THÔNG TIN LUẬN ÁN ĐƯA LÊN MẠNG Tên luận án: Nghiên cứu chế độ vận hành tích nước trong thời kỳ mùa lũ cho hệ thống hồ chứa bậc thang Hòa Bình và Sơn La Chuyên ngành: Phát triển nguồn nước Mã số: 62 44 92 01 Họ và tên NCS: Vũ Thị Minh Huệ Người hướng dẫn: PGS.TS Phạm Thị Hương Lan; 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: Đề xuất được chế độ tích nước sớm có điều kiện cho 2 hồ chứa Sơn La và Hòa Bình. Trên cơ sở đó, đề xuất cơ sở khoa học xác định mực nước giới hạn trên của quá trình tích nước hồ chứa Sơn La trong thời kỳ tích nước hạn chế, đảm bảo tích nước hiệu quả mà vẫn an toàn chống lũ hạ du và công trình. Đề xuất được chế độ vận hành điều tiết chống lũ cho hạ du và phương thức ứng phó khi xảy ra lũ bất thường trong thời kỳ tích nước đầy hồ ở cuối thời kỳ mùa lũ. Hà Nội, ngày tháng năm Người hướng dẫn khoa học Nghiên cứu sinh (đã ký) (đã ký) Phạm Thị Hương Lan Vũ Thị Minh Huệ (đã ký) Hà Văn Khối
Trang 1MINISTRY OF EDUCATION
AND TRAINING
MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT
THUY LOI UNIVERSITY
VU THI MINH HUE
RESEARCH ON WATER ACCUMULATION OPERATING MODE IN FLOOD SEASON FOR HOA BINH AND SON LA TERRACED HYDROELECTRIC
RESERVOIRS
DISSERTATION ABSTRACT Specialization: Water resource development
Code: 62 44 92 01
HA NOI, 2017
Trang 2The project is completed at Thuy Loi University
Principle advisor 1: Associate Professor Pham Thi Huong Lan
Principle advisor 2: Professor Ha Van Khoi
Review 01: Associate Professor Nguyen Tien Giang
Review 02: Associate Professor Duong Van Tien
Review 03: Associate Professor Vu Minh Cat
The thesis will be defended in front of Thesis Evaluation Council at
……… At ……… on …….….… 2017
The Thesis can be studied at libraries below:
- National Library
- Water Resources University library
Trang 3PREFACE
1 The urgency of subject
Currently there are many multi-functional water reservoir projects on the upstream area of Da river They contribute a large proportion of hydroelectric power output, provide water for economic development in Red river delta and help regulate downstream flood control with extremely high efficiency Son La and Hoa Binh reservoirs are two lakes with highest capacity for downstream flood control (7 billion m3) which are designed to be below normal tide rising level Therefore, there are severe conflicts between anti-flood mission and electricity generation, water provision
Inter-reservoir operation regulations on Red river basin issued on Decision no 1622/QĐ-TTg on September 17th, 2015 formed a official operation frame However, actual operation must be based on predictions on the process of water running into the reservoirs Nonetheless, two practical questions for researches
to solve are:
- Is it allowed that the mentioned above reservoirs can accumulate water
in the beginning of flood season? If so, how are water accumulation regulations formed to ensure downstream anti-flood safety?
- According to the regulations, in late flood phase the reservoirs must accumulate water up to normal water rising level However, when expected big floods occur, how can reservoirs function in order to decrease downstream flood and ensure construction safety at the same time?
Therefore, the research student chose the subject “Research on water
accumulation operating mode in flood season for Hoa Binh and Son La terraced hydroelectric reservoirs”, hoping to study scientific foundation on
water accumulation operating mode in Hoa Binh and Son La reservoirs to increase water accumulation efficiency for electricity generation and water provision, ensure construction safety as well as downstream flood prevention
Trang 42 Mission of thesis
- Research on scientific and practical basis to identify water accumulation operating mode in flood season, ensure safety in full water accumulation for reservoirs, increase water provision and electricity efficiency and at the same time assure safety for downstream flood and construction flood in Hoa Binh and Son La reservoirs
- Research on operating mode of downstream flood restriction in late flood period when Son La and Hoa Binh reservoirs are allowed to accumulate full water, minimize negative impact on downstream area
in case unexpected big floods occur
3 Object and scope of the study
Scope of the research: operation and regulation on water accumulation and flood prevention for terraced water reservoir system of Hoa Binh and Son La in flood season
Object of the research: downstream flood prevention regulation is considered in the inter-reservoir system which comprises of 4 reservoirs - Hoa Binh, Son La, Tuyen Quang and Thac Ba However, research on water accumulation operating mode as the topic object focuses on Son La and Hoa Binh reservoirs
on Da river
4 Research method
Methods used in the research are (i) Inheritance method; (ii) Integrated analysis method; (iii) Mathematic model method
5 New contribution of the thesis
- Propose early conditional water accumulation mode for Hoa Binh and Son La reservoirs From that foundation, propose scientific basis to identify above water level limit of water accumulation process of Son
La reservoirs in limited water accumulation period, to ensure efficient
Trang 5water accumulation as well as downstream and construction flood prevention safety
- Propose regulation operation mode to prevent flood in downstream region and coping methods in case unexpected floods occur in full reservoir water accumulation at the end of flood period
6 Structure of the thesis
The thesis consists of 118 pages, 30 tables, 40 figures and 67 reference materials Aside from the introduction and conclusion, the thesis has 3 chapters:
Chapter 1: Overview of researches on multi-functional reservoir operation Chapter 2: Scientific and practical basis to identify water accumulation
operation mode in flood season in Hoa Binh and Son La reservoir system
Chapter 3: Research results on operation mode in water accumulation period of
Hoa Binh and Son La terraced reservoirs
CHAPTER 1 OVERVIEW OF RESEARCHES ON
MULTI-FUNCTIONAL RESERVOIR OPERATION Reservoir and reservoir operation
1.1
To utilize integrated reservoirs for optimal benefit, scientists in the world focus
to find out suitable operation rules, resolve conflicts among different objectives
to reach higher operation efficiency Those researches range from Rippl’s work
on simplifying water storage (1883) to recent complex researches on optimal reservoir operation in real time for multiple purposes of Mehdipour and nnk (2012) Despite systematic and specific research efforts from different investment organizations and various methods applied by scientists to form operation rules for reservoir system, successful applications are mostly related
to typical features of each system There is no common methodology and tool that can be applied for all systems
Trang 6Managing method and operating principles for multi-funtional 1.2
reservoir system
Each reservoir system in the operating phase must comply with an existing operation procedures, in which there are operation procedures for each period that the operating manager must follow Operating procedures of reservoirs are established in technical design period via imitation model or optimization model Operational procedures are presented in graphs or instruction tables according to water level (water capacity) or the reservoir in each year (Yeh, 1985) (Long, N.L, Madsen, H., and Rosbjerg, D., 2007) demonstrated in coordination chart are primary foundations for decision making in reservoir operation Operation procedure curves are one of the most popular and simple management methods in order to support decision making of the manager in reservoir operation For multi-functional reservoirs there are two ways of management: (i) water provision coordination and (ii) real time operation management
Multi-functional terraced reservoirs operation procedures: (i) for purpose of flood prevention, store full water capacity in upstream reservoir in advance when flood needs avoiding, when empty water capacity is needed to prepare for flood regulation afterwards, downstream reservoir needs to be flushed in advance, (ii) for purpose of water provision, it is more simple - higher reservoirs need to store water before and lower reservoirs afterwards
Overview on method to establish multi-functional reservoirs
Trang 7scenarios to select a suitable an operation method, resolve conflicts and optimize objectives of the reservoir system Therefore, in researching the subject of operating multi-functional reservoir, even though optimization method is becoming more popular, there are still challenges in finding the best operating procedures (Labadie, 1997) Because of that, imitation method is still applied widely to identify suitable and flexible operation procedures
Overview of Red river
1.4
Reservoir system
Red river basin is the biggest basin in Northern Vietnam The Red river system originates from Yun Nan, China with 05 big tributaries which unify into 03 main branches- Da, Thao and Lo
Picture 1-1: Map of Da Basin Thanks to favorable terrain conditions, Red river basin is increasingly benefited from upstream water flow In the upstream area of Da river (LyTien river) of China territory, 11 reservoirs are already planned, of which 9 reservoirs are operated In Vietnam territory, in addition to water provision and electricity generating in flood season, Son La and Hoa Binh reservoirs (in Da river) spent
7 billion m3 combined with 1,0 billion m3 of Tuyen Quang (on Gam river) and
Hoa Binh Reservoir
106°0'0"E 106°0'0"E
104°0'0"E 104°0'0"E
102°0'0"E 102°0'0"E
& Meteorological station
" Hydrological station Basin boundary
CHINA
LAO
Trang 80,45 billion m3 of Ba waterfall (on Chay river) to ensure safety of Hanoi not to exceed water level of 13,4 m with periodic flood repeated every 500 years
Operating procedures of reservoir system in Red river basin
Realizing the importance of these reservoirs, as soon as Hoa Binh reservoir comes to operation, many scientists have researched to support management agencies in setting up legal documents for an operation procedure in line with the system development The process has issued reservoir operation regulations
in water accumulation period quite flexibly while maintaining reservoir water level above flood level However, there are no clear regulations about the moment of water accumulation and solutions to cope with flood when water level in reservoirs is high The subject of reservoir operation in water accumulation period still faces some challenges causing difficulties for operation decision makers (this subject is analyzed further in Chapter 2) and needs more research to improve operation efficiency
Flood prediction subject
Prediction on water flowing into a reservoir is one of the most critical tasks in operating the reservoir Prediction quality in forecast news has a big impact on efficiency of inter-reservoir operation, especially prediction of water flow in water accumulation period Flood forecast in Red river is a complicated subject with many challenged as more upstream reservoirs are constructed, lack of information from measurement stations in China territory, unreliable quality of numerical rain forecast Nevertheless, flood forecast for the system has drawn attention of many scientists (Trinh Quang Hoa and nnk, 1994) (Nguyen Van Diep, 2013) (Bui Dinh Lap, 2016) who utilize modern and progressive technology in the world to improve forecast quality and increase efficiency of operating reservoir in Red river basin Flood flow forecast with estimated time
of 72 hours for “good” forecast is one of conditions to resolve conflicts between water accumulation and flood prevention for reservoir system in Red river basin system
Trang 9Research orientation
1.5
Considering Son La and Hoa Binh reservoir system, there have been many researches as scientific basis in constructing procedures for operating reservoir system in Red river, in addition to a lot of reports analyzing operating facts using many modern technology Yet, operational decision makers still face many challenges in periods with no clear regulations As a result, the thesis chooses the research as the scientific basis for operating reservoir system in Red river basin in water accumulation period The research model is illustrated in Figure 1-7 as below
Figure 1-7: Flow chart researching water accumulation operating mode for Hoa
Binh and Son La reservoir system Current reservoir operation procedure in Red river basin (QT1622) suggests a solid operation frame for the reservoir operation management Therefore, the thesis chooses imitation method with different advantages and disadvantages to make the operation of the reservoir system more specific with various scenario From those chosen scenario, a suitable water accumulation method is chosen to resolve conflicts and optimize objectives of the system
Trang 10CHAPTER 2 SCIENTIFIC AND FACTUAL BASIS TO IDENTIFY WATER ACCUMULATION OPERATION MODE IN FLOOD SEASON FOR HOA BINH AND SON LA RESERVOIR SYSTEM 2.1 Comments on published procedures and suggesting research direction
on water accumulation operation mode
Downstream flood prevention mission
QT 1622 provides that Son La and Hoa Binh reservoirs spend a big enough volume to constrict the above limits so that when floods occur, the design can cope with highest level in Hanoi according to 13,1 meter level of 300 year recurring flood and 13,4 meter of 500 recurring flood in Son Tay (see Table 2-1)
Table 2-1: Regulations on distributing flood prevention volume for downstream flood demolition following restricted water level in Hanoi of Son La and Hoa Binh reservoir in QT1622
Water level to
be restricted
in Hanoi
Volume spent for flood prevention following restricted
level in Hanoi (billion m3) Son La reservoir Hoa Binh reservoir Total
ZHN 11,5 m
1,00 (reservoir water level from 197,3÷203 m)
1,13 (reservoir water level from 101÷107m)
2,13
ZHN > 13,1 m
to 13,4 m
3,00 (reservoir water level from 203 ÷217,2 m)
1,87 (reservoir water level from 107 ÷117 m)
4,87
Some limits of operation procedures
In early phase and primary phase of flooding, operation procedures mainly focus on flood prevention when Hanoi water level may exceed 11,5 meter There are no specific operation procedures when Hanoi water level goes below this yet Calculate in technical profiles, establish procedures using 3
Trang 11flood models with disadvantage rate of 0,33% and 0,2% when flood stage level
in Hanoi reaches 10,5 till 11,5 meter without considering cases when big floods
do not occur Therefore, procedures QT198 and QT1622 generally provide that
in case of non- flood and depending on the changes of the weather and the water level in Hanoi, it is allowed to raise reservoir water level above pre-flood water level and in the forecast of flood, flush water to bring reservoir water level back to pre-flood water level Consequently, it is necessary to identify the limit of above water level and in which forecast that water level is allowed to be raised above? On the other hand, according to 56-year statistic documents (from 1959-2015), only in 9 years (16%) Hanoi water level in natural conditions may exceed 11,5m did reservoirs take part in downstream flood prevention Hence, specifying operation mode for reservoir in flood season when floods do not occur (Hanoi water level <11,5m) is highly critical
There have not yet been any specific regulations on downstream flood prevention operation mode in water accumulation period (late flood) as unexpected floods happen When there if forecast that flood season ends early,
reservoirs are allowed to accumulate water since August 10th which means Hoa Binh reaches 110m level and Son La reaches 209m level (according to QT1622), downstream flood prevention remains only 2,65 billion m3, unable to cope with downstream flood with 300 year recurring flood in Son Tay In technical profiles for establishing operation procedures, there are not yet material to calculate and check flood prevention capacity and solutions in reservoir regulating operation in case of unexpected floods in this water accumulation period
Operation mode regulations to prevent downstream floods in case of big floods are reasonable and not yet comprehensive In regulations, reservoirs
can prevent downstream floods when Hanoi water level may exceed 11,5 meter, however there is no reservoir volume distribution between two restricted levels
of 13,1 m and 13,4 m This causes many challenges for reservoir system operator in factual downstream prevention
Trang 12Dividing flood season into 3 periods with fixed timeline to establish regulation and operation mode for each period Published procedures, the
mode to operate reservoir in flood season is always divided into 3 periods: early flood, main flood and late flood In regulations, the starting time to accumulate water into reservoirs is regulated to be in the beginning of late flood period (after August 21st every year) and early water accumulation since annual August 10th is only allowed if flood season is predicted to end early
Even though procedures provided highest water level in flood season, in factual operation system, the operation is proceeded via water accumulation before allowed time Specifically, 4 years (2012-2015) after Son La reservoir’s operation followed QT198 providing that flood prevention water level of Son
La is 194 m and Hoa Binh as 101 m, water accumulation time is not earlier than August 10th and yet, all reservoirs remain water level higher than regulations despite no flood (Figure 2-1) Especially, in 2012, the highest water level of Son La reservoir reached 201,84 m with 5,84 m increase and highest water level of Hoa Binh reservoir reached 201,84 m with 5,76 m increase Even though reservoirs accumulate water early, at the end of flood season when water flow in rivers decrease fast, there are times when these reservoirs reduce water generation capacity to ensure water is accumulated fully in reservoirs to safely provide water for downstream areas in dry season
Figure 2-1: Chart illustrating water level in Son La reservoir in flood season in
2012-2015
Trang 13Research orientation on water accumulation operation mode of Hoa Binh and Son La reservoir From analysis on procedures and operation reality, the
thesis’s orientation comprises of two main themes:
- Research water accumulation operation mode in flood season to increase water generating efficiency, ensure full reservoir water accumulation and still maintain flood prevention safety for downstream areas and constructions
- Research to establish flood prevention regulating mode, minimize negative impact for downstream areas in case of unexpected big floods in water accumulation period after annual August 21st or after annual August 10th when
it is allowed to accumulate water early
2.2 Scientific basis to identify water accumulation operation mode
Point of view The thesis’ research orientation proposes to apply early
conditioned water accumulation (medium method) for Hoa Binh and Son La reservoirs However, the fact that reservoirs are allowed to accumulate water early does not mean that water accumulation up to normal water rising level right after flood season finishes should be done Water should only be accumulated up to a certain limit so that when there is forecast of big flood, reservoir water level can be brought back to pre-flood level, ready to prevent flood as design Water accumulation mode is called “conditional” because in each water accumulation time, accumulated water level in the reservoir depends
on 3 factors (1) reservoir water level and downstream water level (in Hanoi) in water accumulation time; (2) flood forecast scale and water progress flowing into the reservoir and downstream water level in forecast time; (3) Restrictions
on flood flushing regulation via flood flushing constructions Based on that, flood season is divided into 2 operation periods:
Restricted water accumulation period (before annual August 21 st ): restricted
water accumulation operation period including early flood and main flood period This is the period that flood flushing for downstream area is primary, therefore reservoirs only allow accumulating water up to a certain water level