摘要:

Storage‐release systems, in one form or another, are often used to improve the quality of urban storm water. Analytical methods to determine optimal storm water storage‐release strategies are difficult to apply because of difficulties in providing accurate functional representations of the problem components and in solving nonlinear programing problems with economies of scale. In order to circumvent these obstacles robust procedures for selecting an optimal storage‐release strategy are presented. One method takes a graphical approach, the other is based on an application of microcomputer‐based spreadsheet and spatial analysis software. Both methods are demonstrated with an example appl

ISSN:0043-1397    

DOI:10.1029/WR024i011p01831

年代:1988

数据来源: WILEY

摘要:

Conflicts between instream water uses such as fish production and traditional out‐of‐stream uses are an important water resource issue. One criterion for evaluating the merits of alternative water allocations is economic efficiency. This study uses an integrated approach to measure the recreational steelhead fishery benefits of incremental streamflow changes in the John Day River in Oregon. The analysis combines a steelhead fishery production model with a contingent valuation assessment of changes in fishing quality to obtain estimates of the marginal value of water in producing fishing quality. The results suggest that increased summer flows to enhance fishing have a marginal value of about $2.40 acre‐foot. When expressed in terms of water actually consumed, the value may be up to 10 times higher. These values are sensitive to the location of flow alterations in the river, potential for downstream uses and number of anglers in the fi

ISSN:0043-1397    

DOI:10.1029/WR024i011p01839

年代:1988

数据来源: WILEY

摘要:

Residential households in Perth, Western Australia have access to privately extracted groundwater as well as a public mains water supply, which has been charged through a two‐part block tariff. A contingent valuation approach is developed to estimate price elasticity of demand for public supply. Results are compared with those of a multivariate time series analysis. Validation tests for the contingent approach are proposed, based on a comparison of predicted behaviors following hypothesised price changes with relevant independent data. Properly conducted, the contingent approach appears to be reliable, applicable where the available data do not favor regression analysis, and a fruitful source of information about social, technical, and behavioral responses to change in the price of wate

ISSN:0043-1397    

DOI:10.1029/WR024i011p01847

年代:1988

数据来源: WILEY

摘要:

A methodology is developed for discrimination among models of transient solute transport in porous media. The method utilizes nonlinear regression on observations of solute concentration. Discrimination requires comparisons of model predictions to observations, systematic error in residuals, stability in parameter estimates from regression on different observation sets, and other measures of model fit among hypothesized models of transport. The set of observations of solute concentration to which models are fitted strongly influences the assessment of these discrimination criteria. The most desirable observation set for discrimination amplifies the weaknesses of those models that appear to describe existing conditions but are in fact unsuitable for prediction. The inadequacies of various observation sets are illustrated in four examples of discrimination between one‐dimensional models of solute transport. Our purpose in these examples is to understand the physical, deterministic basis of sampling design for model discrimination. In addition to physical attributes such as transport processes, boundary conditions, and flow geometry, the assumed distribution of random error in the regression model is also treated as a model attribute to be tested by the designed experiment. A common problem in field studies occurs when the set of available observations does not include sufficient information with which to discriminate among hypothesized models, hence supporting the need to design a second round of sampling specifically for discrimination. A proposed objective function in the sampling design problem favors design points at locations and times when two hypothesized transport models display the greatest differences in predicted concentration. Two hypothetical examples demonstrate the effectiveness of the objective function and the application of the discrimination criteri

ISSN:0043-1397    

DOI:10.1029/WR024i011p01859

年代:1988

数据来源: WILEY

摘要:

Chlorine 36 and3H have been widely used as laboratory tracers for the advection and dispersion of anionic solutes and water, respectively. Advances in accelerator mass spectrometry have recently made possible the analysis of36Cl in natural soil water samples. Field investigations analogous to the laboratory experiments can now be conducted. Pulses of36Cl and3H released into the atmosphere by nuclear weapons testing in the 1950s and 1960s serve as the tracers. We report36Cl and3H measurements on desert soil profiles from New Mexico. In both cases where the two tracers were measured in the same profile, the3H bomb pulse had penetrated between 1 and 3 m, but much of the36Cl was retained near the soil surface. In contrast, the laboratory experiments usually show more rapid movement of36Cl than3H due to the anion exclusion effect. We attribute the difference to the lower water content, fluctuating temperature gradients, and longer time scale of the field situation, which may enhance vapor movement of the tritiated water relative to solute advection of the36Cl. The spreading of the36Cl and3H pulses may be modeled by dispersivities ranging from 5 to 8 cm, much larger than most corresponding laboratory values. These larger apparent dispersivities are probably more a result of vertical velocity fields varying with depth and time than of soil heterogeneity. These results illustrate how the bomb pulse36Cl and3H can be useful links between laboratory solute transport studies and the corresponding field applications.

ISSN:0043-1397    

DOI:10.1029/WR024i011p01877

年代:1988

数据来源: WILEY

摘要:

Suspended solid particles are introduced into well bores during various operations such as the use of drilling muds. These particles in drilling muds can build a filter cake on the wall of the bore and migrate to the porous formation immediately adjacent to the well bore. In either case, the entrainment and deposition of particles cause an observed decline in productivity of some wells or increase of injection pressures. It is the objective of this work to develop a practical mathematical approach to the formation of a filter cake at the face of the well bore. This is achieved first by defining and identifying relevant mechanisms which contribute to the cake formation and particle migration in porous media. Then, conservation principles expressed in terms of quantifications of these mechanisms lead to a system consisting of governing partial differential equations. These equations are averaged to obtain analytical expressions to predict the cake thickness as a function of solid concentration, injection rate, or filtrate rate, and time. The results are compared with experimental data obtained by some researchers. Excellent match is obtained between the theoretical and experimental results.

ISSN:0043-1397    

DOI:10.1029/WR024i011p01893

年代:1988

数据来源: WILEY

摘要:

Recent investigations of heterogeneity within subsurface media have shown the importance of understanding the structure of hydraulic conductivity fields when considering either flow or transport within porous media. In the present study, a Monte Carlo approach is utilized to investigate the existance and structure of continuous paths of high hydraulic conductivity within low conductivity media. The rock mass is modeled as a discretized grid of elements, each element characterized by a single value for the hydraulic conductivity. By transforming the hydraulic conductivity utilizing the cumulative distribution function of the conductivity, a new random variable is obtained which is uniformly distributed in the range (0, 1). Utilizing this parameter, we can locate the path (termed the extreme path) which (1) connects two specified faces of the simulation grid and (2) contains the maximum value for the minimum conductivity along all such paths. The transform of this maximized minimum is termed the extreme path value. Grids are analyzed which are characterized either by (1) independence between grid elements, (2) correlation between grid elements, or (3) conditioning on field values obtained from a site in southern Arizona. It is shown that for all grids analyzed, there will exist, on average, at least one path crossing the grid along which the hydraulic conductivity is everywhere greater than the effective conductivity of the medium. Further, when the minimum conductivity along such extreme paths is analyzed, it is observed that the expected value of this minimum conductivity increases with correlation. Finally, conditioning simulations on field values resulted in a decrease in the estimation variance of the minimum conductivity.

ISSN:0043-1397    

DOI:10.1029/WR024i011p01901

年代:1988

数据来源: WILEY

摘要:

A simple, quick, and reliable iterative method for the determination of theD‐Θ relationship, based on the outflow analysis, is presented. This method imposes no restriction on the functionalD(Θ) relationship and gives better results than other previous methods even in cases of extreme nonlinearities in the InD(Θ) relationship and in cases where theD(Θ) relationship is not monotonous. The present method, an improvement to the already existing methods, has been verified against simulated and measured one‐step pressure outfl

ISSN:0043-1397    

DOI:10.1029/WR024i011p01911

年代:1988

数据来源: WILEY

摘要:

The global effective permeability and hydrodynamic dispersion tensors due to steady flow in locally heterogeneous and statistically anisitropic aquifers are analysed using the “self‐consistent approximation.” For small perturbations the results for the statistically anisotropic case are shown to be consistent with those derived using stochastic continuum theory. However, for larger perturbations the stochastic continuum theory has not yet produced rigorous results that can be compared with those in this

ISSN:0043-1397    

DOI:10.1029/WR024i011p01921

年代:1988

数据来源: WILEY

摘要:

The water level in a well that taps a partially confined aquifer is often sensitive to atmospheric loading. The magnitude and character of this response is partly governed by the well radius, the lateral hydraulic diffusivity of the aquifer, the thickness and vertical pneumatic diffusivity of the unsaturated zone, and the thickness and vertical hydraulic diffusivity of the saturated zone overlying the aquifer. These key elements can be combined into five dimensionless parameters that partly govern the phase and attenuation of the response. In many cases, the response of a well to atmospheric loading can be broken up into a high‐, intermediate‐, and low‐frequency response. The high‐frequency response is governed largely by the well radius and lateral diffusivity of the aquifer. The intermediate‐frequency response is governed by the loading efficiency of the aquifer. The low‐frequency response is governed by the vertical pneumatic diffusivity and thickness of the unsaturated zone and the vertical hydraulic diffusivity and thickness of the saturated material above the aquifer. Cross‐spectral estimation is used to fit the response to atmospheric loading of three water wells to the theoretical curves in order to yield estimates of three of the key dimensionless parameters. These estimates then are used to make estimates or place bounds on the vertical pneumatic diffusivity of the unsaturated zone, the lateral permeability of the aquifer, and the composite vertical hydraulic diffusivity of the overlying satura

ISSN:0043-1397    

DOI:10.1029/WR024i011p01927

年代:1988

数据来源: WILEY