Optimal design and operation of Kok-Ing-Chao Phraya transbasin diversion system | |
| Author | Thana Boonyasirikul |
| Call Number | AIT Diss. no. WM-97-03 |
| Subject(s) | Chao Phraya River Basin Optimal designs (Statistics) |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. WM-97-03 |
| Abstract | The Chao Phraya river basin is the most important agricultural land area in Thailand. There are four major tributaries, Ping, Wang, Yorn and Nan rivers, giving the annual river runoff of 30,300 MCM on average and providing irrigation of about 2.0 million hectares of . farm during the wet season and half of the area during the dry season. The effects of environmental change and inc~·ease of upstream water use in Northern Thailand cause less inflow from the upstream catchment areas and the stored water in the reservoirs is decreasing year by year. As the water availability is decreasing, the water requirement for agricultural, industrial, social and urban development increases rapidly. Therefore, the shortage of water becomes even more critical after 1987. The irrigation in the downstream basin area is seriously affected and the dry season rice cropping is entirely prohibited. Accordingly, the water shortage problem in the Chao Phraya river basin becomes not only a threat to the regional socio-economic growth but also a great impediment to the national economic development. The environmental improvement to restore the natural water balance ce1iainly takes a long time and the growth of urbanization may never give better condition of water resources nature. One possible solution to improve this deleterious condition is to divert partial amount of water from the adjacent river basin across the basin boundary to the Chao Phraya river basin as the transbasin diversion system. The diversion water will be operated in order to increase the water storage of the Bhumibol and Sirikit reservoirs which are the main and most important storage reservoirs in the Chao Phraya river basin. It is found that the effective transbasin diversion system is to divert water from the Me Kong river and tributaries to the Chao Phraya river basin. The water from Kok and Ing river basins which are the subbasins of the Me Kong river locating in the north of the Chao Phraya river basin can be sufficiently dive1ied to the upper reach of the Nan river which is a main tributary of the Chao Phraya river. The divert~d water will be stored and regulated at the Sirikit reservoir for using in the Chao Phraya river basin. Therefore, the Kok-Ing-Chao Phraya transbasin diversion system was proposed. The objective of study is to determine the optimal design and operation of the KokIng- Chao Phraya transbasin diversion system which is a complex and large-scale system under the uncertainty of hydrologic condition. Since the reliability in optimization due to the uncertainty and stochastic processes is considered, the Reliability-based Stochastic Optimization (RSO) process is developed to determine the optimal operation policy and hydraulic design of the transbasin diversion system. The first order Markov chain is used to described stochastic process of inflow. The effect of inflow uncertainty in the optimization is described by means of uncertainty cost. The degree of preference for the reliability of optimization is expressed in term of "Risk Aversion Coefficient", ~ associated in the uncertainty cost. Since the transbasin diversion system is a complex system composing of three storages and many variables, it is impossible to optimize the whole system by using a single model. The transbasin diversion system is decomposed into three subsystems and the sequential RSO process is developed to optimize each subsystem which is interrelated by specified diversion target. The diversion target is specified for the Kok-Ing and Ing-Nan diversion subsystems based on the release target for the Sirikit reservoir. For the multiobjective optimization in this study, the priority is assigned to specify the significance for each objective. The concept of Goal Programming (GP) formulation is applied in objective function to allow the unavoidable underachievement of the target. The value of target underachievement is indicated by means of loss function. The weight is specified for the irrigation objective since it allows the underachievement of target. The RSO process was applied to derive the optimal operation policies for the Kok-Ing diversion flow, Ing-Nan diversion flow, and Sirikit reservoir and then the diversion system was simulated with respect to synthetic inflow based on the optimal operation policies to examine the operation performance of the system. Since the optimization reliability is considered by means of~. various values of~ are studied. The effect of optimization reliability by the variation of ~ is studied for the base case in which the inflow-weighted diversion target is specified in the RSO process wherein the recommended priority and weight in the objective function are assigned. In order to study the effect of diversion target specification on the sequential RSO process, another two cases of diversion target specification; RSO without diversion target and RSO with feed-back conection of diversion target, are examined. The RSO process was can-ied out for another three cases of priority assignment: no priority, hydropower benefit priority and uncertainty priority, to study their effects on the optimal operation policy and the performance of the diversion system. Furthermore, another three cases of weight assignment: extreme weight, equal weight and adverse weight were studied. Additionally, the RSO process is carried out for two diversion storage cases: small and large storages to determine the effect of the diversion storage capacity on the operation policy derivation and system performance. Furthermore, the alternative optimization is carried out for inigation objective only without hydropower benefit considered in the objective function. The results of the study show that the developed RSO process is applicable for the design and optimization of water resources system with the consideration of reliability due to the uncertainty of hydrologic condition. The optimal hydraulic design and operation policy of the proposed diversion system obtained from the RSO process can give satisfactory performance with relatively high reliability and benefit. The annual net benefit due to the implementation and operation of the diversion system based on the RSO process is over 6,000 million Baht (or US$ 150 million). The operation policy obtained from RSO with the optimal value of the risk aversion coefficient can give the performance indices of 10 % in reliability and 25 % in benefit higher than the classical SDP optimization. In case of multiobjective optimization in this study, the priority assignment is applicable to specify the sequence of significance for each objective according to the master plan of the system. Higher priority assignment for a paiticular objective can improve the RSO policy for better performance in such objective. For optimization of the main irrigation objective, the application of GP concept with weight assignment can provide the optimal operation with satisfied reliability of target achievement. In the sequential RSO process for the serial three-storage Kok-Ing-Chao Phraya transbasin diversion system, the diversion target is specified to inte1Telate the optimization among the three storages. The feedback correction of the diversion target effectively improves the RSO operation policy, which results in much higher performance indices. The study of diversion storage indicates that the RSO process can significantly increase the operation performance of the system if the diversion storage can be increased. |
| Year | 1998 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. WM-97-03 |
| Type | Dissertation |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Tawatchai Tingsanchali; |
| Examination Committee(s) | Fujiwara, Okitsuku;Huynh Ngoc Phien;Simonovic, Slobodan P.; |
| Scholarship Donor(s) | Self Support; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1998 |