摘要:

Literature from diverse sources such as public expenditure economics, management science, geography, agriculture, and engineering reveals a wide range of decision frameworks for deriving flood mitigation strategies. These different types of decision frameworks are reviewed in this paper. The aim is to provide an understanding of these frameworks, along with their relative adequacies and inadequacies. Such an understanding reveals the directions along which the formulation of a more adequate framework should proceed. However, the formulation of a given decision framework is influenced by the types of economic benefits associated with the flood mitigation measures considered in that framework. Hence the various flood mitigation measures are reviewed, prior to the various decision frameworks.

ISSN:0043-1397    

DOI:10.1029/WR021i004p00411

年代:1985

数据来源: WILEY

摘要:

A time series model of daily municipal water use as a function of rainfall and air temperature is developed. Total water use is separated into base use and seasonal use. The seasonal use series is detrended, then a nonlinear heat function relating water use to air temperature during rainless periods is employed to deseasonalize the series. The residuals are modeled using Box‐Jenkins transfer functions with transformed rainfall and air temperature as independent variables. The model is applied to daily data from Austin, Texas from 1975 to 1981 and accounts for 97% of the variance of daily municipal water use over that period. Forecasts of daily usage are made for a two‐week lead t

ISSN:0043-1397    

DOI:10.1029/WR021i004p00425

年代:1985

数据来源: WILEY

摘要:

This study utilized, for the first time, a demand function for municipal water derived from the Stone‐Geary utility function, thereby permitting explicit consideration of the minimum amount of water necessary for daily needs. Using monthly data from Kuwait, this demand function gave greater price elasticity estimates but smaller income elasticity estimates than those of other countries. It was estimated that the “subsistence” water use level in Kuwait is about 42 L per capita per day and the results suggest that at least in that wealthy country, people do respond to changes in the prices of public ser

ISSN:0043-1397    

DOI:10.1029/WR021i004p00433

年代:1985

数据来源: WILEY

摘要:

Increasing water demands have directed new interest toward methods for defining water supply system performance. These demands include not only traditional municipal, industrial, and agricutural demands, but instream flow uses such as power production and fish flow maintenance. This paper suggests procedures for evaluating water supply performance when instream flows for fish are required of a municipal water supply. A computer simulation model is used with synthetic inflow sequences to investigate indices of system performance for the Seattle, Washington water supply system. A review of techniques used to establish instream flow requirements is presented with a history of instream flow requirements established for the Seattle supply. The trade‐offs between values of instream flows and municipal water supply performance are presented to quantitatively illustrate the impacts of instream requirement

ISSN:0043-1397    

DOI:10.1029/WR021i004p00439

年代:1985

数据来源: WILEY

摘要:

Steady unsaturated flow with vertical mean infiltration through unbounded heterogeneous porous media is analyzed using a perturbation approximation of the stochastic flow equation which is solved by spectral representation techniques. The hydraulic conductivityKis related to the capillary pressure headψbyK=Ksexp (−αψ), whereKsis the saturated conductivity, and α is a soil parameter. A general formulation is presented for the case withKsand α represented as statistically homogeneous spatial random fields. In part 1, solutions are developed assuming α is constant and representingKsvariability by one‐dimensional and three‐dimensional isotropic random fields. Results are obtained for head variances and covariance functions, effective hydraulic conductivities, variances of the unsaturated hydraulic conductivity, flux variances, and variance of pressure gradient. When the parameter α is relatively large, corresponding to coarse textured soils, the head variance decreases and all of the results demonstrate a trend toward gravitationally dominated one‐dimensional vertical flow. The effective conductivity is dependent on the correlation scale of lnKsand the mean hydr

ISSN:0043-1397    

DOI:10.1029/WR021i004p00447

年代:1985

数据来源: WILEY

摘要:

Steady unsaturated flow in heterogeneous soil with an arbitrarily oriented mean hydraulic gradient is analyzed using spectral solutions of the stochastic perturbation equation which describes the capillary pressure headψ. The unsaturated hydraulic conductivity is related toψbyK=Ksexp (−αψ), whereKsis the saturated hydraulic conductivity and α is a soil parameter, and bothKsand α are treated as three‐dimensional statistically homogeneous, anisotropic random fields. Analytical results are obtained for the capillary pressure head variance and the effective (mean) unsaturated hydraulic conductivity. The head variance depends upon the degree of anisotropy of the lnKscovariance; when α is random, the head variance increases with mean capillary pressure head. The effective hydraulic conductivity for arbitrary orientation of the mean hydraulic gradientJis shown to have tensorial properties, but its components depend on the magnitude and direction ofJand the orientation of the stratification in the soil. When α is random, the degree of anisotropy of the effective conductivity depends strongly on mean capilla

ISSN:0043-1397    

DOI:10.1029/WR021i004p00457

年代:1985

数据来源: WILEY

摘要:

Results of stochastic theory for flow in heterogeneous soils are analyzed by comparisons with laboratory experiments and field observations, and through applications examples. The two key theoretical results are (1) the variability of capillary pressure or moisture content increases when mean capillary pressure increases and (2) the anisotropy ratio (horizontal/vertical) of effective (mean) unsaturated hydraulic conductivity increases when mean capillary pressure increases or mean moisture content decreases. Comparisons with the field data on moisture content and capillary pressure variability show trends similar to those predicted by the theory. Calculations of hydraulic conductivity anisotropy based on two actual soils show that the variations in soil texture produce large changes in anisotropy as the mean capillary pressure changes. Several previously reported field observations and laboratory experiments support the theoretical finding of a capillary pressure dependent hydraulic anisotropy for unsaturated flow. The importance of this anisotropy effect in applications involving groundwater recharge, irrigation, surface runoff generation, and waste isolation is discussed.

ISSN:0043-1397    

DOI:10.1029/WR021i004p00465

年代:1985

数据来源: WILEY

摘要:

This paper examines the possibility of using derivative‐based optimization algorithms for automatic calibration of conceptual rainfall‐runoff models with threshold structures. A method is discussed for explicit computation of the derivatives based on an analysis of the modality of behavior present in such models. In the method the threshold structures are not replaced by smoothing functions, thereby preserving the conceptual integrity of these models. The discussion includes a theoretical analysis of a single linear reservoir (with threshold) model which provides some insights into the issue of threshold parameter identifiability. Simulation study comparisons of the Newton (derivative based) and the Simplex (direct search) optimization algorithms indicate that the former is more efficient, especially when the number of parameters to be optimized is large. However, the results indicate that careful study of the issues related to model identifiability is required if any significant progress is to be achieved in the area of automatic calibration of conceptual rainfall‐runoff m

ISSN:0043-1397    

DOI:10.1029/WR021i004p00473

年代:1985

数据来源: WILEY

摘要:

The identification of a conceptual hydrologic model involves two stages: selection of a suitable model structure and parameter estimation. These two stages cannot be treated as distinct, and it is important that the limitations of available parameter estimation methodologies be given serious consideration during the procedure of model structure selection. This paper focuses on the concepts and tools necessary for the evaluation of whether the structure of a hydrologic model is such that its parameters can be successfully identified. A definition of structural identifiability is advanced that is based purely on model properties and is independent of the stochastic nature of the output observation errors. The approach is used to develop a measure of local structural identifiability which is useful in the analysis of parameter sensitivity. A measure, called the sensitivity ratio, is introduced which is suitable for studying parameter interactions in the multidimensional parameter space. Also, the use of allowable reparameterizations to improve identifiability is discussed. The utility of the concepts discussed in this paper are demonstrated by a simulation example using a conceptual rainfall‐runoff mode

ISSN:0043-1397    

DOI:10.1029/WR021i004p00487

年代:1985

数据来源: WILEY

摘要:

Disaggregation and multisite autoregressive moving average (ARMA)(1,1) time‐series models provide simple and efficient frameworks for generation of multisite synthetic streamflow sequences that exhibit long‐term persistence. This paper considers multisite ARMA(1,1) models whose Φ and Θ matrices are diagonal; a Monte Carlo study examined the efficiency of three procedures for estimating individual Φ‐θ values for each site and two estimators of the covariance matrix of the innovations. Also included in the study was a univariate ARMA(1,1) model of the aggregate flows with a simple disaggregation algorithm to generate flows at the individual sites. In the realm of most hydrologic interest, simple diagonal multisite ARMAl(1,1) models performed adequately and it is not necessary to fit the more cumbersome nondiagonal models. The disaggregation procedure coupled with an ARMA(1,1) aggregate flow model did as well as the multivariate diagonal ARMA(1,

ISSN:0043-1397    

DOI:10.1029/WR021i004p00497

年代:1985

数据来源: WILEY