摘要:

ABSTRACT:Different probability‐based concepts for design of hydraulic structures are presented that could replace or complement traditional designs based on the concept of design load plus a safety margin. The traditional concept (here called Level I design) does not permit the assignment of the correct probability to the failure event. Concepts which are based on the correct probability of failure are based on descriptions of resistance and load as random variables. Level II design assumes these random variables to be Gaussian distributed. Level III is based on arbitrary distributions of load and resistance. Level II and III concepts are appropriate for evaluation of a design's reliability. Design Level IV is also based on the joint probability density function for loads and resistances; in addition, it requires the assignment of a consequence function to each combination of resistance and loads. The design concepts are illustrated with the design of a flood levee on a rive

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1988.tb02979.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT:A general methodology to study the economics of dual water systems (defined here as a separate distribution system for untreated low quality local surface Water for outdoor municipal water supply) is summarized and the application of the method to a rapidly growing city is presented. In the first step, a cost‐benefit criterion for evaluating dual systems is developed. The criterion is then extended to a dynamic case where the population to be served increases with time and where the dual system is allowed to expand. The optimal investment time to introduce the dual water supply project is obtained by maximizing social welfare. The model is applied to the city of West Jordan, Utah, where a dual system is currently being proposed. Model results indicate that for the city as a whole dual supply is not economically feasible. However, when the model is applied to a part of the city, it is found feasible and the optimal time to initiate the project would be in the year 198

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1988.tb02980.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT:Sediment‐water exchanges of ammonium, nitrate, and phosphate are incorporated into a eutrophication model of Gunston Cove, Virginia. The exchange rates are obtained from laboratory measurements and are modeled as empirical functions of temperature, concentration, and pH. Simulation of the period from June 1 to September 30, 1983, indicates nitrogen, phosphorus, and chlorophyll ‘a’ are correctly modeled only when the sediment‐water nutrient exchanges are taken into

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1988.tb02981.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT:The Nonlinear Risk‐Benefit (NRB) Algorithm includes risk as one of the objectives in a multiple‐objective optimization problem. The NRB Algorithm is derived by extending the Surrogate Worth Trade‐Off method to quadratic programming. This category of problem is common in water resources planning and design, especially multipurpose reservoir systems. Consequently, an example is given using the algorithm for optimally operating a multipurpose rese

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1988.tb02982.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT:Wastewater from a municipal treatment plant was applied in rapid infiltration basins for four years to determine a poorly drained soils effectiveness in removing influent N and P and the soil changes that might limit their removal. About half the total PO4‐P lost from the influent was sorbed in the upper 91 cm of the soil and the other half was sorbed by the soil below the perforated pipe, which was used to drain the basins and collect the effluent for analysis. Drying of the basin soils converted more sorbed PO4‐P to Ca phosphates but the total sorbed was about the same. The in. fluent N decreased, probably by volatilization, because the two basins with surface soil lost soil N rather than gained soil N. The soil total Ca, Mg, and K contents did not change significantly but Na increased slightly. Changes in the physical characteristics of the soils were slight and would have little effect on the longevity of a rapid infiltration ba

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1988.tb02983.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT:An econometric demand function is estimated for residential water use in Metropolitan Manila. Regression results using annual time series data from 1970 to 1981 show that residential water consumption responds to changes in economic variables. Residential demand showed an income (household) elasticity of 0.542 and a combined price elasticity of ‐0.287. Implications for planning and management are discusse

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1988.tb02984.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT:Spatial distribution of soil and water properties and the correlations between them and crop yield were determined for a natural rainfall environment. Hydraulic conductivity, soil texture, water retention, and soil‐water flux were variables used to investigate their relationship to crop yield using multiple regression techniques. Variations in crop yields on a watershed with a 3 to 4 percent slope and moderately erosive soils were related to soil‐water characteristics and soil properties along slope and with depth. Climatic conditions to sustain crop growth and yield ranged from inadequate soil water in 1983 to adequate soil water in 1984. Crop yield was predicted with models using both available and measured soil‐water content. Available water content provided a better model for the prediction of water yield and does not require field measurements of actual soil‐water content. Soil water holding capacity was more significant for predicting crop yield in soils with moderate to high silt content than infiltrability of water into t

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1988.tb02985.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT:Planners should tailor the way they approach a planning study to the particular situation or environment surrounding the study. In order to do this more systematically, this paper suggests a descriptive structure that defines terms and categories of the planning environment. The paper then suggests corresponding terms and categories to define the planning approach as a first approximation. The planner can then tailor the planning approach to the specific study environment. Such an exercise should enhance the success of the planning effort.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1988.tb02986.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT:A weighted average method was used to analyze transition zone vegetation in the Great Dismal Swamp to determine if a more uniform determination of wetland boundaries can be made nationwide. The method was applied to vegetation data collected on four transects and three vertical layers across the wetland‐to‐upland transition zone of the swamp. Ecological index values based on water tolerance were either taken from the literature or derived from local species tolerances. Wetland index values were calculated for 25‐m increments using species cover and rankings based on the ecological indices. Wetland index values were used to designate increments as either wetland, transitional, or upland, and to examine the usefulness of a provisional wetland‐upland break‐point. Most increments were designated wetland or transitional when all species were used. Removal of three or five ubiquitous species either gave a wider range of wetland index values with a more variable designation of increments or caused designation of increments to be similar for all layers. The use of locally‐derived rankings showed the sensitivity of the weighted averages method to ecological indices of species with large importance values. The weighted average method did not provide for an objective placement of an absolute wetland boundary, but did serve to focus attention on the transitional boundary zone where supplementary information is necessary to select a wetland‐upla

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1988.tb02987.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACT:Recent advances in mass transport modeling have made possible computation of the theoretical consequences of intricate multicomponent species interactions during ground water contamination events. Predictions such as strong chromatographic effects and induced downstream precipitations may have considerable impact on environmental analysis and regulation. Results of laboratory attempts to verify theoretical multicomponent transport predictions are discussed. Evidence presented here indicates that natural variability of soil properties make such verifications difficult. Although species interactions are easily confirmed, dramatic effects often exist only within small mathematical windows in strongly variable coefficient sets. Currently, the ability to generate multicomponent predictions apparently exceeds the ability to quantify the necessary, presumably deterministic, information required for real soils.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1988.tb02988.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY