摘要:

Transferable discharge permit (TDP) programs for controlling several pollutants may manage such pollutants as several individual commodities or as a single weighted sum of the various pollutants. This paper shows that the weighted sum permit program may be appropriate for managing pollutants that have an additive or a noninteractive effect on environmental quality. However, under this approach, administrators do not have direct control over the amount of each pollutant that is discharged, and environmental quality may be jeopardized unless the selected weighting factors induce a market equilibrium that satisfies environmental quality standards for the region. Estimates of the cost‐effective weighting factors that would tend to satisfy environmental quality standards under such programs are developed here. These estimates require complete water quality information and, in the case of noninteractive pollutants, treatment costs. An approach is described for estimating the cost‐effective weighting factors for noninteractive pollutants in cases where treatment cost information is unknown. This approach is demonstrated for a weighted sum TDP program for biochemical oxygen demand (BOD) and phosphorus. The results of this demonstration suggest that for weighted sum permits for these pollutants it is possible to determine a set of weighting factors that achieve adequate environmental protection, cost efficiency, and certainty of system outc

ISSN:0043-1397    

DOI:10.1029/91WR01996

年代:1991

数据来源: WILEY

摘要:

Water distribution networks can fail either by the actual demand at one or more nodes exceeding the design demands, or by a pipe between two nodes failing. The implications of each type of failure can be assessed by the shortfall in supply caused by a failure event together with the probability of occurrence of the event, and can be represented by the expected volume of deficit. Converting the implications of the two failure types into these commensurate units permits them to be added directly to give a single consistent measure of reliability. The assessment of shortfall for the pipe failure mode is derived from the observation that when a pipe breaks, a section of pipe must be isolated by valves to permit the repair to be made. Isolating the pipe also isolates the customers who withdraw water from that section of pipe. Thus the shortfall in supply in this case is based on the amount of supply (number of customers) cut off by isolating the pipe for repair. The measure extends previous reliability parameters by recognizing that in reality demand occurs along links rather than being concentrated solely at nodes at the ends of the links which is the normal assumption for both simulation and optimization models. If reliability of the network is found to be unsatisfactory, it can be improved in two ways. One is to increase the design demand at nodes so that the probability of actual demand's exceeding the design value is reduced. The other is to add more valves so that the length of pipe which has to be isolated in order to repair a pipe is reduced, thereby, reducing the number of customers who must have their supply cut off during a repair. Use of the two methods to determine and, if necessary, to improve reliability is demonstrated by their application to an example network.

ISSN:0043-1397    

DOI:10.1029/91WR00590

年代:1991

数据来源: WILEY

摘要:

This paper studies the relation between the structure of river networks and the features of their geomorphologic hydrologic response. A mathematical formulation of connectivity of a drainage network is proposed to relate contributing areas and the network geometry. In view of the connectivity conjecture, Horton's bifurcation ratioRBtends, for high values of Strahler's order Ω of the basin, to the area ratioRA, and Horton's length ratioRLequals, in the limit, the single‐order contributing area ratioRa. The relevance of these arguments is examined by reference to data from real basins. Well‐known empirical results from the geomorphological literature (Melton's law, Hack's relation, Moon's conjecture) are viewed as a consequence of connectivity. It is found that in Hortonian networks the time evolution of contributing areas exhibits a multifractal behavior generated by a multiplicative process of parameter 1/RB. The application of the method of the most probable distribution in view of connectivity contributes new inroads toward a general formulation of the geomorphologic unit hydrograph, in particular generalizing its width function formulation. A quantitative example of multifractal hydrologic response of idealized networks based on Peano's construct (for whichRB=RA= 4,RL= 2) closes the p

ISSN:0043-1397    

DOI:10.1029/91WR02077

年代:1991

数据来源: WILEY

摘要:

Pesticide leaching was simulated numerically assuming Freundlich adsorption, first‐order transformation and passive plant uptake, taking transient flow, hydrodynamic dispersion, and depth as well as temperature dependence of (bio)chemical parameters into account. The dependency of the leached fraction on sorption and transformation parameters appeared to be in good general agreement with the model developed by Jury et al. (1987). We incorporated spatial variability of )bio)chemical parameters into the piston flow model and showed how spatial variability may be accounted for without having to resort to demanding Monte Carlo techniques. Such spatial variability affects the leached fraction significantly. The data requirement of the simple stochastic model is small and the versatility relatively high. For parameter values often not of prime practical interest for pesticide screening this model fails. Considering transport by convection and dispersion in the semi‐infinite domain, this spatial variability can be easily accounted for using parameter ranges for which our original analytical model for spatially variable piston transport failed. In this revised model, hydrodynamic dispersion, preferential flow, and spatial variability of transformation, sorption and soil thickness are dealt with in a similar fashion, while both correlation or the absence of correlation of parameters can be incorporated through an approximation of apparent residence time varia

ISSN:0043-1397    

DOI:10.1029/91WR01990

年代:1991

数据来源: WILEY

摘要:

A 3.8‐ha watershed on the west coast of New Zealand was instrumented with suction lysimeters and automatic water samplers to determine the relationship between subsurface isotopic and chemical concentrations to those of rainfall and resulting streamflow. Attest showed that ±2‰ represented a significant difference between successive sample deuterium values. Eleven rainfall episodes were subdivided into two categories: (1) two events where stream isotopic composition did not deflect>2‰ from prestorm values, and (2) four events which demonstrated new water flushing. Detailed analysis of one 47‐mm rainfall (9.8‐mm runoff) event showed that old water dominated stream water exiting the watershed by 90% using a standard two‐component hydrograph separation for deuterium (corroborated by Cl and electrical conductivity). Three‐component hydrograph separation indicated that 12–16% was in the form of soil water, with<5% as on‐channel precipitation and 80% groundwater. Analysis of over 1000 water samples revealed systematic trends in soil water and groundwater isotopic composition both in a downslope and downprofile direction. Between‐storm suction lysimeter deuterium data showed a systematic dampened response to temporally variable rainfall deuterium concentrations. Multivariate cluster analysis revealed three distinct soil water/groundwater groupings, with respect to soil depth and geographic position within the watershed. Within‐storm suction lysimeter sampling preserved similar groupings, indicating that the subsurface reservoir is poorly mixed on short time scales. Understanding subsurface mixing response to rainfall should greatly improve models of episodic stream response and partitioning of storm flow into w

ISSN:0043-1397    

DOI:10.1029/91WR02025

年代:1991

数据来源: WILEY

摘要:

This paper presents the development and demonstration of a two‐dimensional finite‐element hydrogeochemical transport model, HYDROGEOCHEM, for simulating transport of reactive multispecies solutes. The model is designed for application to heterogeneous, anisotropic, saturated‐unsaturated media under transient or steady state flow conditions. It simulates the chemical processes of complexation, dissolution‐precipitation, adsorption‐desorption, ion exchange, redox, and acid‐base reaction, simultaneously. A set of four example problems are presented. The examples illustrate the model's ability to simulate a variety of reactive transport problems. Important results presented include a depiction of the propagation of multiple precipitation‐dissolution fronts, a display of the large errors in model response if the number of iterations between the hydrologic transport and chemical equilibrium modules is limited to one, an illustration of the development of greater concentration of contaminants In groundwater away from a waste site than near the source, and a demonstration of the variation in distribution coefficients of more than 6 orders

ISSN:0043-1397    

DOI:10.1029/91WR02028

年代:1991

数据来源: WILEY

摘要:

A variable‐aperture channel model is used as the basis to interpret data from a 3‐year tracer transport experiment in fractured rocks. The data come from the so‐called Stripa‐3D experiment performed by Neretnieks and coworkers. Within the framework of the variable‐aperture channel conceptual model, tracers are envisioned as traveling along a number of variable‐aperture flow channels, whose properties are related to the meanand standard deviation σ of the fracture aperture distribution. Two methods are developed to address the presence of strong time variation of the tracer injection flow rate in this experiment. The first approximates the early part of the injection history by an exponential decay function and is applicable to the early time tracer breakthrough data. The second is a deconvolution method involving the use of Toeplitz matrices and is applicable over the complete period of variable injection of the tracers. Both methods give consistent results. These results include not only estimates ofand σ, but also the number of channels involved in the tracer transport and their Peclet numbers and dispersivities. An interesting and surprising observation is that the data indicate that for each channel the Peclet number increases with the mean travel time; i.e., dispersivity decreases with mean travel time. The meaning of this trend is discussed in terms of the strong heterogeneity of th

ISSN:0043-1397    

DOI:10.1029/91WR02270

年代:1991

数据来源: WILEY

摘要:

This paper describes the Stripa three‐dimensional experiment where water and tracer flow has been monitored in a specially excavated drift in the Stripa mine. Several new experimental techniques and equipment were developed and used. The experiment was performed in a specially excavated drift, 100 m long, at the 360 m level in granite. The whole ceiling and the upper part of the walls were covered with 375 individual plastic sheets where the water flow into the drift could be collected. Eleven different tracers were injected at distances between 11 and 50 m from the ceiling of the drift. The flow rate and tracer monitoring was kept up for more than 2 years. The tracer breakthrough curves and flow rate distributions were used to study the flow paths, velocities, hydraulic conductivities, dispersivities and channeling effects in the rock. This paper describes the experimental techniques, the fracture mapping, the tracer and flow rate measurements and the results of the flow rate measurements. The detailed observations made possible by the plastic sheeting technique have given some qualitative as well as quantitative information on flow rate distribution in fractured rock which previously has not been available. These observations may be of importance for assessing the transport of dissolved species such as radionuclides through fractured roc

ISSN:0043-1397    

DOI:10.1029/91WR01405

年代:1991

数据来源: WILEY

摘要:

Water and tracer flow has been monitored in a specially excavated drift in the Stripa mine. Several new experimental techniques and equipment were developed and used. The whole ceiling and the upper part of the walls were covered with 375 individual plastic sheets where the water flow into the drift could be collected. Eleven different tracers were injected at distances between 11 and 50 m from the ceiling of the drift. The flow rate and tracer monitoring was kept up for more than 2 years. The tracer breakthrough curves and flow rate distributions were used to study the flow paths, velocities, hydraulic conductivities, dispersivities and channeling effects in the rock. In a companion paper the experimental design and performed experiments are described. The present paper describes the interpretation of flow and tracer movement in the rock outside the drift. The tracer movement was measured by the more than 160 individual tracer curves. The tracer experiments have permitted the flow porosity and dispersion to be studied. The possible effects of channeling and the diffusion of tracers into stagnant waters in the rock matrix and in stagnant waters in the fractures have also been addressed.

ISSN:0043-1397    

DOI:10.1029/91WR01404

年代:1991

数据来源: WILEY

摘要:

Massively parallel computers will play an increasingly dominant role in hydrological computing. One such computer is the Connection Machine model CM‐2, a single‐instruction stream, multiple‐data stream computer with up to 65,536 processors, as much as 8 gigabytes (Gbyte) of random access memory distributed among the processors, and a FORTRAN compiler based on the proposed FORTRAN‐90 standard. One‐, two‐, and three‐dimensional examples from hydrology are used in this paper to present a tutorial on programming for the CM‐2. The problem of saturated, steady flow in a randomly heterogeneous three‐dimensional porous medium is explored here in some detail. A diagonally preconditioned conjugate gradient (DPCG( iterative solver is applied to this problem for up to 1283nodes. Less than l min of CM‐2 time is required to reduce the error by a factor of 10−6for a 128 × 128 × 128 grid with heterogeneous hydraulic conductivity. Measured CPU times for the DPCG method are significantly smaller than those reported in the literature for a polynomial PCG solver applied to the same domain with different boundary conditions and executed on a Cray X‐MP/48 and an Alliant FX/8. The measured performance is also much greater than that reported in the literature for a strongly implicit procedure solver applied to a similar problem on a Cray 2. The need for continued development of massively parallel algorithms, including effective iterative solution of linear systems of equations and problems with irregu

ISSN:0043-1397    

DOI:10.1029/91WR02026

年代:1991

数据来源: WILEY