Major Intergrated water resources Management: Impact assessment of regulation works in the Thai Binh river downstream

In this study, the MIKE 11 model was used to simulate therecent status of the system and prediet the water distribution according to someproposed scenarios based on the system operation

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURALDEVELOPMENT

IMPACT ASSESSMENT OF REGULATION WORKS

IN THE THAI BINH RIVER DOWNSTREAM

Nguyen Vinh Nguyen MSc Thesis on Integrated Water Resources Management

November, 2017

XMINSTRYOEEDLCXHONANDTRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT

‘THU ITY

Nguyen Vinh Nguyen

‘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

Thereby certify that the work which is being presented in this thesis entitled, “Impactassessment of Regulation works in the Thai Bình river downstream” in partialfulfillment 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 super

Van Quan

ision(s) of Assoc Prof Dr Nguyen Mai Dang and Assoc Prof Dr Ngo

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

Date: 19/11/2017Signature

Nguyen Vinh Nguyen

‘The Thai Binh River System's downstream is a major economic region whieh islocated in the Red River Delta including Hai Phong city and Thai Binh province.Currently, water distribution here is significantly unreasonable for the downstreamwater stakeholders,

‘Therefore, a research regarding current water allocation assessment need andhhas (© be conducted in order to find out appropriate solutions for solving andsurmounting the issues In this study, the MIKE 11 model was used to simulate therecent status of the system and prediet the water distribution according to someproposed scenarios based on the system operation in the future

‘The study determined the existing problems and troubles in water distributionand water use in the Thai Binh River downstream, Accordingly the impact ofstructural measures proposed in this study on flow changing also was analyzed indetails, In addition, the study ilustrated thatthe flow discharge of rivers in the systemwill be changed significantly after building the regulated structure works In addition,

the study proposed some alternatives aiming to strengthen the management of sy

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

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

me during my master th research Thanks for their support, encouragement and

‘guidance that allowed me to complete this tudy in time

Especially, I would like to express my appreciation to Assoc Dr Nguyen MaiDang and Assoc Dr Ngo Van Quan for their unlimited encouragement, guidance,comments and technical supports as well as the thesis writing process from thebeginning of this thesis research,

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

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

1 would like to give my appreciation to Dr Ho Viet Cuong, Mse Nguyen ThiNgoc Nhan, Msc, Nguyen Van Bach and Mr Phan Van Thanh who was willing tohelp me with modelling application in the thesis

1 also would like to thank the National Key Laboratory of River and CoastalEngineering and Institute of Vietnam Academy for Water Resources for theirinformation and useful data input

Last but not Lwant to take this opportunity to show my appreciation to myfamily, friends for their inspiration and support throughout my life; this research issimply impossible without you,

3.1 Description of the study area.

3.1.1 Geography and River Network 183.1.2 Climatic characteristics 203.1.3 Hydrological characteristics 233.1.4 Tide and tidal effects in the river mouth 263.2 Water deman

3.2.1 Water demand for agriculture 23.2.2 Water demand for aquaculture 283.2.3 Water demand for industry 293.2.4 Water demand for domestic 293.3 Water exploitation and utilization issues.

4 METHODOLOGY,

41 The MIKE 11 Model

4.1.1 Governing Equations 334.1.2 Methods used in the performance evaluation 344.2 Mike 11 Model Set-up.

4.2.1, Input data 354.2.1.2 Boundary conditions 374.2.1.3 Cross-sections 38

4.2.1.4 Meteorological and hydrological data 394.3, Modeling calibration

43.1, Step by step

4.3.2 Initial conditions setup 404.3.3 Calibrating the hydraulic parameters 404.3.4, Modeling calibration in flood season ái

4.4.1 Modeling validation in flood season 484.4.2 Modeling validation in dry season

4.5 Proposed regulation works and scenarios

4.5.1, Proposed regulation works

4.5.2, Simulated Scenarios 5ã

5 RESULTS AND DISCUSSIONS

$1 Scenario results simulated in August 1996

5.2 Scenario results simulated in January 200%

6 CONCLUSIONS AND RECOMMENDATIONS ss 726.1 Conelusions

6.2 Recommendations for further researches

APPENDIX

List of figure

Figure 1.1 Thai Binh River downstream area 8Figure 2.1 Simulation interface file of Mike 11 (HD Module) 15Figure 3.1: Map of the study area focus on two districts: Vinh Bao and Tien Lang 18Figure 4.1: The research flowchart 32Figure 4.2: Schematic of network and reservoirs considered in the Red River basin 36Figure 4.3: River network for simulation by Mike 11 model 37Figure 4.4 Model calibration process 39Figure 4.5: Hydraulic parameters interface 4Figure 4.6: The observed and simulated water levels for the 1996 flood event at HaNoi station in the case of calibration 4igure 47: The observed and simulated water level in Van Uc River in 1/2006 —

‘Trung Trang Station 45igure 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 48Figure 4.10: The observed and simulated hydrographs at Ha Noi Station in January

2007 49Figure 4.11: The observed and simulated hydrographs at Tra Ly Station 50

in January 2007 50Figure 4.12: Structure of the regulated dam in Moi River 52igure 5.1 The locations of selected cross-sections 4igure 5.2 Actual water level atthe selected points 55Figure 5.3 Actual discharge at the selected points 55Figure 5.4 Simulated water level of PAL 56Figure 5 5: Simulated discharge of PAL 56Figure 5.6: Simulated water level of PA2 5Figure 57 Simulated discharge of PA2 5Figure 5.8: Simulated water level of PAS 58Figure 5.9: Simulated discharge of PA, 58Figure 5.10: Simulated water level of PAL+2 59Figure 5.11: Simulated discharge of PA 142 59Figure 5.12: Simulated water level of PA1+3 60Figure 5.13: Simulated discharge of PA +3 60

Figure 5.14: Simulated water level of PA 1+2+3.

Figure 5.15: Simulated discharge of PA 1+2+3

Figure 5.16: Actual water level at the selected points

Figure 5.17: Actual discharge at the selected points

Figure 5.18: Simulated water level of PAL

Figure 5.19: Simulated discharge of PAL

Figure 5.20: Simulated water level of PA2

Figure 5.21 Simulated discharge of PA2

Figure 5.22: Simulated water level of PA3

Figure 5.23: Simulated discharge of PAS

Figure 5.24: Simulated water level of PA1#2

Figure 5.25: Simulated discharge of PAL+2

Figure 5.26: Simulated water level of PA 1+3

Figure 5.27: Simulated discharge of PA1+3

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

Figure 5.29: Simulated discharge of PAL+2+3

61616262636364 6466666667616868

List of table

Table 2.1 Comparison of different One-Dimensional (1D) models 12Table 3.1, Monthly average temperature of the year at stations 21Table 3.2 Typical average monthly rainfall at stations 2

‘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 29Table 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 39Table 4.2: Calibrated Manning values of the river system 4đTable 4.3: Model performance of the MIKE 11 for the calibration at some siations 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 47Table 4.6; Error criteria of the model calibration in the 2002 flood event at somestations 49Table 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 PAI 56Table 5.2 Comparison between actual and simulated flows of PA2, 5 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 PAI+3 60

‘Table 5.6: Comparison of actual and simulated flows of PAL+2+3 6

‘Table 5.7 Comparison of actual and simulated flows of PAL 68Table 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 PAL+2 66

‘Table 5.11 Comparison of actual and simulated flows of PA 1+3 6

‘Table 5.12 Comparison of actual and simulated flows PA1+243 68

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 activitiesdemand and need fresh water Fresh water is extremely essential for lives; no othernatural resources can replace it This meant that water has a high potential use forhuman (Zaag & Savenije, 2013),

Nowadays, people have been using water resources in negative way.

Accordingly, water quality and quantity are both declining significantly There aresome reasons for this statement including the effects of natural conditions, climatechange, economic and social development, over exploitation of natural resources as

‘well as the poor management oflocal authorities,

Water crisis has been increasing and affecting widely all over the world It isabout L2 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 iscaused by natural phenomena and human activities Fresh water is availableeverywhere in our planet and much enough for human However, fresh water isdistributed unevenly and overused tremendously on the world, In addition, fresh waterhas been polluted for decades by many polluted sources duc to economic development.Unsustainable development also is one of the reasons for water crisis (FAO, 2007)According (0 plenty of water institutes, 1/3 countries in the world are facing withwater 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 watersources which are considered as external water resources, Accordingly, total annual

fr

‘water volume is about 830 bil m the biggest fet systems Total potential

‘groundwater amount is about 63 billion m’ 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 andlarge scale water shortage occurred regularly in many provinces Vietnam currentlyhas many challenges regarding water resources management, In addition, Vietnam isranked 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 ofpopulation 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 differentstakeholders even exaggerates the issue Besides, erosion and sediment deposition arehappened more frequently on many river systems, These phenomena influencesdirectly 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 beconsidered is sediment deposition at downstream areas of river system In the northernpart of Vietnam, which includes Red and Thai Binh rivers, sediment depositionhappening 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 andmanagement such as hydrological forecasting, reservoir operation, water qualitresearch on flood, inundation and drought, designing irrigation system and supportingfor the integrated water resources management An appropriate model selection isntial for each research project These selections thereby have to be based on studyobjectives, 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 solveproblems 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, irigation system, channels and others bodies

“enarios and alternatives of(DHI 2011) This model will be used for simulation of

proposed management

1.2 Problem statement

pone

“THAI mint

Figure 1.1 Thai Binh River downstream area,

‘According to the report of Hai Phong Department of Agriculture and RuralDevelopment, In the Thai Binh River's downstream, salt intrusion at river mouths isincreasingly happening because of the natural water distribution and sediment (Luoeriver moving and developing on the left side of Van Ue River - Figure 1.1), Thai BinhRiver's downstream has been deposited by sediment since 1960 The average depth ofriver bed is fluctuating from I to 2 meters

Besides, the water resources management here is causing a lot of negative impact onwater 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 agriculturalareas as well as water demand would be increased significantly,

at Do Son Beach due to the

In addition, sediment transport is currently increasi

water diversion to Van Uc River leading to amount of sediment flowing to the seaThis 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 thedownstream of Thai Binh River by using hydrodynamic model To achieve the mainobjectives, the thesis consists of some detailed goals as follows:

+ Analyzing and assessing the current status of the study area in accordancewith problems and troubles,

+ Using the MIKE 11 to simulate the flow regimes according t0 proposedsolutions 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

Bình river's downstream located in Hai Phong province Main purpose of theConstructions 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 Bình river as well

+ Proposing solutions for water allocation, water usagee, water management in

‘order o enhance the quality of water use in the study area,

1.2.8 Thesis overview

‘Structure of the thesis includes those parts:

Chapter 1: Introduction, presents problem statement, needs of study, researchobjectives, and overview of the study area

Chapter 2: Literature review, reviews the previous studies related to the contentand 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 characteristies of the study area as well as the population charactereconomics and society The water demand and management are also discussed in thisstudy

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

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

Chapter 5: Results and discussions, analyses the model performances (MIKE11) in order to obtain the research objectives

Chapter 6: Cconclussions and recommendations, focuses on findings andrecommendations, and future research

In this chapter, existed issues, needs of study, research objectives were beshowed, 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 saltintrusion and Van Uc river has the erosion

2, LITERATURE REVIEW

2.1 Over -w 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, Tohave a better understanding of the processes of hydrology, they can be deseribed inlaboratories by physical models Besides that numerical models have been developedincreasingly due to their advantages such as costs flexibility and applied technology.Accordingly, hydraulic and hydrological models are tools to address the realhydrological cycle in a simplified way Such models are used for understanding thehydrological processes as well as making hydrological predictions in cases where

‘water resources management and utilization activities are implemented The modelsapply several algorithms to provide a quantitative relation between the input data (e.grainfall, meteorological data) and output (e.g runoff) The hydrodynamic models havebeen used for energy production, sediment transportation, water quality andcavironment, Scientists have developed many ID, 2D and 3D dynamic models Thosemodels 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 inestuaries is normally difficult due to the fluctuation of sediment and impacts of othernatural factors The s sdiment transportation process on rivers is relatively complicatedincluding erosion process, sediment transport and deposition Those processes relate t0flow regimes, particles characte ies, size and shape, and intensity and elements ofthe particles The morphological changes are the results of the nonlinear interactionbetween water and sediment and river bed (Hibma et al, 2004), However, numericalmodels are used as valuable tools for simulation of natural phenomena due to thedevelopment of technology in the past decades in order to get a better understanding of

013)

physical processes and numerical technique (Jiang, Ranasinghe & Cowell

in

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 havebeen considered aiming to obtain an appropriate model The selected model need to beconsidered with many factors such as management, variables and main process, dataavailable, and input and proposed solutions (Boorman et al., 2007) Hence, the inputdata of various models have to be collected aiming to get best understanding ofadvantages and disadvantages of them before the model application, Table 2,1 showsthe comparison of different hydrodynamic models,

Eventually, according to the author's knowledge, natural conditions of the studyarea and available input, MIKE I1 model was selected as an effective tool forachieving the research study

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

Model [SWAT (Amoldet | MIKE TL HEC-RAS TRE

al,, 1995; Ndomba | (Doulgeris et al, | (Pappenberger et | (Vanet al.,

&Gri 2012) al 2008) 2012)

Manag |SWAT model was | The Mike 11 model | HEC-RAS model is | ISIS is a fullcement | developed predict | isa software used forvariety | hydrodynamicissue | the impact of land | package for the | types of projects | simulator for

‘management simulation of flow, | suchas steady, | modeling

practices on water, | water quality, ‘unsteady and mixed | flows, water

sediment, and | sediment transport in | flow regimes The | levels in open

agricultural estuaries, rivers, | model is wed for | channels and

chemical yields in | channels and other | multiple purposes | estuaries.large and complex | water bodies,

watersheds,

Taput | -DEM “Hydrological “Reach neiwork | “Hydrological

Data | -Soil and land use | -Topographie Cross section “Cross

required | map “Cross section “Steady flow data _| Section’s

“Climate data “Meteorological | -Unsteady low | Geometry

“Hydrological data | Sediment “Sediment Sediment

sdiment load concentrationKey | The model is based | The model based | HEC-RAS modslis | The model isVariable | on the water fon Saint Venant’s | based onthe | based on one

And | balance equation | equation for continuity equation | dimensionalprocess | for the soil water | continuity and and momentum | Saint Venant’s

content ‘momentum equation | equation equations.

Model [SWAT (Amold et | — MIKEI HEC-RAS ISIS

al., 1995; Ndomba | (Doulgeris et al, | (Pappenberger et | (Van et al.,

‘&Griensven, 2012) „ 2005) 2012)

2011)

Key |= Waierquality | Discharge -Sưeam Flow “Runoif

output | -Stream flow Water level Water level Water quality

Surface runoff | -Water quality Sediment scour | -SedimentSediment yield | -Sediment transport_| and deposition

Time | Dailytime step | Sec, Minute, Hourly | Minute, Hourly, | Minute

Step and daily time step | Dail Hourly: Daily

‘Access [The user can | The user has lo pay | The user can access | The users can

bility to | access to modify | to use the model and | to modify the code | access freely

the the code of the | accesso the code, | of the model to the software

coding | model

Software |The SWAT model | This isnot open [IL is a_ public | ID component

cost | is free and a public | source software | domain and free of | as well asthe

domain software, | The model is very | charge from HEC’s | whole ISIS

bút ArcGIS expensive website 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 ID modelling packagecovering more application areas than any other river modelling package available.MIKE 11 is a fully dynamic, one-dimensional modelling package It includescomprehensive facilites for modelling complex river channel networks, lakes andreservoirs, 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 lowing users to define complex control strategies as well as dam breakstructures Additional application areas include, rainfall-runoff, flood modelling,ecology and water quality, real time forecasting and sediment transport and rivermorphology 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,

B

+ Flood analysis and flood alleviation design studies

+ Realtime 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 ferm asse fer 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:

+ Network editor *NWKIL

* Cross-section editor *XNSI

+ Boundary editor *.BNDIL

+ Time series files * DESO

+ HD parameter file HDI

+ Simulation editor *.SIML1

Figure 2.1 Simulation interface file of Mike II (HD Module)2.3, Applications of Hydro-dynamic Model

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

15

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 waterresources issues such as ID models (MIKE 11, HEC- RAS, etc ) and 2D models

(MIKE 21, TUFLOW, F 3D ) In Vietnam, especially the MIKE models have

‘gained popularity lately These packages have been developed by the DHI water andenvironment (Danish Hydraulic Institute), which is a global organization dedicated tosolving challenges in water environments worldwide There is the question is howmuch is modelling needed? Robyn Johnston and Vladimir Smakhtin illustrated thatmodelling needs to concentrate on uncertainties reports to assess the application ofmodel in reali for policy and management processes New inventions are needed forimproving quahiy and quantity of modelling (Johnston & Smakbtin, 2014) MIKE 11model is used to Tink the hydrodynamic progress and morphological changes (Wang,2014) This is a useful method for this study Numerical models are implemented bythe combination of hydrodynamic proc

update Jiang etal, 2013),

s, wave, sediment transportation and depth,

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

of salinity intrusion (Do Thi Bich, 2000); the effects of river bed change, water intakecapacity 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 (NguyenHuu Hue et al, 2016)

‘To simulate the flows, except MIKE 11, number of models have beenconsidered such as Q_SDM_BASIN_2014 (Dao Tan Quy, 2013), using 1-2D model toassess the effects of constructions on rivers on flow regime and salinity intrusion atestuaries (Luong Quang Xo, 2014) However, the model performances only showedthe 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 ThaiBinh river need to have available data and detailed conditions of study area In year2016,1 tia 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 willfocus 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 dryflow 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 thisresearch were be presented as well Unlike previous studies, the study used two sets ofparameters for the Mike model in the dry season and flood season Thespecificconditions of study area were be showed

17

3 STUDY AREA

3.1, Description of Study Area

4.1.1 Geographic Characteristics and River Network

Figure 3.1: Map ofthe study aca focus on two distrits: Vinh Bao and Tien Lang

‘The Thai Binh River is included over 275 km length and 11 branches and estuaries indownstream These branches transfer the entire flows from Thai Binh River to fourriver 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-Eastdirection, close to the borders of Quynh Phu District, Thai Binh Province in the Westdirection, Hoa river is a natural border defined from the conjunction of Luoe and ThaiBinh Rivers

+ Bound by the East sea in the East direction, bordered with Van Uc river in theNorth-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 Luoe rivers defined from the conjunction of Hoa and Luoe rivers to theconjunction of Moi and Van Ue Rivers,

‘Topography and geomorphology of Thai Binh River downstream are the results ofgeologic 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 northernpartis lowland terrace with hilly regions, the southem part is remained delta area,

The delta area has elevation fluctuating from 2.50 m up to 3.50 m and theclevation 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 largerivers 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 thehuge polders, mangrove forests or new economic areas such as Tran Duong, VinhQuang, Tien Hung, Dong Hung, Tay Hung,

‘The geographic characteristics of Thai Binh River downstream influence theflow 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 toRed ~ Thai Binh river system such as Luoe, 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 hydrologicalstations The river is then divided into wo tributaries including Thai Binh and Rang —Gua Rivers, A segment of Thai Bình tributary flows to Mia River, then merges withVan Uc Another segment of Thai Binh river right after Mia River is depositedstrongly 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 atributary of Luoc River However, the river bed of this segment has been deposited

19

tremendously and flood controlling capacity of this river is mostly zero Thai BìnhRiver, a segment from the conjunction of Moi River to the sea, has low velocity andhas been deposited by sediment, Currently, the river bed of this river is quite large butthe river depth is relatively shallow The river bed elevation changes from -1.00 mdown to -2.50 m, Due to the degradation of the river, the discharge of Luoe Riverflowing into this river is qui 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 Ue 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 isabout 43.5 km, average width of the river is approximately 500-800 m, and river bedelevation changing from -10.00 m down to -16.00 m The lowest point reaches -47.00

m where located nearby Moi River

Luoe 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 thị river istransferred to Moi and Van Uc rivers A segment of Luoc River passing Hai Phong haslength of 14 km, the average width of cross-sections here is 300 meters, bed elevationfuctuating frim -8.00 m down to -12.00 m, Luoe river plays a role as a natural border

‘of Vinh Bao (Hai Phong province) and Hai Duong as well as a main source of watersupply for Vinh Bao and Tien Lanh districts,

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

3.1.2 Climatic characteristies

“The study area is located in the southern part of Hai Phong city The topography ofthe area is mainly delta, Therefore, climatic and hydrologic conditions here have thecharacteristics 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 ot of rain, Winter season (North-east monsoon) is from

November to March of following year with cold temperature and less rain Maincharacteristics 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 cieuladon, annually thetemperature in Hai Phong is split into different seasons: hot summer has high

‘temperature of over 25°C, cold winter has lowest temperature of below 20°C Annual average temperature reaches 23°C, highest monthly average temperature reaches 29°C

in July at Hon Dau, Lowest monthly average temperature reaches 16.3 in January atPhu Lien, Maximum temperature, which was observed in Phu Lien and Hon Dau

respectively, was 41.5% in May ~ 1914 and 38.6°C in Jly-1985

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

Stations [1 jM [mm [iV [V [vt |VH[VHjIX X [XI |XH | Tot!PhuLien |I63 169] 194) 23) 265) 281 |284| 27.7 | 269 247|2L3|I79| 331HonDan [168] 168|192|228) 27/285] 29| 284|a76 253|223| 19| 236Bạch Long Vi | 168 | 166) 187/223 | 262| 28|287| 283/273 253|224|189| 233

© 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 totalrainfall happens in the dry season,

‘Annual average rainfall is approximately 1520 mm, The spatial distribution ofannual rainfall is not too different, Annual yearly total rainfall reaches 1677 mm atPhu Lien, and 1534 mm at Thuy Nguyen, 1544 at Tien Lang and 1514 mm at VinhBao, Yearly rainfall at the northern parts is normally higher than the southern partscaused by the directions and effects of typhoons and tropical low pressure once theyland deeply Hence, the maximum yearly infall is usually occurring in the years

Which affected by typhoons or tropical low pressure Typically, the maximum rainfallreached 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 ThuyNguyen, 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,196% 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 yearlyrainfall, minimum rainfall of three months (from December to February) accounts for4.4% 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 rainfallat stations

Phu Lien station | Vink Baostation | Tien Lang station | Thuy Nguyen stationMonth | AY€"@e | Proportion | Average | Proportion | Average | Proportion | Average | Proportion

Serainy season | — 8S sư 48 sĩ '5 dry season 15 16 15 B

Annually there are about 100 ~ 150 rainy days recorded in Hai Phong In thewinter, there are about 8 to 10 rainy days in a month In the summer, there arenormally 13 to 15 rainy days in a month, Particularly, August has many rainy days andhighest rainfall rather than others.

© Wind and storm

~ Wind: The average wind speed was obtained relatively 3.0 mis at stations located inmain 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

con high and distance from the sea level Annual wind speed reaches from 33 to 35 misappearing mainly in typhoon season (July, August and September) The maximum

‘wind speed, which recorded on September 9" 1968, was 50 m/s.

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

Stations [1 |H [m [wv [v jvi [vn[vmjix [x [xi [xm [NamPhutien | 34| 27) 27| 31| 33) a1| 32| 27| 28] 30| s0| 28) 30HonDaun | 4§| 46) 4a] 47| se] s7| 6| 47| 46} s[a9[ a7) 5BạchLongVi| S 77| 65] S9| 65] 68| 77] 59| 66| 77] §2| 78] 71

‘Typhoons and tropical low pressures: annually there are about 3 - $ typhoons ortropical low pressures landing into Hai Phong province (about 6 ~ 7 typhoons andtropical low pressures coming to Vietnam), Particularly, 1 or 2 typhoons or tropicallow pressures land directly and damage the infrastructures such as dikes, dam as well

as liv hoods 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 inAugust Once typhoons come to the land, wind speed would be very strong and highAverage wind speed during typhoons normally is 30 ~ 40 mís, maximum value couldbbe reached 50 ms

3.1.3 Hydrological characteristics

‘There are 9 hydrological stations located in Hai Phong City Trung Trang andCua Cam are classified as level 1” stations However, total flows on Hai Phong'sriver systems are originated from Red, Thuong, Luc Nam and Cau Rivers, which aretributaries of the Hong ~ Thai Binh river system These flows are transferred through

2B

Duong and Luoe river to Kinh Thay and Thai Binh Rivers So the flow regime ofrivers 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 toOctober, 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 accountingfor | — 2,3% of total flows The flood season spreads in five months However, theamount of water in this season accounts for 80% of total flows The dry season spreads

in seven months accounting for 20% of tata flows

Flood flows:

‘The downstream area of Thai Binh river has been affected by flooding from theDuong and Luce rivers originated from the Red river, Cau, Thuong, Lục Nam riversand 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 Floodpatlern of Duong River and Luoc River is the same hydrograph of Red River withsmaller flood amplitude,

~ Luoe River: amount of water from the Red River is transferred to Luoe Riveraccounting for 1/5 to 1/3 of water of the Red River, which is diverted to Duong River

‘Maximum annual average discharge of Luoe River measured at Trieu Duong station is

approximately 1,650 ms, equals 83% of Red river's discharge measured at Son Tay

Station, Luoe River has small slop The river bed of this river is shallower andnarrower 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 depositedprogressively That leads to flood water from Luoc and Thai Binh mostly flowing toVan Uc River

~ Cau, Thuong and Lue Nam Rivers are upstream rivers So they have variouscharacteristics of flooding compering with the Luoc and Duong Rivers The floodseason normally prolongs from the beginning of Jun to the end of September, 1 monthearlier in comparison with the Red river Due to the small river basins, a short heavyrain event can even cause a large flooding.

In the Red river basin, there are some highest rainfall places surrounding PhaiLai (300 to 500 km), In the Thai Binh river system, the highest rainfall places are quiteclose to Phái Lai (50 to 150 km) So that, flooding from Cau, Thuong and Lue Namrivers usually reaches Pha Lai earlier than the Red River The years that extremeflooding happened also coincided with the years of extreme flooding happening inthree tributaries of Thai Binh river (1968, 1971 and 1996) This proved that the Redriver 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 otherhhand, most rivers here are nearby the sea, so the dry flow is depended on the tidalregime mostly In the recent years, due to the operation of Thạc Ba Reservoir (Chayriver), Tuyen Quang Reservoir (Lo River), Son La and Hoa Binh Reservoirs in DaRiver, the dry season flow in the Red River is increasing significantly This is helpfuland necessary for agricultural development

‘The flows in Cau and Thuong Rivers in the dry season are mostly stored by

“Thác Huong and Cau Dom weirs So that, the flow from Thai Binh to Pha Lai isrelatively small, Behind Pha Lai, due to the water diversion from the Red River, ThaiBinh River gets more water discharge

‘The discharge of Duong and Thai Binh has been increasingly developing due tothe 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 BinhRiver have been improved also,

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

Water resources of Luoe River: the Red River's water, which is transferred tothe downstream rivers through Luoe River, is relatively not much, only accounting for30% of Duong at Thuong Cat In the dry season, severe tidal fluctuation from Ba Latmoves back to the upstream that keeps fresh water in river bed longer So, that is thereason why water diverted from the Red to Luoe Rivers is always available,

Cau, Thuong and Luc Nam Rivers supply small amount of water for thedownstream area of Thai Bình The dry season in those rivers spreads normally longerthan 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 ofthese rivers is unequally and dry flow is mainly supplied by ground water due to

severe evaporation,

Average water level above sea level of rivers pa ng Hai Phong City slightly

fMuctuating 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 atKien An (0.01), Therefore, the lowest water level causes troubles for water intake of

nigation system

3.14 Tide and tidal effects in the river mouth

‘The influences of tidal regime play a important role in studying the coastalareas According to the tidal classification, tidal regime in the Northern part ofVietnam is mainly 24 hours changing from 1.9 to 2.6 meters From 1972 to 1990, thetidal amplitude is 1.92 meters The shape of river mouths depended on tidal regimeand waves of rivers, The estuaries in the northern part of rivers have triangle shapesđúc 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 all,1080; Dyer 1986 and Sassi et al, 2011).

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

‘The average tial water level is normally highest in the beginning of dry seasonfrom November to December, maximum value in October and minimum value at theend of January to April, particularly in March The magnitude of declined tidal regimereaches 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 issupplied for many purposes such as agriculture, aquaculture, industrial zones anddomestics

3.2.1, Water Demand for Agriculture

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

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

Na Areas Water supply (10° mỉ)

Tien Lang system 124,995

Source: Hai Phong PCC, 2015

‘The period of 2020 and 2030:

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

Vink Bao | 1% [a] ow [wm] we [nn] a] om | om] | om] wo] Am

Tien Lang | MỊ | n@ | s@ | om | 3M | | em | | os [os | ow) ae) 83

Source: Hai Phong PCC, 2015

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

Unit: Lm”

‘Areas | 1 |Th2jTh3|Th4|Th5 Th6|Th7|ThS|Th9jThI0|ThI|ThI2] Tông

2020Vinh Bao [9BI]0IS|0BI|OiS]0, otis [ost [aust [ans] tốt | ane | 0BỊ | 178Tien Lang [arss) aro) ors [orm [orss) w1a9]orss [ors] wiay) 133 | 01 | o1ss | 150

2030Vinh Bao [ois [aie] on [ons [arm] ars] ors [ai] ans] on [ons | one [ 2p

‘Tien Lang [019] 0H, 018 [oist | ois), ist] o1s9 jars] wisi) 069 | 05 | 01s» | 1x72

Source: Hai Phong PCC 2015

3.2.2 Water Demand for Aquaculture

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

Total water supply for aquaculture is over 1753 million mẺ Water supply foraquaculture is only 27.1% in comparison with cultivation and livestock.

‘Table 3.7 Water demand of aquaculture in 2012

Unit: 10% mề

No Areas Water supply

1 Vinh Bao | 65,929

2 Tien Lang 22,631

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

Tien Lang |014| 666 | 838 [833 | $25 | 891 [0.51 [0.22 0.15] 706 | TÔI | 701 | 62.82

Source: Hai Phong PCC, 20153.2.3, Water demand for industry

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

‘Table 3.9 Current status of water use of industrial zones

No | Industrialzones Area (ha) Volume (m*/day)

these areas, Ground water for domex is taking a small amount and incliningextremely due to the water table subsidence and salt intrusion,

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

Dig well | Bored wells Tanks NM

SN | SL | §N | SL | SN_| (people)

No | Distriet | Total

156482 | 1934 | 2.100 32782 109715 3428 | 9335 | l6183

130466 | 1289 | 1.703 | 27.653) 92.904 | 3.173 (10133) T396,

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: In

An | 1]2]3)4)5|6|7|8|9| |u| 12 [Tow

220Vinh Bao [090] 0.81 [090 [0.87 [0.90 [0.87 [0.90 [0.90 [0.87 | 090 | 0.87 | 090 [10.60Tien Lang |LI|L07|118)114)118|114|118|118|LHM]|LI8 [LH [ t8 [ison

2030Vinh Bao [155] 1.40] 155] 150) 155] 150] 155] 155] 150] 135 155 [1829Tien Lang |213|197|218,211/218|211|218|218|211| 218211 | 218 |2568

Source: Hai Phong PCC, 20153.3 Water Exploitation and Utilization Issues

‘Management and operation of the system:

‘The hydraulic works of the irrigation system was built since 1970s, 1990s and2000s, The human resources for system operation is too large and unproductive Thestaffs for management and operation are 100 up to 200 people for each system Theequipment 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 toserve the operation and management of the systems

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

Water storage:

Although, the income water in the study area is very huge, but most rivers havehigh sediment volume, or salt intrusion problems Therefore, water here cannot supplyfor socie-economic demands It is only used for other purposes such as navigation,transportation and tourism Water supply for socio-economic development is mainlyextracted 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 pumpingstations are used for water intake On the other hand, the river bed is occupied by locapeople leading to decreasing water storage of rivers

Water quality

Due to the location of rivers in th study area, most river here are progr sivelyaffected by salinity intrusion 1% of salinity appears mostly on the hydraulic workswithin 10 hours/day and 10 days/month Alternatively, the turbidness of rivers is veryhigh Average turbidness is approximately 15 NTU This will probably reduce thecapacity of water supply f 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 demandand management are also discussed in this study Although, the income water in thestudy area is very huge, but Thai Bình river has high sediment volume, or saltintrusion problems, So, water here cannot supply enough [or socie-economic demands,

31

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

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

‘The methodology used in this study will be expressed in detail as the belowflowchart

To collect and process the — “4 Method of data available documents collection survey

Objective 3 «—| Building information systems

‘Writing the report

Figure 4.1: The research flowchart

4.1 The MIKE 11 Model

The MIKE 11 model uses an implicit and finite differential mathematicalscheme to compute unsteady flow in rivers and floodplains “In the model, a rivernetwork imulated like a system of storage tanks that are connected by channelsections, Such a simulated storage tank is called a node and a channel section joining

‘wo nodes is called segment.” (Dang, 2010, p.106)

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

The water is incompressible and homogeneous (i-., negligible variation in density)

“The bottom slope is small, thus the cosine of the angle it makes with the horizontalmay be taken as 1 The wave lengths are large compared to the water depth, assumingthat the flow everywhere can be assumed to flow parallel to the bottom (.e., verticalaccelerations can be ignored, and a hydrostatic pressure variation in the verticaldirection can be assumed)

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

‘The continuity equation or mass conservation equation is:

Equation 4.1

Equation 4.2

3

Where Q = discharge in m/s; A = cross sectional area in m?; ¢ = time inseconds; x = dis ance along the longitudinal axis of water course; q = lateral inflow in

(m'/s/m); h = water level above datum in m; C = Chezy roughness coefficient in

‘Vim /s; R= hydraulic radius in m; a= momentum distribution coefficient in sỀ/mÌ; ý =

‘gravitational acceleration in m”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 andmomentum equations were solved numerically using an implicit finite differenceKnown as the si

ñm

point Abbott scheme, These equations are simultaneous, quasi-linear,

order, partial differential equations of the hyperbolic type The transformation ofthese equations into a set of finite difference equation is performed in a computationalgrid involving altering Q and H points Q point are always placed midway between

‘wo adjacent H points, while the distances between the H points may vary

“A simulated segment linking two nodes possesses average geometric andhydraulic characteristics of the actual channel section A frictional co-efficient andinertial force exists between to nodes of a river segment Inflow and outflow of thenode control the storage in a node A positive (+) sign and a negative sign are impliedfor 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 atthe confluence of river tributaries are defined as follows:” (Dang , 2010, p 107)

Equation 4.3

sr Equation 4.4

4.1.2 Methods used in the performance evaluation

‘The level of accuracy and reliability of the model depend on the assessment ofthe model performance, Both graphical and statistical comparison between simulatedand measured hydrographs are recommended by American Society of Civil Engin(ASCI

performance evaluation Firstly, in order to assess the model performance evaluation,

1993) The MIKE 11 model provides both graphical and numerical

‘graphical comparisons between modeled and measured hydrographs were done, For

Sutcliffethe statistical assessment, this study followed on evaluation of Nas

efficiency (Nash & Sutcliffe, 1970) The equation of Nash-Sutcliffe efficieney is

NSE Equation 4.5

where

ge the observed data

Ông: the average observed data

nthe simulated data

a sample size

“The Value of NSE lies between -2 to +1, The value I indicates a perfect matchbetween measured and simulated data Model performance is perfect, if values ofNash-Suteiffe efficiency range from 09 to 1 Model performance is good andacceptable, ifthe values range from 0.8 to 0.9 and 06 to 0.8

4.2 Mike 11 Model Set-up

Within the scope of the thesis study, the author has inherited the input data fromthe National Key Laboratory of River and Coastal Engineering and Institute ofVietnam Academy for Water Resources Through Modeling calibration Modelingvalidation, the author will define a complete model parameters to simulate the flowregime 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 manylarge basins such as Da, Thao, Lo rivers in the upstream; and huge river delta in thedownstream as well as dense river intensity The Red River is connected with ThaiBinh river system by Duong and Luoc rivers The Red River's flow reaches to the

35