Impact assessment of regulation works in the thai binh river downstream major intergrated water resources management code 62 58 02 0

The study determined the existing problems and troubles in water distribution and water use in the Thai Binh River downstream.. Problem statement Figure 1.1 Thai Binh River downstream ar

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURALDEVELOPMENT

THUYLOI UNIVERSITY

IMPACT ASSESSMENT OF REGULATION WORKS

IN THE THAI BINH RIVER DOWNSTREAM

Nguyen Vinh Nguyen MSc Thesis on Integrated Water Resources Management

November, 2017

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT

THUYLOI UNIVERSITY

Nguyen Vinh Nguyen

IMPACT ASSESSMENT OF REGULATION WORKS

IN THE THAI BINH RIVER DOWNSTREAM

Major: Integrated Water Resources Management

THESIS OF MASTER DEGREE

Supervisors:

1 Assoc Prof Dr Nguyen Mai Dang

2 Assoc Prof Dr Ngo Van Quan

This research is done for the partial fulfilment of requirement for

Master of Science Degree at Thuyloi University (This Master Programme is supported by NICHE – VNM 106 Project)

November, 2017

DECLARATION

I hereby certify that the work which is being presented in this thesis entitled, “Impact assessment of Regulation works in the Thai Binh river downstream” in partial fulfillment of the requirement for the award of the Master of Science in Integrated Water Resources Management, is an authentic record of my own work carried out under supervision(s) of Assoc Prof Dr Nguyen Mai Dang and Assoc Prof Dr Ngo Van Quan

The matter embodied in this thesis has not been submitted by me for the award of any other degree or diploma

Date: 19/11/2017 Signature

Nguyen Vinh Nguyen

Abstract

The Thai Binh River System’s downstream is a major economic region which is located in the Red River Delta including Hai Phong city and Thai Binh province Currently, water distribution here is significantly unreasonable for the downstream water stakeholders

Therefore, a research regarding current water allocation assessment need and has to be conducted in order to find out appropriate solutions for solving and surmounting the issues In this study, the MIKE 11 model was used to simulate the recent status of the system and predict the water distribution according to some proposed scenarios based on the system operation in the future

The study determined the existing problems and troubles in water distribution and water use in the Thai Binh River downstream Accordingly, the impact of structural measures proposed in this study on flow changing also was analyzed in details In addition, the study illustrated that the flow discharge of rivers in the system will be changed significantly after building the regulated structure works In addition, the study proposed some alternatives aiming to strengthen the management of system operation as well as water use in the downstream of Thai Binh River

Key words: Red River Basin, Thai Binh River, MIKE 11 model, flow regime

Acknowledgement

I would like to give a big thank to all people who have supported and assisted

me during my 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 Assoc Dr Nguyen Mai Dang and Assoc Dr Ngo Van Quan for their unlimited encouragement, guidance, comments and technical supports as well as the thesis writing process from the beginning of this thesis research

I wish to thank Dr Ilyas Masih, Assoc Dr Nguyen Thu Hien and Assoc Dr Ngo Le An for their feedbacks, references and support on the proposal process

I also want to thank to all instructors and staff of Thuy Loi University who have helped me a lot during the master course

I would like to give my appreciation to Dr Ho Viet Cuong, Msc Nguyen Thi Ngoc Nhan, Msc Nguyen Van Bach and Mr Phan Van Thanh who was willing to help me with modelling application in the thesis

I also would like to thank the National Key Laboratory of River and Coastal Engineering and Institute of Vietnam Academy for Water Resources for their information and useful data input

Last but not least, I want to take this opportunity to show my appreciation to my family, friends for their inspiration and support throughout my life; this research is simply impossible without you

Contents

DECLARATION i

Abstract ii

1 INTRODUCTION 6

1.1 Overview 6

1.2 Problem statement 8

1.2.1 Objectives of the study 9

1.2.2 Research questions 9

1.2.3 Thesis overview 10

2 LITERATURE REVIEW 11

2.1 Overview of hydraulic modeling 11

2.2 Mike 11 Model 13

2.3 Related studies 15

3 STUDY AREA 18

3.1 Description of the study area 18

3.1.1 Geography and River Network 18

3.1.2 Climatic characteristics 20

3.1.3 Hydrological characteristics 23

3.1.4 Tide and tidal effects in the river mouth 26

3.2 Water demand 27

3.2.1 Water demand for agriculture 27

3.2.2 Water demand for aquaculture 28

3.2.3 Water demand for industry 29

3.2.4 Water demand for domestic 29

3.3 Water exploitation and utilization issues 30

4 METHODOLOGY 32

4.1 The MIKE 11 Model 33

4.1.1 Governing Equations 33

4.1.2 Methods used in the performance evaluation 34

4.2 Mike 11 Model Set-up 35

4.2.1 Input data 35

4.2.1.2 Boundary conditions 37

4.2.1.3 Cross-sections 38

4.2.1.4 Meteorological and hydrological data 39

4.3 Modeling calibration 39

4.3.1 Step by step 40

4.3.2 Initial conditions setup 40

4.3.3 Calibrating the hydraulic parameters 40

4.3.4 Modeling calibration in flood season 41

4.3.4 Modeling calibration in dry season 44

4.4 Modeling validation 48

4.4.1 Modeling validation in flood season 48

4.4.2 Modeling validation in dry season 49

4.5 Proposed regulation works and scenarios 52

4.5.1 Proposed regulation works 52

4.5.2 Simulated Scenarios 53

5 RESULTS AND DISCUSSIONS 54

5.1 Scenario results simulated in August 1996 55

5.2 Scenario results simulated in January 2007 62

6 CONCLUSIONS AND RECOMMENDATIONS 72

6.1 Conclusions 72

6.2 Recommendations for further researches 73

APPENDIX 77

List of figure

Figure 1.1 Thai Binh River downstream area 8

Figure 2.1 Simulation interface file of Mike 11 (HD Module) 15

Figure 3.1: Map of the study area focus on two districts: Vinh Bao and Tien Lang 18

Figure 4.1: The research flowchart 32

Figure 4.2: Schematic of network and reservoirs considered in the Red River basin 36

Figure 4.3: River network for simulation by Mike 11 model 37

Figure 4.4 Model calibration process 39

Figure 4.5: Hydraulic parameters interface 41

Figure 4.6: The observed and simulated water levels for the 1996 flood event at Ha Noi station in the case of calibration 42

Figure 4.7: The observed and simulated water level in Van Uc River in 1/2006 – Trung Trang Station 45

Figure 4.8: The observed and simulated water level in Duong River in January 2006 – Thuong Cat Station 45

Figure 4.9: The observed and simulated hydrographs at Son Tay Station 48

Figure 4.10: The observed and simulated hydrographs at Ha Noi Station in January 2007 49

Figure 4.11: The observed and simulated hydrographs at Tra Ly Station 50

in January 2007 50

Figure 4.12: Structure of the regulated dam in Moi River 52

Figure 5.1 The locations of selected cross-sections 54

Figure 5.2 Actual water level at the selected points 55

Figure 5.3 Actual discharge at the selected points 55

Figure 5.4: Simulated water level of PA1 56

Figure 5.5: Simulated discharge of PA1 56

Figure 5.6: Simulated water level of PA2 57

Figure 5.7 Simulated discharge of PA2 57

Figure 5.8: Simulated water level of PA3 58

Figure 5.9: Simulated discharge of PA3 58

Figure 5.10: Simulated water level of PA1+2 59

Figure 5.11: Simulated discharge of PA1+2 59

Figure 5.12: Simulated water level of PA1+3 60

Figure 5.13: Simulated discharge of PA1+3 60

Figure 5.14: Simulated water level of PA1+2+3 61

Figure 5.15: Simulated discharge of PA1+2+3 61

Figure 5.16: Actual water level at the selected points 62

Figure 5.17: Actual discharge at the selected points 62

Figure 5.18: Simulated water level of PA1 63

Figure 5.19: Simulated discharge of PA1 63

Figure 5.20: Simulated water level of PA2 64

Figure 5.21 Simulated discharge of PA2 64

Figure 5.22: Simulated water level of PA3 65

Figure 5.23: Simulated discharge of PA3 65

Figure 5.24: Simulated water level of PA1+2 66

Figure 5.25: Simulated discharge of PA1+2 66

Figure 5.26: Simulated water level of PA1+3 67

Figure 5.27: Simulated discharge of PA1+3 67

Figure 5.28: Simulated water level of PA1+2+3 68

Figure 5.29: Simulated discharge of PA1+2+3 68

List of table

Table 2.1 Comparison of different One-Dimensional (1D) models 12

Table 3.1 Monthly average temperature of the year at stations 21

Table 3.2 Typical average monthly rainfall at stations 22

Table 3.3 Typical monthly average wind speed at three stations 23

Table 3.4: Total water used for cultivation and livestock in year 2012 28

Table 3.5: Water demand of cultivation in period of 2020 and 2030 28

Table 3.6 Water demand of livestock in the period of 2020 and 2030 28

Table 3.7 Water demand of aquaculture in 2012 29

Table 3.8 Water demand of aquaculture in the period of 2020 và 2030 29

Table 3.9 Current status of water use of industrial zones 29

Table 3.10 Water supply for domestic in Tien Lang and Vinh bao districts 30

Table 3.11 Water demand of domestic in the period of 2020 and 2030 30

Table 4.1: The upstream and downstream boundary of the model setup 39

Table 4.2: Calibrated Manning values of the river system 43

Table 4.3: Model performance of the MIKE 11 for the calibration at some stations 44

Table 4.4: Calibrated Manning values of the Red and Thai Binh Rivers 46

Table 4.5: Model performance of the MIKE 11 for the calibration in the dry season 47

Table 4.6: Error criteria of the model calibration in the 2002 flood event at some stations 49

Table 4.7: Model performance of the MIKE 11 for the model validation in the dry season 50

Table 5.1 Comparison between actual and simulated flows of PA1 56

Table 5.2 Comparison between actual and simulated flows of PA2 57

Table 5.3: Comparison of actual and simulated flows of PA3 58

Table 5.4 Comparison of actual and simulated flows of PA1+2 59

Table 5.5 Comparison of actual and simulated flows of PA1+3 60

Table 5.6: Comparison of actual and simulated flows of PA1+2+3 61

Table 5.7 Comparison of actual and simulated flows of PA1 63

Table 5.8 Comparison of actual and simulated flows of PA2 64

Table 5.9: Comparison of actual and simulated flows of PA3 65

Table 5.10: Comparison of actual and simulated flows of PA1+2 66

Table 5.11 Comparison of actual and simulated flows of PA1+3 67

Table 5.12 Comparison of actual and simulated flows PA1+2+3 68

1 INTRODUCTION

1.1 Overview

Water is a useful natural resource and plays an important role in human being The water users in a river basing include some stakeholders such as agriculture, industry, households, recreation and environment Obviously all human activities demand and need fresh water Fresh water is extremely essential for lives; no other natural resources can replace it This meant that water has a high potential use for human (Zaag & Savenije, 2013)

Nowadays, people have been using water resources in a negative way Accordingly, water quality and quantity are both declining significantly There are some reasons for this statement including the effects of natural conditions, climate change, economic and social development, over exploitation of natural resources as well as the poor management of local authorities

Water crisis has been increasing and affecting widely all over the world It is about 1.2 billion people; similar to 1/5 global population, living in water shortage areas and other 500 million people are being exposed by this trouble Water shortage is caused by natural phenomena and human activities Fresh water is available everywhere in our planet and much enough for human However, fresh water is distributed unevenly and overused tremendously on the world In addition, fresh water has been polluted for decades by many polluted sources due to economic development Unsustainable development also is one of the reasons for water crisis (FAO, 2007) According to plenty of water institutes, 1/3 countries in the world are facing with water shortage In year 2025, it will be predicted that approximately 35% of global population will be able to face with tremendous water shortage problems

Based on the report of Ministry of Natural Resources and Environment (2009), Vietnam has about 3450 rivers with above 10 kilometers length There are 206 water sources which are considered as external water resources Accordingly, total annual water volume is about 830 billion m3 from the biggest river systems Total potential groundwater amount is about 63 billion m3 per year and distributed mainly in the hilly and mountainous regions (Le Mai, 2013) It can be seen that Vietnam has a lot of

water due to the heavy rainy season and dense river intensity However, droughts and large scale water shortage occurred regularly in many provinces Vietnam currently has many challenges regarding water resources management In addition, Vietnam is ranked as one of the most affected countries by climate change and sea level rise

In recent years, the demand for water is rising day by day under the pressure of population and development - social growth Moreover, the uneven distribution of water resources in time and space with the requirements of environmental flows, leading to water shortages appear Besides, the competing interest of different stakeholders even exaggerates the issue Besides, erosion and sediment deposition are happened more frequently on many river systems These phenomena influences directly on lives, economics and lives surrounding affected areas as well as the safety

of hydraulic works in the system One of the natural disasters that needed to be considered is sediment deposition at downstream areas of river system In the northern part of Vietnam, which includes Red and Thai Binh rivers, sediment deposition happening regularly Particularly, in Thai Binh river basin, at the downstream area, Hai Phong city is the most affected area by erosion, deposition as well as salinity intrusion

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 and supporting for the integrated water resources management An appropriate model selection is essential for each research project These selections thereby have to be based on study objectives, considering input data and output data, expected results and solutions There are many studies on the water field that use models as effective tools to solve problems The MIKE 11 model has been developed by DHI Water and Environment (Danish hydraulic institute) and is used popularly in Vietnam This model is a professional engineering software package for simulation of flow, water quality and sediment transport in estuaries, rivers, irrigation system, channels and others bodies (DHI 2011) This model will be used for simulation of scenarios and alternatives of proposed management

1.2 Problem statement

Figure 1.1 Thai Binh River downstream area

According to the report of Hai Phong Department of Agriculture and Rural

increasingly happening because of the natural water distribution and sediment (Luoc river moving and developing on the left side of Van Uc River - Figure 1.1), Thai Binh River’s downstream has been deposited by sediment since 1960 The average depth of river bed is fluctuating from 1 to 2 meters

Besides, the water resources management here is causing a lot of negative impact on water use Water quality and quantity are predicted that they are not good enough for water supply in the area in the future Those problems mentioned above did, do and

will influence strongly on the socio-economic development of Tien Lang and Vinh Bao districts Because, these two areas play a role as key development of agricultural areas as well as water demand would be increased significantly

In addition, sediment transport is currently increasing at Do Son Beach due to the water diversion to Van Uc River leading to amount of sediment flowing to the sea This will affect tourism and economic development of Hai Phong City

1.2.1 Objectives of the study

Overall objective is to assess the impact of water regulation works in the downstream of Thai Binh River by using hydrodynamic model To achieve the main objectives, the thesis consists of some detailed goals as follows:

+ Analyzing and assessing the current status of the study area in accordance with problems and troubles

+ Using the MIKE 11 to simulate the flow regimes according to proposed solutions and scenarios in order to suggest the water allocation

+ Determining the water diversion between Red River and Thai Binh River in general, particularly determining the impact of regulation works to flow regime in Thai Binh river’s downstream located in Hai Phong province Main purpose of the constructions is to increase the flow in Thai Binh river and to decrease the flow in Van

Uc river Also, other purpose is to prevent saltwater intrusion in Thai Binh river as well

+ Proposing solutions for water allocation, water usage, water management in order to enhance the quality of water use in the study area

1.2.3 Thesis overview

Structure of the thesis includes those parts:

Chapter 1: Introduction, presents problem statement, needs of study, research

objectives, and overview of the study area

Chapter 2: Literature review, reviews the previous studies related to the content

and cope of this research An overview of hydrodynamic models also analyzed here MIKE 11 model will be presented in this chapter as well

Chapter 3: Study area and data collection, presents the natural conditions,

climatic characteristics of the study area as well as the population characteristics, economics and society The water demand and management are also discussed in this study

Chapter 4: Metholodology, shows the methodology and steps to achieve the

objectives of the thesis The chapter discusses the data input as well Modeling calibration and validation are also presented here

Chapter 5: Results and discussions, analyses the model performances (MIKE

11) in order to obtain the research objectives

Chapter 6: Cconclussions and recommendations, focuses on findings and

recommendations, and future researchs

In this chapter, existed issues, needs of study, research objectives were be showed Because of the uneven river flow distribution between the Van Uc river and Thai Binh river in the study area, Thai Binh river has high sedimentvolume and salt intrusion and Van Uc river has the erosion

2 LITERATURE REVIEW

2.1 Overview of Hydrodynamic Model

Any scientific field always needs to develop some processes such as monitoring data, recording and measuring data, simulation and explanation of natural phenomena To have a better understanding of the processes of hydrology, they can be described in laboratories by physical models Besides that numerical models have been developed increasingly due to their advantages such as costs, flexibility and applied technology Accordingly, hydraulic and hydrological models are tools to address the real hydrological cycle in a simplified way Such models are used for understanding the hydrological processes as well as making hydrological predictions in cases where water resources management and utilization activities are implemented The models apply several algorithms to provide a quantitative relation between the input data (e.g rainfall, meteorological data) and output (e.g runoff) The hydrodynamic models have been used for energy production, sediment transportation, water quality and environment Scientists have developed many 1D, 2D and 3D dynamic models Those models are used for sustainable water resources management

Estuaries can be seen as potential and valuable natural resources of environment, society and economics (Nordstrom, 1992) The research on sediment transportation in estuaries is normally difficult due to the fluctuation of sediment and impacts of other natural factors The sediment transportation process on rivers is relatively complicated including erosion process, sediment transport and deposition Those processes relate to flow regimes, particles characteristics, size and shape, and intensity and elements of the particles The morphological changes are the results of the nonlinear interaction between water and sediment and river bed (Hibma et al, 2004) However, numerical models are used as valuable tools for simulation of natural phenomena due to the development of technology in the past decades in order to get a better understanding of physical processes and numerical technique (Jiang, Ranasinghe & Cowell, 2013)

There are many numerical models from open sources, for example Delft3D developed by Deltares to commercial models MIKE models developed by DHI A lot

of hydraulic models that simulate the hydrologic regimes and sediment transport have been considered aiming to obtain an appropriate model The selected model need to be considered with many factors such as management, variables and main process, data available, and input and proposed solutions (Boorman et al., 2007) Hence, the input data of various models have to be collected aiming to get best understanding of advantages and disadvantages of them before the model application Table 2.1 shows the comparison of different hydrodynamic models

Eventually, according to the author’s knowledge, natural conditions of the study area and available input, MIKE 11 model was selected as an effective tool for achieving the research study

Table 2.1 Comparison of different One-Dimensional (1D) models

al., 1995; Ndomba

&Griensven, 2011)

MIKE 11 (Doulgeris et al., 2012)

HEC-RAS (Pappenberger et al., 2005)

ISIS (Van et al., 2012)

HEC-RAS model is used for variety types of projects such as steady, unsteady and mixed flow regimes The model is used for multiple purposes

ISIS is a full hydrodynamic simulator for modeling flows, water levels in open channels and estuaries

-Reach network -Cross section -Steady flow data -Unsteady flow -Sediment

-Hydrological -Cross

Section’s Geometry -Sediment concentration Key

HEC-RAS model is based on the continuity equation and momentum equation

The model is based on one-dimensional Saint Venant’s equations

Model SWAT (Arnold et

al., 1995; Ndomba

&Griensven, 2011)

MIKE 11 (Doulgeris et al., 2012)

HEC-RAS (Pappenberger et al., 2005)

ISIS (Van et al., 2012)

-Stream flow -Water level -Sediment scour and deposition

-Runoff -Water quality -Sediment

Time

Step

Daily time step Sec, Minute, Hourly

and daily time step

Minute, Hourly, Daily

Minute, Hourly, Daily Access-

The user has to pay

to use the model and access to the code

The user can access

to modify the code

The SWAT model

is free and a public

ID component

as well as the whole ISIS component is free for users

(Source: Tania Hassan, 2016)

2.2 Briefs of Mike 11 Model

Modelling of rivers and channels MIKE 11 is a versatile 1D modelling package covering more application areas than any other river modelling package available MIKE 11 is a fully dynamic, one-dimensional modelling package It includes comprehensive facilities for modelling complex river channel networks, lakes and reservoirs With the hydrodynamic engine as a core module, MIKE 11 offers a variety

of add-on modules and large selection of hydraulic structures, including operational structures allowing users to define complex control strategies as well as dam break structures Additional application areas include, rainfall-runoff, flood modelling, ecology and water quality, real time forecasting and sediment transport and river morphology assessments (DHI, 2007) MIKE 11 has been used widely all over the world The model includes some modules as follows:

● HD Hydrodynamic

● AD Advection-Dispersion

• Flood analysis and flood alleviation design studies

• Real time flood or drought forecasting

• Dam break analysis

• Optimization of reservoir and canal gate and structure operations

• Ecological and water quality assessments in rivers and wetlands

• Water quality forecasting

• Sediment transport and long term assessment of river morphology changes

• Salinity intrusion in rivers and estuaries

• Wetland restoration studies

• Integrated modelling of river and groundwater interaction

HD module requires the following input files:

• Simulation editor *.SIM11

• Result files *.RES11

Figure 2.1 Simulation interface file of Mike 11 (HD Module)

2.3 Applications of Hydro-dynamic Model

All over the world, many researchers have experimented in order to estimate the flow changing (Yan et al, 2010, Lajoie et al, 2007, Matteau et al, 2009; Magilligan

and Nislow, 2005) Using the MIKE 11 model has become popular nowadays because

of the effective simulation of model

Many kinds of hydraulic models have been applied widely in solving water resources issues such as 1D models (MIKE 11, HEC- RAS, etc…) and 2D models (MIKE 21, TUFLOW, DELF3D….) In Vietnam, especially the MIKE models have gained popularity lately These packages have been developed by the DHI water and environment (Danish Hydraulic Institute), which is a global organization dedicated to solving challenges in water environments worldwide There is the question is how much is modelling needed? Robyn Johnston and Vladimir Smakhtin illustrated that modelling needs to concentrate on uncertainties reports to assess the application of model in reality for policy and management processes New inventions are needed for improving quality and quantity of modelling (Johnston & Smakhtin, 2014) MIKE 11 model is used to link the hydrodynamic progress and morphological changes (Wang, 2014) This is a useful method for this study Numerical models are implemented by the combination of hydrodynamic processes, wave, sediment transportation and depth update (Jiang et al., 2013)

In Vietnam, scientists assessed changes of the flow and sediment regime due to the effect of hydropower plants, hydraulic works, regulation works For example in the Red River Delta, there are some researches as follows: environment flows (Nguyen Van Hanh and et al., 2010), sediment transportation (Do Minh Duc, 2004), assessment

of salinity intrusion (Do Thi Bich, 2000); the effects of river bed change, water intake capacity of hydraulic works (Le Van Hung and Pham Tat Thang, 2015); flow changes

in dry and wet seasons to water distribution (Nguyen Thi Thu Nga and Ha Van Khoi, 2016); water diversion proportion and its effects to erosion and deposition (Nguyen Huu Hue et al., 2016)

To simulate the flows, except MIKE 11, number of models have been considered such as Q_SDM_BASIN_2014 (Dao Tan Quy, 2013), using 1-2D model to assess the effects of constructions on rivers on flow regime and salinity intrusion at estuaries (Luong Quang Xo, 2014) However, the model performances only showed the Nash Coefficient from 0.70 to 0.82 MIKE 11 model for flow modelling is still

applied in many projects (Nguyen Thanh Hung et al, 2015, Nguyen Van Tuan et al, 2014) However, the studies concentrated on surrounding areas and large scale as well

as lack of information from the study area Studying on the downstream area of Thai Binh river need to have available data and detailed conditions of study area In year

2016, Tania Hasan and others studied for Hai Phong area However, this study was only concentrated on sediment transportation due to the interaction of upstream reservoir systems

In order to solve completely the existing issues on the study area, this study will focus on gathering input data including natural conditions, society, water demands, water management in Thai Binh River, Hai Phong city Besides, to strengthen the effectiveness and accuracy of MIKE 11, this study will simulate the flood flow and dry flow by implementing the model calibration and validation processes

The chapter presented overview of hydrodynamic model and focus on the MIKE

11 model Some reviews the previous studies related to the content and cope of this research were be presented as well Unlike previous studies, the study used two sets of parameters for the Mike model in the dry season and flood season The specificconditions of study area were be showed

3 STUDY AREA

3.1 Description of Study Area

3.1.1 Geographic Characteristics and River Network

Figure 3.1: Map of the study area focus on two districts: Vinh Bao and Tien Lang The Thai Binh River is included over 275 km length and 11 branches and estuaries in downstream These branches transfer the entire flows from Thai Binh River to four river mouths including Thai Binh, Van Uc, Lach Tray and Cam estuaries

The geographic location of the study area shown as follows:

+ Bordered with Thai Thuy district, Thai Binh province in the South-East direction, close to the borders of Quynh Phu District, Thai Binh Province in the West direction, Hoa river is a natural border defined from the conjunction of Luoc and Thai Binh Rivers

+ Bound by the East sea in the East direction, bordered with Van Uc river in the North-East direction defined from the upstream of Moi – Van Uc river’s conjunction

to the Sea

+ Bordered with Hai Duong province in the North-West direction, bound by Moi and Luoc rivers defined from the conjunction of Hoa and Luoc rivers to the conjunction of Moi and Van Uc Rivers

Topography and geomorphology of Thai Binh River downstream are the results of geologic movement in million years in relation with sediment deposition of the Red and Thai Binh River basins It can divide the geography into two main regions: the northern part is lowland terrace with hilly regions, the southern part is remained delta area

The delta area has elevation fluctuating from 2.50 m up to 3.50 m and the elevation declining from the West to the East directions The surface mainly covered

by mixed clay, sandy clay and sediment In this area, there are many ponds, lakes and wetlands affected by tidal fluctuation These water bodies are laid along the large rivers such as Van Uc, Lach Tray, Thai Binh and Hoa rivers Particularly, the study area has a long shoreline with many estuaries (Thai Binh and Van Uc estuaries) leading to transfer amount of sediment to the Sea significantly This helps forming the huge polders, mangrove forests or new economic areas such as Tran Duong, Vinh Quang, Tien Hung, Dong Hung, Tay Hung

The geographic characteristics of Thai Binh River downstream influence the flow regime of the local rivers The incline of topography towards Northwest – Southeast directions leads to flow downwards once tidal happening

The study area’s river network consists of large main rivers which belong to Red – Thai Binh river system such as Luoc, Moi, Hoa, Thai Binh and Van Uc Rivers The location of those rivers described as below:

Thai Binh River is flowing through Cat Khe and Phu Luong hydrological stations The river is then divided into two tributaries including Thai Binh and Rang – Gua Rivers A segment of Thai Binh tributary flows to Mia River, then merges with Van Uc Another segment of Thai Binh river right after Mia River is deposited strongly Dai Thang weir was built on this river to get water for irrigation purpose Another segment of Thai Binh River identified from Quy Cao to the sea becomes a tributary of Luoc River However, the river bed of this segment has been deposited

tremendously and flood controlling capacity of this river is mostly zero Thai Binh River, a segment from the conjunction of Moi River to the sea, has low velocity and has been deposited by sediment Currently, the river bed of this river is quite large but the river depth is relatively shallow The river bed elevation changes from -1.00 m down to -2.50 m Due to the degradation of the river, the discharge of Luoc River flowing into this river is quite small This will definitely lead to extreme salt intrusion Thai Binh River, from the conjunction of Moi River to the sea, plays an essential role

in supplying water for Tien Lang district

Van Uc River has several tributaries such as Mia, Moi, Gua and Lai Vu Rivers This river divers a small amount of water to Lach Tray River Van Uc River’s length is about 43.5 km, average width of the river is approximately 500-800 m, and river bed elevation changing from -10.00 m down to -16.00 m The lowest point reaches -47.00

m where located nearby Moi River

Luoc River is a tributary of the Red River Luoc River transfers a small amount

of water to Hoa and Thai Binh Rivers, meanwhile, the entire water from this river is transferred to Moi and Van Uc rivers A segment of Luoc River passing Hai Phong has length of 14 km, the average width of cross-sections here is 300 meters, bed elevation fluctuating frim -8.00 m down to -12.00 m Luoc river plays a role as a natural border

of Vinh Bao (Hai Phong province) and Hai Duong as well as a main source of water supply for Vinh Bao and Tien Lanh districts

Hoa River is another tributary of Luoc, which defined from Chanh Chu conjunction The river reaches to the sea throughout Thai Binh estuary The length of the river is about 37 km, and wide of river bed from 150 - 250 meters, elevation of river bed from -5.00 m down to -7.00 m Hoa River is a natural border between Vinh Bao district and Thai Binh Province and is a water supply source for Vinh Bao district

3.1.2 Climatic characteristics

The study area is located in the southern part of Hai Phong city The topography of the area is mainly delta Therefore, climatic and hydrologic conditions here have the characteristics of typical red river delta in general and Hai Phong city in particular

The study area has the tropical monsoon climate of coastal zone There are two opposite seasons here Summer season (South-West monsoon) is from May to October with high humidity and a lot of rain Winter season (North-east monsoon) is from November to March of following year with cold temperature and less rain Main characteristics of climate of Hai Phong province described below:

• Temperature

The temperature in Hai Phong is normally high and suitable with development

of annual agriculture Due to the controlling of pole circulation, annually the temperature in Hai Phong is split into different seasons: hot summer has high temperature of over 250C, cold winter has lowest temperature of below 200C Annual average temperature reaches 230C, highest monthly average temperature reaches 290C

in July at Hon Dau Lowest monthly average temperature reaches 16.3 in January at Phu Lien Maximum temperature, which was observed in Phu Lien and Hon Dau respectively, was 41.50C in May – 1914 and 38.60C in July-1985

Table 3.1 Monthly average temperature (0C) of the year at stations

Phu Lien 16.3 16.9 19.4 23 26.5 28.1 28.4 27.7 26.9 24.7 21.3 17.9 23.1 Hon Dau 16.8 16.8 19.2 22.8 27 28.5 29 28.4 27.6 25.3 22.3 19 23.6 Bach Long Vi 16.8 16.6 18.7 22.3 26.2 28 28.7 28.3 27.3 25.3 22.4 18.9 23.3

• Rainfall

The rainy season starts usually from May and ends in October The total rainfall

in this season obtains 85% of the total rainfall in year Accordingly, 15% of total rainfall happens in the dry season

Annual average rainfall is approximately 1520 mm The spatial distribution of annual rainfall is not too different Annual yearly total rainfall reaches 1677 mm at Phu Lien, and 1534 mm at Thuy Nguyen, 1544 at Tien Lang and 1514 mm at Vinh Bao Yearly rainfall at the northern parts is normally higher than the southern parts caused by the directions and effects of typhoons and tropical low pressure once they land deeply Hence, the maximum yearly rainfall is usually occurring in the years

which affected by typhoons or tropical low pressure Typically, the maximum rainfall reached 2653 mm in 1973 at Tien Lang, and 2577 mm at Thuy Nguyen in 1973, 2271

mm in 1965 at Vinh Bao and 2298 mm at tien Lang in 1960 By contrast, the year

1991 obtained 826 mm at Phu Lien, and 493 mm was obtained in 1968 at Thuy Nguyen, 686 mm in 2007 at Vinh Bao and 637 in 1991 at Tien Lang

In the rainy season, the rainfall of August reaches highest proportion of 20.9 %

at Phu Lien in comparison with annual rainfall, and similarly 18.6% at Vinh Bao, 19.6% at Tien Lang and 20.7% at Thuy Nguyen The maximum rainfall of three months (from July to October) accounts for 50.3 to 53.9 % of yearly rainfall

In the dry season, the lowest rainfall in July only reaches 0.8 to 1% of yearly rainfall, minimum rainfall of three months (from December to February) accounts for 4.4% of yearly rainfall at Phu Lien, 4.7% at Vinh Bao, 3.9% at Tien Lang, 3.4% at Thuy Nguyen

Table 3.2 Typical average monthly rainfall at stations

Phu Lien station Vinh Bao station Tien Lang station Thuy Nguyen station

Month Average

(mm)

Proportion (%)

Average (mm)

Proportion (%)

Average (mm)

Proportion (%)

Average (mm)

Proportion (%)

Annually there are about 100 – 150 rainy days recorded in Hai Phong In the winter, there are about 8 to 10 rainy days in a month In the summer, there are normally 13 to 15 rainy days in a month Particularly, August has many rainy days and highest rainfall rather than others

• Wind and storm

- Wind: The average wind speed was obtained relatively 3.0 m/s at stations located in main land and reached 5 to 7 m/s at station located in Islands The wind direction in year changes and fluctuates toward the circulations Wind speed fluctuation depends

on high and distance from the sea level Annual wind speed reaches from 33 to 35 m/s appearing mainly in typhoon season (July, August and September) The maximum wind speed, which recorded on September 9th 1968, was 50 m/s

Table 3.3 Typical monthly average wind speed (m/s) at three stations

as livelihoods Rainfall caused by storms accounts for high rates of total yearly rainfall (about 20 – 30%), especially storm rainfall accounts for 50 – 60% of total rainfall in August Once typhoons come to the land, wind speed would be very strong and high Average wind speed during typhoons normally is 30 – 40 m/s, maximum value could

be reached 50 m/s

3.1.3 Hydrological characteristics

There are 9 hydrological stations located in Hai Phong City Trung Trang and Cua Cam are classified as “level 1” stations However, total flows on Hai Phong’s river systems are originated from Red, Thuong, Luc Nam and Cau Rivers, which are tributaries of the Hong – Thai Binh river system These flows are transferred through

Duong and Luoc river to Kinh Thay and Thai Binh Rivers So the flow regime of rivers in Hai Phong is pretty similar to the upstream rivers

Annual flow distribution:

Flows are distributed unequally in a year The flows in the study prolong from Jun to October, and account for 80% of total flows The flows in August are maximum, accounts for 24% of total flows Minimum flow usually appears in March accounting for 1 – 2,3% of total flows The flood season spreads in five months However, the amount of water in this season accounts for 80% of total flows The dry season spreads

in seven months accounting for 20% of total flows

Flood flows:

The downstream area of Thai Binh river has been affected by flooding from the Duong and Luoc rivers originated from the Red river, Cau, Thuong, Luc Nam rivers and depended on the tidal regime of the East sea as well as the topographic conditions

of downstream rivers

- Duong River is one of the tributaries of Red River Duong River transfers water from the Red River to downstream rivers surrounding Thai Binh River System Therefore, the characteristics of Duong River are similar to the Red river Flood pattern of Duong River and Luoc River is the same hydrograph of Red River with smaller flood amplitude

- Luoc River: amount of water from the Red River is transferred to Luoc River accounting for 1/5 to 1/3 of water of the Red River, which is diverted to Duong River Maximum annual average discharge of Luoc River measured at Trieu Duong station is approximately 1,650 m3/s, equals 83% of Red river’s discharge measured at Son Tay Station Luoc River has small slop The river bed of this river is shallower and narrower than Duong River, so that water from the Red river is diverted slightly A segment of Thai Binh river system from Ro sluice to the sea has been deposited progressively That leads to flood water from Luoc and Thai Binh mostly flowing to Van Uc River

- Cau, Thuong and Luc Nam Rivers are upstream rivers So they have various characteristics of flooding compering with the Luoc and Duong Rivers The flood season normally prolongs from the beginning of Jun to the end of September, 1 month earlier in comparison with the Red river Due to the small river basins, a short heavy rain event can even cause a large flooding

In the Red river basin, there are some highest rainfall places surrounding Phai Lai (300 to 500 km) In the Thai Binh river system, the highest rainfall places are quite close to Phai Lai (50 to 150 km) So that, flooding from Cau, Thuong and Luc Nam rivers usually reaches Pha Lai earlier than the Red River The years that extreme flooding happened also coincided with the years of extreme flooding happening in three tributaries of Thai Binh river (1968, 1971 and 1996) This proved that the Red river and Thai Binh River have the same climatic pattern causing rain events

The dry flow:

The flow in the dry season is only supplied by groundwater and surface water

as well as retention water, which are stored in the end of wet season On the other hand, most rivers here are nearby the sea, so the dry flow is depended on the tidal regime mostly In the recent years, due to the operation of Thac Ba Reservoir (Chay river), Tuyen Quang Reservoir (Lo River), Son La and Hoa Binh Reservoirs in Da River, the dry season flow in the Red River is increasing significantly This is helpful and necessary for agricultural development

The flows in Cau and Thuong Rivers in the dry season are mostly stored by Thac Huong and Cau Dom weirs So that, the flow from Thai Binh to Pha Lai is relatively small Behind Pha Lai, due to the water diversion from the Red River, Thai Binh River gets more water discharge

The discharge of Duong and Thai Binh has been increasingly developing due to the water diversion from upstream reservoirs in Da River as well as river bed change Therefore, water supply and salt intrusion prevention at the downstream of Thai Binh River have been improved also

Water from Duong River is the main source supplying for the downstream rivers of Thai Binh River system Amount of water measured at Thuong Cat in the dry season accounts for 66% - 80% of total water in dry season of Thai Binh’s downstream rivers Similar to the Red river, the dry season normally prolongs 7 months, from November to April of the following year

Water resources of Luoc River: the Red River’s water, which is transferred to the downstream rivers through Luoc River, is relatively not much, only accounting for 30% of Duong at Thuong Cat In the dry season, severe tidal fluctuation from Ba Lat moves back to the upstream that keeps fresh water in river bed longer So, that is the reason why water diverted from the Red to Luoc Rivers is always available

Cau, Thuong and Luc Nam Rivers supply a small amount of water for the downstream area of Thai Binh The dry season in those rivers spreads normally longer than the Red river within 8 months, from October to May of following year Total water of three rivers is only 1/3 of Duong River The seasonal distribution of flow of these rivers is unequally and dry flow is mainly supplied by ground water due to severe evaporation

Average water level above sea level of rivers passing Hai Phong City is slightly fluctuating The highest average water level was measured in Van Uc River at Trung Trang (0.58 m), the lowest average water level was measured in Lach Tray River at Kien An (0.01) Therefore, the lowest water level causes troubles for water intake of irrigation system

3.1.4 Tide and tidal effects in the river mouth

The influences of tidal regime play an important role in studying the coastal areas According to the tidal classification, tidal regime in the Northern part of Vietnam is mainly 24 hours changing from 1.9 to 2.6 meters From 1972 to 1990, the tidal amplitude is 1.92 meters The shape of river mouths depended on tidal regime and waves of rivers The estuaries in the northern part of rivers have triangle shapes due to tidal force In the northern part, river mouths have U shape Both tide and waves impact on formation of river mouths (Pruszak et al., 2005) Tidal regime plays

an important role in water exchange and sediment transport at estuaries (Allen et al., 1080; Dyer 1986 and Sassi et al., 2011)

Due to the estuaries reaching the Gulf of Tonkin, water level fluctuation at the estuaries is usually similar to tidal fluctuation of the Gulf The tidal regime here is daily tide, and huge amplitude, which is one of the large amplitudes in Vietnam In one day, a tidal peak and tidal foot appear with the amplitude of 3.5 to 4.0 meters The strong tidal period is 11 hours and weak tidal period is 13 hours The strongest tide and standing tide normally appear in 15 days In the strong period of tide, flows on the Red and Thai Binh River are affected by the Gulf of Tonkin’s tide Particularly, the dry season is affected mostly rather than the wet season Tidal peaks in the dry season usually penetrate deeply inside rivers, about 150 km long and 50 to 100 km in the wet season

The average tidal water level is normally highest in the beginning of dry season from November to December, maximum value in October and minimum value at the end of January to April, particularly in March The magnitude of declined tidal regime reaches highest value in December and lowest value in March and April The maximum amplitude was 3.94 m occurring in 23 Dec 1968

3.2 Water Demand

The study area includes Tien Lang and Vinh Bao districts The fresh water is supplied for many purposes such as agriculture, aquaculture, industrial zones and domestics

3.2.1 Water Demand for Agriculture

Water demand for agriculture is mainly supplied for cultivation, and a small amount of water is for livestock demand Water supply for agriculture consists of two types of systems such as water storage and gravity Water demand for agriculture is extracted from surface water of upstream rivers transferring through irrigation system Based on the investigation of division of Agriculture and Rural development, water for cultivation and livestock is determined as the following table:

Table 3.4: Total water used for cultivation and livestock in year 2012

Source: Hai Phong PCC, 2015

The period of 2020 and 2030:

Table 3.5: Water demand of cultivation in period of 2020 and 2030

Unit: 10 6 m 3

2020

Vinh Bao 5.28 24.52 14.48 16.51 10.57 18.12 7.61 9.28 3.88 2.61 0.07 3.13 116.05 Tien Lang 4.13 18.41 8.81 10.85 4.55 12.06 10.96 5.56 3.58 0.93 2.63 3.11 85.60

2030

Vinh Bao 3.74 15.20 9.02 10.29 6.62 11.23 4.73 5.73 2.46 1.91 0.08 3.04 74.04 Tien Lang 3.01 11.42 5.50 6.78 2.88 7.48 6.78 3.46 2.25 0.58 2.67 3.16 55.98

Source: Hai Phong PCC, 2015

Table 3.6 Water demand of livestock in the period of 2020 and 2030

Source: Hai Phong PCC, 2015

3.2.2 Water Demand for Aquaculture

Surface water from irrigation system is only used for aquaculture Water supply from Tien Lang accounts for large proportion with nearly 66 million cubic meters (37.6%)

Total water supply for aquaculture is over 175.3 million m3 Water supply for aquaculture is only 27.1% in comparison with cultivation and livestock

Table 3.7 Water demand of aquaculture in 2012

Unit: 10 6 m 3

Source: Hai Phong PCC, 2015

In the period of 2020 and 2030

Table 3.8 Water demand of aquaculture in the period of 2020 và 2030

Unit: 10 6 m 3

2020 Vinh Bao 0.12 5.62 6.67 6.58 6.36 6.83 0.42 0.19 0.13 5.96 5.92 5.92 50.71 Tien Lang 0.22 10.71 13.80 13.39 13.23 14.32 0.83 0.36 0.25 11.36 11.26 11.26 100.99

2030 Vinh Bao 0.07 3.50 4.15 4.09 3.96 4.25 0.26 0.12 0.08 3.71 3.68 3.68 31.55 Tien Lang 0.14 6.66 8.58 8.33 8.23 8.91 0.51 0.22 0.15 7.06 7.01 7.01 62.82

Source: Hai Phong PCC, 2015

3.2.3 Water demand for industry

In the Tien Lang and Vinh Bao areas, there are two industrial zone including Vinh Niem (14,5 ha) and Tien Lang (139,39 ha) Water supply for industrial zones in Hai Phong city was planned in details

Table 3.9 Current status of water use of industrial zones

No Industrial zones Area (ha) Volume (m 3 /day)

Source: Hai Phong PCC, 2015

3.2.4 Water Demand for Domestic

Water supply for domestic is currently from intake sources of irrigation systems and groundwater constructions Surface water is the main source of water supply in

these areas Ground water for domestic is taking a small amount and inclining extremely due to the water table subsidence and salt intrusion

Table 3.10 Water supply for domestic in Tien Lang and Vinh bao districts

(people)

Source: Hai Phong PCC, 2015

In the period of 2020 and 2030:

Table 3.11 Water demand of domestic in the period of 2020 and 2030

Unit: 10 6 m 3

2020 Vinh Bao 0.90 0.81 0.90 0.87 0.90 0.87 0.90 0.90 0.87 0.90 0.87 0.90 10.60 Tien Lang 1.18 1.07 1.18 1.14 1.18 1.14 1.18 1.18 1.14 1.18 1.14 1.18 13.91

2030 Vinh Bao 1.55 1.40 1.55 1.50 1.55 1.50 1.55 1.55 1.50 1.55 1.50 1.55 18.29 Tien Lang 2.18 1.97 2.18 2.11 2.18 2.11 2.18 2.18 2.11 2.18 2.11 2.18 25.68

Source: Hai Phong PCC, 2015

3.3 Water Exploitation and Utilization Issues

Management and operation of the system:

The hydraulic works of the irrigation system was built since 1970s, 1990s and 2000s The human resources for system operation is too large and unproductive The staffs for management and operation are 100 up to 200 people for each system The equipment of systems is too old and backward as well as is not suitable for management requires Lack of information of water level and salinity, etc in order to serve the operation and management of the systems

Infrastructures:

The hydraulic works have not been maintained, and repaired regularly, so that water intake is not productive and effective In addition, due to the urdimentary method of operation processes, so the systems are not running 100 percent Besides,

the canals, chanels and streams in these areas have been deposited and penetrated progressively causing unproductive water transfer

Water storage:

Although, the income water in the study area is very huge, but most rivers have high sediment volume, or salt intrusion problems Therefore, water here cannot supply for socie-economic demands It is only used for other purposes such as navigation, transportation and tourism Water supply for socio-economic development is mainly extracted throughout 5 irrigation systems At some points in months and days, the water level is very low causing the gravity system is not working So that, the pumping stations are used for water intake On the other hand, the river bed is occupied by local people leading to decreasing water storage of rivers

Water quality:

Due to the location of rivers in the study area, most river here are progressively affected by salinity intrusion 1‰ of salinity appears mostly on the hydraulic works within 10 hours/day and 10 days/month Alternatively, the turbidness of rivers is very high Average turbidness is approximately 15 NTU This will probably reduce the capacity of water supply of the systems

The chapter presents the natural conditions, climatic characteristics of the study area as well as the population characteristics, economics and society The water demand and management are also discussed in this study Although, the income water in the study area is very huge, but Thai Binh river has high sediment volume, or salt intrusion problems So, water here cannot supply enough for socie-economic demands

4 METHODOLOGY

In this study, according to the research objectives, the methodology consists

of data collection survey, filed work and modelling The method of data collection survey and method of field work will conduct the objective 1 Meanwhile, Objective 2 and 3 will be obtained by the method of modelling

The methodology used in this study will be expressed in detail as the below flowchart:

Figure 4.1: The research flowchart

To collect and process the available documents

To implement Field surveying from detailed plan

To analyze and process

database

Building information systems

Writing the report

Method of fieldwork

Method of Modelling

4.1 The MIKE 11 Model

The MIKE 11 model uses an implicit and finite differential mathematical scheme to compute unsteady flow in rivers and floodplains “In the model, a river network is simulated like a system of storage tanks that are connected by channel sections Such a simulated storage tank is called a node and a channel section joining two nodes is called segment.” (Dang, 2010, p.106)

Following assumptions were considered for the modeling (DHI, 2007a)

The water is incompressible and homogeneous (i.e., negligible variation in density) The bottom slope is small, thus the cosine of the angle it makes with the horizontal may be taken as 1 The wave lengths are large compared to the water depth, assuming that the flow everywhere can be assumed to flow parallel to the bottom (i.e., vertical accelerations can be ignored, and a hydrostatic pressure variation in the vertical direction can be assumed)

The flow is sub-critical (a super-critical flow is modeled in MIKE 11; however, more restrictive conditions are applied)

4.1.1 Governing Equations

Mass and momentum conservation equations are used for the mathematical expression of gradually varied, unsteady flow in open channels Two governing equations for unsteady open channel flow are well known as Saint Venant’s equation system The model was developed based on these principles It uses the unsteady free surface flow equations of continuity and momentum to find the discharge and water level in each cross-section

The continuity equation or mass conservation equation is:

The momentum equation is:

Where Q = discharge in m3/s; A = cross sectional area in m2; t = time in seconds; x = distance along the longitudinal axis of water course; q = lateral inflow in (m3/s/m); h = water level above datum in m; C = Chezy roughness coefficient in

R = hydraulic radius in m; α = momentum distribution coefficient in s2

/m3; g = gravitational acceleration in m2/s

Mike 11 model solves Saint Venant’s equation for each channel segment, which

is considered as basic finite difference elements For this study, continuity and momentum equations were solved numerically using an implicit finite difference known as the six-point Abbott scheme These equations are simultaneous, quasi-linear, first-order, partial differential equations of the hyperbolic type The transformation of these equations into a set of finite difference equation is performed in a computational grid involving altering Q and H points Q point are always placed midway between two adjacent H points, while the distances between the H points may vary

“A simulated segment linking two nodes possesses average geometric and hydraulic characteristics of the actual channel section A frictional co-efficient and inertial force exists between two nodes of a river segment Inflow and outflow of the node control the storage in a node A positive (+) sign and a negative sign are implied for inflow and outflow respectively Nodes are coded by positive integers from 1 to

NN which is total number of nodes in the river network The constraint equations at the confluence of river tributaries are defined as follows:” (Dang , 2010, p 107)

4.1.2 Methods used in the performance evaluation

The level of accuracy and reliability of the model depend on the assessment of the model performance Both graphical and statistical comparison between simulated and measured hydrographs are recommended by American Society of Civil Engineers (ASCE, 1993) The MIKE 11 model provides both graphical and numerical performance evaluation Firstly, in order to assess the model performance evaluation,

graphical comparisons between modeled and measured hydrographs were done For the statistical assessment, this study followed on evaluation of Nash-Sutcliffe efficiency (Nash & Sutcliffe, 1970) The equation of Nash-Sutcliffe efficiency is:

NSE = 1 – Equation 4.5 where:

: the observed data

: the average observed data

the simulated data

n: sample size

The value of NSE lies between - to +1 The value 1 indicates a perfect match between measured and simulated data Model performance is perfect, if values of Nash-Sutcliffe efficiency range from 0.9 to 1 Model performance is good and acceptable, if the values range from 0.8 to 0.9 and 0.6 to 0.8

4.2 Mike 11 Model Set-up

Within the scope of the thesis study, the author has inherited the input data from the National Key Laboratory of River and Coastal Engineering and Institute of Vietnam Academy for Water Resources Through Modeling calibration Modeling validation, the author will define a complete model parameters to simulate the flow regime of the study area

4.2.1 Input data

4.2.1.1 River network and model schematization

The Red and Thai Binh river system is a very complicated network with many large basins such as Da, Thao, Lo rivers in the upstream; and huge river delta in the downstream as well as dense river intensity The Red River is connected with Thai Binh river system by Duong and Luoc rivers The Red River’s flow reaches to the