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Tài liệu Optimal reservoir operation for water supply in dry season the case study of cua dat reservoir in the chu ma river system thanh hoa province

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MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT THUYLOI UNIVERSITY ************** OPTIMAL RESERVOIR OPERATION FOR WATER SUPPLY IN DRY SEASON: THE CASE STUDY OF CUA DAT RESERVOIR IN THE CHU-MA RIVER SYSTEM THANH HOA PROVINCE TRINH XUAN MANH MSc Thesis December 2014 Optimal reservoir operation for water supply in dry season: the case study of Cua Dat Reservoir in the Chu – Ma river system Thanh Hoa province Master of science thesis By Trinh Xuan Manh Supervisor Dr. Nguyen Mai Dang HA NOI December 2014 This research is finished for the partial fulfillment of requirements for the Master of science degree at Thuy Loi University, Ha Noi, Vietnam (This Master Programme is supported by NICHE-VNM106 project) DECLARATION I hereby certify that the work which is being presented in this thesis entitled, “Optimal reservoir operation in dry season: the case study of Cua Dat Reservoir in the Ma-Chu River system, Thanh Hoa province” in partial fulfillment of the requirement for the award of the Mater of Science on Integrated Water Resource Management, is an authentic record of my own work carried out under supervision of Dr. Nguyen Mai Dang. The matter embodied in this thesis has not been submitted by me for the award of any other degree or diploma. Date: …../12/2014 i Abstract Water supply of reservoirs and especially reservoirs used for irrigation, hydropower, aquaculture, navigation, environment…in the dry season are often troubled due to increasing water demands according to the economic development and society, while the flow to the reservoir is limited. In recent years, the depletion of the river flow during the dry season occurs more frequently and at a more intense level. This is partly due to forest coverage reduction in the upstream of river basins, and partly due to the effects of climate change. Hence, computation of the optimum water supply of reservoir for the water demands in the dry season is needed. This study presents the initial research on applying Fuzzy Logic Algorithm for optimal operation of water supply in the dry season of 2011-2012 of the Cua Dat Reservoir in the Chu River basin, Thanh Hoa province. The Cua Dat Reservoir is a multi-purpose reservoir for the following tasks: flood prevention, water supply, irrigation, power generation, and environmental flows. In addition, MIKE 11 model is also used to simulate the release from the reservoir to the downstream to evaluate the efficiency of the optimal method. The research used Fuzzy Logic algorithm based on the rule, the principle of "IF - THEN" and built the membership functions for the input variables: water level, inflow to the reservoir, the water demands, and discharge from the reservoir. It is developed for the Fuzzy operating systems for the Cua Dat Reservoir and is meant to determine the optimal discharge process in case of shortage of water in the dry season. Inflows, releases and water levels of the Cua Dat Reservoir were collected from actual operation of the reservoir. For water demand of stakeholders, the author determined that the total water demand for whole area was about 4547 Mi.m3. For hydropower based energy production water is used at the largest rate (67% of total water demand), while domestic purposes water is obtained smallest rate of water use of the Cua Dat Reservoir. Finally, the results from optimal method, the reservoir can meet 80% of water demand more than actual release throughout the dry season of 2011-2012. The initial research has been successful and the results showed that this method can be applied well to the optimal reservoir operation in Vietnam. Key words: Cua Dat, reservoir operation, optimization, Fuzzy Logic, water demand, Fuzzy rule, MIKE 11 model. Trinh Xuan Manh MSc Thesis ii Acknowledgement First of all, I would like to give a big thank to all people who have supported and assisted me during the Master Thesis Research. Thanks for their support, encouragement and guidance that allowed me to complete this study in time. Especially, I would like to express my appreciation to Dr. Nguyen Mai Dang, my supervisor, for his unlimited encouragement, guidance, comments and technical supports on the Fuzzy Logic approach and other models as well as the thesis writing process from the beginning of the thesis research. I would like to thank NICHE-VNM-106 project from the Government of the Netherlands for their financial support during the MSc study in the ThuyLoi University. I thank to Mrs. Hoang Nguyet Minh and Mrs. Vu Thi Thuy Ngan who made a linkage between me and NICHE. I also would like to thank Assoc. Prof. Dr. Nguyen Thu Hien, Dean of the Faculty of Water Resources Engineering, for her help and comments during the Master study in the ThuyLoi University. I wish to thank Dr. Ilyas Masih and Ms. Martine Rutten for their feedback, references and support from the proposal process. I also wish to thank Mrs. Mariette Van Tilburg, my English teacher, for her comments and support from the final thesis report. I also want to thank the ThuyLoi University (TLU), Song Chu Irrigation Company, National center for Hydro-Meteorological Service (HMS) for providing me very useful data sets. Thanks to all of my colleagues at the HaNoi University of Natural Resources and Environment in Vietnam for your assistance in the last two years. You will always be in my mind. Last but not least, I want to take this opportunity to show my appreciation to my family, my close friends for their inspiration and support throughout my life; this research is simply impossible without you. Trinh Xuan Manh MSc Thesis iii Table of Contents CHAPTER I: INTRODUCTION ................................................................................. 1 I.1. Background ........................................................................................................... 1 I.2. Problem statement ................................................................................................. 2 I.3. Objectives and Research questions ....................................................................... 3 I.3.1. Objectives of the study .................................................................................. 3 I.3.2. Research Questions ....................................................................................... 3 I.4. Structure of the thesis ............................................................................................ 3 CHAPTER II: LITERATURE REVIEW ................................................................... 5 II.1. Studies on reservoir operation using optimal theory ........................................... 5 II.2. Fuzzy logic theory ............................................................................................... 8 II.3. Overview of hydraulic and hydrological modeling ............................................. 9 II.4. MIKE model ...................................................................................................... 11 CHAPTER III: THE STUDY AREA ........................................................................ 13 III.1. Description of the study area ............................................................................ 13 III.1.1. Location of the study area ......................................................................... 13 III.1.2. River network ........................................................................................... 14 III.1.3. Topographical characteristics ................................................................... 16 III.1.4. Geological, land and vegetable characteristics ......................................... 18 III.2. Climate and hydrological condition ................................................................. 18 III.2.1. Climate condition...................................................................................... 18 III.2.2. Hydrological condition ............................................................................. 23 III.3. Population and economic characteristics ......................................................... 23 III.3.1. Population of the study area ..................................................................... 23 III.3.2. Economic characteristics .......................................................................... 24 III.4. Description of the Cua Dat Reservoir .............................................................. 24 CHAPTER IV: DATA AND METHODOLOGY..................................................... 29 IV.1. Data collection .................................................................................................. 29 IV.1.1. Meteorological data .................................................................................. 30 IV.1.2. Hydrological data ..................................................................................... 32 IV.1.3. Cua Dat reservoir operation data .............................................................. 34 IV.1.4. Determining total water demand .............................................................. 35 IV.2. Optimal analysis and Fuzzy logic approach for Reservoir operation .............. 50 IV.2.1. Methods using in optimal reservoir operation .......................................... 50 IV.2.2. Objective functions and constraints.......................................................... 53 IV.2.3 Using Fuzzy logic technique to optimize the Cua Dat reservoir operation54 IV.3. Hydraulic and hydrological model setup ......................................................... 62 IV.3.1. Determination of the model inputs ........................................................... 62 IV.3.2. Model setup .............................................................................................. 63 IV.3.3. Model calibration and validation .............................................................. 65 Trinh Xuan Manh MSc Thesis iv CHAPTER V: RESULTS AND DISCUSSIONS ...................................................... 73 V.1. Optimizing the Cua Dat reservoir operation ..................................................... 73 V.2. Routing the release to the downstream .............................................................. 74 CHAPTER VI: CONCLUSIONS AND RECOMMENDATIONS ......................... 77 VI.1. Conclusions ...................................................................................................... 77 VI.2. Recommendations ............................................................................................ 78 REFERENCES ............................................................................................................ 80 APPENDICES ................................................................................................................. i Trinh Xuan Manh MSc Thesis v List of Figures Figure 2-1: Relationship between the various representations of a model....................10 Figure 3-1: Location of study in the Thanh Hoa province in Viet Nam .......................13 Figure 3-2: Ma – Chu River Network in Viet Nam.......................................................16 Figure 3-3: Digital Elevation Model (DEM) of Thanh Hoa province ..........................17 Figure 3-4: The location of the Cua Dat Reservoir on Ma-Chu river system ...............26 Figure 3-5: The main dam of the Cua Dat Reservoir ....................................................28 Figure 3-6: The spillway of the Cua Dat Reservoir ......................................................28 Figure 3-7: The storage of the Cua Dat Reservoir ........................................................28 Figure 3-8: The intake tower of the Cua Dat Reservoir ................................................28 Figure 3-9: The gate of spillway of the Cua Dat Reservoir ..........................................28 Figure 3-10: The Bai Thuong weir ................................................................................28 Figure 4-1: Distribution of monthly rainfall pattern at Thanh Hoa station ...................30 Figure 4-2: Distribution of monthly air temperature at Thanh Hoa station 31 Figure 4-3: Distribution of monthly average evaporation at Thanh Hoa station in 2011 & 2012 ............................................................................................................................31 Figure 4-4: Distribution of relative humidity at Thanh Hoa station in 2011 & 2012 ...32 Figure 4-5: Annual discharge of the Cam Thuy and Cua Dat station ...........................33 Figure 4-6: Schematization of hydrological station network ........................................34 Figure 4-7: Monthly average discharge of Turbin of hydropower plant in years of 2011, 2012 and 2013 ......................................................................................................35 Figure 4-8: Inflow discharge of the Cua Dat reservoir in 2011 and 2012.....................35 Figure 4-9: Seasonal period and chart of water requirement of Spring paddy in 2011 39 Figure 4-10: Seasonal period and chart of water requirement of winter paddy in 2011 ........................................................................................................................................41 Figure 4-11: Seasonal period and chart of water requirement of sugar cane in 2011 ...42 Figure 4-12: Water use structure of whole downstream area of the Cua Dat reservoir in 2011 ................................................................................................................................48 Figure 4-13: General flow chart of optimal reservoir operation in dry season .............52 Figure 4-14: Fuzzy inference system for Fuzzy Mamdani ............................................56 Figure 4-15: Transformation of input variable to membership value ...........................57 Figure 4-16: Membership function for reservoir level for Fuzzy Mamdani model ......58 Figure 4-17: Membership function for inflow for Fuzzy Mamdani model ...................58 Figure 4-18: Membership function for water demand for Fuzzy Mamdani model.......59 Figure 4-19: Membership function for release for Fuzzy Mamdani model ..................59 Figure 4-20: Fuzzy rules base for operation of Cua Dat reservoir ................................60 Trinh Xuan Manh MSc Thesis vi Figure 4-21: Process of application, implication and aggregation ................................61 Figure 4-22: Hydraulic network of the Ma – Chu river basin .......................................65 Figure 4-23: Observed and simulated hydrograph at Cua Dat station in 2006 .............67 Figure 4-24: Observed and simulated hydrograph at Cua Dat station in 2008 .............68 Figure 4-25: Observed and simulated hydrograph of water level at Ly Nhan Station in 2006 ................................................................................................................................69 Figure 4-26: Observed and simulated hydrograph of water level at Xuan Khanh Station in 2006 ............................................................................................................................69 Figure 4-27: Observed and simulated hydrograph of water level at Giang Station in 2006 ................................................................................................................................70 Figure 4-28: Observed and simulated hydrograph of water level at Ly Nhan Station in 2008 ................................................................................................................................71 Figure 4-29: Observed and simulated hydrograph of water level at Xuan Khanh Station in 2006 ............................................................................................................................71 Figure 4-30: Observed and simulated hydrograph of water level at Giang Station in 2006 ................................................................................................................................72 Figure 4-31: Structure of fuzzy system for Cua Dat reservoir ......................................73 Figure 4-32: Comparison of water demand and fuzzy and actual releases ...................74 Figure 5-1: Hydrograph of optimal operation at the Bai Thuong weir .........................75 Figure 5-2: Hydrograph of optimal operation at the Xuan Khanh station ....................75 Figure 5-3: Hydrograph of optimal operation at the Giang station ...............................76 Trinh Xuan Manh MSc Thesis vii List of Tables Table 3-1: Distribution of natural areas according to provincial border of the Ma river basin (ha) ........................................................................................................................14 Table 3-2: Characteristics of river shape of some large tributaries ...............................15 Table 3-3: Average annual rainfall for many years at some stations of the Ma river basin ................................................................................................................................19 Table 3-4: Annual rainfall characteristics ......................................................................20 Table 3-5: Monthly and annual wind speed at some stations of the Ma river basin (m/s) ........................................................................................................................................21 Table 3-6: Average monthly temperature for many years at some stations ..................22 Table 3-7: Monthly average evaporation of some stations of the Ma River Basin .......22 Table 3-8: Some main parameters of the Cua Dat Reservoir ........................................25 Table 4-1: Kinds of data have been used in the study ...................................................29 Table 4-2: Crop distribution of different cultivated area in downstream of the Cua Dat reservoir ..........................................................................................................................36 Table 4-3: Plant coefficients of paddy ...........................................................................39 Table 4-4: Plant coefficients of other plants ..................................................................39 Table 4-5: Water requirement of Spring paddy in 2011 ................................................40 Table 4-6: Water requirement of winter paddy in 2011 ................................................41 Table 4-7: Water requirement of sugar cane in 2011 ....................................................42 Table 4-8: Monthly water demand of agriculture of whole area in the Cua Dat reservoir downstream in 2011 .......................................................................................................44 Table 4-9: Water demand of industrial production at downstream of the Cua Dat reservoir ..........................................................................................................................45 Table 4-10: Domestic water demand of downstream area ............................................46 Table 4-11: Structure of water use of whole area in 2011 .............................................48 Table 4-12: Water demands and inflows in ten-day period in 2011 .............................49 Table 4-13: List of tributary basin on the Ma – Chu river basin ...................................64 Table 4-14: Results of MIKE 11HD model calibration at Ma-Chu river basin in 2006 ........................................................................................................................................70 Table 4-15: Results of MIKE 11HD model validation at the Ma-Chu river basin in 2008 ................................................................................................................................72 Table 4-16: The NASH for calculation of alternatives ..................................................74 Table 5-1: Flow characteristics at the Chu River downstream using optimal operation ........................................................................................................................................76 Trinh Xuan Manh MSc Thesis 1 CHAPTER I INTRODUCTION I.1. Background Reservoirs play an important role in the development of many countries. Nowadays, there are many reservoirs and dams which were built in many developing countries for various purposes, for example, water supply, flood control, electric generation, environment and recreation…However, in 18th Century reservoirs were built to supply water, flood control and navigation as the main purposes, after that reservoirs were built for hydropower generation purpose by increasing demand for energy consumption of human. As mentioned above, most of reservoirs are used for multiple-purpose. All those purposes need to be satisfied but the capacity of reservoir is limited. For this reason some conflicts may happen among the water users who have other interests and conflicts also may happen in reservoir itself. For hydropower generation, higher storage of water is needed, on the contrary, much water should be relaesed for cultivated areas in dry season especially. Besides this, there are also many other conflicts in user factors such as transportation and hydropower generation, flood control and environment…etc. Vietnam has many big river networks with nine major river basins spread along the country. At present, many multi-purpose reservoirs were built to serve the socioeconomic issues such as Cua Dat, Hoa Binh and Dau Tieng Reservoir...etc. The management and operation for many purposes are really difficult. On the other hand, the operation of each reservoir is a challenge for management and operators. Reservoir operation is needed to balance efficiently interests of water users and satisfy constraint systems aim to get maximum interests. An optimal policy is necessary to accomplish the problem objective and rule curve is one of appropriate methods to determine operation policy of reservoir. Reservoir operation policy specifies the criteria to retain or release water in or from a reservoir at different times of the year depending upon the inflows and demands. Trinh Xuan Manh MSc Thesis 2 Optimization model used the mathematical programming technique to find the best possible solution based on a specific performance function and some physical constraints. Mathematical programming includes several techniques such as dynamic programming (DP), nonlinear programming (NLP), linear programming (LP), genetic algorithms (GAs) and optimal control theory (OCT) (Hirad and Ramamurthy 2000). Within the development of soft computing technique, optimal technique has been used in number water resources issues. In this thesis, the author will use Fuzzy technique combine with hydraulic model to develop an operation policy for multipurpose reservoir in an efficient way. I.2. Problem statement Ma river basin is located in North-West region of Vietnam, it bordering Laos on the West. The upstream basin is located in Vietnam, the middle basin is located in Laos and the downstream is located in Vietnam. Accordingly, Ma river basin is an international basin. The catchment area of Ma river basin is about 31.060 Km2 of which that in Vietnam is 20.190 Km2 (IWRP 2003). The Chu River is a main tributary of the Ma River. It is located in the downstream area (IWRP 2003). Based on potential water resources of this river system, many kinds of reservoir such as single purpose and multi-purpose were built on the main river of the Ma river system. The Cua Dat Reservoir is one of the biggest projects related to water resource projects in Thanh Hoa province. The Cua Dat Reservoir is a multi-purpose reservoir. Those purposes include as: to reduce flood peak and protect downstream area due to probability of flood of 0.6% and control water level in downstream area at Xuan Khanh station on the Chu river (under 13.71m) in high flow season; To supply discharge of 7.715 m3/s for domestic and industrial water demand; To irrigate about 86.862 ha cultivated area; To generate electricity with capacity of 97 MW; To prevent salt water intrusion lower than 1‰ at Ham Rong measured station (MARD 2013). As mentioned above, the Cua Dat Reservoir has purposes are to supply water for some water users such as hydropower generation, agriculture, industry, domestic and environment. However, in dry season the increasing water demand of water users is one of the important problems within water shortage in this river basin due to less rainfall will enhance the conflicts among all the factors. In order to balance different Trinh Xuan Manh MSc Thesis 3 water interests and solve the problems which related to using water, the Cua Dat reservoir needs to optimize reservoir operation. I.3. Objectives and Research questions I.3.1. Objectives of the study The main objectives of this research are: - To optimize operation of the Cua Dat Reservoir in dry season, Thanh Hoa province by using simulation model (MIKE 11 model) and optimal model (Fuzzy Logic Technique). - To provide management recommendations or alternatives and suggest appropriate method of operation of the Cua Dat Reservoir in the Ma – Chu river basin. I.3.2. Research Questions 1. What is Fuzzy logic theory and how to apply fuzzy logic in reservoir operation? 2. How to balance the water demand and water interests of the stakeholders in operation of the Cua Dat Reservoir? 3. What are the objective functions and constraints in operation of the Cua Dat Reservoir? 4. Does the Cua Dat Reservoir supply enough water for all of sectors in downstream area regarding to current scenarios? I.4. Structure of the thesis This thesis structure includes those parts as below: Chapter 1: This chapter discusses an overview of the study, the problem statement and the objectives of the study are presented. Chapter 2: This chapter reviews several researches of optimal reservoir operation. Overview of hydrological model and optimization formulation are presented. MIKE 11 model also is briefly introduced in this chapter. Chapter 3: This chapter presents natural characteristic, natural conditions of the study as well as population and economic characteristics of the study. Moreover, this chapter also briefly introduces characteristics of the Cua Dat Reservoir and water demand of each water user in downstream area. Chapter 4: This chapter describes all kind of data collection and data analysis which are used in this study. In this chapter, the author also shows the results of data Trinh Xuan Manh MSc Thesis 4 calculation as the input of hydrological modeling and calculating water demand of each water user in the downstream area. This chapter determines the objective functions and all of constraint systems in the Cua Dat reservoir as well as using optimization model to determine optimal rule curve (standard rule curve). Hence, the author also presents MIKE 11 model set up for calibration and validation model and the results of routing flow from the Cua Dat Reservoir by MIKE 11 model in this chapter. Chapter 5: The results of optimal model and simulation model are shown in this chapter through figures and evaluation tables. The chapter also analyzes the results from two models in order to achieve the objectives of the study. Chapter 6: This chapter also focuses on the main performances, conclusions and recommendations for future studies. Trinh Xuan Manh MSc Thesis 5 CHAPTER II LITERATURE REVIEW II.1. Studies on reservoir operation using optimal theory Optimization is scientific field about best choice in some possible alternatives. Optimal theory has been developed and investigated for many years over the world. Optimization has been applied to a lot of fields in human life. Especially, in water resource issues are used optimal theory as one of the effective tools for management and decision making. Furthermore, optimization techniques have become increasingly important in management and operations of complex reservoir systems. In reservoir management, a lot of researchers have developed reservoir optimal operation during the past four decades using dynamic programming (DP), linear programming (LP), nonlinear programming (NLP), etc.(Cheng et al. 2008). Rama and Sharad (2009) have developed operation policy for multi-purpose reservoir in India using Neuro – Fuzzy technique including Fuzzy Mamdani and ANFIS (Adaptive Neuro Fuzzy Interactive system). Their research determined operation policy for monsoon period and non-monsoon period of Ramganga reservoir and optimum releases against demands for domestic supply, irrigation and hydropower generation. In other research, Omid et al. (2008) used optimal algorithm (HBMOHoney Bee Mating Optimization) for single and multi-purpose reservoir to minimize the total present net cost of the system and maximum possible ratio for generate electricity with installed capacity. In a case study of Hirakud Reservoir in Mahanadi basin, India, D.Nagesh Kumar et al. (2009) used Folded Dynamic Programming (FDP) to develop a long -term optimal operation policies for flood control. He showed that FDP is a new search technique which can take care of all difficulties of other methods to certain extend faced. Long N.L et al. (2007) presented successfully a method as a tool for optimizing operation of reservoir by using a combination of the simulation model and optimal model. The authors optimized control strategies for the largest reservoir in Vietnam, Hoa Binh Reservoir, in order to neutralize the conflicts in regulating water between flood control and hydropower generation. The authors also organized two main purposes in the flood season. With simulation model, they used MIKE 11 to guide the Trinh Xuan Manh MSc Thesis 6 releases of the reservoir system according to the current storage level, the hydrometeorological conditions, and the time of the year. Afterward, the shuffled complex evolution (SCE) algorithm was chosen as a perfect tool for optimizing the reservoir operation. Babel et al. (2011) analyzed that the tradeoff between hydropower production and environmental flow requirements for the hydropower system and the impact of alternative scenarios of a hydropower system operation on energy production and natural flow regime in the La Nga river basin in Vietnam. The authors used different alternative operation policies to simulate the system by the Range of Variability Approach (RVA) method. Hirad and Ramamurthy (2000) showed a new composite algorithm as an alternative model to solve the problem related to the size of reservoir when operating policy of multi-reservoir systems is applied based on Pontryagin’s minimum principle. Genetic algorithms have been widely applied in optimization to solve water resources system. Cheng et al. (2008) used Chaos Genetic Algorithm (CGA) which based on the Chaos Optimization Algorithm (COA) and Genetic Algorithm (GA) to apply to the global optimum of the Rosenbrock function, the Schaffer function and the optimal operation of hydropower station reservoir. M.Habese, Y. Nagayama (2002) used Neural Network and Fuzzy System to optimize multi-purpose Dam of flood and non- flood seasons. Base on their results, the fuzzy system is an effective operation system when the major objective is water use. Besides that Network Fuzzy System is effective for flood control. In other research, fuzzy mathematical programming was used in research of Jairaj and Vedula (2001), their study area is a three reservoir system in the upper Cauvery river basin, south China. As the results illustrated that, use of fuzzy linear programming in multi-reservoir system optimization presents a potential alternative to get the steady state solution with less efforts than classical stochastic dynamic programming (Jairaj and Vedula 2001). Panigrahi and Mujumdar (2000) also used Fuzzy Logic in their study to reservoir operation modeling, the case study of the Malaprabha irrigation reservoir in Karnataka, India. Besides that, there are many researches in reservoir operation in Vietnam. They also used many optimization and simulation methods. Nghia T.T (2009) used combination method between optimization and simulation model within advanced tools Trinh Xuan Manh MSc Thesis 7 such as hydraulic dynamic model MIKE 11 and optimal technique GAMS. The research had three major contents as follow: i) Determining water demand of water users (such as Industry, Agriculture, Navigation and Environment); ii) Determining upstream constraints of system due to periods; iii) Propose the operation process for three reservoirs including Thac Ba, Hoa Binh, Tuyen Quang based on optimal calculation in order to ensure that multi-reservoir can supply enough water for water requirements in downstream. Hung N.T et al (2010) proposed models for optimal operation of multiple purpose reservoir. The research proposed three distinct alternatives including: i) Reservoir has mutual purpose for irrigation and hydropower; ii) Reservoir’s major purpose is hydropower generation and second is irrigation; iii) Reservoir has major purpose is irrigation and hydropower generation is second. Based on models of the authors were built by using Delphi programming language and applied Dynamic programming. The models were applied on Dinh Binh Reservoir (Binh Dinh province) and A Vuong Reservoir (Quang Nam province). In other research, optimization and simulation method were also used in the research of Tuyen M.H (2009) for supplying water in dry season of reservoir system on Huong River basin. The research combined GAMS optimization model and MIKE 11 hydraulic dynamic model to control flow in downstream. The author illustrated that environmental flow is about 31,5 m3/s in location of Thao Long Weir thoughout GAMS optimal model. In dry water year with probability of 90%, the reservoir system can still ensure the lowest discharge into dowstream area is 75m3/s. Finally, optimization theories have been applied in a number of water resources issues, especially in reservoir operation. Fuzzy logic technique is one of the useful optimal tools for supporting reservoir operation and decision making. Using optimization and simulation models in reservoir operation research are common over the world. However, the Fuzzy Logic theory has been never applied in any research about reservoir operation in Vietnam. That is reason in this research the Fuzzy theory will be used as an optimization tool to optimize operation policy of Cua Dat Reservoir thoughout objective function and constraints. Trinh Xuan Manh MSc Thesis 8 II.2. Fuzzy logic theory According to Rama and Sharad 2009, the Fuzzy logic is another area of artificial intelligence. It has been applied successfully in different water resources applications. The key content about fuzzy logic theory is that it allows for something to be partly this and partly that, rather than having to be either all this or all that. The degree of “belongingness” to a set or category can be described numerically by a membership number between 0 and 1.0 (Rama and Sharad 2009). In fuzzy logic theory, variables are “fuzzification” through the use of Membership Function (MF) that defines the membership degree to fuzzy sets. These variables are called linguistic variables. A fuzzy subset A of a universe of discourse U is characterized by a membership function μA(x) in the interval [0,1] and represents the grade of membership in A (Rama and Sharad2009). The fuzzy objectives and constraints are characterized by their membership functions. Membership functions are curves that define how each point in the input space is mapped to a membership value (or degree of membership) between 0 and 1. It can be of different forms including triangular, trapezium, Gaussian, B-spline, sigmoid etc. Membership function can be symmetrical or unsymmetrical (Rama and Sharad2009). Fuzzy rule base system can be used as a suitable representation of simple and complex physical systems. The fuzzy rule based model operates on an “IF–THEN” principle, where the “IF” is a vector of fuzzy explanatory variables or premises and “THEN” is fuzzy consequence. Fuzzy logic theory allows the user to capture uncertainties in data. A fuzzy tool is available with the MATLAB software. Two types of fuzzy inference systems including: Mamdani type and Takagi Sugeno type. Fuzzy logic theory also has been used widely in modeling of reservoir operation. According to Panigrahi and Mujumdar 2000 when applying fuzzy theory need to follow several steps: (a) Fuzzification of inputs, where the crisp inputs such as the inflow, reservoir storage and release, are transformed into fuzzy variables, (b) Formulation of the fuzzy rule set, based on an expert knowledge base, (c) Application of a fuzzy operator, to obtain one number representing the premise of each rule, (d) Shaping of the consequence of the rule by implication, and (e) Defuzzification. Trinh Xuan Manh MSc Thesis 9 Similarly, the Fuzzy logic will be used in this study for the Cua Dat reservoir operation. And this is the initial research using the Fuzzy Logic in operating reservoir in Vietnam. II.3. Overview of hydraulic and hydrological modeling Any scientific field always need a developed process including monitoring data, recording and measuring data, simulation and explanation of natural phenomenon. Hydrology is a science of water on the earth. To understand the hydrological events can be described in laboratory by physical models. Based on theory and practice, people have explained clearly the most of hydrological phenomenon such as rainfall, infiltration, evaporation, and simulated them by hydrological models (hydraulic and hydrological models). Accordingly, hydraulic and hydrological models are tools to address the real hydrological cycle in a simplified way. That kind of models are used for understanding the hydrological processes as well as making hydrological prediction if there are some water resources management and utilization activities are implemented (Tuan 2012). The models are applied several algorithms to provide a quantitative relation between the input data (e.g rainfall, meteorological data) and output (e.g runoff). The mathematical models have been developed from 19th century with the simplest rainfall-run off model by Mulvaney (1851) to more sophisticated models such as MIKE Package developed by Danish Hydraulic Institute; Soil and Water Assessment Tools (SWAT), HEC model developed by Hydraulic Engineering Center- USA; SIMONA 2D/3D hydrodynamic models by the Dept of Public Works and Delft 2D/3D by WL|DELFT HYDRAULICS. Those models are used for simulation of flow, water quality and sediment transport in estuaries, rivers, irrigation system, channels and others bodies. They are fundamental to integrated water management as used for planning and decision making (Tuan 2012). The figure below shows the relationship between the various representations of a model (Van Waveren et al 1999). Trinh Xuan Manh MSc Thesis 10 The conceptual model is developed on the basis of knowledge of the system and serves as the basis for a mathematical model. This model may be solved either analytically or numerically. The model reated is further refined into a model program and finally into a Computer Model by entering the proper input data. (Van Waveren et al 1999). Figure 2-1: Relationship between the various representations of a model Hydrological models have been used frequently in water resources planning and management such as hydrological forecasting, reservoir operation, water quality, research on flood, inundation and drought, designing irrigation system, supporting for the integrated water resources management…etc. Appropriate model selection are essential for each research or project. These selections should based on study objectives, considering input data and output data, expected results and solutions. There are many studies on water field that using model as an effective tool to solve problems. According to Piman et al (2012), the authors used HEC and SWAT models to simulate and evaluate flow changes from hydropower development and operation in rivers: SeKong, Se San and Sepork of the Mekong basin. Long et al (2007) used MIKE 11 simulation model to set up control strategies for Hoa Binh reservoir operation. They concluded that this model is an effective tool for optimizing complex system. Bahremand and Smedt (2007) used distributed hydrological modeling (WETSPA) and sensitivity analysis in Torysa Watershed, Slovakia to predict daily discharge value. They also presented that a strategy by incorporating a model-independent parameter estimator PEST for automatic calibration and sensitivity analysis. In this study, MIKE 11 model will be selected to rout the flow, which is released from the Cua Dat Reservoir operation to the downstream area in order to evaluate or test discharge value within constraint system at control points. MIKE 11 model is a Trinh Xuan Manh MSc Thesis
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