DESIGN OF SEWER SYSTEMS1

In order to cope with the ever increasing problems of the urban environment, new approaches are being sought to their solution. The objective of this paper is to review and evaluate the merits of certain new methods aimed at finding optimal solutions in sewer design. Based on principles similar to the ones advanced by Deininger [1966] and Holland [1968] the authors propose an integer programming algorithm for optimizing pipe sizes and slopes. The new algorithm is applied to an actual situation and compared with a solution arrived at by a traditional design approach.     

ON THE CAPACITY-EXPANSION OF DESALINATION PLANTS AND STORAGE TANKS1

ABSTRACT A mathematical programming model is structured to find the optimal time and capacity expansion path of desalination plants and storage tanks for a hypothetical community which depends on desalination as its sole, or major, water supply source. The objective is to determine the least costly combination of sues and times of installation (of both desalting plants and storage tanks) which can meet a rising water demand over a finite planning horizon. The optimality criterion used in the model is based on two major economic elements: the economies of scale inherent in such facilities and the time-value of money represented by the interest rate, the former favoring large capacities and the latter small capacities. The model is applied using three population growth patterns and two interest rates. The water demand components for every year in the planning period are computed using empirical formulas which are based on population and other basic data. The model is solved for each of the above cases with the aid of a computer program based on the method of feasible conjugate directions. The results clearly reflect the balance between the economies of scale and the time-value of money under every demand growth function.     

Solid waste management in urban areas: Development and application of a decision support system

A decision support system (DSS) developed to assist the planner in decisions concerning the overall management of solid waste at a municipal scale is described. The DSS allows to plan the optimal number of landfills and treatment plants, and to determine the optimal quantities and the characteristics of the refuse that has to be sent to treatment plants, to landfills and to recycling. The application of the DSS is based on the solution of a constrained non-linear optimization problem. Various classes of constraints have been introduced in the problem formulation, taking into account the regulations about the minimum requirements for recycling, incineration process requirements, sanitary landfill conservation, and mass balance. The cost function to be minimized includes recycling, transportation and maintenance costs. The DSS has been tested on the municipality of Genova, Italy, and the results obtained are presented.     

THE USE OF BINARY OPTIMIZATION AND HYDROLOGIC MODELS TO FORM RIPARIAN BUFFERS1

ABSTRACT: Riparian buffers are considered important management options for protecting water quality. Land costs and buffer performance, which are functions of local environmental characteristics, are likely to be key attributes in the selection process, especially when budgets are limited. In this article we demonstrate how a framework involving hydrologic models and binary optimization can be used to find the optimal buffer subject to a budget constraint. Two hydrologic models, SWAT and REMM, were used to predict the loads from different source areas with and without riparian buffers. These loads provided inputs for a binary optimization model to select the most cost efficient parcels to form a riparian buffer. This methodology was applied in a watershed in Delaware County, New York. The models were parameterized using readily available digital databases and were later compared against observed flow and water quality data available for the site. As a result of the application of this method, the marginal utility of incremental increases in buffer widths along the stream channel and the set of parcels to form the best affordable riparian buffer were obtained.     

GENERATING FARM DESCRIPTIONS IN A WATERSHED FROM INCOMPLETE DATA USING SIMULATED ANNEALING1

ABSTRACT: A fundamental problem faced in developing spatially explicit, simulation‐based analyses of watershed management and policy options is determining the distribution and spatial location of agricultural resources within a watershed based on incomplete information. This paper describes the use of simulated annealing, a heuristic scheduling process, to generate an assignment of all livestock and agricultural fields in a watershed to hypothetical farms such that the combined distribution of farm types, livestock, and farmland within the watershed is a reasonable representation of watershed‐level data. Compared to a manual method using GIS‐based analysis and data from aerial photography, the heuristic method was more likely to generate realistic spatial characterizations of the distribution of agricultural resources and practices in a watershed. Also compared to the manual method, the heuristic process was considerably more efficient and could more easily accommodate multiple criteria and modifications to those criteria.     

AN ECONOMIC ANALYSIS OF ALTERNATIVE WATER USE STRATEGIES AT CATCHMENT LEVEL TAKING INTO ACCOUNT AN INSTREAM FLOW REQUIREMENT1

ABSTRACT: A mathematical model of agricultural water use and a hydrological and economic simulation model were linked to quantify the economic and hydrological impact of deficit irrigation, increased water application efficiency, and farm storage dams when maintaining an IFR (instream flow requirement) under stochastic water supply conditions. The main finding was that a water conservation policy aimed at reducing the amount of water withdrawn from the river could bring more pressure to bear on stream flow. Water can only be saved if consumptive use is reduced. Increased water application efficiency is detrimental to other users as a result of reduced return flow. The economic cost of maintaining a specific IFR increases with the use of all three strategies as the probability of maintaining the IFR increases. Because of the control that can be exercised over the supply of water, a farm storage dam is the best strategy for minimizing the costs for irrigators. The interaction between water legislation, water policy administration, technology, hydrology, and human value systems necessitates an integrated approach to facilitate water management at catchment level and to formulate policies that will be in the interest of society.     

基于χ~2优化方法的铸钢侧架原始裂纹尺寸分布研究

将铸钢侧架清砂后未经修复的原始裂纹尺寸进行了统计 ,综合运用参数的点估计方法和区间估计方法 ,以置信区间作为优化的约束条件 ,提出了对检验值进行最优化处理的方法 ,并运用二参数约束非线性优化方法的直接解法 ,搜索出最佳点估计值。经过对裂纹尺寸分布参数的计算证明 ,其结果符合对数正态分布     

用矿井通风仿真系统(MVSS)确定通风系统优化改造方案

论述了矿井通风仿真系统 (MVSS)的功能 ,用MVSS仿真模拟增加或减少风路对周围其他风路的影响 ,仿真模拟拆除或增加机站对周围通风系统的影响 ,并以金川矿井 115 0水平为例 ,阐明了用MVSS确定通风系统优化改造方案的方法 ,对通风系统现状分析、通风网络优化、通风系统的设计提供了科学的依据和实用方法。     

OPTIMIZATION OF THE HYDROMETRIC NETWORK OPERATION BY A HEURISTIC TRAVELING SALESMAN ALGORITHM1

ABSTRACT: The problem of determining the optimal route to operate a network of hydrometric gauges within a given area is formulated and solved by an original heuristic traveling salesman algorithm. The algorithm used for solving the problem takes into account the variation of station service time, the eight-hour maximum working day, existence of more than one home base, and the budget constraint. The traveling salesman algorithm is used to solve the optima! assignment problem within a one-day time limit, locating a starting base, stations to visit, and the closest home base. The ending base for the previous day becomes the starting base for the next day, and the assignment procedure is repeated. The computation proceeds from day to day, until all the stations in the considered region are serviced. The solution obtained presents the optimal route to operate a network of hydrometric gauges. The optimization procedure has been applied to the Dauphin hydrometric field area in Manitoba.     

THE OPTIMAL STEADY-STATE IN GROUNDWATER MANAGEMENT1

Groundwater use is likely to be inefficient in the absence of regulation and hence there is substantial interest in optimal groundwater withdrawals over time. Under an optimal regime withdrawals, pumping lifts, and profits converge to steady-state levels. In this paper we show that optimal steady-state lifts, withdrawals, and marginal user costs can be readily calculated for multi-cell models of confined aquifers. Applications to the design of economically efficient groundwater management policies are discussed, comparisons to previous work and to the safe yield concept are made, and an illustrative example is given.