Nghiên cứu thiết lập mô hình thủy văn kinh tế phân bổ nước tối ưu lưu vực sông Ba Tiếng Anh

THÔNG TIN LUẬN ÁN ĐƯA LÊN MẠNG Tên luận án: Nghiên cứu thiết lập mô hình thủy văn – kinh tế phân bổ nước tối ưu lưu vực sông Ba Chuyên ngành: Thủy văn học Mã số: 62 44 90 01 Họ và tên NCS: Nguyễn Thị Thu Nga Người hướng dẫn: GS. TS. Hà Văn Khối, Trường Đại học Thủy lợi, Việt Nam Cơ sở đào tạo: Trường Đại học Thủy lợi Tóm tắt những đóng góp mới của luận án: Nghiên cứu ứng dụng mô hình tối ưu trong phân tích đánh giá, phân bổ nguồn nước trong lưu vực sông và có bổ sung, điều chỉnh phù hợp cho LVS Ba. Lượng hóa được quan hệ tương quan giữa thủy văn và kinh tế cho lưu vực sông Ba trong mối ràng buộc về tự nhiên, kết cấu hạ tầng, môi trường và xã hội. Đánh giá hiệu ích kinh tế của một số chính sách dự kiến trong quy hoạch và quản lý tài nguyên nước, từ đó đề xuất các biện pháp tăng cường hiệu quả trong khai thác sử dụng nước trên lưu vực sông Ba. Hà Nội, ngày 26 tháng 12 năm 2016 Người hướng dẫn khoa học GS. TS. Hà Văn Khối Nghiên cứu sinh Nguyễn Thị Thu Nga THESIS INFORMATION ON WEBSITE Name of thesis: Research on hydroeconomic model development for optimizing water allocation in Ba river basin Speciality: Hydrology Code: 62 44 90 01 Full Name of Candidate: Nguyen Thi Thu Nga Advisor: Prof. Ha Van Khoi New contributions • Study on applying an optimizing model in analysis, assessment, and allocation of water resources in a river basin, and modifying the model for Ba river basin. • Quantifying correlation between hydrology and economic factors in Ba river basin with consideration of natural, infrastructural, environmental, and social conditions. • Evaluating economic benefits of some proposed policies in water resources planning and management, and proposing measures in order to improve water use efficiency for Ba river basin. Hanoi, December 26th ,2016 Advisor Prof. Ha Van Khoi Candidate Nguyen Thi Thu Nga

MINISTRY OF EDUCATION

AND TRAINING

MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT

THUYLOI UNIVERSITY

NGUYEN THI THU NGA

RESEARCH ON HYDRO-ECONOMIC MODEL DEVELOPMENT FOR OPTIMIZING WATER ALLOCATION IN BA RIVER BASIN

DISSERTATION ABSTRACT Speciality: Hydrology Code: 62 44 90 01

HANOI, 2017

This dissertation is completed at Thuyloi University

Principal Advisor: Professor Ha Van Khoi

Reviewer 01: Dr Nguyen Lan Chau

Reviewer 02: Assoc Prof Nguyen Tien Giang

Reviewer 03: Assoc Prof Ngo Le Long

This dissertation will be presented to the Evaluating Committee at

INTRODUCTION

1 Statement of the problem

Ba river basin is one of the largest inter-provincial river basins in Vietnam Based on the results of previous irrigation and hydropower planning, a series of hydraulic structures had been built In particular, there are two main irrigation structures named Ayun Ha and Dong Cam, and five large hydropower plants named An Khe, Kanak, Song Ba Ha, Song Hinh, and Krong Hnang However, when these projects went into operation, there had some impacts back to the water resource system As a result, the allocation of water resources over space and time had been changed, which thereby affects the exploitation of water in the whole basin This is one of the causes leading to the conflicts between irrigation and hydropower, upstream and downstream, economic development and environment protection Therefore, it is necessary to reconsider the issue of water allocation in Ba river basin on the basis of coordination of existing irrigation and hydropower structures to improve water use more efficiently

In this context, "research on development of hydro-economic model for optimizing water allocation in Ba river basin" is chosen to study to find out a

mathematical model supporting in water resources management in Ba river basin The model aims to improve water using in a more efficient way in the field of economy, social balance, and environmental protection

2 Research Objective

This research aims to address the difficult situation of water allocation problem

in Ba river basin by analyzing the relationship between relative water availability and economic benefit from key-water using sectors Four following steps were taken to meet the research objective: establishing the water allocation problem for Ba river basin; developing a hydro-economic model applied for Ba river basin; applying the developed model to assess potential

policies regarding to water resource management; and proposing several water resource management measures for Ba river basin

4 Methodology

The following methods applied in the research are including (i) inherited method; (ii) synthetic analysis method; (iii) statistical method; and (iv) nonlinear programming method;

5 New contributions

Study on applying an optimizing model in analysis, assessment, and allocation

of water resources in a river basin, and modifying the model for Ba river basin Establishment of the quantified relationship between water availability and economic benefit from key-water using sectors

Application of the model to evaluate several potential policies in water resources planning and management Based on the results, some management measures are proposed to improve water use efficiency

6 Structure of the thesis

The thesis consists of 113 pages, 30 tables, 19 figures and 72 references Besides the introduction and conclusion, the thesis consists of 4 chapters as follows:

Chapter 1: Overview of hydro-economic model applications in water resources planning and management

Chapter 2: Establishment of hydro-economic problem for water allocation in Ba river basin

Chapter 3: Simulation and solve hydro-economic problem of Ba river basin in GAMS

Chapter 4: Impact assessment of water exploitation scenarios to socio-economic benefits in Ba river basin

CHƯƠNG 1 OVERVIEW OF HYDRO-ECONOMIC MODEL APPLICATIONS IN WATER RESOURCES PLANNING AND MANAGEMENT

1.1 Nomenclature and definitions

A hydro-economic model is the combination of a hydrology model and an

economic model, thereby it can represent hydrologic, technical, environmental, and economic aspects of water resource system in an integrated framework (Harou, 2009)

1.2 Introduction of hydro-economic models

In a hydro-economic model, water allocation was driven and evaluated by economic value of water Water is considered as a special economic good, with the properties of both private goods and public goods The economic value of water varies by type of uses (consumptive uses or non-consumptive uses, instream uses or offstream uses, uses as intermediate good or uses as final good) Water value is also changeable over time and space The researchers can apply different methods to estimate the water value for certain situation In general, the residual method was used to estimate water value in agriculture, producer's demand function method was used to estimate water value in hydropower and industry, and consumer's demand function method was used to estimate the water value in domestic uses The hydro-economic models are different from traditional hydrological models by taking additional consideration of "varied" water values The hydro-economic models are different from economic models which usually focused on economic effects of

projects Therefore, hydro-economic models were developed in order to integrate hydrologic models and economic models

1.3 Literature review of hydro-economic models

Hydro-economic models have been widely applied in many researches in the field of water allocation, infrastructure, groundwater and surfacewater, institution, market and water price, transboundary conflict, water management

in climate change, flood management (Harou, 2009) The study of economic models in the world has been implemented since 1960s The study of hydro-economic models in Vietnam started later, but not widely A number of case studies were found in Ringler et al (2006), Vu Van Tuan (2007), IWARP (2007), which mostly applied for large river basins like Donna, Mekong, and Red river basins There has been no study of hydro-economic model for Be river basin, especially when the current situation of institution and natural condition has changed dramatically

hydro-1.4 Overview of integrated water resources management in Vietnam

So far, integrated water resources managment (IWRM) in Vietnam has achieved some certain achievements, but there was still some limitation, especially regarding to river basin management One of the main causes of conflictions in water uses came from water resources planning Most of existing plannings are sectoral or provincial Also the procedure to issue a water resources planning is still very complex

1.5 The gaps have not been studied in water resources planning and management in Ba river basin

In general, previous studies of Ba river basin were implemented basing on the assumption that water demands were fixed at certain locations Most of the studies applied traditional hydrological models to simulate the process of water allocation in the basin The results focused on finding the regions which were water shortage according to considered scenarios Some hydraulic structures or management measures would be proposed for those regions All of the studies

had not considered the economic value of water which would depend on the water users, the time and the location of withdrawal In addition, some solutions were not quantitative, giving decision makers difficulty to deeply understand on the potential decisions

CHƯƠNG 2 ESTABLISHING THE OPTIMAL WATER ALLOCATION PROBLEM FOR BA RIVER BASIN

2.1 Current situation of water uses in Ba river basin

Ba river basin is one of the largest national river basins in Vietnam The basin consists of roughly 13,900 square kilometers of land of Gia Lai, Dak Lak, Phu Yen, and Kon Tum provinces The topography of the basin is strongly separated by Truong Son mountains, this creates valleys from An Khe to Phu Tuc The northern, western, and southern mountains in downstream region cover the Tuy Hoa delta of 24,000 hectares which is widened toward the sea The combination of topography and south-western and north-eastern moonsoons made the basin has three different climate regions, West Truong Son, East Truong Son, and the Middle Region With these characteristics, water resources vary unevenly over time and space The annual rainfall depth in the basin is about 1,740mm The rainfall varies over space The upstream of Ba river and Hinh river have the annual rainfall depth of 3,000mm, while Cheo Reo and Phu Tuc regions have around 1,300mm The rainfall is also unevenly distributed over time The rainy season in upstream region is from May to

October or November The rainy season in downstream region is later and last shorter, about 3 to 4 months from September to December

The annual flow of Ba river basin is approximate 10 billion cubic meters The river network includes 36 1st - level, 54 2nd - level, and 14 3rd - level tributaries

In general, Ba river system has a very important role in hydropower generation, irrigation, water supply, and environmental protection for Gia Lai, Dak Lak, and Phu Yen provinces

2.2 Developing process of water resources planning in Ba river basin

In many years, irrigation planning, hydropower planning and other sectoral plannings had some achievements In recent years, several provinces has issued multi-sectoral planning Water resources planning of Phu Yen province was issued in 2011, and that of Gia Lai province was issued in 2015 However, the sectoral planning or multi-sectoral plannings all have disadvantages The sectoral planning was not interested in other sector uses of water Provincial water resources planning did not consider the flow connection in river basin scale This would have impact on the effect of water resources planning solutions

2.3 Reservoir system in Ba river basin

Almost plannings regarding to water resources chose the solution of building hydraulic structures There are major hydropower and irrigation reservoirs, which play very important roles in water allocation They are Ayun Ha, Krong Hnang, Song Hinh, Song Ba Ha and An Khe – Ka nak reservoirs Recently, the conflicts between hydropower and agriculture, upstream and downstream, and economic development and environmental protection has appeared in Ba river basin Many researchers pointed out that the causes of these conflicts originated from the building and operation of large reservoirs

The large reservoirs were built without considering fully the impacts to irrigation and environmental protection at downstream In order to get over these problems, a procedure of reservoir system regulation was issued in 2014

This newly procedure needs time to testify the effectiveness and reasonableness

2.4 Establishment of optimal water allocation problem in Ba river basin

2.4.1 Objective

The allocation of water for multi-sectors in Ba river basin should have maximized economic benefit, but also ensure the requirement of balanced society and environmental protection

2.4.2 Objective function

2.4.2.1 Full objective function

The most common type of objective functions in water allocation problems is to find maximize value of overall economic benefit (Brooker and Young, 1994),

as in

max𝑧∈(𝑧)𝐸𝐵 = 𝐸𝐵𝑖 𝑖 𝑄𝑖, 𝑢 (2-1)

Where Q = {Qi} is the vector of water withdrawals for different sectors, including agriculture, aquaculture, domestic, industry, hydropower, environment, and recreation …; EBi is the economic value, or benefit, associated with water withdrawals Qi The units for EBi are currency per unit time (e.g $/month)

There are many methods for water valuation for various economic sectors In general, economic benefits in agriculture, aquaculture, industry and hydro-power can be calculated with production functions However, it is usually very difficult to determine economic benefits associated with recreational or environmental water uses

The objective function in water allocation problem for Ba river basin was chosen based on previous researchs for Dong Nai river basin (Ringler, 2006), and Red River Basin (IWARP, 2008) as followed:

𝑀𝑎𝑥 𝐟 𝐱 = ( 𝑉𝐴a 𝑎+ 𝑉𝑀𝑚 𝑚+ 𝑉𝐼𝑖𝑛 𝑖𝑛+ 𝑉𝑃𝑝 𝑝) (2-3)

where VAa is water value from agriculture (including irrigation and livestock water uses); VPp is water value from hydro-power production; VIin is water value from industrial water use; VMm is water value from domestic water use

2.4.2.2 Reduced objective functions

The amount of water withdrawal for agriculture in Ba river basin took about more than 90% of water consumption The largest reservoir (Song Ba Ha) in the Ba river system is located near to the downstream region With these reasons, the thesis's author proposed to reduce the original objective function to following ones:

𝑀𝑎𝑥 𝐟𝟏 𝐱 = ( 𝑉𝐴a 𝑎+ 𝑉𝑃𝑝 𝑝) (2-4) 𝑀𝑎𝑥 𝐟𝟐 𝐱 = ( 𝑉𝐴a 𝑎) (2-5)

2.4.3 Decision variables and state variables

Decision variables are independent For full objective function, the decision variables include irrigated areas (ha) for every crop in all regions; number of cattles in seven regions; flows through turbines of hydropower plants; water demands for industry, domestic, and aquaculture For reduced objective function, the number of decision variables is reduced according to the economic components to be considered

State variables are dependent variables The state variables include inflows of irrigation and livestock nodes, storages and water levels of reservoirs, inflows and outflows of river nodes, power generation yields, and ouflows of reservoirs

2.4.4 Constraints

2.4.4.1 Simulation of hydro- systems

The hydrologic component of the hydro-economic model included simulation

of water balance of the system (Simulation of water balance of the system was included in the hydrologic component of the hydro-economic model) The operation of each node in the system had to be simulated considering the relationship with other nodes

Qcap i,t Qgh i,t (2-13)

Where Qgh i,t is the flow of node i, at time t Note that Qgh i,t is not static but changing depending on water allocation alternative of the system The variables have static bounds such as water level and storage of the reservoirs

2.4.5 Nonlinear programming problem and solving methods

Water allocation problem for Ba river basin is non-linear programming problem with constraints

2.4.5.1 Nonlinear programming problem

min 𝒇 𝒙 𝑠𝑢𝑏𝑗𝑒𝑐𝑡 𝑡𝑜 𝑔𝑖 𝒙 = 0, 𝑖 = 1, … , 𝑚 (2-24)

𝑥𝑗 ≤ 𝑥𝑗 ≤ 𝑥𝑗, j=1, …, n 2.4.5.2 Solving methods

There are many solving methods for nonlinear programming problems, but none of them can be always effective To solve nonlinear programming problem with constraints, it is usually to be transferred to nonlinear programming problem without constraints (by Lagrange method) Maximizing problems are often to be transferred to minimizing problems In very few problems, the solution can be found directly The most frequently method is applying searching algorithm

2.4.5.3 Generalized Reduced Gradient (GRG)

The main concept of GRG method is separating the variable vector (x) into basic vector (xB) and nonbasic vector (xN) In theory, m basic variables can be

expressed as function of (n-m) nonbasic variables The reduced objective function will be:

𝑭 𝒙𝑁 = 𝒇 𝒙𝐵 𝒙𝑁 , 𝒙𝑁 (2-27) The original problem will be reduced as nonlinear programming problem without constraints:

Subject to 𝑥𝑁 ≤ 𝑥𝑁 ≤ 𝑥𝑁GRG method was developed by Abadie and Carpenter, based on GRG method

by Wolfe This method was available in solver CONOPT integrated in GAMS and would be applied to solve the optimized water allocation problem for Ba river basin

2.4.6 Selection of mathematical tool

There are a lot of tools solving optimizing problems in water resources planning and management In fact, they are computer languages that can develop mathematical models connecting with a library of opimizing solvers Although the effort needed to develop the code, these tools allow users describing system in detail GAMS is a suitable tool for solving nonlinear programming problem and was chosen in this thesis The solver CONOPT 3 with GRG algorithm was chosen to solve the problem of Ba river basin

2.5 Summary of Chapter 2

In this chapter, water resources characteristics and existing exploitation situation Ba river basin have been analyzed An optimized water allocation planning problem was established The objective function, decision variables, state variables, and the constraints were described in details Because of the large nonlinear programming problem, GAMS was chosen to develop a hydro-economic model for Ba river basin

CHƯƠNG 3 SIMULATING AND SOLVING HYDRO-ECONOMIC PROBLEM IN GAMS

3.1 Introduction of GAMS

GAMS (General Algebraic Modeling System) is high-level language to solve optimizing problem GAMS includes a compiler and many solvers The general form of nonlinear programming problem in GAMS/CONOPT is as follow:

All the variables in GAMS have to be declared by the statement Variables

Example3-2Decision variable in GAMS

ar(n) the area of irrigated spring rice at node n

Constraints

The constraints are declared in GAMS by the statement Equations

Bounds

The lower and upper bounds of a variable can be described in two ways: using

equations or using lower bound (lo) and upper bound (up)

Domain