SYSTEMS ANALYSIS OF A COMPLEX WATER RESOURCES SYSTEM

Abstract

Basin resources planning has become an increasingly important concept in comprehensive planning of a complex water resources system. Comprehensive basin water resources planning is a complex and a difficult task, posing numerous social, economic, environmental and engineering problems. Water resources systems analysis has now been generally accepted to provide an efficient way of answering the numerous questions regarding planning of large scale water resources systems for which the conventional methods of analysis will be inadequate. The approach and appropriate technique will naturally vary from problem to problem as the configuration, state of development of the system, and stage of decision making is likely to vary over a vast range. For a large scale water resources system the difficulty in the system analysis is primarily due to large number of possible alternative development strategies, and hence the vast computational effort required to establish an optimal development plan. Therefore, in a large and complex system, one of the major challenge is to reduce the large set of alternative configurations that need to be examined in detail to a reasonable number without mistakenly eliminating an attractive option. The most commonly suggested approach has been first to screen all alternative configurations with mathematical programming technique to determine the most attractive alternatives, then further screen them with a detailed simulation model. In this study an attempt was made to combine the major advances of systems analysis by optimization-simulation screening models, which are to be used for analyzing a complex water resources system. Linear programming has been used as an optimization technique for very obvious reasons of large number of variables involved in such problems. iv ABSTRACT The specific decision problem under consideration was screening of a multiple reservoir system (multi purpose, multi reservoir, and multi irrigation areas system) on the Karun river in Iran, to meet the current and forecast growth in demand of water, for irrigation, hydropower, flood control, and municipal and industrial water supply. The system consisted of 5 major dams, one run-of-river hydropower scheme and a number of multi-irrigation areas. The various alternative configurations of the above system were studied, based on various project proposals and engineering considerations for deciding the optimal configuration and the optimal project targets. The approach was to develop a suitable methodology to identify the combination of multi-reservoir alternative to maximize the economic benefits as well as to obtain desired project dependabilities, subjected to continuity constrains, technological constrains, and policy constraints. In this context, it was profitable to investigate the value of linear programming in preliminary screening and how it should be coupled with a finer screening simulation study. The computer software (INDMAG PACKAGE) developed for generation of Input Data Matrix coupled with simplex algorithm for linear programming, and a flexible simulation package were used for screenings in two phases. The Phase-I was project by project analysis, and the Phase-II was analysis of integrated developmental strategies. The average monthly flows and the monthly flows of a representative dependable flow year were used independently in preliminary screening optimization model, where as 38 years historical monthly flows were used in simulation model. For screening, the economic, and water use dependability criterias were used. Thedevelopment of INDMAG software package to create the Input Data Matrix for LP model made the construction of the optimization model for all potential feasible alternatives a less data-intensive and non-Herculean task. The approach used in INDMAG software algorithm is one such step towards preparing a generalized algorithm ABSTRACT (computer programme) very well fitting to the basic multireservoir design and planning problems. The results of linear programming model were helpful in simulation as they could select the upper and lower ranges of the design variables by regulating the average and the annual flow of a given dependability based on the desired project success respectively. The use of optimization-simulation models for screening and analysis by (a) project by project analysis and (b) integrated development strategy analysis, suggest a suitable scheme in the reduction in the number of alternatives of development to be examined and analyzed. The project by project analysis and the integrated developmental strategy analysis is likely to guarantee a configuration of reservoirs and project sizes very near to a global optimum. Based on the results, it can be concluded that the approach used in this study is simple and can be easily used to analyze large and complex river basins planning problems.