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

Overall objectives The goal of this study is to develop a model for operating reservoir system during dry season to help support operational decisions for inter-reservoir systems in the

DISSERTATION OVERVIEW

1 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, RESSIM, 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

HEC-research topic: "Building a mathematical model to operate

multi-purpose reservoir system in dry season for Ba river basin"

2 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

3 Objectives of the research

3.1 Overall objectives

The goal of this study is to develop a model for operating reservoir system during dry season to help support operational decisions for inter-reservoir systems in the Ba river basin

5 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

6 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

7 The new contributions

1 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;

2 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;

3 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 inter-reservoir operation procedure that has been issued

8 The thesis structure

In addition to the overview, conclusion and recommendations parts, the thesis consists of 4 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 1 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 2 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

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, 2014)

1999-Hình Figure 2.4a: The flow dischage in dry season at An

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

Hình Figure 2.4b: The flow dischage in dry

season at Song Hinh station

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 time in the Ba river basin during the dry season

real-The main contents of the real-time operation problem that needs to be studied are:

- Xác định được phương pháp dự báo dòng chảy đến các nút

hồ chứa và các nút nhập lưu trên lưu vực sông;

- X y dựng mô h nh mô ph ng h th ng trên cơ s t ch hợp quá tr nh dự báo dòng chảy đến các nút sông, c n bằng nước của h th ng và sự mô ph ng các quyết định vận hành của h

th ng hồ chứa theo mục đ ch vận hành đã được xác định

- Với điều ki n h th ng trạm quan trắc thủy văn như hi n nay,

dự báo nước đến các hồ chứa và các nút nhập lưu chỉ có thể căn cứ vào lượng mưa thực đo và lượng mưa dự báo, kết quả

dự báo dòng chảy được thực hi n theo mô h nh mưa-dòng chảy Mô h nh mô ph ng h th ng sẽ bao gồm các mô ph ng

CBN h th ng và hoạt động của các nút hồ chứa bao gồm cả các hồ chứa thủy lợi

- Determine the method of forecasting flow to reservoir nodes and tributary nodes in the river basin;

- Develop a model to simulate the system based on the integrating of forecasting the flow to the river nodes, the water balance and the operating decisions of the reservoir system with the purpose operation has been defined

- Based on the conditions of hydrological monitoring stations, the forecast of water to reservoirs and the tributary must be based on the measured rainfall and the forecasted rainfall The results of the forecasted flow are carried out according to the rain-flow model Simulation models will include water balance simulations and reservoir operations include irrigation reservoirs

Hình Figure 2.8: The diagram of the principle of setting up the

problem of operating the reservoir system in real time

The problem of operating the reservoir system in real-time in dry season is divided into two phases

- Setting up the problem and simulate the system according to diagram in figure 2.8

- Operating the system in real-time according to the simulated model as shown in Figure 2.9

The decision-making process according to the diagram as shown in Figure 2.9 is a continuous update of operating decisions according to the flow forecast results The decision to operate at any time is carried out in the following steps:

- Bước 1: Tại thời điểm bất kỳ trong giai đoạn vận hành, tiến hành dự báo dòng chảy đến từ thời điểm đang xét đến cu i thời kỳ vận hành;

- Bước 2: Ph n t ch trạng thái h th ng bao gồm mực nước hồ, mực nước tại các nút kiểm soát dòng chảy hạ du Ph n t ch, xác định các kịch bản vận hành hồ chứa của h th ng hồ chứa;

- Bước 3: T nh toán c n bằng nước h th ng và điều tiết hồ chứa, lưu lượng của các nút kiểm soát dòng chảy trên toàn h

th ng theo mô h nh mô ph ng;

- Bước 4: Đ i chiếu với nhi m vụ vận hành cấp nước cho hạ

du để quyết định phương án quản lý nước và vận hành hợp lý cho thời gian còn lại của thời kỳ vận hành, từ đó ra quyết định vận hành h th ng

- Step 1: At any time during operation time, the incoming flow is forecasted from that time to the end of the operation period;

- Step 2: Analyzing the system state including reservoir water level, water levels at the nodes to control the downstream flow Analyzing and selecting scenarios for reservoir operation of the reservoir system;

- Step 3: Calculating water balance and reservoir regulation, flow discharge at control nodes throughout the system;

- Step 4: Comparing with the task of downstream water supply to make decisions on water management and reasonable operation plans for the remaining time of operation period, then making decision to operate the system

Figure 2.9: General diagram of decision-making process

when operating reservoir system in real-time

CHAPTER 3: SETTING UP SIMULATION MODEL FOR FORECASTING AND OPERATING THE RESERVOIR SYSTEM IN REAL - TIME FOR BA RIVER

3.1 Overview of simulation models in water resource planning and management

The advent of high-speed computer systems has paved the way for the development of application models in the planning and management of water resources, including problems in flood planning and management The general trend in the world today is to develop system simulation models on the basis of integrating component models including models describing the physical laws of the system with the simulations of all works on the system Such models are called "river basin models" or "system models"

3.2 Building the simulation model “Ba-Model” to solve the problem of water management and reservoir system operation in

Ba river basin

Hình Figure 3.2: Position the main nodes on the system

Note: IRR irrigation node;

Reservoir node; weir;

Water supply for industrial and residential areas;

Ba river basin includes 14 sub-basins, as shown in the figure

Figure 3.3 Simulation of water

balance in the Ba river basin