Xây dựng mô hình toán vận hành hệ thống hồ chứa đa mục tiêu thời kỳ mùa kiệt cho lưu vực sông ba tt tiếng anh

1 DISSERTATION OVERVIEW The necessity of the research In recent decades, many reservoirs have been built around the world including Vietnam Vietnam is a country with many reservoirs that serve different purposes from irrigating agriculture to generating electricity However, until now, there is no exact solution for how to operate the reservoir system to obtain the maximum benefits to society Numerical modeling is an effective tool for water management in river basins It is well known that MIKE-BASIN, MIKE11, HECRESSIM, WEAP, HEC-HMS models are widely used in the world These models have also been used in water planning and management for river basins in Vietnam, including the Ba river basin Each model has its own advantages and also and certain limitations, especially when they are applied in specific research conditions Therefore, the researchers around the world continue to develop and improve them In this thesis, on the basis of based on approaching and inheriting existing studies, the author chooses the research topic: "Building a mathematical model to operate multipurpose reservoir system in dry season for Ba river basin" Subject and scope of the research The result is carried out on a multi-purpose reservoir system in the Ba river basin The operation process is considered during the dry season for the large reservoirs on the mainstream This study also takes into account the regulation of irrigation water supply for all small reservoirs on the system Objectives of the research 3.1 Overall objectives The goal of this study is to develop a model for operating interreservoir system during dry season to help support operational decisions for inter-reservoir systems in the Ba river basin 3.2 Specific objectives Build a model that meets the requirements: Research methodology In this thesis, the author has used the methods including inheritance method; mathematical modeling method, and experiment method Scientific and practical significance of the dissertation The author has developed a simulation model with the integration of rain-flow model This model is capable of calculating and forecasting the incoming flows into reservoir system This is a new contribution that will contribute to the development of the methodology in the research and operation of multi-purpose reservoir systems The research on operation techniques for real-time reservoir regulation will be the scientific basis for improvement of existing operating procedures This model can be applied to the forecasting of flow and safe operation during dry season in the Ba river basin The Scientific approach The thesis approaches in the direction of building a model to operate the inter-reservoir system in the dry season, capable of supporting operation decisions The new contributions Developed a potential water reduction graph in the dry season for the main reservoirs in the Ba river basin as a basis for identifying dry season flows After that, plan of water use and operation of reservoirs system were presented; Developed a Ba model which integrates the rain - flow model, water balance model and reservoir regulation to serve water management and decision-making for reservoir operation in Ba river basin in dry season; Built operation techniques for real-time reservoir regulation in the Ba river basin based on the analysis and calculation of water storage at the end of the rainy season and water change in river during dry season In addition, a reasonable operation regime is proposed to ensure the safety of water supply and improve the efficiency of reservoir operation in the dry season This is the basis for the additional study of the interreservoir operation procedure that has been issued The thesis structure In addition to the overview, conclusion and recommendations parts, the thesis consists of chapters: - Chapter 1: Literature review of studies on reservoirs operation in dry season - Chapter 2: Scientific and practical basis to set up the problem of reservoir operation in real-time in dry season for Ba river - Chapter 3: Setting up simulation model for forecasting and operating the reservoir system in real-time for Ba river - Chapter 4: Study on reservoir operations in dry season for Ba river basin CHAPTER LITERATURE REVIEW OF STUDIES OF RESERVOIRS OPERATION IN DRY SEASON 1.1 Role of reservoir system in water balance Reservoirs can be considered as the main solution in the development plan of surface water sources A reservoir is considered as a node of the system and is built with the purpose of changing the flow on the system in accordance with the task of exploiting the water source 1.2 Overview of studies on reservoirs operation 1.2.1 Overview of reservoir operation studies in the world There are many researches on operations of independent reservoirs as well as multi-reservoir systems and using different control algorithms These studies can be divided into two main groups including optimization and simulation methods 1.2.2 Overview of reservoir operation studies in Vietnam In Vietnam, there are several studies on reservoirs operation The researchers studied solutions to operate single and multi-purpose reservoirs These studies are considered as a scientific and practical basis to help authorities issue reservoir operation procedures 1.2.3 Studies in the Ba river basin Reasonable management and effective use of water in the Ba river basin is a complex problem that has been studied in several projects and scientific topics 1.3 Comments on studies on reservoirs operation and determination of research topic 1.3.1 Methodology Currently, studies on reservoir operation include main groups: Optimization method and simulation method 1.3.2 Research situation of reservoir operation in Ba river basin To the best of the author’s knowledge, the water resources management and real-time operation in the dry season for the reservoir system in the Ba river has not been studied in detail 1.3.3 Orientation on thesis topics The author will develop a model to operate the inter-reservoir system in the dry season, which has ability to support operational decisions, applied to the Ba river basin as a case study The model will be built based on inheriting the methodology of existing models and overcome the limitations that make it difficult to use in the operation of the inter-reservoir system 1.4 Topic suggestions for thesis From the problem in reservoir operations in Ba river basin, the author will study and propose a "reasonable" operation plan The method of system simulation and real-time operation model will be the main content in this thesis The operation plan is called “reasonable” when it both improves the downstream water supply and also does not affect the ability to generate electricity CHƯƠNG 2: SCIENTIFIC AND PRACTICAL BASIS TO SET UP THE PROBLEM OF RESERVOIR OPERATION IN REAL-TIME IN DRY SEASON FOR BA RIVER 2.1 Geographic limit of the Ba river basin The study area includes the administrative boundaries of 26 districts and cities Natural area is 16,471 km2 2.2 River characteristics There are 36 tributaries (level I), 54 tributaries (level II) and 14 tributaries (level III) in the Ba river basin 2.3 Analysis of climatic characteristics and river flows affecting to the reservoirs operation regime during the dry season 2.3.1 Climate characteristics The Ba river basin is strongly influenced by the two types of monsoon winds in the east and west of Truong Son range 2.3.2 Rainfall characteristics The distribution of the rainy season in a year is strongly influenced by the climate in the West and East of Truong Son range as well as and the terrain characteristics of the basin 2.3.3 Flow regime characteristics In the Ba river basin, the changes in seasonal flows are quite complex, except for the flows in the Hinh river and other small tributaries in the lower river basin) 2.3.4 Characateristics of water reduction graph in dry season 2.3.4.1 The water reduction graph in dry season The process of gradual reduction of flow at the end of a rain is defined as the water reduction graph If there is no rain in the next period, the water reduction graph will be reduced steadily At the beginning of the dry season, the flow in the river will gradually decrease until the end of the dry season If during the dry season there is a heavy rain that exceeds the permeability of the soil, the water reduction graph will have local increase points However, this process usually occurs in a very short time and the water reduction graph quickly returns to the general form because the reserve of groundwater does not increase much Drawing curves when ignoring some mutations due to rain effects in the dry season, we get a smooth curve continuously decreasing named “potential water reduction graph" The potential water reduction graph is generated from the measured data of reservoirs: An Khe reservoir has real data measured from year (1979-2010), Ayun Ha (1989-1992), Krong H'Nang (1979, 1989, 2003-2008, 2012 - 2018) and Song Hinh (1978-1995, 19992014) Discharge, Q(m3/s) 250 1981 1984 1987 1990 200 1993 1996 1999 2002 2005 2008 2011 150 100 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 1983 1986 1989 1992 1995 1998 2001 2004 2007 2010 50 12/15 1/4 1/24 2/13 3/5 3/25 4/14 5/4 Time, (Month/day) Hình Figure 2.4a: The flow dischage in dry season at An Khe station 1200 1978 1980 1982 1984 1986 1988 1990 1992 1994 1999 Lưu lượng, Q(m3/s) 1000 800 600 1979 1981 1983 1985 1987 1989 1991 1993 1995 2000 400 200 12/15 1/4 1/24 2/13 3/5 Thời gian, (tháng/ngày) 3/25 4/14 5/4 Hình Figure 2.4b: The flow dischage in dry season at Song Hinh station 2.6 Setting up the problem of operating and regulating the reservoir system in the Ba river basin in dry season 2.6.1 Determining tasks and contents of the study on reservoirs operation in the Ba river basin in the dry season) The problem of operating power generation reservoirs in the dry season including two subproblems: (i) Operating and regulating for downstream water supply; and (ii) Optimizing operation of power generation reservoir when Hydropower reservoirs participate in the electricity trading market The second task of power generation reservoirs is a large and complex problem that has been solved in other studies In this thesis, only the first problem related to operating power generation 10 reservoirs according to the task of downstream water supply in dry season is studied The results of the first operation problem will be the input condition of the second problem that hydropower plants need to implement In this thesis, the author will focus on studying the first problem It is easy to see that the above two problems interact with each other, therefore, in the process of solving the content of the second problem, the thesis will have to consider some scenarios related to the capacity of hydropower plants on the system 2.6.2 The description of the problem of reservoir operation in realtime in the Ba river basin during the dry season The main contents of the real-time operation problem that needs to be studied are: - Xác định phương pháp dự báo dòng chảy đến nút hồ chứa nút nhập lưu lưu vực sông; - X y dựng mô h nh mô ph ng h th ng s t ch hợp tr nh dự báo dòng chảy đến nút sơng, c n nước h th ng mô ph ng định vận hành h th ng hồ chứa theo mục đ ch vận hành xác định - Với điều ki n h th ng trạm quan trắc thủy văn hi n nay, dự báo nước đến hồ chứa nút nhập lưu vào lượng mưa thực đo lượng mưa dự báo, kết dự báo dòng chảy thực hi n theo mơ h nh mưa-dòng chảy Mơ h nh mơ ph ng h th ng bao gồm mô ph ng 19 except for some short periods with sudden changes due to the additional rain However, the flow rate will decrease rapidly to get the general trend after the rain ends because the rainfall in the dry season is usually very small Drawing smooth curves when ignoring some mutations due to rain effects in the dry season, we get a curve named "potential water reduction graph" Thus, the potential water reduction graph is the water reduction curve because the underground water in the basin decreases continuously during the dry season In the case of having measured data Nếu tuyến hồ chứa có s li u đo đạc lưu lượng s năm, sử dụng tài li u thực đo để vẽ biểu đồ rút nước tiềm Đ y trường hợp đ i với nút hồ chứa An Khê (có hi u chỉnh s li u thực đo trạm thủy văn tuyến hồ chứa theo tỷ l di n t ch), Ayun Hạ, Krông H’Năng, Sông Hinh ta biểu đồ rút nước tiềm lưu vực thuộc hồ chứa Biểu đồ rút nước tiềm tuyến hồ An Khê, Sông Hinh, Ayun Hạ Krông H’Năng thể hi n h nh 3.12a, 3.12b, 3.12c, 3.12d If there are flow measurement data in several years, these data can be used to draw a potential water reduction graph For the reservoir nodes of An Khe (where the data is adjusted from from the location of the hydrological station to the location of the reservoir according to the area ratio), Ayun Ha, Krong H'Nang, Song Hinh the potential water reduction graphs for their basins were obtained and shown in figures 3.12(a – d) 20 Figure 3.12a: The potential water reduction graphs at Song Hinh reservoir basin Figure 3.12b: The potential water reduction graphs at Ayun Ha reservoir basin 21 Qmax Qtb Qmin Figure 3.12c: The potential water reduction graph at An Khe hydrological station Fiugre 3.12d: The potential water reduction graph at Krong H’Nang hydrological station 22 3.6 Conclusions For reservoir operation in real-time in the Ba river basin, based on the analysis of some limitations of available model, the thesis has proposed a model that is convenient and suitable for the Ba river basin The model is built on the basis of integrating rain-flow models, water balance models and reservoir operation models The program is initially written in FORTRAN 77 language including a main program and subprograms The parameters of NAM model in Ba-Model model has acceptable reliability The program is applied in the realtime operation problem with the case study of the Ba river basin as shown in chapter The Ba-Model model is used not only for the management and operation of the reservoir in Ba river basin during dry seasons but also used for calculation of water balance on the river system when planning water resources in this basin In addition, the model also allows forecasting the flow to the reservoir from the rain data or calculating the flow changes in the dry season to improve the efficiency of water management and reservoir system operation in the river basin The potential water reduction grapth is the basis for identifying the dry season flow, serving for planning of water use for the entire dry season, not only for hydropower reservoirs on the main river but also for all irrigation reservoirs throughout the Ba river basin 23 CHAPTER 4: STUDY ON RESERVOIR OPERATIONS IN DRY SEASON FOR BA RIVER BASIN 4.1 Research tasks and contents Research tasks - Identifying method of water management of irrigation and hydropower reservoirs, how to operate large reservoirs including An Khe-Ka Nak, Ba Ha and Krong H'Nang, Song Hinh River, and Ayun Ha reservoirs according to the mission of downstream water supply and electricity generation in the dry season It can be used to suggest additional provisions of the inter-reservoir procedure of the Ba river basin - Proposing the method of operation in real-time for the above reservoir in the dry season - Calculating and checking the ability to meet the requirements of regulating water supply for the downstream according to the procedure of inter-reservoir operation in the Ba river basin Research content: From the research task stated above, the research contents including: Applying the Ba-Model to assess the operation scenarios of An Khe-Ka Nak, Ba Ha, Krong H'Nang, Song Hinh and Ayun Ha reservoirs, proposing reasonable operation methods in the dry season Developing methods to identify and forecast the flows for real-time operation of reservoirs in the dry season Developing a method to operate the reservoir system in realtime in the dry season 24 4.2 Calculating and checking the ability to meet water supply requirements for downstream according to the inter-reservoir operation procedure in the Ba river basin 4.2.1 Purpose of calculation - Assessing the reasonableness of the provisions in the interreservoir proceduce, detect the limitations if any, and then suggesting additional modifications to the issued proceduce - The result is the basis for building flexible operation plans for reservoirs, in order to improve the operation efficiency of the above reservoirs - The result is the basis for implementing the plan to operate reservoirs in real-time 4.2.2 River network River network system includes 63 confluence, 65 river nodes including 52 water supply nodes 4.2.3 Calculation methods of flow to the reservoir and tributary nodes During the calculation process, only the incoming flows of nodes corresponding to the 14 sub-basins are calculated Therefore, to calculate the water to the river nodes according to the diagram as shown in Figure 4.1, it will be calculated according to the similar method in equation 4-1: Qi (t )  QiNam (t ) * Fi FNam (4-1) where: Qi(t) is the discharge at time t of the confluence (i); QiNam is the flow at time t of the basin which is calculated by NAM model, 25 in which the confluence (i) is in that basin; Fi is the catchment area of the confluence (i) and having area of FNam 4.2.4 Method of operating the reservoirs in the calculation 4.2.4.1 For irrigation reservoirs At the irrigation reservoir node, water will be supplied according to irrigation requirements: - If the total amount of water in the reservoir plus the incoming water is greater than or equal to the required flow (Qyc), the water supply is qcấp = Qyc; - If the total amount of water in the reservoir plus the incoming water is less than the required water flow (Qyc), then the water supply qcấp = Qđến The lack water is Qthiếu = Qyc - qcấp At the dam nodes: - If the incoming flow is greater than or equal to the required flow (Qyc), the water supply qcấp = Qyc; - If the incoming flow is less than the required flow (Qyc), the water supply: qcấp = Qđến The lack water is Qthiếu = Qyc - qcấp 4.2.4.2 For hydroelectric reservoirs Hydropower reservoirs have two regulatory tasks: regulating electricity generation according to the capacity chart and regulating based on water supply downstream 4.2.5 Material The years from 1982 to 2010 are chosen to test These years have continuous and reliable rain measurement data 4.2.6 Calculation results for the requirements of downstream water supply according to the inter-reservoir proceduce of 878 / QD-TTG 26 An Khe-Ka Nak: there are years without regulating the flow downstream Ayun Ha reservoir: excess water occurs in many years compared with the design calculation so they are not listed in Table 4.3 Ba Ha reservoir: If during the dry season, the hydropower plants must generate a capacity not greater than the guaranteed capacity, unless the reservoir shows signs of excess discharge, in most years, the reservoir can generate guaranteed capacity during dry season Krong H'Nang: There are 18 years out of 23 years the reservoir does not guarantee to regulate water down to the downstream as required by the inter-reservoir procedure Song Hinh reservoir: There are 16 years out of 23 years the reservoir does not guarantee to regulate water down to the downstream as required by the inter-reservoir procedure Flow to Dong Cam dam site: In the inter-reservoir procedure of the Ba river basin, it is not specified how much flow at the control position is, but in the report of setting up the procedure, the flow requirement at Dong Cam dam must be 40 m3/s during the dry season However, according to the calculation of the Irrigation Planning Institute, only 30 m3/s is enough According to the calculation results of years out of 23 years, the flow in Dong Cam is less than 40 m3/s and only years in which the flow is less than 30 m3/s These years are severe drought years and regulating reservoirs are also difficult to ensure irrigation requirements  Conclusion The regulation of the flow of three reservoirs including Krong H'Nang, Ba Ha and Song Hinh is little changed during the dry season 27 and without considering the difference at the beginning and end of the season or at the time of the most water shortage, that are unreasonable The regulation on the flow to downstream of the above reservoirs are also not reasonable because they has not taken into account the ability to meet the regulation of each reservoirs * Recommendation: It is recommended to continue to study the water regulation schemes for downstream of reservoirs of Krong H'Nang, Ba Ha and Song Hinh to ensure the downstream water supply and improve the efficiency electricity and fairness among hydropower plants 4.2.7 Proposing a plan to regulate water supply for downstream in the dry season for reservoirs of Krong H’ Nang, Ba Ha and Song Hinh 4.2.7.1 Proposing a plan Adjusting the regulating flow to downstream of reservoirs for irrigation periods From May to August, Song Hinh and Krong H'Nang reservoirs are regulated according to the capacity of the reservoir In the early period of the dry season (from December to March of the following year), reservoirs are not allowed to generate electricity higher than the guaranteed capacity if there is no sign of excess water to ensure enough water for the remaining months of the dry season 28 Table 4.4: Proposed regulatory plan 4.2.7.2 Calculation results Krong H'Nang reservoir has only years of water shortage instead of 18 years Song Hinh reservoir has only years of water shortage instead of 16 years Ba Ha reservoir is still capable of operating according to regulations, except for years of water shortage in March but they are very small and can be easily adjusted during operation For Dong Cam dam, there are still years of water shortage according to the regulations of the inter-reservoir procedure In these years, the upstream reservoirs are unable to secure water supply and need to have their own plan when there are forecasted data in dry season 4.3 Calculation to ensure the water supply for downstream in dry season of 2018-2019 29 In 2018, there is very little rain in the Ba river basin in the rainy season Therefore, the risk of water shortage in the Ba river basin is very large According to the document collected from the National Hydrometeorological Forecast Center, there is little rain at An Khe and Krong Pa stations There is only the biggest rain at the end of November in rainy season However, rainfall is not very large and only occurs in downstream areas in the Hinh river basin, Cung Son areas and lowland areas of Dong Cam To test the applicability of the model, the thesis predicts the flow in dry season according to the scenarios of rain, the possibility of water shortage and the operation regime of the reservoirs The data used are calculated as follows: (1) the daily rainfall data of rainfall gauges in the basin from the beginning of the year to November 28, 2018; (2) the rainfall from December 2018 to August 31, 2019 taking into account the rainfall scenario in 2018 - Calculation is performed using the Ba-Model - Calculation results show that all reservoirs are water shortage 30 CONCLUSIONS AND RECOMMENDATIONS The results of the thesis The Ba River basin is one of the largest basins in Central Vietnam The changes on the flow in this river basin also lead to great impacts in the surrounding provinces which have a lot of water exploitation works Especially if the irrigation and hydropower reservoirs operate properly, it will bring significant benefits to many different purposes However, it is very difficult for the system to truly deliver optimal benefits and it requires specific calculations The thesis has studied the flow in dry season and achieved the following results: 1) The thesis has approached in the direction of real-time operation to solve an urgent problem have scientific and practical significance The author has built a predictive simulation model combined with real-time operation in dry season This model has been successfully tested for reservoirs systems in Ba river basin 2) The thesis has fully reviewed the researches related to the operation of reservoir system in real-time From the principles of operating the system in real-time and based on the analyzing the characteristics of the low flow in the Ba river basin, the author has established the problem of water balance in the Ba river system, determined research content in the approach of real-time operating system problem 3) The Ba-Model program is built by the author on the basis of integrating rain-flow models, reservoir operation model and river flow calculation to allow the forecasting time of flow to reservoir and river nodes to be extended This model has features equivalent to the 31 flow model of MIKE NAM, TANK and reservoir operation model in HEC-RESSIM as well as water balance model WEAP The model can be applied in operation of reservoir system in dry season in real time in order to meet the current inter-reservoir procedure in Ba river basin This model is set up in a general direction, therefore, if further developed in terms of graphical interface, it is possible to apply for other river basins in Vietnam 4) The thesis has studied to build a potential water reduction graph for severeal large reservoirs in this basin This is as a basis for identifying dry season flow and help plan management and operation of reservoirs during the dry season 5) The thesis has calculated and analyzed the limitations in the inter-reservoir procedure for the Ba river basin and proposed additional procedures Limitations and future research directions The limitations of the thesis (1) Due to the limitation of the number of rain gauges in the basin, the results of the flow to the reservoir and the confluence nodes may not be close to reality Therefore, it is necessary to update more rain gauge stations to improve the authenticity of the model (2) Ba-Model model is written in FORTRAN language, so there is limitation on interface function Moreover, the model has not considered automatic processing of priority regimes in the operation of water supply regulation (3) In the framework of a doctoral thesis and due to limited time, there has been no experimental research in practice Further research directions 32 (1) Continue to improve the Ba-Model model and apply it to other basins to assess applicability (2) Continue to update the rain measurement data, the results of calculating the flow to the reservoir from monitoring documents to improve the authenticity of the model parameters (3) In favorable conditions, the author will test the model in practice to check the applicability in operating in real-time for the reservoir system in the Ba river during dry season Recommendations The thesis has approached the problem of real-time operation and is limited to "build simulation models for real-time operation" In order to continue to develop the operation of the reservoir system in the Ba river, it is necessary to have the following studies: (1) The results need to be transferred to the user units and apply to practice to evaluate and adjust model to make it to be more complete and relevant to reality; (2) The author will improve the Ba-model for flexibility, generalization and wide application, espcically it can be run in Windown operating system for ease of use; (3) It is necessary to propose to the authorities to establish a river basin management board, and combine with the forecasted data of the Hydrometeorological Station to operate smoothly, quickly and effectively 33 LIST OF PUBLISHED WORKS (2018), Nghiên cứu t nh tốn dòng chảy đến h th ng hồ chứa sông Ba, Tuyển tập công tr nh Hội Thủy kh 2017, Hà Nội (2018), Đánh giá thay đổi dòng chảy lưu vực sông Ba xét đến tác động Biến đổi kh hậu, Tuyển tập công tr nh Hội Thủy kh 2017, Hà Nội (2018), Nghiên cứu đánh giá CBN h th ng sông Ba hồ chứa vào vận hành, Tuyển tập công tr nh Hội Thủy kh 2017, Hà Nội (2018), Đánh giá mô h nh mô ph ng thủy văn, c n nước điều tiết hồ chứa lưu vực sông Ba, Tạp ch khoa học kỹ thuật môi trường - s 63, Hà Nội (2018), X y dựng mô h nh mô ph ng thủy văn, c n nước điều tiết hồ chứa lưu vực sông Ba, Tạp ch khoa học kỹ thuật môi trường - s 63, Hà Nội ... nhập lưu lưu vực sông; - X y dựng mô h nh mô ph ng h th ng s t ch hợp tr nh dự báo dòng chảy đến nút sông, c n nước h th ng mô ph ng định vận hành h th ng hồ chứa theo mục đ ch vận hành xác định... ng; - Bước 4: Đ i chiếu với nhi m vụ vận hành cấp nước cho hạ du để định phương án quản lý nước vận hành hợp lý cho thời gian lại thời kỳ vận hành, từ định vận hành h th ng 13 - Step 1: At any... n t ch, xác định kịch vận hành hồ chứa h th ng hồ chứa; - Bước 3: T nh toán c n nước h th ng điều tiết hồ chứa, lưu lượng nút kiểm sốt dòng chảy tồn h th ng theo mơ h nh mô ph ng; - Bước 4: Đ