bluuebunny/crossref_metadata_2025 huggingface dataset:
Industrial economic model of water use and waste treatment for ammonia
Authors: Calloway James A. , Schwartz Andrew K. , Thompson Russell G.
Published: February 2008

A linear programing model is developed for analyzing the effects of policy, particularly water policy, on the use of water in ammonia production and on the cost of ammonia. Solution of the model for each policy specification gives the least‐cost ammonia production process, the marginal costs of the resource limitations, and the cost of water use and waste water treatment. The effect of systematically decreasing each effluent standard to zero was evaluated, and the effect of increasing the water price on water withdrawals was determined. The following results were obtained: (1) zero discharges of suspended solids, heat, and total dissolved solids increased production costs 3.8% with injection wells; (2) an effluent tax of 3.6¢/lb dissolved solids will reduce dissolved solid discharges 95%, and an effluent tax of 29.5¢/lb dissolved solids will reduce dissolved solid discharges 100%; (3) a water withdrawal price of 3.2¢/103 gal. will reduce water withdrawals 95%; and (4) zero discharge of residuals and high water prices increase production costs less than 4%. The modeling was done for a newly designed plant. Both naphtha and natural gas feedstocks were evaluated.
Analysis of flow to an extended fully penetrating well
Authors: Javandel I. , Zaghi N.
Published: February 2008

An analytic solution is derived yielding the potential distribution in a bounded confined aquifer pumped by a well that is radially extended at the bottom. An exact solution for the rate of discharge is found by which the effect of local radial extension on the increase of the pumping rate is studied. Solutions have been evaluated numerically, and the results are presented graphically in terms of dimensionless parameters. The results show that production rate is doubled in some cases by extending the bottom of the well.
On the impossibility of a partial mass violation in surface runoff systems
Authors: Diskin M. H. , Boneh A. , Golan A.
Published: February 2008

The class of nonnegative, initially relaxed, and nonanticipating systems has many applications in engineering. In this paper a proof is given to a theorem stating that in this class of systems, if the input total mass is equal to the output total mass, then for any nonnegative input‐output pair, the system fulfills also a partial mass condition. In applying this theorem to systems expressed by the Volterra series it is concluded that the input functions must be bounded. Two such bounds on the input functions are considered: (1) bounds resulting from the requirement of a nonnegative output and (2) bounds resulting from the mass‐conserving property of the system. The theorem mentioned above implies that the set of input functions causing nonnegative output functions is a subset of the set of input functions that do not violate the mass‐conserving property of the system. It is therefore clear that the bounds of type 1 are the dominant among the two bounds for any nonnegative input function. In a system expressed by an Nth order Volterra series the bounds on the input can be evaluated by solving a polynomial inequality of order N ‐ 1. An example is given for a system expressed by a third‐order Volterra series in which the bounds on the input form two regions. Explicit equations for the bounds of type 1 and 2 are derived for a second‐order system.
On the peak‐load pricing of urban water supply
Authors: Feldman Stephen L.
Published: February 2008

Peak‐load pricing through seasonal price increases without changes in metering and billing practices may produce distortions in efficiency and equity in urban water systems. Demand management models using parameters to evaluate the effect of seasonal price policy upon maximum day sprinkling demands may be misleading because of behavioral constraints to price responsiveness. Proposed are alternative pricing schemes that are likely candidates for improving the operating cost structure and design capacity of water supply systems without violating popular notions of equity.
Averaging errors in monthly evaporation estimates
Authors: Hage Keith D.
Published: February 2008

The problem of computing evaporation from monthly mean values of temperature, relative humidity, and wind is considered with specific reference to a Dalton‐type evaporation formula. Leading contributions due to nonlinearities, covariances, and their interactions are identified separately by expanding saturation vapor pressure as a Taylor series in temperature using the Clausius‐Clapeyron equation. A truncated form of the expansion is tested by using observations from a land station. A crude model of diurnal variations in air temperature, relative humidity, and wind speed is used to predict nonlinearity and covariance evaporation errors from monthly mean observations at 2 times per day. The model appears to be accurate to within ±5% in warm season months but fails in winter when diurnal variability is negligible in comparison with air mass changes in weather elements at mid‐latitude continental locations. Covariance and nonlinearity errors do not compensate each other in winter with the result that averaging errors can reach 20–25%.
A dependent domain model of capillary hysteresis
Authors: Mualem Y. , Dagan G.
Published: February 2008

A model of capillary hysteresis which takes into account the phenomenon of blockage against air (and water) entry is presented. The model is based on our previous (1974) model II, which predicts any hysteretic path with the aid of two functions, L(ψ) and H(ψ). This model is generalized by adding a new function,рd(θ)(and
), as has been suggested by D. H. Everett (1967) and G. C. Topp (1971). It is found that
is of a lesser significance and can be neglected in most cases. A technique of deriving L(ψ),H(ψ), and
from the measured boundary loop and one primary drying scanning curve is presented. A simple method of predicting any hysteretic path is suggested. It is found that the generalized model leads to better results than the models based on independent domain theories for soils having a major portion of their hysteretic loop in the range of air entry value.
Estimating energy budget components to determine Lake Huron evaporation
Authors: Bolsenga S. J.
Published: February 2008

Evaporation is estimated for Lake Huron by the energy budget method and compared to available mass transfer estimates. Data were from representative shoreline station measurements and vessel cruise measurements. Agreement between evaporation by the energy budget and by mass transfer was reasonable from February through July with the exception of May when measurement of the heat content was a problem. For the remainder of the year the disparity is marked. The principal difficulty encountered was the lack of meteorological measurements on the lake or adequate techniques to extrapolate the quantities from shoreline data. Quantitative monthly values for each component in the budget equation are the first published for Lake Huron and one of the few sets available for the Great Lakes.
Identification in nonlinear, distributed parameter water quality models
Authors: Yih Siu‐Ming , Davidson Burton
Published: February 2008

Systematic and efficient numerical algorithms are developed and applied to the identification of unknown functional parameters in nonlinear estuarine water quality models based on input‐output measurements. As an illustration of the methodology the longitudinal dispersion coefficient is identified from an intratidal, time‐varying, variable area, salinity intrusion model by using both simulated data and actual data from the Delaware River estuary. A comparison among three proposed algorithms through extensive simulation research shows that Marquardt's algorithm emerged as the most efficient one. Effects of noise content and the number of data measurement locations on parameter sensitivity are investigated. Actual monitored salinity data for 3 days in September 1965 are tested in the saline portion of the Delaware River estuary. The spatial variation of the longitudinal dispersion coefficient for this period is estimated. The results obtained indicate that the methodology is generally applicable and it represents a different and supplementary alternative to the methods based on analytical predictions and empirical correlations.
Determining aquifer transmissivity by means of well response tests: The underdamped case
Authors: van der Kamp Garth
Published: February 2008

Well response tests, often referred to as slug tests, provide a relatively simple and inexpensive method for estimating aquifer transmissivity. An approximate theory is developed for the problem of underdamped well response where the inertia of the water in the well column results in force‐free oscillation of the water level in the well. This type of response is often encountered in conjunction with highly permeable aquifers. The theory is applicable for nearly all such cases except those where the oscillation is very quickly damped out. Theoretical predictions compare well with empirical results and indicate that the theory may be used to obtain estimates of aquifer transmissivity. This theory for the underdamped case together with existing theory for overdamped response makes it possible to obtain an estimate of transmissivity from well response tests for almost any aquifer.
Flow interference effects at fracture intersections
Authors: Wilson Charles R. , Witherspoon Paul A.
Published: February 2008

A series of laboratory experiments were conducted to determine the magnitude of laminar flow interference effects at fracture intersections. Circular conduits were used in these experiments to maintain strict dimensional tolerance, and the intersection head loss, if expressed in terms of equivalent length of straight conduit, should be the same order of magnitude for a circular pipe as for a parallel plate fracture model. The results indicate that interference effects at intersections are negligibly small in most fracture systems when flow is in the laminar regime.
Capillary hysteresis and the relationship between drying and wetting curves
Authors: Parlange Jean‐Yves
Published: February 2008

A simple microscopic model predicts the wetting and drying scanning curves from only one boundary of the main hysteresis loop. Comparison with experiments shows that if the shape of the drying scanning curves varies smoothly, then the drying boundary of the loop is indeed sufficient to predict all scanning curves. However, if the shape of the drying curves changes abruptly, the model is still applicable, but the drying boundary yields only the wetting scanning curves, and the wetting boundary yields only the drying scanning curves. For this case the model seems more reliable for predicting the scanning curves than for the application of interpolation techniques between the two boundaries.
Effect of atmospheric stability on water temperature predictions for a thermally loaded stream
Authors: DeWalle David R.
Published: February 2008

A steady state one‐dimensional energy budget equation was numerically integrated to predict water temperatures in a 5.45‐km‐long thermally loaded stream reach for 131 five‐ or six‐hour periods. Downstream water temperature prediction errors (measured minus predicted) using Jobson's Lake Hefner evaporation equation averaged −2.11°C and were well correlated (R2 = 46%) with an index to atmospheric stability. Use of a modified form of Shulyakovskiy's evaporation equation, which includes a term for evaporation by free convection, significantly reduced the average prediction error to 0.89°C and eliminated the effects of atmospheric stability (R2 < 1%). Correction of wind velocity data for the velocity of the air relative to the stream velocity also reduced prediction errors.
Estimating selected parameters for the Kentucky Watershed Model from watershed characteristics
Authors: Magette W. L. , Shanholtz V. O. , Carr J. C.
Published: February 2008

Multiple linear equations to predict selected parameters for the Kentucky watershed model (KWM) are presented. The independent variables consist of easily determinable watershed characteristics. The relationship provides a means by which the KWM can be used to predict streamflows from ungaged drainage basins. Examples are given for five test watersheds. Results are variable.
Analytical solution of the equation for transport of reactive solutes through soils
Authors: Selim H. M. , Mansell R. S.
Published: February 2008

Mathematical solutions of the differential equation governing reactive solute transport in a finite soil column were developed for two spcific cases: continuous solute input and pulse‐type solute input at the soil surface. These solutions incorporate reversible linear adsorption as well as irreversible solute adsorption. The irreversible adsorption was expressed by a sink/source term which either may be a constant or may have a concentration‐dependent form. The boundary condition used across the surface (X = 0) was that of the third type, which accounts for advection as well as dispersion. To illustrate the significance of using the proper boundary conditions, comparisons were made with two other mathematical solutions, one by Cleary and Adrian (1973) and another by Lindstrom et al. (1967). We conclude that the solution presented here is highly recommended for low flow velocities, or specifically for v0L/Ds values less than 20. For large pore velocities, or specifically for v0L/Ds > 20, all three solutions are in agreement.
On the species transport equation for flow in porous media
Authors: Blake Thomas R. , Garg Sabodh K.
Published: February 2008

A derivation of the species transport equation for flow through porous media is presented. In this study, which is based on the space‐averaging formalism developed by Anderson and Jackson (1967), we examine the effects of both flow field fluctuations and tortuosity as well as the influence of solute transport at the fluid‐solid interfacial boundary.
Evidence for nonstationarity as a physical explanation of the Hurst Phenomenon
Authors: Potter Kenneth W.
Published: February 2008

Analysis of six precipitation records from the east coast of the United States supports nonstationarity of the mean as a physical explanation of the Hurst phenomenon. One possible mechanism is ‘almost intransitivity,’ a concept which implies that the atmosphere‐earth‐ocean system may exist in a number of distinct quasi‐stable regimes.
Water yields resulting from treatments on the Workman Creek Experimental Watersheds in central Arizona
Authors: Rich Lowell R. , Gottfried Gerald J.
Published: February 2008

The three Workman Creek watersheds were instrumented to determine the hydrology of mixed conifer forests and to determine the changes in streamflow and sedimentation as a result of manipulating the forest vegetation. A small riparian cut on North Fork did not increase water yields. A selection timber harvest, improvement cut, and fire which removed 45% of the basal area on South Fork increased yields slightly. In contrast, converting 32.4 ha (80 acres) of moist site forest to grass significantly increased water yields on the 100.4‐ha (248 acre) North Fork watershed. Water yields were increased even more after 40.5 ha (100 acres) of dry site pine forest were converted to grass. An increase of 69 mm (2.70 in.), or 84%, of expected runoff resulted from the combined treatment. Clearing 83% of the South Fork watershed preparatory to planting ponderosa pine significantly increased water yields by 93 mm (3.67 in.), or by 111%.
Classification of nested tributary basins in analysis of drainage basin shape
Authors: Jarvis Richard S.
Published: February 2008

Tributary basins in Strahler‐ordered drainage systems may be classified as order w formative or order w excess according to whether the order w mouth stream outflows into a stream of order equal to or greater than w. This classification distinguishes spatial nesting among tributary basins, formative tributaries locating farther from the main basin mouth than excess tributaries. Basin shape is analyzed by using standard indices and applying the method of unrolling perimeter radials for Fourier series analysis. The empirical results from 336 drainage basin shapes demonstrate differentiation of basin shapes between gemorphologic environments, between basin order levels 3 and 4, and between formative and excess tributary basin types at the order 3 level. The order level contrasts indicate scale dependency in drainage basin shapes, and the tributary order type contrasts suggest spatial nesting controls such that basins sampled solely by Strahler order level are not homogeneous with regard to shape properties.
Assessment of available water storage capacity of soils with restricted subsoil permeability
Authors: McCown R. L. , Murtha G. G. , Smith G. D.
Published: February 2008

The pasture production of most of the tropics is largely a function of the water regime. One of the few options for control of the water regime in these environments is choice of site. A site parameter of great importance is the available water storage capacity (AWSC) in the root zone. Although estimation of the AWSC is straightforward on freely drained soils, it is complicated on poorly drained soils by the inapplicability of the concept of field capacity. The latter soils, however, commonly have a buildup of salts at depth in the profile, presumably due to prevailing leaching conditions. The study reported herein was conducted to test the hypothesis that this salt profile can be used to indicate the depth of wetting under conditions similar to those producing maximum subsoil water recharge in this climate. Twenty sites on mainly texture contrast soils, most with poorly drained subsoils, were examined in detail. A close relationship between the observed depth of wetting and the depth to the salt bulge was found. This relationship, together with the total porosity of the top (wettest) stratum of the B horizon, provides a means of estimating the AWSC of the subsoil.
Thermal convection in a cavernous aquifer
Authors: Rubin Hillel
Published: February 2008

Geothermal activity may lead to convection currents in saturated permeable layers within the earth. This article concerns instability criteria for such a flow field in which the fluid flows initially at moderate Reynolds numbers. Supercritical conditions were analyzed by expanding the finite amplitude perturbations through truncated eigenfunctions. This approach yielded expressions for the intensity of transport processes through the aquifer. It was found that mechanical dispersion due to convection motions reduces the intensity of transport processes.
Seasonal streamflow estimation in the Himalayan region employing meteorological satellite snow cover observations
Authors: Rango A. , Salomonson V. V. , Foster J. L.
Published: February 2008

Low‐resolution meteorological satellite data and simple photo interpretation techniques have been used to map snow‐covered areas during early April over the Indus River and Kabul River basins in Pakistan. The early spring snow‐covered area was significantly related to April 1 through July 31 Streamflow in regression analyses for each watershed (Indus River, 1969–1973, r2 = 0.82, and Kabul River, 1967–1973, r2 = 0.89). Predictions of 1974 seasonal Streamflow using the regression equations were within 7% of the actual 1974 flow. Because of inadequate hydrometeorological data, conventionally based Streamflow predictions are not possible in some of these remote regions, and the satellite‐derived runoff estimates have immediate applicability for improved water resources management.
Effect of temperature and hydroxy aluminum interlayers on the adsorption of trace radioactive cesium by sediments near water‐cooled nuclear reactors
Authors: Elprince A. M. , Rich C. I. , Martens D. C.
Published: February 2008

The adsorption of 137Cs by sediments from the Savannah River Plant follows a theoretically expected linear relationship between ln Kd* and l/T where Kd* and T are the equilibrium distribution coefficient (Cs adsorbed, meg g−1/Cs+ in solution, meq ml−1) and the temperature in kelvins, respectively. The slope of these plots decreases after removal of hydroxy Al interlayers with citrate pretreatment. Hydroxy Al interlayers thus make Cs+ adsorption more temperature dependent. This thermal effect of hydroxy Al interlayers becomes more significant in sediments containing a nonswelling 2:1–2:2 intergrade clay mineral than in those containing a swelling 2:1–2:2 intergrade clay mineral. The phenomenon is explained by considering hydroxy Al interlayers as a source of hydronium ions H3O+ which compete with Cs+ for exchange positions in wedge zones. An increase in temperature favors an increase in H3O+ ions, which in turn favors less adsorption of Cs+. Aside from their thermal effect the positively charged hydroxy aluminum polymeric groups drastically decrease the cation exchange capacity and consequently the adsorption of cesium.
Seasonal variations in the impact of suburban development on runoff response: Peterborough, Ontario
Authors: Taylor C. H.
Published: February 2008

A small basin in Peterborough, Ontario, has been instrumented to investigate the contrasts in runoff response between rural and suburbanized sections of the basin. Data have been collected over three seasons (summer, fall, and spring) to evaluate seasonal variations in the rural‐urban contrast. Results indicate that the effect of the urban development is felt most strongly in the spring under snowmelt conditions and least strongly in the summer. Urban direct runoff volumes exceed rural volumes by factors of 1.2 for summer rainstorms, 2.3 for fall rainstorms, and 7.5 for spring snowmelt and rain‐on‐snow events. Urban peak discharges exceed rural peaks for the same seasons by factors of 4.5, 2.4, and 7.1. Direct runoff‐rainfall ratios (infall and snowmelt in the spring case) are fairly consistent in the rural basin, being 0.05 for the summer, 0.07 for the fall, and 0.06 for the spring. The corresponding ratios in the urban basin are 0.06, 0.16, and 0.76. It is believed that seasonal variations in the rural‐urban response ratios are caused mainly by seasonal fluctuations in the extent of the runoff contributing area in the urban basin.
Chemical character of headwater streams in Vermont and New Hampshire
Authors: Johnson Arthur H. , Reynolds Robert C.
Published: February 2008

Stream water samples were collected from headwater streams in Vermont and New Hampshire during low‐flow periods in the fall and analyzed for principal dissolved constituents. Dissolved solids are qualitatively and quantitatively related to bedrock type. Streams draining watersheds underlain by plutonic bedrock are acid, mixed cation sulfate waters with little buffering capacity and very low solute content (about 16 mg/1). Streams draining metamorphic and sedimentary terrains are characterized by neutral pH, alkaline earth cations, and mixed anions or bicarbonate. Concentrations of Ca + Mg + Na + K and pH of streams draining granitic bedrock are lower than those of streams draining similar rock types in small watersheds in the Sierra Nevada and Sangre de Cristo mountains.
Rainfall infiltration into bare soils
Authors: Morin Joseph , Benyamini Yoram
Published: February 2008

Raindrop impact destroys the surface aggregates of soils and gradually forms a continuous crust. Infiltration rates of bare soils are determined by this process. A theoretical model presented previously was tested under field conditions with a sandy loam soil. The effect of the crust's structure was tested under three rainfall intensities and in wetting and drying cycles. The results of the tests confirmed the theoretical model. According to the model potential infiltration rates, in bare soils, can be predicted by the equation It = (Ii ‐ If) ·e−γptl + If. The study demonstrated quantitatively that the major factor determining the reduction of infiltration rates is crust formation and not moisture regime.
Experimental evaluation of theoretical solutions for subsurface drainage and irrigation
Authors: Tang Y. K. , Skaggs R. W.
Published: February 2008

The Richards equation for two‐dimensional saturated‐unsaturated water movement was solved for drainage and subirrigation boundary conditions by using finite difference methods. The solutions were compared to results of experiments conducted for various initial and boundary conditions in a large laboratory soil tank. The soil water characteristic and hydraulic conductivity function were measured by conventional methods and used as inputs in the numerical solution to the Richards equation. Although predicted water table drawdown was somewhat slower than was observed, agreement between the numerical solutions and experimental observations was generally good. Approximate methods were also used to characterize drainage and subirrigation and were found to be in good agreement with solutions to the more exact Richards equation and with experimental results when a variable drainable porosity is considered. In view of significant field variability of soil properties and the difficulty of measuring those properties, required by the Richards equation, it appears that simpler, approximate methods will continue to be more useful than the exact approach for predicting water table movement under drainage and subirrigation conditions.
The small sample expectation of rescaled population and rescaled adjusted ranges
Authors: Şen Zekâi
Published: February 2008

The expected value of the rescaled range R/S, which is a measure of long‐term persistence in hydrology, has analytically been obtained by making use of t distribution. The application of the model has been performed for various hydrological processes. Finally, the asymptotic equivalence for expectations of the range and the rescaled range has been proven.
The dishonest method in stream temperature modeling
Authors: Morse William L.
Published: February 2008

The unidimensional form of the thermal energy conservation principle as a quasi‐linear partial differential equation (PDE) has been shown accurate for point temperature forecasts on completely mixed streams and river‐run reservoir systems. Two methods of solution are presented which lead to a unique solution. Yet this nonrandom solution is contrary to the behavior of nature, and so a philosophic change is introduced. From the PDE subsidiary differential system a stochastic differential equation (SDE) is obtained with random forcing function from the meteorologic and forebay‐depth analyses. With random initial conditions (time‐averaged components of the in situ water temperature vector) the SDE is then recast as a random nonlinear Volterra integral equation (RIE). Then a solution to the random‐initial‐conditions RIE (fixed points of the expectations), by the so‐called dishonest method (Keller, 1962), is compared with a solution obtained by repetitively solving the PDE as a random equation (expectations of the fixed points). Of course, these solutions, obtained by ‘dishonest and honest’ methods, are not necessarily unique, but they may be sufficiently close in some sense. Hence proper interpretation and use of this RIE model would enable water resource planners economically to determine stream temperatures in probability during critical climatic or river flow conditions. And then intelligent planning and scheduling could avoid some catastrophic aquatic event which might occur as a result of extreme water temperatures.
An analysis of design life standards for interceptor sewers
Authors: Binkley Clark
Published: February 2008

A simple capacity expansion model based on existing data concerning interceptor scale economies and inflation of sewer construction costs relative to the economy as a whole is used to analyze optimal design life standards for interceptor sewers. The economic losses from errors in policy assumptions are also assessed. In keeping with the premise of the current water pollution control program, cost minimization is the objective for choosing a design life standard. No benefit estimates are made, and other effects of water pollution control are treated only tangentially. Using the scale economies most frequently reported in the literature, the optimal design life is 21 years if relative inflation is ignored and 29 years if the relative inflation of sewer construction during the past 15 years is assumed to persist forever. These findings run counter to the traditional 50‐year design life for interceptor sewers but support current policy initiatives, both through amendments to the Water Pollution Control Act of 1972 and through revisions of Environmental Protection Agency guidelines, which would shorten interceptor design periods to from 20 to 40 years.
An adaptive algorithm for analyzing short‐term structural and parameter changes in hydrologic prediction models
Authors: Wood Eric F. , Szöllösi‐Nagy Andras
Published: February 2008

An adaptive unbiased recursive prediction algorithm, based upon the state space description of hydrologic systems, is discussed. Discrete linear systems with white Gaussian disturbances are considered. The algorithm allows for short‐term structural and parameter changes due to random environmental effects. A prediction model is set up from a representation of the rainfall‐runoff processes with the unknown parameters modeled by a random walk. The predictions are obtained by the use of linear Kaiman filters where the unknown noise covariance matrices are also adaptively estimated. The behavior of the adaptive prediction algorithm is illustrated by a real‐world example taken from rainfall‐runoff flood forecasting.
Generation of skewed annual flows using fast fractional Gaussian noise generator
Authors: Srikanthan R. , McMahon T. A.
Published: February 2008

The fast fractional Gaussian noise process is modified to generate skewed streamflows and those having negative lag 1 autocorrelation. The modified procedures are applied to two Australian streams, and the results are compared with the corresponding historical values.
Climate, soil, and vegetation: 1. Introduction to water balance dynamics
Authors: Eagleson Peter S.
Published: February 2008

A statistical dynamic formulation of the vertical water budget at a land‐atmosphere interface is outlined. Physically based dynamic and conservation equations express the infiltration, exfiltration, transpiration, percolation to groundwater and capillary rise from the water table during rainstorms and interstorm periods in terms of independent variables representing the precipitation, potential evapotranspiration, soil and vegetal properties, and water table elevation. Uncertainty is introduced into these equations through the probability density functions of the independent climatic variables and yields derived probability distributions of the dependent water balance elements: surface runoff, evapotranspiration, and groundwater runoff. The mean values of these quantities give a long‐term average water balance which, to the first order, defines the annual water yield and water loss in terms of the annual precipitation and potential evapotranspiration and in terms of physical parameters of the soil, vegetation, climate, and water table. This analytical framework provides physical insight into the dynamic coupling of climate‐soil‐vegetation systems. Details are presented in a series of subsequent papers.
An iterative quasi‐three‐dimensional finite element model for heterogeneous multiaquifer systems
Authors: Chorley Don W. , Frind Emil O.
Published: February 2008

A quasi‐three‐dimensional flow model is developed for the analysis of hydrogeologic systems consisting of several aquifers interconnected by aquitards. Provided only that each layer is continuous within the domain and that a permeability contrast of 2 orders of magnitude or more exists between adjoining layers, a system can be completely heterogeneous. Any of the aquifers can be pumped, and discharge rates can be arbitrary. Flexibility is achieved by utilizing finite element discretizations for aquifers as well as aquitards. The solution is iterative, aquifers and aquitards being solved separately and coupling being provided through the leakage flux. Aquitard storage and interaction between aquifers are rigorously accounted for at all times. Convergence is demonstrated experimentally by comparison with the analytical solution of Neuman and Witherspoon. The multiaquifer model is shown to be much more economical than an equivalent three‐dimensional model.
Simulated streamflow response to possible differences in transpiration among species of hardwood trees
Authors: Federer C. Anthony , Lash Douglas
Published: February 2008

Possible differences in transpiration among species of hardwood trees were simulated in a hydrologic model, called Brook, to estimate the effects of these differences on monthly and annual streamflow. Brook is a deterministic, lumped‐parameter model that simulates streamflow from small, forested watersheds in the eastern United States. The model uses only daily mean temperature and daily precipitation as input. A 4‐week difference in timing of leaf development in spring or color change in autumn caused differences of 10–60 mm in simulated annual streamflow. When daily transpiration varied by 20%, as it might with differences in leaf diffusive resistance among species, differences in simulated streamflow ranged from 15 to 120 mm annually. Differences in root distribution with depth can affect the availability of soil water; varying this availability caused differences in simulated streamflow of 15–60 mm. In all cases the smaller differences occurred when the soil was dry at the times of differing transpiration. On a deep residual soil the differences in streamflow were spread through the year, but on a shallow till soil the differences were restricted to the months in which there were changes in transpiration. Differences in response among 15° north‐facing and 15° south‐facing slopes and a horizontal surface were south‐facing slopes and a horizontal surface were minor.
The computational efficiency and taylor expansion derivation of approximating equations to the groundwater flow equation
Authors: Kuiper Logan K.
Published: February 2008

A general procedure is presented for the derivation of the approximating equations to a differential equation. As is the case with many such approximating equations, values of the dependent variable evaluated at a cluster of points in the independent variable space are related in a relatively simple manner. The total set of such relations, each with a corresponding cluster, one for each of a set of chosen points in the independent variable space, forms the approximating equations to the differential equation. In the procedure presented, each of these relations is formulated by the use of Taylor expansion about a point centrally located within each corresponding cluster. The procedure is used to derive new approximating equations to the one‐dimensional groundwater flow equation, both homogeneous and nonhomogeneous. These approximating equations are shown to exhibit superior accuracy and speed in comparison with others that are in common use presently. Twelve different varieties of approximating equations to the one‐dimensional homogeneous groundwater flow equation, many of which are in common use, are compared for accuracy. Results of these comparisons and others for the nonhomogeneous case show that approximating equations with higher‐order error e give superior results. For any given variety of approximating equations it is shown that maximum accuracy is achieved when the quantity g, the magnitude of the spacial increment Δx squared divided by the magnitude of the time increment Δt, is properly chosen. What this optimal value of g should be is shown to depend upon the error e and character of the approximating equations, the variability and accuracy of the solution being obtained, and the variability of the transmissivity and storage coefficient.
Entropy concepts in fluvial geomorphology: A reevaluation
Authors: Davy Bryan W. , Davies Timothy R. H.
Published: February 2008

The thermodynamic basis of entropy concepts as applied in fluvial geomorphology is examined closely. It is shown that the principle of minimum entropy production rate and the principle that the most probable state of a system is that which corresponds to a maximum of entropy are not applicable in stream situations. It is concluded that the use of entropy as an approach to stream behavior and sediment transport is of dubious validity.
Effect of the Suwannee River Sill on Okefenokee Swamp water level
Authors: Finn John T. , Rykiel Edward J.
Published: February 2008

An 11‐cm increase in mean water level at the Camp Cornelia boat basin in Okefenokee Swamp is attributable to the Suwannee River sill. This increase represents about 45% of the average total increase after sill construction. The remaining 55% can be explained as natural variation in the hydrologic cycle. A reduction of about 18–30% of the normal variation in water level has occurred since sill construction. Apparent surface water gradients have been substantially altered, and the potential impact area may approach 28% of the total swamp area. Changes in hydroperiod and water level amplitude in the sill impact area may affect the floristic character of the Okefenokee Swamp over the long term.
The asymptotic distribution of the maximum deficit of partial sums of independent random variables
Authors: Gomide Francisco L. S.
Published: February 2008

Studies of storage capacity of reservoirs lead to the problem of finding the distribution of the maximum deficit of partial sums of independent random variables. In this paper, the asymptotic distribution of the maximum deficit is derived using the theory of Markov chains. The range and the adjusted range of partial sums of independent random variables are also discussed.
Geothermal reservoir simulation: 3. Application of liquid‐ and vapor‐dominated hydrothermal modeling techniques to Wairakei, New Zealand
Authors: Mercer James W. , Faust Charles R.
Published: February 2008

A quasi three‐dimensional, areal model based on finite‐difference approximations is applied to the hydrothermal field at Wairakei, New Zealand. The model simulates heat transport associated with the flow of steam and water through porous media. An analysis is made of the production aquifer under steady‐state and transient flow conditions, allowing vertical flow of heat and fluid through confining beds. Computed steady‐state results correlate well with observed data and indicate that portions of the aquifer had a steam cap prior to exploitation. Computed transient results also match observed data and support the hypothesis that the production aquifer is recharged through underlying confining beds. The limiting factor on production is the amount of mass available, both from storage and leakage. Although simulation results indicate that the field can maintain production rates to the year 2000, such long range predictions are unreliable due to the lack of information on the leakage properties of the confining beds.
The limnological response of a West Virginia multipurpose impoundment to acid inflows
Authors: Koryak Michael , Stafford Linda J. , Montgomery William H.
Published: February 2008

Periodic intrusions of acid mine drainage enter Tygart River Lake during the summer and autumn months. In spite of only moderate vertical thermal gradients in the reservoir, these inflows penetrate the impoundment as well‐defined temperature‐density currents. The depth of penetration and resulting mixing patterns of the acid inflows are influenced by the design and operation of the dam. The internal hydrodynamics of the reservoir in turn influence the chemistry and biology of both the impoundment and the outflow.
Northern lake modeling: A literature review
Authors: Fox Patricia M. , LaPerriere Jacqueline D. , Carlson Robert F.
Published: February 2008

While there are many diverse temperate lake models available, there are none which are comprehensive annual northern lake models. Northern lakes are those which lie above 40°N latitude, have continuous winter ice cover, and experience large seasonal differences in daylight patterns. Therefore it is necessary to review the temperate ecosystem and smaller process models along with reported field studies to assess model adequacy for northern application. While most northern lake processes have been described in the literature, there is little agreement between investigators as to specific formulations. However, lake modeling can be a viable tool in northern lake utilization studies provided certain precautions are taken. When using the various formulations presented in this review to develop and apply a model, all assumptions of each component should be considered. Also, the uncertainty in the data and model should be incorporated or at least considered with the resulting estimates.
Experimental and numerical study of a transient, two‐dimensional unsaturated‐saturated water table recharge problem
Authors: Vauclin M. , Khanji D. , Vachaud G.
Published: February 2008

Transient two‐dimensional water flow is studied in relation to the recharge of a water table aquifer. The approach is based on the physics of water transfer in the complete domain defined by both the saturated and unsaturated zones of soil. Experimental data were first obtained in a slab of soil (3 m in length, 2 m in height, and 5 cm in thickness) in which the changes of water content and water pressure occurring in the flow domain were measured throughout an artificial recharge event. These were compared with the predictions of a numerical model based on the continuity of transfer between the unsaturated and saturated zones. The validity of the model is proved by the excellent agreement between simulated and experimental results. Furthermore, comparison with the results obtained by a viscous flow analog reveals the errors associated with the traditional free surface approach, which neglects transfer in the unsaturated zone.
Boundary integral equation solution to axisymmetric potential flows: 2. Recharge and well problems in porous media
Authors: Lennon Gerard P. , Liu Philip L.‐F. , Liggett James A.
Published: February 2008

The boundary integral equation method (BIEM) is employed to solve both steady and transient axisymmetric flow problems in porous media. The problems analyzed here are governed by Laplace's equation; however, the unsteady and nonlinear behavior result from the presence of a free surface. Both finite and infinite domains are easily handled with the BIEM. Results are presented for a variety of well and recharge problems. Comparisons of BIEM results to a linearized theory show excellent agreement for recharge problems where the linearized theory is valid. In addition, results were obtained for cases where the linearized theory cannot be used. The BIEM solutions for steady state well problems are in excellent agreement with solutions obtained by a finite element method, as well as the analytic solution using the Dupuit assumption. Finally, the BIEM yields solutions to a variety of transient well problems. It is concluded that the BIEM is both an accurate and efficient method for solving well and recharge problems.
Stochastic optimization of water supply expansion
Authors: Bogle M. G. V. , O'Sullivan M. J.
Published: February 2008

Stochastic dynamic programming is used to schedule the annual expansion of a water supply facility which is being used to supplement a catchment reservoir of fixed storage capacity. The optimal plant construction programme over a planning period of many years is that which optimises the total expected discounted cost, which is made up of investment cost, operating cost, and shortfall penalty cost. Reservoir storage is used as the state variable, and the stochastic structure of the system is derived from the probability distributions of monthly inflows. Storage carryover from year to year is incorporated into the model as an important feature.
Storm travel distance calculations for total phosphorus and suspended materials in rivers
Authors: Verhoff Frank H. , Melfi David A. , Yaksich Stephen M.
Published: February 2008

From previous work it appears that total phosphorus is transported through rivers by a series of storm events. This paper presents a method for calculating the average distance of travel during any given storm event. The method uses the hydrograph, chemograph, and flow characteristics at a point in the river. Comparisons were made between storm events at the same station in a river, between different stations in the same river basin, and between stations in different rivers. Results show the distance of travel is dependent upon the magnitude and duration of the storm event but not on the magnitude of the total phosphorus concentration.
Discharge response analysis and hydrologic similarity: The interrelation between the geomorphologic IUH and the storm characteristics
Authors: Rodríguez‐Iturbe Ignacio , Devoto Gustavo , Valdés Juan B.
Published: February 2008

It is shown that the dynamic parameter v of the geomorphologic instantaneous unit hydrograph (IUH) can be taken as the velocity at the peak discharge time for a given rainfall‐runoff event in a basin. This transforms the time variant IUH throughout the event into a time invariant IUH in each storm occurrence. The errors which the a priori estimation of the velocity in the IUH may cause in the calculation of the peak and time to peak of the runoff discharge are estimated for different types of basins and storms; the relative weights of the storm characteristics and the drainage network parameters in the prediction procedure are also studied in detail. Drainage basins are defined as hydrologically similar if they have the same IUH when kinematic conditions are kept the same; through the geomorphologic IUH theory it is shown that the controlling parameter in hydrologic similarity is RL0.43/LΩ.
Determination of recharge rates using temperature‐depth profiles in wells
Authors: Boyle Joseph M. , Saleem Z. A.
Published: February 2008

Recharge rates to the shallow dolomite aquifer in northeastern Illinois are determined using a theory which describes the simultaneous transfer of heat and fluid in a porous medium. Temperature‐depth profiles in a nonpumping well are used to determine vertical groundwater velocities of the downward leakage of water recharging the aquifer which is overlain by semiconfining beds of clay‐rich glacial drift. Calculated and observed depths of penetration (19 m) of the annual surface temperature wave, and demonstration of the thermal stability of the well, validate application of the theory, which uses a dimensionless parameter β to relate curvature in temperature‐depth profiles to the magnitude of vertical leakage. Generally, the magnitude of β decreases as the depth interval L within the aquitard increases. The corresponding decrease in the vertical component of groundwater velocity accompanies a gradual coarsening with depth of the aquitard materials. Temperature differences over time at a given depth within a thermally stable well are found to be within the accuracy of the temperature measuring system. Analysis of variations in β Over time shows that the variability can be due to the limitations of the resolution (0.01°C) of the temperature measuring system. Recharge rates determined by analyses of temperature‐depth profiles range from 2.47×10−9 to 9.86×10−9 m/s and agree with estimates resulting from water‐budget method.
Estimating soil water retention characteristics from particle size distribution, organic matter percent, and bulk density
Authors: Gupta S. C. , Larson W. E.
Published: February 2008

Regression models are presented for estimating soil‐water‐retention curves from particle‐size distribution, percentage of organic matter, and bulk density. Models were developed from the measured soil‐water‐retention curves of artificially packed cores (7.6×7.6 cm) of 43 soil materials. These soil materials included 13 agricultural soils. Curves predicted with these models approximated reasonably well the measured water retention of 61 Missouri soils. Because conventional methods of obtaining retention curves are expensive and time consuming, these equations will be valuable for modeling salt and water flow in soils and for estimating available water capacities.