摘要:

A new dynamic modeling methodology, SLIN (Simulação Linguistica), allowing for the analysis of systems defined by linguistic variables, is presented. SLIN applies a set of logical rules avoiding fuzzy theoretic concepts. To make the transition from qualitative to quantitative modes, logical rules are used as well. Extensions of the methodology to simulation‐optimization applications and multiexpert system modeling are also discus

ISSN:0043-1397    

DOI:10.1029/WR023i011p02015

年代:1987

数据来源: WILEY

摘要:

SLIN (Simulação Linguistica) is a new method for qualitative dynamic simulation. As was presented previously (Camara et al., this issue), SLIN relies upon a categorical representation of variables which are manipulated by logical rules. Two applications to water resources systems are included to illustrate SLIN's potential usefulness: the environmental impact evaluation of a hydropower plant and the assessment of oil dispersion in the sea after a tanker wrec

ISSN:0043-1397    

DOI:10.1029/WR023i011p02019

年代:1987

数据来源: WILEY

摘要:

In the risk‐based design for hydraulic structures, the major task is the evaluation of the annual expected damage costs caused by floods. Due to the use of a limited amount of data in flood frequency analysis, the computed flood magnitude of a specified return period is subject to uncertainty. A methodology to integrate such uncertainty in the evaluation of annual expected flood damage is developed and illustrated through an example in culvert design. The effect of uncertainty in estimating flood magnitude using different hydrologic probability models with different sample sizes on the annual expected damage cost is examined. Results of the study show that the effect of the uncertainty in a flood magnitude estimate on annual expected damage is quite significant and is sensitive to the sample sizes and the probability distribution models use

ISSN:0043-1397    

DOI:10.1029/WR023i011p02023

年代:1987

数据来源: WILEY

摘要:

In river basins where water is used intensively and by many activities and facilities, the essential questions of water quality management are changing from being issues of planning alone to being problems of operational decision making. In the past 10 years in the United Kingdom, for example, the technology, economics, legislation, and institutional structure of management have all changed substantially. Together these changes have overturned the traditional assumptions made about the nature of managing river water quality. This paper discusses the foundations for a case study in operational water quality management. The basis of the case study is a dynamic model for stream discharge and quality covering a 54‐km stretch of the Bedford Ouse River in England. The model describes interactions among biochemical oxygen demand, dissolved oxygen, ammonium N, nitrate N, and chlorophyllaconcentrations at various points along the river; preliminary identification results are presented using daily time series data for the whole of 1974. The behavior of the river, which relates the effects of a major upstream discharger to a downstream abstractor, is dominated by the dynamics of algal population growth and mortality. In addition to the presentation of these results the paper sets out the technical, economic, and policy questions central to the practical feasibility and potential of operational water quality management. This includes questions in quantifying the stochastic, dynamic aspects of river basin management, the development of improved operating strategies, and the development of operational decision support system

ISSN:0043-1397    

DOI:10.1029/WR023i011p02030

年代:1987

数据来源: WILEY

摘要:

A model of social cost minimizing spillway capacity for dams is constructed using (1) the estimated distribution of peak flows from historical data, (2) the estimated relationship between spillway capacity and cost, and (3) a characterization of downstream flood damage from dam failure. Net social cost is the sum of construction costs and expected flood damage. This model is applied to data for the Rio Grande River at Embudo, New Mexico. Minimum social cost is attained at a spillway capacity much smaller than that needed to handle a probably maximum flood.

ISSN:0043-1397    

DOI:10.1029/WR023i011p02043

年代:1987

数据来源: WILEY

摘要:

An energy balance procedure was developed to determine regional evapotranspiration using only regularly recorded solar radiation and rawinsonde data. The major input terms in the basic energy balance equation are daily surface net radiation and sensible heat flux. Net radiation was determined by empirical and semiempirical radiation balance equations and the sensible heat flux term from an aerodynamic mass transfer equation derived from concepts of planetary boundary layer similarity theory. The procedure gave better results for a small (100 ha) agricultural watersheds than a comparable procedure based on purely aerodynamic mass transfer considerations, especially on 1‐ and 2‐day periods. For a larger (1000 ha) hydrologic watershed the model achieved acceptable accuracy for monthly estimates of regional evapotranspiration. On this time scale, comparison with observation yielded slopes from 0.97 to 1.14 with correlations between 0.90 and 0.91. For the monthly comparison, the purely aerodynamical model achieved virtually the same accuracy. These results were obtained using the same data set that was used to calibrate the model. When independent data were used, the accuracy for the monthly estimate degraded (slope 0.75, correlation 0.40). For bimonthly estimates, accuracy improved (slope 0.92, correlation 0.

ISSN:0043-1397    

DOI:10.1029/WR023i011p02050

年代:1987

数据来源: WILEY

摘要:

Transport is studied for reactive solutes and one‐dimensional fluid flow with sorption described by the Freundlich equation (Q=kcn). For a physically and chemically homogeneous soil column and if the constant feed concentration is larger than the initial concentration, the transport occurs in a traveling wave–type displacement, with a constant shape of the solute concentration front and constant front propagation velocity, provided 0

ISSN:0043-1397    

DOI:10.1029/WR023i011p02059

年代:1987

数据来源: WILEY

摘要:

Fixed gradient models result when the gradient term in the soil moisture equation is assumed to vary only with depth (remains invariant in time). The fixed gradient assumption results in a first‐order partial differential equation that is transformable to a mathematical form identical to that for a uniform soil. When the transformation was applied to field data, all water content data were found to plot along a single curve. Assuming a fixed gradient and an exponential form forK(Θ) resulted in a fitted curve with anr2= 0.847 (d.f. = 405) when data from three sites and seven depths were used. Assuming a power function forK(Θ) resulted in a similarr2. Prior to applying the transform, hydraulic conductivity required 42, 42, and 63 parameters to fit data obtained at the 21 spatial points sampled, assuming a Davidson, Watson or Brooks and Corey function, respectively. With the transform 23, 23, and 24 parameters were required for the threeK(Θ) functions, respecti

ISSN:0043-1397    

DOI:10.1029/WR023i011p02071

年代:1987

数据来源: WILEY

摘要:

Chemical reactions with minerals occur in groundwater flow in permeable media to produce zones of constant solid and aqueous phase compositions. These zones are separated by “waves” or step changes in composition. The occurrence of wave‐wave interactions resulting from nonuniform boundary conditions has important implications in inorganic pollutant transport through permeable formations. Three physical flow situations produce these conditions : injection of a finite volume of fluid followed in time by a compositionally different fluid, the flow of a reactive fluid through a compositionally layered media, and reversal in the direction of flow of a chemically reactive fluid. The theory we present when applied to contaminant transport indicates that a significant amount of contaminant initially precipitated can be redissolved during subsequent flow, and the patterns thus evolved can indicate the nature of the contaminating s

ISSN:0043-1397    

DOI:10.1029/WR023i011p02076

年代:1987

数据来源: WILEY

摘要:

Solute distribution around a trickle source for three‐dimensional steady state flow is studied in terms of an approximate analytic model. Ion and water uptake by the root system are taken into account. Moisture flow and ion concentration profiles are assumed to have hemispherical symmetry. The distributions are nearly constant near the source, with a sudden increase or decrease closer to the wetting front, depending on the ion balance. A simple criterion for the highest allowed concentration is developed. The calculated profiles are compared with the results of field measurements on potassium and nitrate ion

ISSN:0043-1397    

DOI:10.1029/WR023i011p02091

年代:1987

数据来源: WILEY