Thesis of master degree: Optimal operation of the bac Nam Ha dainage system under climate change

During the rainy season, frequent flooding by storm water is one of the most serious problems in lowland areas, causing heavy effect on transportation, agriculture, industries and many economic activities The required drainage water levels in this area are generally lower than the water levels of the virulent rivers Under such cases, pumping systems should be designed from a viewpoint of the integrated control floods Nam Ha lowland, in Vietnam, bounded by four surrounding rivers, is selected as a case study The operated plan in this area is the key factor for drainage and flood protection In this study, the mathematical model is used as a tool to evaluate the present drainage system as well as the scenario to improve its performance, considering the released water from agricultural areas Under climate change, there is change in rainfall of 14% in the region according to climate change scenario for Viet Nam updated 2016 of MONRE These changes were taken in to the simulation The results show both the flooding processes in the field as well as inundation areas and water levels along drainage channels It is found that the proposed model can be applied to evaluate integrated flood control systems for pumped field lowland Such a proper operating system provides an effective tool by means of which the drainage

system can be operated appropriately taking account of rainfall intensity and effects ofclimate change.

I hereby certify that the work presented in this thesis entitled, “Optimal operation of the Bac Nam Ha drainage system under climate change.” in partial fulfillment of the

requirement for the award of the Master of Science in Integrated Water Resource

Management, is my own work carried out under the supervision of Assoc Dr Nguyen Cao Don

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

Date: 15/04/2017 Signature:

Nguyen Thi Huong

il

ACKNOWLED GEMENT

I would like to give many thanks to all people who has supported and assisted me during the Master Thesis Research Without their continuous support, encouragement and guidance, it would have been impossible for me to complete the study in time.

I would like to express my appreciation to Assoc Dr Nguyen Cao Don, my devoted mentor, for his unlimited encouragement, guidance, comments and technical supports on VRSAP modeling as well as thesis writing process from the beginning of thesis research He always keeps track on his students and brings them back to the right way I wish to thank Assoc Dr Nguyen Thu Hien for her feedbacks, comments and supports from the proposal process.

I would like to thank to the NICHE - VNM 106 Project for their financial support during the post graduate study at Thuyloi University.

I would like to thank to all teachers and professors of Thuyloi University.

Last but not least, I want to take this opportunity to show my appreciation to my parents, my siblings and all of my friends for their helps and encouragements.

1H

‘Structure of the thesis,

CHAPTER 1: LITERATURE REVIEW.

CClimate change including floods Overview of hydrodynamic models

Review on application of the hydrodynamic model Review of climate change study in Viet Nam

Zonation of the drainage system Drainage channel systems, CHAPTER 3 METHODOLOGY

31 32

Research framework

Data collection and data analysis, 3.2.1 Pumping station system

CHAPTER4 APPLICATION OF THE MODEL.

4.5 Application of HD model for operational scenarios 45.1 Gate operating scenarios

452 _ Results and discussion.

LIST OF FIGURES

Figure 1.1: Projected change in water eycle Source: (USGCRP (2009), Figure 2.1: Map showing the study area

Figure 3.1: Intergrated operational model Figure 3.2: Modeling field plot

Figure 4.1; Schematic diagram of the drainage systems showing nodes, links and files plots

Figure 4.2: Rainfall pattern taking into account of climate change Figure 4.3: The adjustment steps.

Figure 4.4: Model calibration for water levels at NhuTrac and Cau Sat Figure 4.5: Inundation area at NhuTrac drainage zone

Figure 4.6: Inundation area at Huu Bi drainage zone Figure 4.7: Inundation area at CocThanh drainage zone Figure 4.8: Inundation area at Vinh Tri drainage zone Figure 4.9: Inundation area at Co Dam drainage zone Figure 4.10: Graph of inundation area for 5 drainage zones

Figure 4.11: Graph of situations giving the smallest inundation area.

LIST OF TABLES

Table 2.1 Field elevation distribution in the area of 6 independent pumping stations 21 Table 2.2 Distribution of area by elevation for the area of 6 pumping stations 22

Table 3.3 Monthly average precipitation of rainfall at gauging stations in the study

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Danish Hydraulic Institute

Department of Agriculture and Rural Development Geographic Information System

Hydrodynamic Model

Nedbor Afstromnings Model Mekong River Commission

Ministry of Natural Resources and Environment Soil and Water Assessment Tool

Intergovernmental Panel on Climate Change Root Mean Square Error

United Nations Development Program

United Nations Framework Convention on Climate Chang Vietnam River Systems and Plains

Water Resources and Environment Administration Water Evaluation and Planning

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INTRODUCTION 1.1 Introduction

During the rainy season, frequent flooding by storm water is one of the most serious problems in lowland area, causing heavy effect on transportation, agriculture, industries and many economic activities The required drainage water levels in this area are generally lower than the water levels of the boundary rivers In the development of this area, conventional functional drainage systems have been built, including channels, sluiceways, gates, regulator, pumping stations, etc In operation, the drainage system should be operated appropriately taking account of tidal effect, rainfall intensity and reaching time of the rainwater Such a proper operating system has not been established yet in the region At present, the development of agriculture is extensive and intensive, based on the diversified crop patterns, two or three cropping seasons in a year, and high yielding crop varieties with high demands of irrigation and drainage and level of its management However, after many years, operation and having exploited for a long time, most of the drainage systems are heavily deteriorated, with uncompleted canals and control structures Generally, the drainage

system in this area is no longer suitable for the present stage of the agricultural landuse For these reasons, the improvement of drainage system’s operation is now verynecessary and important Moreover, according to IPCC (Intergovernmental Panel onClimate Change) and MONRE (Department of Agriculture and Rural Development),Viet Nam is one of the countries being affected by climate change that sea level riseand saline water intrusion The average rise in the global sea level is expected to be59cm by 2100, according to the highest greenhouse gas emission scenario used in thefourth assessment of the Intergovernmental Panel on Climate Change (IPCC) 2007.However, according to a medium global greenhouse gas emission scenario, the sealevel rise along the Viet Nam coast would be on average of 75cm by 2100 The VietNam Government recognizes climate change as a major challenge In order to solvethose existing problems, it is necessary to understand the characteristics of thecomplicated unsteady flow regime in the drainage canal system Simulation approachis the best way to estimate the unsteady flow and to give the best suitable measures for

improving drainage systems Under such circumstances, pumping systems should be designed from a viewpoint of the integrated control floods Furthermore, Nam Ha is lowland, in Vietnam, bounded by four surrounding rivers, is selected as a case study The operation scheme in this area is the key factor for drainage and flood protection The mathematical model is applied as a tool to evaluate the present drainage system as well as the scenario to improve its performance, considering the released water from agricultural areas and climate change The results show both the flooding processes in the field as well as inundation areas and water levels along drainage channels It is found that the proposed model can be applied to evaluate integrated flood control systems for pumped field lowland Such a proper operating system provides an effective tool by means of which the drainage system can be operated appropriately taking account of tidal effect, rainfall intensity and reaching time of the rainwater.

This thesis aims to set up a model hydrodynamic flow to the river network with its pumping stations and other drainage facilities to find a suitable operation of gate regulators so as to minimize total flooded area under a rainfall event.

1.2 Problem Statement

Ha Nam and Nam Dinh provinces are located in the lowland regions The region is surrounded by large rivers like the Red river, Day river, the Dao river in infield in addition also Chau Giang river and some other smaller rivers The study area is frequently inundated during rainy season To resolve this situation, the system of large pumping stations was built in the year 1970 However, head works and canals and other drainage facilities were over 30 years of operation, and thus they have severely deteriorated The pumping equipment were not well performed.

The gate regulators that connect sub-drainage basin did not work properly andefficiently Therefore, in this study, aims at finding out a suitable operation of gateregulators so as to minimize total flooded area.

1.3 Objectives of the study

“The long term goal of this research is to set up a model hydrodynamic flow in the river network with its pumping stations and other drainage facilities to find a suitable ‘operation of gate regulators so as to minimize total flooded area

Particularly, the study has the following sub-objectives:

1) To have an overview of the existing drainage system and inundation status in Bac

Had ‘am under current and future climate change.

2 To apply a hydrodynamic model for simulating flows in the drainage systems corresponding to an operation of gate regulator.

3) Based on the results of the hydrodynamic model, measures for inundation mitigation will be proposed.

3) How to apply a hydrodynamic model to have recommendations for inundation

mitigation for decision makers?

4) What is the optimal operation of gate regulators proposed to Bac Nam Ha so as to minimize the flooded area.

1.5 Methodology

In this research, the framework of methodology has been developed as follows Figure 1-1 Firstly, basing on previous studies and analysis, available informations can be use to define current status of drainage system and situation in Bac Nam Ha Secondly, collection of data: These data are used as input and for calibration and verification of models These consist of : Topography, channel networks pumping station, channel geometry, weather data, ect.

‘Thirdly, model set up : Applying a hydrodynamic model to the study area to simulate flows in river channels, the model willbe calibrated using observed data.

Fourthly, The system scenarios will be studied formany combinations of gate ‘operationso as to find a suitable operation that minimizes the flooded area

In the last, coneludon and recomandation will be given

Model setting

(calibration and verification)

Figure 0.1: Framework of methodology 1.6 Structure of the thesis

+ INTRODUCTION: This part discusses the overview of the drainage situation in Jowland including: Introduction to thesis topic and method, the significance of the study, problem statement and the objectives of the study

+ Chapter 1 (LITERATURE REVIEW): This chapter reviews several past researches,

which relate to flow regime analysis and researches which applied the HD model The Scope of the study will be shown in this chapter as well.

+ Chapter 2 (OVERVIEW OF SUDY AREA): The chapter presents natural characteristic, natural condition of the study as well as population and economic characteristics of the study area, The problem of the study is discussed in detail

¢ Chapter 3 (METHODOLOGY): This chapter presents about the data collection, data analysis such as rainfall, river networks, runoff, pumping rate The chapter will also set up the VRSAP model and calibration and validation steps.

¢ Chapter 4 (APPLICATION OF THE MODEL): The chapter will show the simulation’s result and analyzes the results in order to achieve the objective of the study.

¢ CONCLUSIONS: The part focuses on the main findings and including of a summary of entire thesis.

* REFERENCES

¢ ANNEX: List of the figure proving of inundation in the field plots

CHAPTER 1: LITERATURE REVIEW 1.1 Climate change including floods

Currently, to simulate masterpiece flood, salinization, pollution, organic status in rivers, engineers and technicians often use software to simulate flow regime Models

simulate flow and water quality in the river by the system of equations Saint - vennant 1-D (in various forms) and the equation transmission of 1 -D However, diagrams and algorithms solve the governing is different, depending on the author’s lead to the accuracy of the results as well as time is different.

Many software and modelling have been developed and applied to simulate flowregime In studies of the IPCC, the UNDP climate change scenarios, the modelsaccounting, atmospheric aerodynamics, hydrodynamics are developed and used toassess quantify the impact of climate change on global climate, water levels of theoceans of the world For each region, each country on the basis of global climatechange scenarios will have the detailed study evaluated the impact of climate changeon individual meteorological factors (temperature, rain, humidity, evaporation ),hydrological conditions, oceanographic (in river flow, tidal oscillations, sea levelchange) Mathematical models used in this case are usually the hydrodynamic modelHEC (USA), SOBEK (Netherlands), MIKE (Denmark), ISIS (UK) Some studies ofclimate change impacts to demand of crops, using CROPWAT for total water demandfor crops, as well as seasonal changes, the stage of plant development by warming airtemperatures Apirumanekul and Mark in 2001 applied a combined approach based onmodeling and GIS to do modelling of urban flooding and MOUSE to structure theurban drainage in Dhaka City, Bangladesh This model, therefor, has been shown anddevelopment by Norwegian University of Science and Technology (Nie, 2004) Someother software were applied such as hydrodynamic modelling using MIKE 1 and urbansewer system modelling using info Works-CS as show in the article “ ComparativeAssessment of Unburn Flood Risked due to Urbanization and Climate Change in theTurnout Valley of Belgium”(Alam, Willems, & Alam, 2014) The article presents theNAM model as a well calibrated model with the Nash-Sutcliffe efficiency of 0.61

while the calibration and validation of MIKE 11 Model was a better result As the result, there was an average increase of 36% in the peak runoff from two sub-catchments due to these urban runoffs whereas an average increase of peak runoff by 23% for higher return periods, while an average decrease of relatively lower peak runoff by 19% for lower return periods as compared to the current conditions Therefore, flooding areas will increase by 5.36% and 6.1% in all of the entire floodplain while 22.31% and 25.8% in the lower valley.

Climate change was once definate by the Inernational Panel on Climate Change (IPCC) as “Climate change refers to a change in the state of the climate that can be identified (e.g., using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer”(Materials 2007)

The well know of change in climate is the global warmming, change in precipitation, seasonal shift and increase in frequency and intensity of extreme events, including droughts and floods (UNFCCC 2007) The relationship between water, energy, agriculture and climate is a significant one More and more, that relationship is falling out of balance jeopardizing food, water and energy security Climate change is a phenomenon we can no longer deny as its effects have become increasingly evident worldwide.

On the global scale, among various environment factors influenced by climate change,water resources are of the major concern (Frederick and Major, 1997) Globalwarming due to the increase of greenhouse concentration is likely to have significanteffects on the hydrological cycle IPCC, 1996) In the researching of the relationshipbetween climate change and water resources, especially the impacts of climate change,USGCRP (2009) emphasized that the hydrological cycle is strongly affected becausechanging of climate and shows the consequence of the change on water cycle as thediagram below.

Figure 1.1: Projected change in water cycle Source: (USGCRP (2009)

The diagram shows changes in water cycle for both hotter/drier conditions and hotter/wetter conditions Heat trapped by the atmosphere cause more evaporation and more precipitations A warmer atmosphere holds more water vapor, which is also a heat trapping gas The diagram highlights several conditions, include: decrease in

rainfall, decrease in extent of snowpack and glacier, earlier peak stream flow and the reduction of runoff It also shows cycle of decrease in snowfall due to warming lead to

proportional increase in rainfall The combination of decrease late-summer water flow which increase water temperature and increase water usage would lead to increase severs drought Additional change includes: decrease in light rains, more severe drought between rains, decrease in lake ice, increase potential evaporation and water temperature Also, an increase of amount of heavy precipitation events leads to increase flooding.

The hydrological cycle will be intensified and changed in time and space It will bemore precipitation and more evaporation, but the extra precipitation will be unevenlydistributed all over the world, as a result, some parts of the world may witness the

decline in precipitation or major alteration in thẻ timing of rainy and dry season (Amell, 1999),

Most urban climate change risk and impact assessments for storm water management to date have concentrated on the need for quantity control to limit the risks of flooding or combined sewer overflows due to increased rainfall intensity, and, in some cases, land change (Beeneken & Lindenberg, 2012; Davies & Semadeni-davies, 2016; Hosseinpour, 2009; Osman, 2014; Yardanfar & Sharma, 2015)

Paludan et al., 2010 published an article entitled * imate change management in drainage systems —A “Climate Cookbook” for adapting to climate changes” with the purposes to describe methods for adapting to climate changes in urban areas with respect 10 the total water eyele, (0 suggest ways of communication with the political system, describe interdisciplinary issues, to describe how to prioritize the efforts when ‘adapting to climate changes in a city, and to propose methods and hydraulic tools which can be used in the adapting process They showed some model as GIS, ID surface model, 1D-1D coupled model, ID-2D model, and 1D-2D-Groundwater model 1.2 Overview of hydrodynamic models

‘There are some hydrodynamic models popular in the world developed and introduced

in several references The below are reviewing some of commonly used models

MIKEL] Model: the model in the family model MIKE(DHI, 2003), commerical model developed by the Danish Hydraulic Institute This model has proved extremely popular in the world and also to simulate, predict floods `, water quality and saltwater

MIKE 11 is a professional engineering software package for the simulation of flows, ‘water quality and sediment transport in estuaries, rivers, irrigation systems, channels and other water bodies MIKE 11 is a user-friendly, fully dynamic, a one-dimensional modelling tool for the detailed analysis, design, management and operation of both simple and complex river and canal systems With its exceptional flexibility, speed and user friendly environment, MIKE 11 provides a complete and effective design environment for engineering, water resources, water quality management and planning

applications The Hydrodynamic (HD) module is the nucleus of the MIKE 11 modelling system and forms the basis for most modules including Flood Forecasting, Advection-Dispersion, Water Quality and Non-cohesive sediment transport modules The MIKE 1] HD module solves the vertically integrated equations for the conservation of continuity and momentum, ie the Saint Venant equations.

Applications related to the MIKE 11 HD module include:

¥- Flood forecasting and reservoir operation¥ Simulation of flood control measures

Operation of irrigation and surface drainage systems

¥ Design of channel systems

¥ Tidal and storm surge studies in rivers and estuaries,

‘The primary feature of the MIKE 11 modelling system is the integrated modular

structure with a variety of add-on modules each simulating phenomenon related to

river systems.In addition to the HD module described above, MIKE 11 includes add: ‘on modules for:

¥ Hydrology

¥ Advection-Dispersion

Y Models for various aspects of Water Quality

¥ Cohesive sediment transport

/ˆ Non-cohesive sediment transport

ISIS model: Developed by Halcrow và Walingford, UK like the MIKE 11 ISIS solvels equations Saint - vennant 1-D flow ISIS uses Preissman difference schieme for flow and transport, ISIS interface is quite nice and handy, but also exposed some sweakn s and difficulties in solving the problem on a large scale, many links as the Mekong Delta

EFDC Model (Environmental Fluid Dynamic Code: The Model has been protected by U $ Environment (US EPA) which has been developed since 1980 This Model can be used to simulate aquatic systems in one, (Wo, and three dimensions Dynamically-coupled transport equations for turbulent kinetic energy, turbulent length scale, salinity and temperature are also solved.

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SOBEK Model: SOBEK is a powerful modelling suite for flood forecasting, ‘optimization of drainage systems, control of irrigation systems, sewer overflow design, river morphology, salt intrusion and surface water quality The modules within the SOBEK modelling suite simulate the complex flows and the water related proces almost any system The modules represent phenomena and physical processes in an accurate way in one-dimensional (ID) network systems and on two-dimensional (2D) horizontal grids It isthe ideal tool for guiding the designer in making optimum use of Duflow Model: Duflow is a computer program to model steady-state and transient surface-water systems (EDS, 1995; STOWA, 2000) The surface-water flow is modelled in a one-dimensional network of nodes connected by sections with a certain length and hydraulic resistance For each section the bottom height and the dimensions

Of the cross-section have to be specified Within the network several types of hydraulic

structures, like weirs, culverts and pumps can be included, Duflow solves the Saint-‘Venant equations for conser tion of mass and momentum, using the initial and ‘boundary conditions, such as an incoming flow atthe upstream part ofthe model and a measured downstream water level For each section and for each time step Duflow calculates the discharge, water level and mean velocity Supply or removal of water takes place at the nodes of the network

Fluxes between the groundwater system and the modelled watercourses can be defined as known boundary conditions or a special module in Duflow, the RAModule, can be used for a transformation of rainfall to discharges at the sections This module makes a distinction between processes for open water, paved and unpaved surfaces The used equations, in which several linear reservoirs are linked in a parallel and/or sequential

mode, have a strong empirical character In the coupling with MieroFem this

RAModule is not used; the flux to each section is calculated by MicroFem.

The software has been prompted name by local officials and apply various domestic projects include:

HydroGIS Software: Developed by Dr N

having been builtin some recent years, HydroGl

'euyen Huu Nhan This is a new software solve Saint - vennant equation one-way by Preissmann different scheme But, solving directly difference equations by

"

iteratively method so speed is not quickly The authors add some intermediate point Recently, Dr Nhan has add calculating flow use kinematic wave method However in the mountains the kinematic wave method is not applicable.

AMK4 Software: Developed by Dr Le Song Jiang, University of Technology This software is more academic and mainly used in teaching The application for the real big problem is limited Part of MK¢ interface is quite good and is in the stage of development.

SAL (or Sall BOD): Developed by Prof Dr Nguyen Tat Dae In 80s SAL can be applied to many large projects in the Mekong Delta, Saigon River system Dong Nai -‘Thi Vai, as well as for intemational projects (hydraulic, salinity, pollution, acid sulfate), SAL also solves Saint - vennant equations uses Preissmann finite differential scheime However, SAL has linearization method should not need to repeat SAL user

can calculate the flow elements (water level, flow, velocity ) and salinity and some

clements of water quality (organic pollution, water coolers, alum ) disadvantages of SAL are part of the interface, connectivity and GIS databse This section is in the

process of construction and finishing SAL academic part is the main basis for

improvement VRSAP so called VRSAP-SAL.

VRSAP Model: Since 1978, Prof Nguyen Nhu Khue and the modeling group of Southern Institute for Water Resources Planning (SIWRP) has developed the hydraulic and salinity intrusion model namely VRSAP (Vietnam River Systems and Plains), a program for mathematical modeling of one-dimensional hydrodynamic flow and transport dispersion of mixed substances On the basic of a one-dimensional problem in an open-channel system, the program has been improved to simulate the overland flow by assuming quasi-two-dimensional scheme and the flow under pressure in a filled sewer Through its application in the water resources planning and water control design, it has been refined and upgraded, nowadays a new user-friendly version in Visual Basic can be run on a microcomputer for a very large scale and complex network.

‘This program has been used widely and successfully for several projects on water

resource planning Red River Delta and Mekong Delta, During the application process,

VRSAP has been finalized gradually which run on DOS environment replace by

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WINDOWS environment VRAP program meets the requirements calculation; However, due to de clopment needs, the si of the programming is increasing ‘gradually, not only in the level of delta of Vietnam but also level delta (ie both in Vietnam and Cambodia) and to describe long time, complicated senario which operate sewer dam system, Some advantages and disadvantages of VRSAP (without upgrades):

+ To meet the computing requirements for the big problem of the Mekong River delta despite must calculate individual floods that time is lack of water

+ There is a program source code can be understandable and can actively repair, chăng, although understanding the codes source is not easy.

+ The interface is simple and not friendful

+ Computing speed is slow due to calculate again more times

+ The ability to connect with GIS tools and Database is yet powerful

+ The organization of the data needs to be upgraded.

In Viet Nam, the VRSAP has been continuously updated to better reflect the ever-changing conditions inthe several decades ago, The VRSAP is popular and is used by ‘governmental agencies In my study, I have used the software VRSAP (River System and Plan Vietnam, Prof Nguyen Nhu Khue) because of its advantages in data requirement the code of the program is open so That user can add some more subroutines suitable to the current problem.

1.3 Review on application of the hydrodynamic model

In Vietnam, Mai Due Phu applied MIKE 11 in his scientific research Applying the MIKEII Model combined with some model to provide sewer operating strategies in the tidal area in Go Cong ~ Tien Giang under the scenarios of climate change As the

result, he gave some suggestions that: the MIKKI] software was suitable for an

analysis and simulate in the system which includes the complex network canal Based ‘on modelling parameters, primary conditions, boundary condition and simulation, the result was same with observe, applying the hydraulic model to simulate the water demand in dry season, and applying the MIKE software to predict the salt intrusion and flooding.

A hydrological model is a tool to express the teal hydrological cycle in a simplified

‘way That kind of model is used for understanding the hydrological processes as well as making hydrological prediction if there are some water resources management and utilization activities implemented The model is an application of several algorithms to provide a quantitative relation between the input data (e.g rainfall, meteorological data) and output (e.g runoff), Themathematical models have been developed from 19th century with the simplest rainfall-run off model by Mulvaney (1851)(Johnston and Kummu 2012) to more sophisticated models such as MIKE suite developed by Danish Hydraulic Institute, Soil and Water Assessment Tools (SWAT) by U.S Department of Agriculture (Gassman et al 2007) those models are fundamental to integrated water management as used for planning and decision making.In Mekong River Basin, a wide range of hydrological model has been applied for flood forecasting as well as for

studying the feasibility of proposed plans for development at different scales Johnston

and Kummu 2012) The early models applied are the Streamflow Synthesis and Reservoir Regulation (SSARR) developed by U.S Army Corps of Engineers (US Army Comps of Engineers 1972) to simulate the changes in the flow of the Mekong Delta to forecast the flood events as well as the feasibility of main river dam constructions After the shift to agricultural development, the evaluation of reservoir ‘operation was considered with two models used, namely Hydro System Seasonal Regulation (Johnston and Kummu 2011) and Massachusetts Institute of Technology River Basin Model (Strzepek 1981) After 1995, when the Mekong River Commission ‘was established, the hydrological models have been used for predicting the possible impacts of river alteration activities in order to test and monitor the mutual agreements signed by related countries, supporting for the integrated water management of the river basin.For every study using model simulation, the suitable model should be selected to achieve the main study objectives.

‘The Viet Nam river systems and Plains (VRSAP) model have been applied Dong Nai river to account for the tidal effect and saltwater intrusion in the lower basin The surrounding basins have not been included in VRSAP In Dong Nai basin, VRSAP

9 cells (Ngoc 2000), cludes a total of 451 nodal, 528 segments,

In China, SWAT software has been applied to several important river basins with

‘great successes, One of those is the research impact of water project (Dams and floodgates) on river flow regime and water quality in the Huai River Basin (Y Zhang et al., 2010), Their modified SWAT model provides a feasible method to assess the impact of dams & floodgates on flow regime and water q ality, without suffering from the lack of data, In other research, they have analyzed the flow regime of three outlets ‘on the south bank of River, which are being effected by the Three Gorges dam They analyzed the data in two periods: the period before and after TGR storage stages, during 1991-2002 and 2003-2010, respectively They fit data by applying a positive ‘quadratic polynomial model and by comparing the runoff of the three outlets in both stages (Under the similar discharge at the main stream in the Yangtze River) to show the change of flow regime From the result of comparing the flow processes in different scenarios by SWAT, dams and floodgat S actually effect to water bodies and river flow regime of rivers in the Hi i River Basin The biggest dam in the world has been built eross a big river in China; the Three Gorges dam was analyzed to strongly effect on its downstream flow

Based on knowledge of author, characteristics of the study area and the available data, VRSAP model was selected to achieve the main objectives of this study which aims to ‘evaluate the tabiity of those models and using them in solving the problem related to dam operation and climate change.

1.4 Review of climate change study in Viet Nam.

Climate change is one of the most significant challenges fa ng human being today, Climate change has already affected agricultural production and socioeconomic structures and will extensively and intensively alter the development process and

security wes including food, water, energy and social safety as well as political,

cultural, economic, diplomatic and commercial security (MONRE 2008, 2010, 2012 a, b, 2013) Vietnam is considered as one of the countries to be severely affected by climate change (IPCC 2001), and thus response to climate change is of crucial importance to Vietnam, particularly in coastal areas Therefore, the development of suitable adaptation solutions for Vietnamese coastal provinces is extremely essential

1s

‘The rainfall of the Viet Nam has been affected by northeast monsoons (which catry

humid air from the South China Sea) giving a peak rainy season in September and fir the last 9 decades October At every location, change oi

period The annual rainfall decreasing over Northern climate change zone white nual average rain

2000) was not distinct and not consistent with each other, There were ascending past 50 years (1958-2007) decreased by about 2% (NTP, MONRE, 2008)

sing over Southern one One average for the whole country, the rainfall over the Annual mean temperature in different regions ranges from 18 to 290 C Monthly mean

‘of the coldest month is about 13 ~ 20° Cin the northern mountainous part and from 20 to 280 C in the Southern parts Temperature of the summer varies from 25 to 30°C.

Viet Nam is located in the area affected by typhoon and tropical cyclones inthe North West Pacific Ocean In average, annually, there are 4-5 typhoons/tropical cyclones

affecting Viet Nam Annual rainfalls are very different in different regions, ranging

from 600mm to 5,000mm About 80- 90% of rainfall concentrates in rainy season, the number of rainy days in the year is also very different between the regions and ranges from 60 to 200 In several regions, floods and inundation occur during rainy season but in dry season, drought is often recorded As the rainfall distribution is not even during the year

In Viet Nam, there are some project such as:

Climate change scenario construction by using the coupled method (MAGICC SCENGEN software) and the statistical downscaling method for Viet Nam domain and other smaller regions (IMHEN, 2006)

Climate change scenario developed by using the MAGICC/SCENGEN 5.3 software and the statistical downscaling method (IMHEN, 2008)

Climate change scenario for VietNam domain developed by using dynamical method (IMHEN, SEA START and Hadley Centre, 2008

By the end of the 21st century, the number of days with maximum temperature of over

350 °C increases from 15 to 30 days in almost all regions in the country based on the medium emission scenario A1B (MONRE 20128, b).

In the future, the general trend is that the maximum daily precipitation increases in the North West, North East, Red River Delta and North Central Regions, and decrease in the South Central Coastal, Central Highlands, and the South Regions (MONRE 2012a,

If the sea level rises by one meter, about 39 % of the Mekong river delta area (MRD),

over 10 % of the Red River delta, over 10 % of the Quang Ninh province, 20 % of the Ho Chi Minh City area (HCMC) are flooded, which constitute 6.3 of the total land area, According to this scenario 35 % of the MRD population and 7 % of HCMC population will be affected (MONRE 2012a, b, 2013).

Climate change and sea level rise scenarios developed for Vietnam are based on

different greenhouse gas emission scenarios of IPCC’s 4th report (PCC 2007), namely a low scenario (BI), medium scenatios (B2, AIB), and scenarios of the high anthropogenic greenhouse gas emission (A2, AIFD Climate change scenarios for temperature and precipitation are developed for seven climate regions in Vietnam North Wes 1 North Bast, Northern Delta, North Central Region, South Central Region, Central Highlands, and Southern Region,

1.3 Concluding remarks

Vietnam is considered as one of the countries to be severely affected by climate change and thus response to climate change is of crucial importance to Vietnam,

particularly in coastal areas Rises in average temperatures have been observed over

the last decades, as well as substantial changes to precipitation patiers The average temperatures have been rising and the total precipitation has inereased, especially during the rainy seasons, which is important for flood water management In northern View um the precipitation during the dry seasons has decreased, which poses important challenges to water management,

Review on hydrodynamic modelling applied to river network system in the world and in Viet Nam shows that the re many different model developed to solve the flow regime in open channel Models were developed based on the Saint-Venant system equations which formed by the expressions for mass and momentum conservation, describe the transient flow, gradually varied, ina channel with irregular cross sections and lateral contribution In Viet Nam, there are many models for flood, salinity intrusion and spreading substances Most of them had packaged in from of computer software as: Mike 11, ISIS, KOD, Hydrogis, VRSAP, SAL, TL, Sobek and many of them are commercial There is also some HD model Such as mikell, mike 21, VRSAP developed by local researcher to be good in hydrodynamic simulation With inheriting the previous fundamental studies and orienting to apply for Vietnamese condition, The VRSAP has been continuously updated to better reflect the eve

lal software, VRSAP is

changing conditions in the delta Among non- commer

popular one and it has been used by many agencies In this study, we use VRSAP model to simulate flow in the river system of Bac Nam ha in order to inundation conditions in its field plots evaluate.

CHAPTER2 — STUDY AREA

2.1 Location of Bac Nam Ha

Ha Nam area located at about 20036" North and 106010" East isa relatively flat and low-lying land area of the Red River delta, Vietnam, as shown in figure: 3-1 The interior land is protected by banks and dykes system and bordered by 4 surrounding rivers, namely the Chau River and the Red River in the North, the Day River and the Dao River in the South The hydraulic network systems with total length of 105 km, Which perform both as irrigation system in dry season and drainage system in rainy season, consist of many other canals and pumping stations.

‘Thote are six large pumping stations, namely Coe Thanh, Co Dam, Huu Bi, Nhu Trac, Vinh Tri and Nham Trang, for draining purpose They were planned in 1960s then orderly built in the period of 1962-1972 The total pumping capacity is of 220 m3 ‘The current situation is caused by a number of reasons that gravity drainage capacity is limited due to high water level in the boundaries, and the drainage pumping capacity is not large enough Moreover, drainage canal systems and on-canal control structures are not completed, causing many difficulties in draining water Canals are heavily suffered from sedimentation leading to reduction of drainage capacity of the system.

During rainy season, frequent flooding by storm water is one of the most serious

problems of this area, causing heavy effect on transportation, agriculture, industries and economic activity The required drainage water levels in this area are lower than the water levels of the bounded rivers, Under such circumstances, the excessive water cannot be drained out of the area by gravity flow; therefore it must be pumped out In the development of this area, conventional functional drainage systems have been built, including channels, sluiceways, gates, regulators, pumping stations, etc In

operation, the drainage system should be operated appropriately taking account of,

boundary water levels, rainfall intensity and reaching time of the rainwater Such a proper operating system has not been established yet in the region At present, the development of agriculture is extensive and intensive, based on the diversified crop patterns, two or three cropping seasons in a year, and high yielding crop varieties with high demands of irrigation and drainage and level of itsmanagement, However, after

30 years in operation and having exploited for a long time, most of the drainage systems are heavily deteriorated, with uncompleted canals and control structures Generally, the drainage system in this area is no longer suitable forthe present stage of the agricultural land use For these reasons, the improvement of drainage system's

‘operation is now very necessary and important In order t0 solve those existing

problems, itis necessary to understand the characteristics of he complicated unsteady flow regime in the drainage canal system Simulation approach is the best way to estimate the unsteady flow and to give the best suitable measures for improving drainage systems.

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2.2 Topography

Total area is 85.326 ha with complicated topography, highland interleaved with lowland and hollow terrain The area includes districts: Ly Nhan, Thanh Liem, Binh Luc, Vu Ban, Y Yen, Phu Ly and Nam Dink city.

Field elevation rangls almost from +0.75 to +1.5m, Some highland areas are Bac Ly Nhan, surrounding Dao River and Chau River Some lowland areas (+07 to +0.8m) are Binh Luc, Y Yen and Vu Ban, Some areas have mountain as Vu Ban, Thanh Liem and Y Yen.Field elevation distribution is shown in the table 2.1

Table 2.1 Field elevation distribution in the area of 6 independent pumping stations

Elevation (m) | Area(ha) | Percentage (%) | % accumulated

With highland interleaved with lowland and hollow terrain, especially 31.639 ha of arable land and non-cultivated land accounting for 37%, investment in drainage for inundation of the area is difficult and costly.

Results for the relationship F ~ Z for the whole area is shown in the table 2.2

Table 2.2 Distribution of area by elevation for the area of 6 pumping Stations 5 awe |2ss [3076 [00 joo |isar_| 1967 |rsoo4 | rissa

6 viawta | 29006 [2040 |2760 joo |12193 |2or20 [97980 | 46500

Grand | 79.736 | 103056 | 1382.3 | 678.4| 360467 | 65328 | 29.5565 | 14,1673

2.3, Zonation of the drainage system.

‘There are six drainage subriverbasin that were designed and specified when desiging 6 pumping station including:

~ Nhu Trae pumping station; main drainage canals are Long Xuyen canal and Nhu

‘Trac canal which are linked to Huu Bi drainage canal at Vua sluice (the end of Long

Xuyen canal is connected to Chau River).

Huu Bi pumping station: main drainage canal is Chau River connected to Nhu Trac River at Vua sluice, Coc Thanh River at sluice 3/2 and to Vinh Tri River at An Bai sluice.

2

= Coc Thanh pumping station: main drainage canals are Tien Huong River, Chanh River, main West canal, canals T3 and T'S which are connected to Nhu Trac River at sluice 3/2 and Vinh Tri River at Canh Ga sluice.

Vinh Trí pumping station: main drainage canal is Sat River linked to Coe Thanh River at Canh Ga sluice, Huw Bi River at An Bai sluice and Co Dam River at My Do sluice.

= Co Dam pumping station: main drainage canals are Bien Hoa River, Kinh Thuy River and My Do River connected to Vinh Tri River at My Do sluice, Trieu Xa and Dinh Xa Rivers at Gheo sluice, and Nham Trang at Lay sluice,

~ Nham Trang pumping station: main drainage canal is Nham Trang River linked to Co Dam River at Lay sluice

~ Dinh Xa and Trieu Xa pumping stations: main drainage canals are Kinh Thuy and

Tricu Xa connected to Co Dam at Gheo sluice.

Pumping stations including Quy Do, Yen Quang, Quan Chuot, Quang Trung, Dinh Xa and Trieu Xa are determined as independent working stations, not based on the common control network of 6 main pumping stations.On the other hand, Nham Trang

— Kinh Thanh drainage zone, currently, is not connected to the Š remaining zones (Nhu

Trae, Huw Bi, Coc Thanh, Vinh Tri and Co Dam), and is operated separately in current calculation process Inthe future, while constructing operation system and network, it can be widened to include 6 pumping stations system,

24 Drainage channel systems

Drainage canal system in the area have been constructed completely from main canal to level-T canal The details are follows:

~ Co Dam system includes main canal system:

+ Bien Hoa River is 12.6 km long and connected to Kinh Thuy River and My Do River.

+ Kinh Thuy River with the length of 18 km + My Do River with the length of 10.5 km

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~ Vinh Tri system takes the advantage of Sat River which is 37.7 km long to become main drainage canal connected to Chau River (at An Bai sluice), canal $17 (at sluice 'S7), My Do River (at My Do sluice) and Tien Huong River (at Canh Ga sluice)

Huu Bi system has Chau River which is 27.3 km long as main drainage canal connected to Long Xuyen River at Vua sluice.

~ Coc Thanh system includes 4 main drainage canals:

+ Tien Huong River is 18 km long connected to Chanh River, canal T3 and canal TS + Chanh River with of the length 8,8 km

+ Canal T3 with of 12 km long + Canal T5 with of 8.6 km long

Nham Trang system with 8km long of main drainage canal (North canal and South Canal)

~ Nhu Trac system with main drainage canal is Long Xuyen River with 12 km long Table 2.3 Main drainage canal system and works on the canal

N Main

Drainage drainage | Length Confluence Control | Dimension

z canal

Tong Tong Xuyen River

NheTae |Xuyen |I2 | connects to Long Chau | Vua, Do River River at Vua sluice

Vinh Tm, haw Chau River connects to | Vas, An

Huu Bí River 273 ‘Sat River at An Bai sluice

Canal Tổ connects to vg Westmain cana at La

{8 | chostuice Huong River || Gy, | osm

| Cink Ga, Tien Huong River connects to Chan River and canal T3

Sat River connects to HO Chau RiveratAnBai | gy, |Ú96mand Vinh | SarRiver |377 | siuce, Cannal 17 at [MBA | 309.24)

sluice $17, My Do River | M¥ 3 gate

at My Do sluice, Tien (16m and

24

-River |jyg |KhhuyRheremmnsss [CHỢ

copam | KmWPmy|!2® |foxTioand Bien Hoa: (hi Ree” | 185 /MyDocomectstoSat_ |MY P&:

MyDo Rivera My Do dược [NE River

North Cama RTT comes],

: can |4 |KmMhayRie

NowmTrang Sout) |4 — |CamlKHOsemees | NA"

canal North canal ay

‘Main drainage canals have not been dredged since 1976 Sedimentation in the e canals hinders flow Surveys for the drainage canals show that their design width is ensured, but their cross-sections are distorted and suffered serious sedimentation, Current canal bottom elevation is 0.8 = 1.0 m higher than design elevation Noticeably, Kinh Thuy River, Bien Hoa River and My Do River (Co Dam system) have not been dredged since 1964, so sedimentation occurs seriously with the thickness of 1.2

m in some places,

15 mand20

CHAPTER3 METHODOLOGY 3⁄1 Research framework

In this research, the methodology has been developed as shows in figure 3-1, On the

basis of data collection, a data processing procedure is used to prepare all kinds of data

(weather, topography, geometric data) to supply for other models as the input values ‘The hydrological model is applied to storm design and forecast based on frequency analysis Usually, each rainfall occurs in several days with a certain amount of rainfall Hence, the rainfall pattem in certain Duration is needed for design calculation The

‘main one, is applied after each scenario of drainage operation has been specified, to

predict the flooding process and inundation area in the field The computation process

will be repeated by changing the operation scenario These allow to find a suitable

combination of gate so as so to minimize the inundation area,

3.2 Data collection and data analysis

‘The data sets for this study were collected from various sources in study area during field trip; some of missing data were obtained from other sources and agencies such as IMC, MONRE DARD, ect The major data set used in this study are listed in the

table below:

Table 3.1: The source of required data for model

Categor Data Souree of data

Climate data = Rainfall Department of

= Evaporation Meteorology and

Relative humidity | hydrology Vientian capital

= Wind speed

~ Sunshine hours

Climate change Climate change scenarios | MONRE Map Digital elevation map |MONRE

Water use ~ Irigation Ha Nam, Nam Dinh and

= Agriculture NinhBinh DARD = Domestic BNHIMC

Economie Provincall Administration

development office of Ha Nam, Nam = Agriculture Dinh and NinhBinh

development | province 3.2.1 Pumping station system

From 1964 to 1972, 6 independent pumping stations have been constructed with the following parameters:

Table 3.2 Design parameters of 6 independent pumping stations

No | Pumping station | Pump ape | Numberof (Dan ee

1 | coethanh | onsss | 7 ws | %6 2 | copm | onus | 7 | ata | 8

3 | mum | ones | 4 "x 7

Number of | Drainage

No | Pumping station | Pump type

pins type | "pumps | area (ha)

4 Vinh Tri OIj6-145 5 14,784 40

5 Nham Trang of6-87 6 5,508 18

6 Như O|j6-8? 6 6406 18

Total T1488 220

Source: Bac Nam Ha irrigation management company Total design discharge was 220m3/s; drainage area was 77.448 ha, and drainage coefficient met 9l/s-ha Until 1973, some was adjusted and added to the drainage

systems some nec sary works:

- Nhu Trac system: Q=18m3/s, adjusted area: 6,800 ha

~ Huu Bi system: Q=32m3/s, adjusted area: 8,400 ha

- Coe Thanh system: Q=S6m3/s, adjusted area: 24.817 ha

Some drainage pumping stations have been constructed + Chanh River: 34*4000 m3/h

+ Quan Chuot:20*1000 m3/h

+ Gia canal: 20 1000 m3/h (mainly for the city)

- Vinh Tri system: Q=40 m3/s; adjusted area: 17,850 ha

Some drainage pumping stations have been constructed + Yen Bang: 13*1000 m3/h

+ Yen Quang: 20°1000 m3/h

~ Co Dam system: Q=56 m3/h, adjusted area: 18,672 ha

Some irrigation combined with drainage pumping stations have been constructed: + Trieu Xa: 2071000 m3/h + 3*4000 m3/h

+ In 1992, Quy Do drainag

drainage for an area of 2,832 ha

pumping station was constructed: 20*1000 m3/h, + In 1997, Dinh Xa drainage pumping station was constructed: Q: mys, combined with Trieu Xa pumping station to drainage for an area of 3,633 ha

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~ Nham Trang system: Q=18 m3/s; drainage area: 6,850 ha

+ In 1993, Kinh Thanh drainage pumping station was constructed: 12*4000 mâh, drainage for an area of 2,195 ha.

in the highland area of 6 communes Bac Ly Nhan and Binh Nghĩa, Quang Trung pumping station was constructed with Q=19*4000 mi/h to drainage for an area of

1,937 ha

Besides, in the system, 179 small in-field pumping station have been constructed to service for local irrigation and drainage Total area is 85,326 ha,

3.2.2 Control sluices

Works on the main drainage chanel system includes sluice gates controlling water ‘among areas, which helps to coordinate drainage between sub-drainage zones in the

~ An Bai sluice in the beginning of Sat River regulates water between Chau River and

Sat River and separates drainage basins of Vinh Tri system anh Huu Bi system Sluice consists 3 gates including 1 gate with b=6m and 2 gate with =2.24m Bottom elevation is in — 1.8m,

~ My Do sluice in the beginning of My Do River regulates water in Sat River and

separates drainage basins between Co Dam and Vinh Tri, Sluice consists 3 gates including 1 with b=6m and 2 gate with b=2.24m, Bottom elevation isin ~ 2.0m.

Canh Ga sluice in the beginning of Tien Huong River, regulates water in Sat River and Tien Huong River and separates basins between Coe Thanh and Vinh Tri, Sluice consists | gate with b=6m Bottom elevation isin ~ 2.0m,

~ La Cho slui regulates between Huu Bi basin and Coc Thanh basin, Sluice has 1 gate with b=4m, bottom elevation is in -1.5m,

~ Vua sluice regulates between Huu Bi basin and Nhu Trac basin Sluice has 1 gate

with 2m, bottom elevation is in -1.2m 3.2.3 Hydrological data

‘Most of the collected data is recorded from 1994 to 2014 The figure: 3.1 and Table

3.4 shows the annual rainfall of the region, as given in Table 3.4 , is about 1800 mm 29

and about half of the amount falls during July to September, the rainy season Precipitation data of the study area is sufficient for calculation and analysis with more than 30-year data recorded in national rainfall gauging stations Due to being covered by dyke in all 4 directions, flood in the rivers surrounding the area comes from flood in the upstream of Da River, Thao River and Lo River Rainfall in the area is the direct reason for inundation in the area.

There are tow emphasized characteristics of rainfall in the study area are:

- Rainfall changes markedly by each month, so rainfall calculation must be implemented for the period which is suitable with the growth and development of crops Precipitation concentrates in July, August and September Precipitation is highest in September, and it is also the time for cultivating winter rice season.

- Rainfall changes very much and is not temporally synchronous among stations With this characteristic, it is impossible to use only | rainfall gauging station to represent for the whole area, and it is also not reliable to use high rainfall event in all areas for calculation Hence, rainfall value in each area in the drainage zone has to be determined by rainfall contours constructed by rainfall of all stations in the same time Therefore, in drainage calculation, it is necessary to determine rainfall gauging stations related to inside-field drainage cells Each rainfall gauging station representing for each component area is joining in water balance model for the whole area.

As can be seen from the figure above, the value of rainfall is different in each station; most of stations are considered to be very high value of rainfall (Over 150 mm/day) and reach a peak at Septerday in Ninh Binh (450 mm/day , 333.1mm/day, 382.3 mm/day, 5377.2 mm/day at Ninh Binh, Phu Ly, Nam Dinh, Van Ly ) Otherwise, lower rainfall is present at station which reach a peak at January (29.9 mm/day , 27.8 mm/day, 23.7 mm/day, 25.7 mm/day at Ninh Binh, Phu Ly, Nam Dinh, Van Ly )

85% of rainfall occur in wet season (May — October) and contribute to be higher.

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Table 3.3 Monthly average rainfall at gauging stations in the study area

Flow in an open channel is governed by the equations of motion and conservation of mass The basic equations are expressed in the partial differential form as:

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