摘要:

The linear programing‐superposition method is presented for managing multiple sources of groundwater pollution over time. The method uses any linear solute transport simulation model to generate a unit source‐concentration response matrix that is incorporated into a management model. This series of constraints indicates local solute concentration histories that will result from any series of waste injection schedules. The linear program operates on the matrix to arrive at optimal disposal schedules. An example demonstrates application of the method to maximizing groundwater waste disposal while maintaining water quality of local water supplies within desired limits. Flow field variations associated with waste injection are ignored as an approximation. Parametric programing is shown to be an important tool in evaluating waste disposal trade‐offs at various injection sites over time. Mixed‐integer programing permits restrictions to be placed upon the number of injection wells which may operate during given management

ISSN:0043-1397    

DOI:10.1029/WR018i001p00071

年代:1982

数据来源: WILEY

摘要:

The components of heat flux at the surface of Lake Ontario during the stratified season of 1972 are estimated using a lake thermal model, which has previously been verified with respect to temperature simulation. The model inputs are lake geometry and optical properties and surface weather observations. The heat flux components are compared with independent observationally based estimates. The net flux is simulated accurately by the model; the radiative input to the lake is significantly overestimated. The error in the radiative flux is traced to the expression accounting for the effect of cloud cover on insolation. This error leads to compensating errors in sensible and latent heat fluxes, resulting in accurate simulation of the net heat flux. Evaporation rates estimated by the model are approximately 50% higher than other estimates. The use of observed insolation, or a more accurate formula for the effect of clouds, would probably lead to accurate simulation of evaporation rates.

ISSN:0043-1397    

DOI:10.1029/WR018i001p00077

年代:1982

数据来源: WILEY

摘要:

Previous studies of the water balance of the Mediterranean have relied on estimating evaporation (E) and precipitation (P) rates separately over the basin. An independent approach is to obtain the net difference between these rates by evaluating the divergence of the atmospheric flux of water vapor over the region. We apply this aerological approach to compute the annual mean value ofE‐Pover the Sea using upper air data collected during the 5‐year period 1968–1973. Our result is in general agreement with those obtained by the more classical methods. In addition we present maps of the two‐dimensional fields of precipitable water, of the vertically integrated water vapor flux vector, and of the divergence of water vapor over the region. These analyses are discussed in light of various climatological and hydrological conside

ISSN:0043-1397    

DOI:10.1029/WR018i001p00083

年代:1982

数据来源: WILEY

摘要:

The quasianalytical approach to hydrodynamic dispersion during horizontal absorption under constant concentration conditions is discussed, and an integral solution presented for the case of a constant dispersion coefficient. Experimental results for Bungendore fine sand, obtained during constant concentration absorption, are compared with concentration profiles calculated using the integral solution. The comparison is good when a constant dispersion coefficient of 10−8m2s−1is used. An explicit computer‐based numerical analysis is then described briefly and checked against the integral result with excellent correspondence being achieved. The numerical analysis is used to determine concentration profiles for the case when the dispersion coefficient is velocity dependent. These profiles are compared with the experimental data, and it is observed that the bandwidth of the scatter of the data is greater than the spread of the concentration profiles. It is concluded that a definitive statement on the existence and magnitude of a velocity‐dependent effect cannot be made solely on the basis of the experimental data. However, the Péclet numbers appropriate to the system are greater than unity, suggesting that the dispersion coefficient is velocity dependent and that the parameters used in the numerical analysis to express this dependence are satisfactory for Bungendore fine sand under constant concentration ab

ISSN:0043-1397    

DOI:10.1029/WR018i001p00091

年代:1982

数据来源: WILEY

摘要:

The response function of a crop yield to soil salinity level is essential in decision‐making in regard to irrigation with saline water. A switching regression approach to estimate the piecewise linear response function with critical threshold level is presented, and the asymptotical stochastic properties of the estimates are described. The empirical estimates, based on grapefruit yield data, are compared with those of a recent published study by Maas and Hoffman (1977) and the statistical significance of the differences is discussed. Finally, the threshold hypothesis is tested empirically against some alternative formulations. It turns out that the ‘threshold hypothesis’ is conf

ISSN:0043-1397    

DOI:10.1029/WR018i001p00101

年代:1982

数据来源: WILEY

摘要:

Some of the characteristics that complicate the analysis of water quality time series are non‐normal distributions, seasonality, flow relatedness, missing values, values below the limit of detection, and serial correlation. Presented here are techniques that are suitable in the face of the complications listed above for the exploratory analysis of monthly water quality data for monotonie trends. The first procedure described is a nonparametric test for trend applicable to data sets with seasonality, missing values, or values reported as ‘less than’: the seasonal Kendall test. Under realistic stochastic processes (exhibiting seasonality, skewness, and serial correlation), it is robust in comparison to parametric alternatives, although neither the seasonal Kendall test nor the alternatives can be considered an exact test in the presence of serial correlation. The second procedure, the seasonal Kendall slope estimator, is an estimator of trend magnitude. It is an unbiased estimator of the slope of a linear trend and has considerably higher precision than a regression estimator where data are highly skewed but somewhat lower precision where the data are normal. The third procedure provides a means for testing for change over time in the relationship between constituent concentration and flow, thus avoiding the problem of identifying trends in water quality that are artifacts of the particular sequence of discharges observed (e.g., drought effects). In this method a flow‐adjusted concentration is defined as the residual (actual minus conditional expectation) based on a regression of concentration on some function of discharge. These flow‐adjusted concentrations, which may also be seasonal and non‐normal, can then be tested for trend by using the seasonal K

ISSN:0043-1397    

DOI:10.1029/WR018i001p00107

年代:1982

数据来源: WILEY

摘要:

A one‐dimensional steady state probabilistic river water quality model is developed to compute the joint and marginal probability density functions of BOD and DO at any point in a river. The model can simultaneously consider randomness in the initial conditions, inputs, and coefficients of the water quality equations. Any empirical or known distribution can be used for the initial conditions. Randomness in each of the water quality equation inputs and coefficients is modeled as a Gaussian white noise process. The joint probability density function (pdf) of BOD and DO is determined by numerically solving the Fokker‐Plank random differential equation. In addition, moment equations are developed which allow the mean and variance of BOD and DO to be calculated independently of their joint pdf. The probabilistic river water quality model is examined through sensitivity study and an application to a hypothetical river sys

ISSN:0043-1397    

DOI:10.1029/WR018i001p00122

年代:1982

数据来源: WILEY

摘要:

A model for predicting the concentrations of leachate organics, measured as chemical oxygen demand, in groundwaters below sanitary landfill sites is developed. Simultaneous Michaelis‐Menten substrate utilization and microbial mass production equations, with convection and dispersion included for the former, were used for the modeling of biodegradation. For substrate concentrations significantly less than the half utilization rate coefficient and for microbial populations approaching a steady state the Michaelis‐Menten equations are reduced to a first‐order reaction kinetic model. The nonlinear model equations are solved using a Galerkin finite element technique, with a Newton Raphson iteration procedure being used to solve the resulting matrix equations. Model sensitivity studies are undertaken to determine the extent to which COD reduction might vary in the field with respect to time and space. The results indicate that substantial removal of leachate organics can be expected within short distances of the landfill even under the conditions of widely varying biological parameters. Model results are compared to the leachate organic reduction occurring below the Canadian Forces Base Borden sanitary lan

ISSN:0043-1397    

DOI:10.1029/WR018i001p00135

年代:1982

数据来源: WILEY

摘要:

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 calibrat

ISSN:0043-1397    

DOI:10.1029/WR018i001p00146

年代:1982

数据来源: WILEY

摘要:

A computer model, previously used to simulate the transport of conservative chemical components in streams, has been used as a basis for a more complex model which includes the effects due to processes such as precipitation and sedimentation and adsorption onto stationary reactive surfaces which render the reactants nonconservative with respect to the flowing waters. The model uses, as before, the program MINEQL as a basis for the chemical equilibrium submodel. The physical transport submodel employs a convolution integral procedure, with an approximate form of the impulse function to solve a one‐dimensional convective‐diffusion equation. Although the model essentially assumes chemical equilibrium, a pseudokinetic treatment is necessary to deal with redissolution of precipitates and dissociation of surface species. Simple hypothetical examples are given to illustrate the operation of the model. The model is then applied to an experiment in which the base NaOH is injected into a creek draining an abandoned base metal mine. Concentrations of the metals Zn, Al, Cu, Fe, and Na in the flowing waters, expressed in terms of total metals and as suspended solids, are followed as a function of time and distance downstream. Significant sedimentation of the precipitates formed is evident, and the existence of substantial quantities of protons and/or metal ions, adsorbed on the streambed, is implied from the model calculations. The model was able to simulate successfully the major features observed. This simulation involved the simultaneous formation of five distinct precipitates and one surface spec

ISSN:0043-1397    

DOI:10.1029/WR018i001p00155

年代:1982

数据来源: WILEY