation programs in a pair of California communities during the 1976–1977 drought.
Multicomponent equilibrium chemistry in groundwater quality models
Authors: Jennings Aaron A. , Kirkner David J. , Theis Thomas L.
Published: February 2008

A technique is described for modeling the groundwater transport of a multicomponent solution of metals and ligands. By this method both soluble complexation and competitive sorption among chemical species may be accommodated. A finite element solution is presented for an arbitrary number of components. It is shown that although this technique leads to strongly nonlinear equations, accurate solutions may still be achieved. It is also shown that the interaction mechanisms modeled can have significant impact on the transport potential of solution components.
The Mixed Gamma Model for channel link lengths
Authors: Abrahams Athol D. , Miller Alan J.
Published: February 2008

An investigation of the lengths of exterior and interior links in 12 disparate areas suggests that link length distributions for most, if not all, natural landscapes represent a mixture of link length populations from different parts of the landscape characterized by different ground slope and/or environmental conditions. The mixed gamma density is derived for link lengths by assuming that both the component link length distribution for each relatively homogeneous part of the landscape and the mixing distribution of weights assigned to the various component distributions can be represented by gamma distributions. The mixed gamma density satisfactorily fits 84% of the 70 link length distributions examined, compared with 67% fitted by the log normal and 59% fitted by the gamma density. Deviations from the mixed gamma density are largely ascribed to spatial distributions of slope and environmental conditions which give rise to nongamma‐mixing distributions.
A theoretical investigation on the transport of chemicals in reactive porous media
Authors: Nguyen V. V. , Gray W. G. , Pinder G. F. , Botha J. F. , Crerar D. A.
Published: February 2008

This paper presents a general theoretical analysis of the transport problem of reactive chemical species in a class of statistically homogeneous porous media. Convection, diffusion, dispersion, erosion (or deposition), and reaction are included as the fundamental processes. A system of coupled kinetic operators representing the physicochemical interaction of fluid and solid phases together with the associated constitutive relations are derived using averaging theory and a set of constitutive axioms. A method of utilizing experimental information to obtain the chemical rate expressions is also presented. A practical application of the analysis is made to the investigation of the in situ mining of low‐grade uranium ores. An extension of the theory is suggested to form a rational basis for future investigation of sedimentary diagenesis.
Interpretation of pH and Eh trends in a fluvial‐sand aquifer system
Authors: Jackson R. E. , Patterson R. J.
Published: February 2008

Ground waters and aquifer materials from a shallow fluvial‐sand aquifer system (1‐km‐long flow path) were sampled and analyzed to determine the hydrogeochemical processes affecting pH and Eh (measured Pt electrode potential). The aquifer system is a fine‐grained sand (K ∼ 10−3 cm/s) composed principally of quartz and plagioclase (70% of all grains) with minor biotite (partially altered to vermicuiite) and trace amounts of calcite. Acid neutralization capacity measurements and X ray diffractograms suggest that acid precipitation recharging the aquifer undergoes a two‐step neutralization process; the first step involves reactions with the surfaces of mineral grains, mainly with plagioclase and biotite, and the second step involves an irreversible neutralization involving biotite alteration to vermiculite and carbonate mineral dissolution. During migration through deep confined parts of the aquifer ground waters attain equilibrium with calcite. A thermodynamically based redox model of a closed‐oxidant system satisfactorily accounts for the sequential reduction of dissolved oxygen, ferric oxides, and sulfate in the aquifer by the oxidation of dissolved organic carbon and (for oxygen only) ferrous iron. Because of the problems of using Pt electrodes in ground waters it is recommended that Eh measurements be supplemented with dissolved oxygen and sulfide measurements.