Risk based optimal reservoir operation for irrigation systems : Mae Klong Irrigation Project, Thailand | |
| Author | Rajasekaram, Veerakcuddy |
| Call Number | AIT Diss. no.WM-96-04 |
| Subject(s) | Mae Klong Irrigation Project Water--Distribution--Mathematical models |
| Note | A dissertation submitted in partial fulfillment of the requirements for the Degree of Doctor of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Disseration ; no. WM-96-04 |
| Abstract | The Mae Klong River basin, located in the western part of Thailand with a total drainage area of 30,840 sq. km, consists of two major reservoirs, namely, the Sri Nagarind and the Khao Laem having total capacities of 17,745 and 8,860 MCM respectively, and a large scale irrigation scheme, namely, the Greater Mae Klong Irrigation Project (GMKIP) having the Vajiralongkorn diversion dam and a total command area of 483,000 ha. The stochastic variability of hydrological variables such as inflows into reservoirs, local flows, rainfall, evaporation etc., and the climatological variables relating to crop water requirement results in considerable uncertainty in the prediction of seasonal water availability and water requirement for the purpose of proper cultivation planning and future development. Moreover, unsatisfactory yield from the GMKIP has been realized in many dry cropping seasons, due to unforeseen scarcity of water in the past. With further development of command area in the GMKIP and additional requirement of water for domestic and industrial use in the future, measures to improve the system operation have been proposed and the modification of the present operation ruling levels of reservoirs with due consideration to the stochastic variability of hydrologic and climatological variables, attains considerable importance among others. The prime objective of this study is to determine an optimal set of lower operation ruling levels for reservoirs in order to fulfill the domestic water supply with shortage minimized for irrigation and salinity control, and to achieve the highest possible reliability of system operation. Different hydrological and climatological stochastic variables that give rise to the uncertainty of the system operation have been identified. The static reliability theory has been used to estimate the reliability of system operation by formulating a performance function which expresses the monthly available water in excess of demands in terms of the stochastic variables such as inflow, net-evaporation etc., and the deterministic variables such as the reservoir water levels. To maximize the system water availability in excess of demand in each month and hence the overall reliability of operation, a set of new lower operation ruling levels for each reservoir has been determined using a dynamic programming approach. The analysis has been carried out using the observed monthly data from 1965 to 1994, and the newly developed lower operation ruling levels are found to yield better reliability of operation compared to the set of present lower operation ruling levels. The results of this study have been verified by using the HEC-3 model for reservoir operation using the observed and generated hydrological data. With the new lower operation rule curves, defined as the lower envelope of the monthly lower operation ruling levels, the simulation results show that the amount of water shortage has been reduced significantly and hence, better crop yield has been assured. The major problems faced by the Mae Klong River basin system are categorized as, (1). development of additional cropping area in the GMKIP and, (2). water supply to the Bangkok Metropolitan Authority (BMA) area to supplement the domestic and industrial water use. Hence, the whole study has been divided into four scenarios based on two sets of command areas, i.e., the present command area and the future command area, and the cases of having or not having the BMA water supply. By planning less cropping area in the GMKIP in a scenario concerned, the use of system of water resources could be reduced and this will ensure higher reliability of system operation. However, in the economical point of view, the net benefit from the system will reduce with reduction of cropping area. The reliability of system operation and the net-benefit are conflicting objectives, therefore, optimal cropping area in the GMKIP that gives a compromise solution among these objectives is found in respect of each scenario. In conclusion, the present study contributes specific means of applying the static reliability theory to solve for the reliability of operation of a complicated water system such as the Mae Klong River basin with major reservoirs, a large scale irrigation project, diversion schemes etc., with a number of hydrologic random variables representing the basin. Whereas, in the past, only simple systems with single component (for example, spillway, culvert, etc.) with few random variables have been handled. The study also contributes to the fact that the Shinozuka's approach, which has never been applied to water resources system before, can be applied as the first time in this study to solve for the reliability of operation of the Mae Klong River basin water resources system. Moreover, the reliability of system operation derived based on the static reliability theory has been proved to be a suitable index of a water resources system in contrast to the conventional simulation procedure. In addition, a relationship between the reliability of system operation and the shortage index from simulation (i.e., HEC-3 shortage index) has been established with appropriate physical justification. Hence, the use of reliability as the suitable index of system operation is confirmed. This study also contributes to the fact that by adjusting the operation rule curves of reservoirs, the available water resources of the Mae Klong River basin, which is under controversy, can be effectively used to irrigate the additional extent of the Greater Mae Klong Project area that is under development, and to supply the domestic/industrial water requirement of the Bangkok Metropolitan area, according to the present situation and the future plan. |
| Year | 1997 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. WM-96-04 |
| Type | Dissertation |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Tawatchai Tingsanchali; |
| Examination Committee(s) | Fujiwara, Okitsugu;Huynh, Ngoc Phien;Apisit Eiumnoh;Takeuchi, Kuniyoshi; |
| Scholarship Donor(s) | The Government of Japan; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1997 |