Water balance in the huong river basin in context of climate change

THUY LOI UNIVERSITY WATER BALANCE IN THE HUONG RIVER BASIN IN CONTEXT OF CLIMATE CHANGE NONG BAO ANH MSc Thesis on Integrated Water Resources Management... THUY LOI UNIVERSITY NONG BA

THUY LOI UNIVERSITY

WATER BALANCE IN THE HUONG RIVER BASIN IN

CONTEXT OF CLIMATE CHANGE

NONG BAO ANH

MSc Thesis on Integrated Water Resources Management

THUY LOI UNIVERSITY

NONG BAO ANH

WATER BALANCE IN THE HUONG RIVER BASIN IN

CONTEXT OF CLIMATE CHANGE

Major: Integrated Water Resources Management

THESIS OF MASTER DEGREE

Supervisor (s):

1 Assoc Prof Nguyen Thu Hien

2 Dr Ngo Le An

This reseacrch is done for the partial fulfilment of requirement for

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

May 2015

TABLE OF CONTENTS

ABSTRACT 3

DECLARATION 5

ACKNOWLEDGMENT 6

ABBREVIATIONS 8

LIST OF FIGURES 9

LIST OF TABLES 11

CHAPTER 1: INTRODUCTION 13

1.1 Background 13

1.2 Problem statement 14

1.3 Research questions 15

1.4 Methodology 16

1.5 Structure of the thesis 18

CHAPTER 2: LITERATURE REVIEW 19

2.1 Water allocation: An overview 19

2.2 Integrated Water Resources Management 20

2.3 Climate change impacts on water resources 22

2.4 Climate change scenarios 24

2.5 Models for IWRM 26

CHAPTER 3: DESCRIPTION OF STUDY SITE 32

3.1 Geographical location and topography 32

3.2 Climate 33

3.2.1 Temperature 33

3.2.2 Humidity 34

3.2.3 Evaporation 34

3.2.4 Rainfall 35

3.2.5 Hydrology conditions 37

3.3 Socio-economic development 40

3.3.1 Population 40

3.3.2 Economy structure 41

3.4 River network 41

3.5 Water Storage 41

3.6 Water use activities 43

CHAPTER 4: WATER BALANCE SIMULATION FOR THE HUONG RIVER BASIN

46

4.1 Schematization of the Huong River Basin 46

4.2 Data Requirements 48

4.2.1 Runoff 48

4.2.2 Water demand 54

4.2.3 The return flow 58

4.2.4 Reservoirs 59

4.3 The computation of scenarios 59

CHAPTER 5: RESULTS ANALYSIS 61

5.1 Water supply and water requirement results 61

5.1.1 Water supply 61

5.1.2 Water requirements 62

5.2 Results analysis 68

5.2.1 SC1 scenario 68

5.2.3 SC2 scenario 76

5.2.2 SC3 scenario 78

5.2.3 SC4 scenario 80

CHAPTER 6: CONCLUSIONS AND RECOMMENDATIONS 84

6.1 Conclusions 84

6.2 Recommendations 85

REFERENCES 86

APPENDICES 89

ABSTRACT

Water is essential for human, however, is finite and vulnerable (ICWE, 1992) In recent years, water crisis has been singled out as a major worldwide concern World-wide water demand has been reported to increase by over six times during the last century (Gourbesville, 2008) It is claimed to be the consequence of growth

in world population, which has been tripled during the last century, and speedy industry enlargement as well as agriculture development As a result, developing countries are those who mostly have to face with water scarcity Moreover, in recent years, the impacts of climate change on water scarcity have become an emerging concerned Extreme weather events, increasing uneven distribution of seasonal water leading to drought, floods and, for example, are some negative impacts of climate change, which has been alarmingly threatening the water balance

in developing countries

This research investigates the water availability and water demand in Huong River Basin in order to find out appropriate management measure to mitigate the water shortage problem in dry season

Huong River Basin which lies within Thu Thien Hue province, located in the specific monsoon climate area of Central Part of Vietnam with severe hydrological regime: very long dry season, short rain season but often with very large runoff This area usually witnesses water shortage in the long dry season Bearing the stress

of explosive increase of water demand from excessive population growth and blossoming economic development, combined with the decrease of water supply in dry season as a result of climate change impacts, the Huong River Basin’s water management need to be exquisitely investigated

The water use activities in this basin include domestic, irrigation, industry, livestock and aquaculture The purposes of this study are to analyze the water balance of Huong River Basin in three scenarios, the current scenario in 2010 and the future scenario in the future with the projected socio-economic development as well as

changes in the climate system characteristic according to B2 scenario To complete this task, the WEAP model is implemented to simulate the water balance in the basin with the help of MIKE-NAM model to calculate the water inflow to river basin from rainfall data and CROPWAT to compute the water requirement for crop The research shows there are currently imbalances between water supply and water demand in the dry season especially in March and April In 2030, the system cannot supply sufficient water quantity for the projected growing demand of socio-economic development scenario in June and July which are in dry season, right after the periodic flood The unmet demand is slightly go up compared to the current scenario However, the situation is much more severe in the scenario in which the climate change impacts are considered The water deficit is about four times bigger than it was in the scenario which only reflects the socio-economic development Moreover, it appears from February to July within different areas

After analyzing the results of simulation models, several structure and non-structure solutions are proposed

DECLARATION

I hereby certify that the work which is being presented in this thesis entitled, ―Water balance in the Huong River Basin in context of climate change‖ in partial fulfillment of the requirement for the award of the Master of Science in Integrated Water Resource Management, is an authentic record of my own work carried out under supervision of Associate Professor Nguyen Thu Hien and Dr Ngo Le An The matter embodied in this thesis has not been submitted by me for the award of any other degree or diploma

Date:

to this Master course, she always be there willing to instruct me about professional researching skills, turning me into an independence thinker which assists me to grow as a lecturer, a researcher and a better learner

I would also wish to express my deeply gratefulness to my second supervisor, Doctor Ngo Le An, who is the Deputy Head of Thuyloi University’s Hydrology and Water Resources Division for his tutor and corrections in the application of simulation models, the field which I had very few experience His mentorship was paramount in providing a well rounded experience consistent my long-term career goals He was the one to point out for me the importance of balancing the theoretical knowledge and ability to mastering in models use in Water Engineering and Water Management, at the same time, was the one enable me to do so He encourages me to run all the models used in my thesis on my own but was always there as a blanket to help me to learn from mistakes I am not sure many postgraduate students are given such treasured opportunity like mine

For everything you have done for me, Assoc Prof Hien and Dr An, I thank you

I would especially like to thank the Management Board including members from Thuyloi University, Hanoi University of Natural Resources and Environment

University and UNESCO-IHE for organizing this wonderful Master course and providing me a chance to sharpen my professional knowledge

Many thanks to my colleagues in the Department of Climate Change and Sustainable Development, HUNRE where I am working for supporting me in many way during the time I am busy with my Thesis

I would also like to acknowledge my friends from Thuyloi University including Ms Dao Thi Xuyen, Mr Nguyen Son Tung and many others for their help with the preparing input for models

Finally, words cannot express how grateful I am to my parents and my girlfriend who is currently staying in England for theirs unwavering support and continuous encouragement throughout my year of study and through the process of researching and writing this Thesis This achievement would not be possible without them, thank you

ABBREVIATIONS

CMS Cubic Meter per Second

DARD Department of Agriculture and Rural Development HRB Huong River

Basin

FAO Food and Agriculture Organization

GWP Global Water Partnership

HUNRE Hanoi University of Natural Resources and Environment

IMHEN Institute of Meteorology, Hydrology and Environment

IWRM Integrated Water Resources Management

MONRE Ministry of Natural Resources and Environment

MARD Ministry of Agriculture and Rural Development

MCM Million Cubic Meter

MW MegaWatt

NCAP the Netherlands Climate Assistance Program

NWC National Water Commission

TLU ThuyLoi University

UN United Nation

VNCID Vietnam National Commission on Irrigation and Drainage

WRS Water Resources System

LIST OF FIGURES

Figure 1.1: The location of Huong River Basin…… ……… 13

Figure 2.1: Cycle diagram of climate change impacts…… ……… 23

Figure 2.2: The Schematization of Huong River Basin………….……… 28

Figure 2.3: The general structure of NAM model (Nielsen & Hansen, 1973) … 30

Figure 3.1: Huong River Basin ……….………… … ……… 32

Figure 3.2: The annual average rainfall of observe stations…… ………….… 36

Figure 3.3: Monthly average rainfall of observed stations…… ………….…… 37

Figure 3.4: The annual runoff in the period from 1977 to 2010……… 38

Figure 3.5: Monthly inflow to the basin in the period 1977-2010……… 39

Figure 3.5: Map of cultivated area……… ………… 44

Figure 4.1: Schematization of Huong River Network……… 48

Figure 4.2: Map of 9 sub-basins in the Huong River Basin……… ……… 49

Figure 4.3: The variance between observed and simulated discharge in Thuong Nhat Station……… ……… 53

Figure 4.4: The variance between observed and simulated discharge in Binh Dien Station……… ……… 54

Figure 4.5: The variance between observed and simulated discharge in Co Bi Station ……… ………54

Figure 5.1: The inflow to branches in 2010, SC1 scenario……… ……… 68

Figure 5.2: Water requirements by sectors in 2010, SC1 scenario……….… … 69

Figure 5.3: Unmet demand by months in 2010, SC1 scenario……… …… 70

Figure 5.4: The monthly inflow to the upstream area of Bo River in SC1 scenario ……… 71

Figure5.5: The monthly water requirement of upstream Bo River Agriculture area

……… 81

Figure 5.14: Monthly unmet demand in 2030, SC4 scenario……… … 82 Figure 5.15: Monthly inflow to the area………… ……… 82

LIST OF TABLES Table 2.1: The changes in average temperature (0C) compared to the period

1980-1999 in Thua Thien Hue province by seasons in B2 scenario……… 25

Table 2.2: The changes in average rainfall compared to the period 1980-1999 in Thua Thien Hue province by seasons in B2 scenario ……… 26

Table 3.1: Monthly average temperature in Huong River Basin from 2009 to 2012 ……… 34

Table 3.2: Average humidity in Huong River Basin from 2009 to 2012………… 34

Table 3.4: Mean evaporation in Huong River Basin from 2009 to 2012 …………34

Table 3.5: Hydrological and hydro-meteorological stations network in the Huong River Basin………35

Table 3.6: Average population by Gender and by District in 2010……… 40

Table 3.7: Average population by District from 2009-2012……… 40

Table 3.8: Location and area of industrial zones ………45

Table 4.1: Description of sub-basins ……… 50

Table 4.2: NAM parameters explanation and boundaries (Shamsudin & Hashim, 2002) ………51

Table 4.3: The reliability of Nash coefficient……… 52

Table 4.4: Calibrated parameters……… 52

Table 4.5: Nash coefficient ……….53

Table 4.6: Vietnamese standard for domestic water use……… 56

Table 4.7: Vietnamese standard for livestock consumption ………57

Table 4.8: Water requirement for aquaculture ………58

Table 4.9: The scenarios development……….59

Table 5.1: Population by District in 2030 ……… 64 Table 5.2: The increasing rate of the amount of livestock ……… 65 Table 5.3: Monthly water requirement of nodes in SC1 and SC2 scenario……… 67 Table 5.4: Monthly water requirement of nodes in SC3scenario ………67 Table 5.5: Monthly water requirement of nodes in SC4 scenario……… 67 Table 5.6: Comparison of water requirement by sectors between SC2 and SC3

scenario……….79

Table 5.7: Comparison of water requirement by sectors between SC1, SC3 and SC4

scenario ………81

CHAPTER 1: INTRODUCTION

1.1 Background

Huong River, with its length of 128 km, is the largest river system in Thua Thien Hue province The river lies within the province and covers 3/5 of the total area which is the consist of Nam Dong, Huong Thuy, Huong Tra, Phong Dien District, part of A luoi, Quang Dien, Phu Vang, Phu Loc District and Hue city The drainage area is 3000 km2 In 2010, the population of Huong River Basin is about 1,137,962 people, most of them are living in the rural area which accounted for 92% of the population The topography of the river basin is complex including mountainous area, hills, lagoon, coastal plain and coastal sand dune Huong River is the main water source in this province which supplies water for almost all domestic usage and economic development activities

Figure 1.1: The location of Huong River Basin

1.2 Problem statement

Huong River basin lies in Thua Thien Hue Province, which located in the specific monsoon climate area of Central Part of Vietnam with severe hydrological regime: very long dry season, short rain season but often with very big flow and discharge Every year, this area has to bear number of extreme weather events such as typhoons, tropical cyclones which bring heavy rain with high density Moreover, the topography of the basin changes rapidly from the upstream high mountain zone down to the plain and large lagoon system, with hardly any transition area This results in a high runoff in the rainy season, and large floods and inundations downstream The annual average rainfall of this basin is 2800-3200 mm; however, nearly 80% of rainfall concentrates in the 4 months of rainy season causing uneven water distribution in the research area Additionally, the high temperature in dry season also increases the chance of losing water through evaporation Many reservoirs had been built to mitigate the water shortage in dry season by storing water from the rainy season Nevertheless, water shortage in dry season is still appeared as an emerging issue

Besides, the population growth and the development of water demand in every sector in this area leading to extremely high competing requirements of different stakeholder which exaggerate the water shortage status and intensify the pressure on water management tasks Also, Tran Thuc (2010) proved in his project ―Impact of climate change on water resources in the Huong River basin and adaptation measures‖ that the decrease of rainfall results in the decline of river flow in dry season and the increase of evapotranspiration due to higher temperature is appeared

in most of the climate change scenarios

All of the water use activities in Thua Thien Hue province, consisting irrigation, aquaculture, domestic, livestock, and industry as well as power generation depend mainly on Huong River There are currently large imbalances between water availability and water demand in this region as the existing system cannot supply

sufficient water for all stakeholders in dry season; as well as the exaggerated situation might appear in the future under the pressure of increasing demand and negatively influences on water supply due to climate change impacts To deal with this set of troubles and moving toward a sustainable society, there is a new paradigm which was proved its effectiveness in many regions with the similar situation such as South Africa, Myanmar, etc… with its own holistic approach, Integrated Water Resources Management (IWRM) As there are inter-links between all sectors to the Water Resources System (WRS) (Arnell, 1999), as well as the close interaction from the three components of WRS itself, the holistic approach of IWRM offers an ultimate solution to ease the increasing water scarcity for developing countries However, before drawing any optimal solutions and specific strategy for planning, IWRM requires huge numbers of exquisite analysis of WRS components Therefore, this study was brought out in order to contribute to IWRM planning with an insight of the balance between water availability and water demand among different stakeholder at the present as well as in projected future scenarios under climate change context Then, management measures will be proposed after considering changes within problems To achieve this goal, hydrological model MIKE11-NAM, Crop water requirement simulation model CROPWAT 8.0 and river basin simulation model (WEAP) are employed to address the impacts of changing water availability and water demands under different scenarios

3 How climate change impacts can affect the water shortage status in the river basin?

4 What are the recommended solutions to mitigate the water shortage in dry season with the consideration of climate change scenario in 2030?

1.4 Methodology

In order to carry out this research, relevant data and information in the study area must be collected, analyzed and simulated Basically, the data collection comprises (1) time series of the river discharge; (2) water demands of all water use activities in each region, including agriculture, aquaculture, domestic, livestock, industry and environment in the present and the forecast of those water use activities in the future under Climate Change Scenarios; (3) the characteristics of the infrastructures in the basin such as reservoirs (initial water level, operational rule curves, stage-area-volume curve, time series of rainfall and evaporation, linkages to users, priority of delivery, linkages to upstream) The set of information included the potential proposed measures that can be implemented to mitigate water shortage status in dry season of research area The methodology applied to conduct the Thesis can be summary in the following framework

Collecting data and simulation Data analysis Devoloping

scenarios

Result analysis

Proposing management measure

The approach of the study is using models to simulate the water status in Huong River Basin, therefore, a conceptual framework of basic step to apply models was developed

The focus is on WEAP model’s simulation; however, it is possible only when the input data of water supply and water demand are carefully evaluated The water supply input is the runoff calculated by MIKE-NAM The water demand input is the combination of the requirement of five main water use sectors, including irrigation requirement which was computed by CROPWAT 8.0 as well as domestic, livestock, industry, aquaculture which were evaluated based on Vietnamese statistic yearbook and Vietnam standard After that, WEAP was applied to examine the current water status in 2010 as well as alternative projected situation in 2030 based on developed scenarios both with and without the changes of climate system

1.5 Structure of the thesis

This thesis is divided into six main chapters including the introduction, literature review, the description of study area, the simulation of water balance in Huong River Basin, the result analysis, and finally, the conclusions and recommendations

Chapter 1: The chapter provides a brief overview of the physical characteristic of

Huong River Basin as well as brings out the problem statement about water resources management in the basin In addition, a set of research questions which objectify the purpose of the research and the methodology are also mentioned

Chapter 2: The literature review shows an overview of ―water allocation‖,

―Integrated water resources management‖, ―climate change impacts on water resources‖, ―Climate change scenarios‖ and ―Models for IWRM‖

Chapter 3: This chapter gives a closer look into the characteristics of Huong River

Basin with regard to the Geographical location and topography, the climate conditions, the socio-economic development, the illustration of river network, the current water use activities, and the water storage

Chapter 4: In this chapter, the simulation of models in Huong River Basin is

described The schematization of the basin is brought out; the data requirements for applying WEAP model are demonstrated Moreover, this chapter also defines three main scenarios

Chapter 5: The results of the three scenarios with respect to the water supply and

water requirement will be brought out and analyzed in this chapter It illustrates and compares the water shortage in of each water user node corresponding to each scenario

Chapter 6: Conclusions and recommendations will be shown in this chapter

CHAPTER 2: LITERATURE REVIEW

2.1 Water allocation: An overview

Water access entitlement was defined under the National Water Initiative as the exclusive right to access an amount of water from the executive water supplier, which fitted in water master plan (National water commission, 2011) The water access entitlement is determined through an allocation process which basically aims for satisfying the needs of different individual consumers The requirement for achieving an effective water allocation plan in any country all over the world initiated from the 1992 UN Conference on Environment and Development where water was asserted as a vulnerable resource that can be vanished over time by the excessive use without conservation of human’s activities

Water allocation plan is created based on the water allocation system which is the set of policies and rules for maintaining the equilibrium between water availability and water demand without disrupting the sustainable development process of a country and its environment Fundamentally, there are two approaches of water allocation system, the non-volumetric systems and volumetric systems (NWC, 2011) The non-volumetric systems control the use of water based on the input and output of water rather than the particular amount of water for each sectors On the other hand, the volumetric systems, which are the mostly used one, relied on quantity of water used through some methods such as block tariff, market-based pricing, single rate or multi rates (Tsur, Dinar and Doukkali, 2002) Recently, it is proved that the water allocation process shows its highest efficiency when it is evolved in basin level However, allocation focuses on basin level still need to take

in to account the national level water allocation plan and variety of stake-holders’ agreements (Speed, 2013) The objective of water allocation lies under the umbrella term ―balancing water supply and demand‖, within this concept, there are four main focus including equity, environment protection, development priorities and promoting efficiency use of water (Speed, 2013)

According to the National Report on Water Resources in 2012, Vietnam has rick sources of water considering the total amount of surface water However, among eight main basins over the country, only four of them have enough water to satisfy demands in dry season That fact raises a challenge for water resources planning task to balancing the uneven seasonal rainfall, then to achieve maximum efficient water use Water allocation systems in Vietnam are created based on volumetric systems varies within sectors The institutional arrangement in Vietnam is referred

to a hierarchical organization structure, with the centralized Government Therefore, the water resource are managed by the Government, at highest level, then, at the lower level, the Ministry of Natural Resources and Environment and the Ministry of Agriculture and Rural Development are cooperated to building the overall water resources planning to propose to the Government The subordinate level of Ministry

is the provincial local authorities including provincial People’s committees, the Departments which are directly under Ministries (VNCID, 2010) The overlay of authorities is also a challenge while applying Integrated water resources management

2.2 Integrated Water Resources Management

Date back to the past, where the water management approaches only consider about separate sectors such as water supply, irrigation, sanitation, and energy generation

In 1977, attention of international experts was still pay in the water supply and sanitation in UN Conference in Mar de Plata; the water related issue was pronounced in Brundtland Report of the World Commission on Environment and Development in 1987 is about pollution and water supply (Savenije& Van Der Zaag, 2008) Until 1992, when the UN Conference on Environment and Development was held in Rio de Janerio and the International Conference on Water and Environment was held in Dublin, the concepts of IWRM as well as its key principles were widely discussed The principles of IWRM are based on the Dublin Principles which emphasized that water is finite, vulnerable, and essential for

management Moreover, it is stated that participatory approach is crucial in water management as well as the consideration of water as social economic good has to be added in water management plans The prevalent use of term ―Integrated Water Resources Management‖ was appeared in the late 1990s by the promotion of it uses

by the Global Water Partnership (Biwas, 2008) In 2002, at the Johannesburg World Summit on Sustainable Development (WSSD), The Technical Advisory Committee

of the Global Water Partnership defined Integrated Water Resources Management

―as a process, which promotes the coordinated development and management of water, land and related resources in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems‖ (GWP, 2000)

As the new challenges in the new era put pressure on every aspects of water resources, IWRM with it holistic system view approach is widely accepted by many scholars and practitioners due to several reasons: it provide a comprehensive cross-cutting approach through all types of resources and sectors; it creates a connection between livelihood of the catchment and resources perspective; it also focus on the collaboration between elements of good government as well as stakeholders (Gain

& Schwab, 2012) From that perspective, IWRM itself specifically enhances the traditional water resources management in three ways: cross-sectoral of goals and objectives, the spatial focus on river basin instead of on administrative boundary, the participation of stakeholders in decision-making process (Cap-net, 2009) In particular, Gooch and Stalnacke (2003) indicated that the distinction between IWRM or Integrated River Basin Management (IRBM) and ―Traditional‖ Water Resources Management relies on the scope and sphere of operation of the two The

―traditional‖ one only focused on satisfying the perceived demand with oriented approach while the ―integrated‖ one attempts to bring out water resource management on the demand, supply, and use of water with a cross-sectoral approach This new paradigm was applied to many river basins in South Africa, Australia, Europe, and Mozambique

sector-However, the concept of integrated water management considering climate change has not been well discussed and reported in literature (Lin et al., 2010) Further, due attention has not been given to such practices in developing countries (Qin and Xu, 2011) A few attempts have been made to address the water resources management issues considering one or another issue of climate change (Ragab and Prudhomme, 2002; Mitchell et al., 2007) However, integrated water management considering integration of various possible water sources to satisfy the demands of different users, environment protection, land and urban planning have not been considered

2.3 Climate change impacts on water resources

On the Global scale, among various environment factors influenced by climate change, water resources are of the major concern (Frederick and Major, 1997) Global warming due to the increase of greenhouse concentration is likely to have significant effects on the hydrological cycle (IPCC, 1996) In the researching of the relationship between climate change and water resources, especially the impacts of climate change, Yang Nan, Bao-Hui and Chun-Kun emphasized that the hydrological cycle is the theoretical basis; they also sum up the relationship into a cycle diagram of climate change impacts:

Figure 2.1: Cycle diagram of climate change impacts (Nan, Bao-hui & Chun-kun,

2011)

The hydrological cycle will be intensified and changed in time and space It will be more precipitation and more evaporation, but the extra precipitation will be unevenly distributed all over the world, as a result, some parts in the world may witness the decline in precipitation or major alteration in the timing of rainy and dry season (Arnell, 1999) The threat from the Second Assessment Report of Intergovernment Panel on Climate Change was about the growing trend of floods and droughts There are numerous of study on water resources negatively influenced by global climatic change, especially in arid area and semi-arid area such

as United States, Australia, Canada, South Africa, Greece, South Asia or Mediterranean (Dawadi& Ahmad, 2012; Arnell, 1999; Beck &Bernauer, 2011; Mcfarlane& Stone et al., 2012) In Vietnam, one of the most vulnerable countries exposed to climate change impacts, especially in water resources sectors, there are several studies about this problem, however, these are mostly the assessment in the general impacts without holistic approach In 2010, there was one prominent project

in Huong River Basin which was done by the cooperation between Vietnamese Institute of Meteorological, Hydrological and Environment (IMHEN) and The Netherlands Climate Assistance Program (NCAP) called ―Climate Change Impacts

in Huong River Basin and Adaptation in its Coastal District PhuVang, ThuaThien Hue province‖ Another separated research was brought out by Tran Thuc (2010) which is contributed to NCAP’s Project The two projects share the same ideal is that climate change causes high river flow resulted in the appearance of more floods due to the intensive rainfall in rainy season and the decline in rainfall a long with the rise of evapotranspiration causing more droughts in dry season under most scenarios However, specific management measures still remain unrevealed

2.4 Climate change scenarios

Climate change scenarios are Special Report on Emissions Scenarios (SRES) which have been developing and updating by IPCC since 2000 (IPCC, 2000) The changes

of green house gases emissions were approved to be used as the references for the major changes in natural factors such as physical characteristic of hydrological systems, temperature, sea level …etc.SRES is the set of projections of future green house gases emission with considering the changes of population, economics, political structure and lifestyle in the next few decades (Arnell, 1999) Each scenario starts with a storyline which describes the way these factors change The storylines were gathered into four scenario families which contained six scenarios These four families can be characterized as follow:

A1: intensive population growth, very rapid economic development, increase in general wealth with convergence between regions and reduced differences in regional per capita income Materialist-consumerist predominant with rapid technological change A1 family was sub-divided into three assumption about sources of energy: focusing on fossil fuel (A1F1), non-fossil fuel (A1T), and balance between these resources (A1B)

B1: same population growth as A1, however, economic development focuses on environmentally sustainability with cooperation and regulation within global scale Green and efficient technologies are developed

A2: the economic is heterogeneous, market-led, less rapid growth than A1 but faster population growth The underlying theme is self-reliance and preservation of local identities Economic growth is regionally oriented, and hence both income growth and technological change are regionally diverse

B2: Population increases at lower rate than A2 but at higher rate than A1 and B1, the general development follows environmentally, economically and socially sustainable locally oriented pathways

Due to these characteristics, the scenarios can be classified into three groups; the high emission group contains A1F1 and A2, the medium one is B2 and the least emission is B1

Based on the IPCC’s global-scale database about SRES, The MONRE developed the Greenhouse gases emission scenarios for Vietnam in 2009 and updated it in

2012 It is appeared that the B2 scenario is the most suitable with the orientation of socio-economic development as well as the current conditions of Huong River Basin, therefore, this study will reveal the insight of the balance between water availability and water demand at the present as well as in projected future circumstances considering B2 scenario physical characteristics as the primary influence factors These factors are shown in the following tables:

Table 2.1: The changes in average temperature ( 0 C) compared to the period

1980-1999 in Thua Thien Hue province by seasons in B2 scenario

The time mark in XXI century

2020 2030 2040 2050 2060 2070 2080 2090 2100 Winter from XII to II 0.5 0.8 1.1 1.4 1.7 2.0 2.3 2.5 2.8 Spring from III to V 0.6 0.9 1.2 1.6 1.9 2.2 2.5 2.8 3.0 Summer from VI to VIII 0.5 0.7 1.0 1.2 1.5 1.8 2.0 2.2 2.4 Autumn from IX to XI 0.5 0.7 1.0 1.3 1.6 1.9 2.1 2.3 2.5

Unit: %

Table 2.2: The changes in average rainfall compared to the period 1980-1999 in

Thua Thien Hue province by seasons in B2 scenario

The time mark in XXI century

2020 2030 2040 2050 2060 2070 2080 2090 2100 Winter from XII to II -0.9 -1.2 -1.7 -2.2 -2.7 -3.2 -3.6 -3.9 -4.3 Spring from III to V -1.7 -2.4 -3.4 -4.4 -5.4 -6.3 -7.1 -7.8 -8.5 Summer from VI to VIII 1.4 2.0 2.8 3.6 4.4 5.1 5.8 6.4 6.9 Autumn from IX to XI 2.4 3.5 4.9 6.4 7.8 9.1 10.2 11.3 12.2

Unit: %

2.5 Models for IWRM

In a river basin, there are numerous factors which influent water resources, however, it can be classified into two major kinds of factors, namely Internal factors and external factors The internal factors are the direct influences to the water amount in supply side and demand side including hydrological conditions, demand

of different stakeholders or sectors These factors are always changing in time and space Besides, the external factors such as economic growth, policy orientation, production prices, etc constrain internal factors and it changes so fast that pose urgent threats of developing tools to respond to variety circumstances Moreover, there must be tools to fill the gap between watershed hydrology and water management through combining physical components of hydrological process and integrated water management context (Yates et al, 2009) Throughout the last decade, along with the excessively growth of technology, simulation model progressively developed to support decision making process with the approach of integrated water resources management

MIKE-BASIN

MIKE BASIN is an integrated water resource management and planning computer model which is fully integrated into the ArcGIS environment (DHI, 2006) Basically, this model represents mathematically the simulation of water availability and water demand In the working environment, a network model is created with

the river and their tributaries are represented by a network containing branches and nodes The branches represent individual tributary sections and the nodes represent confluence, locations where certain water activities may occur and important locations where model results are required MIKE BASIN model calculates a mass balance equation in every node and branch of river basin where multi-sectoral allocation and environmental issues can be schematized (Seppelt &Voinov et al.,

et al, 2009) The system is represented in terms of its various sources of supply (e.g rivers, groundwater, and reservoirs), withdrawals, transmission, wastewater treatment facilities, water demands (i.e., user-defined sectors but typically comprising industry, mines, irrigation, domestic supply, etc.), and ecosystem requirements

WEAP model has two primary functions (Sieber et al 2004):

 Simulation of natural hydrological processes (e.g., evapotranspiration, runoff and infiltration) to determine the availability of water in catchment

 Simulation of human activities that have effect on the natural system to influence water resources and their allocation (i.e., consumptive and non-consumptive water demands) to evaluate these impacts

WEAP represents a water system in a schematization of main supply, demand nodes and their reaches The data layer and level of data can be customized (e.g., by combining demand sites) to fit with the particular purpose of analysis, and minimize data shortage issues The physical characteristics of the network are visualized by graphical boundary which can highly cooperate with ArcGIS environment

One of the most important tools in WEAP is the developing alternative scenarios tool which can be applied by adjusting parameters such as reservoir operation curves, hydropower generation capacity, etc and the hydrology characteristics such

as rainfall, runoff, evaporation, etc as well as the impact of different development scheme and management practices

By setting priorities and supplying references for each node, the allocation rules can

be created or changed following scenarios The priorities of all demand sites are between 1 and 99, where 1 is the highest priority and 99 the lowest

Figure 2.2: The Schematization of Huong River Basin

WEAP is being applied in a number of international projects such as the Jordan River basin, study of the hydrologic, economic, ecological, health, and institutional dimensions of small reservoir ensemble planning and management in the Volta (Ghana), Limpopo (Southern Africa), and Sao Francisco (Brazil) basins It can be applied in data-rich basin such as Neckar basin, Germany and data-scarce basin in Oueme, Benin (Hoff et al., 2007)

In order to provide input for WEAP in water allocation process, several models were used in this thesis such as MIKE 11-NAM (Nedbør Affstrømnings Model) to calculate inflow in supply side and CROPWAT to compute water requirement for irrigation in demand side

MIKE 11 - NAM

Due to its ability to simulate the hydrological process in detail, NAM was chosen to apply in this project NAM is ―a deterministic, lumped conceptual rainfall-runoff model which is originally developed by the Technical University of Denmark‖ (Nielsen & Hansen, 1973) Particularly, hydrological cycle is considered as the basis of quantitative simulation of the runoff in watershed and the evaluation of parameters is the average value of the whole watershed based on physical process (Shamsudin and Hashim, 2002) The general structure of NAM comprises 4 storages, including snow storage, surface storage, lower zone storage and underground storage that shown in Figure 2.3

Figure 2.3: The general structure of NAM model (Nielsen & Hansen, 1973)

However, within the scope of this thesis, only the surface storage was taken into account since there is no snow in the research area and the thesis is only about surface water balancing Basically, the input data required in this model are daily rainfall and potential evaporation, and then the outcome of the model is the basin runoff over time

CROPWAT 8.0

CROPWAT FOR WINDOW 8.0 is a decision supporting tool developed by the Land and Water Development Division of FAO The model helps developing irrigation scheme under various management and water supply scenarios by providing result of the calculations with regard to evapotranspiration, crop water requirement, and irrigation requirement (Nazeer, 2009) The crop water requirement

is the amount of water needed for various kinds of crops to grow optimally, and it depends mainly on the climate conditions, crop types, and the growth stage of crop The potential evapotraspiration (ET0) was calculated by Penman-Monteith equation, the equation can be developed into direct calculation of any crop

To carry out this thesis, WEAP was chosen to calculate water balance in Huong River Basin Additionally, to provide input for WEAP, MIKE-NAM was employed

to define the inflow from the rainfall data and CROPWAT was adopted to compute the water requirement for irrigation

CHAPTER 3: DESCRIPTION OF STUDY SITE

3.1 Geographical location and topography

Huong River Basin totally fits in Thua Thien Hue province, which is located in coastal area of Northern Central Vietnam The area of Huong River basin is about

3000 km2, occupied nearly 3/5 of province’s area It is situated between 15059’–16036’N and 107009’ - 107051’E Huong River Basin is adjacent to the lagoon system Tam Giang– Cau Hai to the North, Da Nang City, Quang Nam Province to the South, Asap–A Luoi River Catchments and O Lau River Catchment to the West and Nong River Catchment to the East, including all or a part of districts: Nam Dong, Huong Thuy, Phu Vang, Phu Loc, Phong Dien, Quang Dien, A Luoi, Huong Tra and Hue City

Source: VACNE, 2012

Figure 3.1: Huong River Basin

The topography of Huong River Basin is mostly mountainous area occupied 70% of the area, the distance from the mountainous area to the plain is short resulting in a

steep slope The West and South-Western part of the province is the location of Truong Son Mountain with the average elevation of 1000m The direction of the mountain’s peak combines with the South-East circulation created one of the highest rainfalls among other area

The elevation of mountainous area in the West and South-Western part of the province varies from 250 – 750 m in the low area and 750 – 1800 m in the high area The mountains form a curvy shape surrounding the plain, plus, the degree of the cliff’s slope is about 35 degree and the length of the river here is short Therefore, it is not only causes the increase in the inflow, it also creates flood to the downstream area

The hilly region which separated into 3 typical types, the low area with the elevation of 10 – 50 m, the medium area with 50-125 m and the high area with 125 – 250 m The direction of this region is vague and the hydrology regime is complicated then, it is hard to determine the sub-basin However, this kind of topography creates many valleys which are extremely important for building multi-purposes reservoirs such as Binh Dien reservoir, Duong Hoa reservoir, etc

The coastal plain concentrated in the North and North-Eastern part of the province, adjacent to the lagoon system The sand dune which the elevation is 20-30 m surrounds the Tam Giang- Cau Hai lagoon to the East and protect the lagoon from the ocean circulation impacts

3.2 Climate

3.2.1 Temperature

The temperature in Huong River Basin varies from 19-290C January has the lowest average temperature of about 210C in the plain and 190C in the mountainous area The highest monthly average temperature usually appears in June or December of

250C in the mountainous area and 280C in the coastal plain since the South-West wind strikes

Table 3.1: Monthly average temperature in Huong River Basin from 2009 to 2012

Month

Station I II III IV V VI VII VIII IX X XI XI Year

Hue 21 23.2 23.7 26.1 29.3 29.4 28.8 27.4 27.4 24.8 22.6 21.3 25.4 Nam Đong 21.6 23.8 24.4 26.7 29.3 28.8 28.2 27.2 26.9 24.5 22 21.3 25.4

Table 3.4: Mean evaporation in Huong River Basin from 2009 to 2012

Month

Station I II III IV V VI VII VIII IX X XI XI Year

Hue 46,2 42,0 62,5 85,5 118,4 139,0 156,2 136,0 84,6 60,3 49,4 42,3 1022,3 Nam Đong 47,0 52,4 81,7 99,6 104,7 103,4 111,0 98,6 66,7 44,1 33,3 32,5 875,1

A Luoi 41,1 44,0 62,3 73,1 88,4 132,6 148,2 129,7 62,2 39,7 33,4 30,7 885,4

Source: Vietnamese Statistic Yearbook 2012

Unit:%

3.2.4 Rainfall

There are 10 gauge stations and 8 hydrological stations in this basin Among these 8 hydrological stations, there are 5 stations that observed the water elevation and runoff, the others 3 station only collected data of water elevation

Table 3.5: Hydrological and hydro-meteorological stations network in the Huong

5 Duong Hoa hydrological

Source: National center for documentation, Ministry of Natural Resources and Environment, 2014

Thua Thien Hue province has one of the largest amounts of rainfall in Vietnam with annual average rainfall of 2800-3800mm in the period 1977-2010 However, the

rainfall slightly varies different parts of this province The highest annual rainfall of approximately 3800 mm/a which had been recorded concentrated in the south-west part including Aluoi, Nam Dong and Phu loc District The least exprerienced annual rainfall of about 2741 mm/a are in the Northern Part consisting Co bi and Phu Oc stations which are located in Phong Dien and Quang Dien District, respectively The central part received the annual rainfall of nearly 2980 mm/a

Figure 3.2: The annual average rainfall of observe stations

In this province, there are two typical seasons including rainy seasons and dry season The rainy season starts from September to December, and the rest of the year is dry season This area witnesses the tremendous unevenly distribution of monthly rainfall since the amount of rainfall concentrate mostly in the four months

of rainy season, occuping 70% of total monthly average which is 2232 mm During the rest 8 months of the year which belongs to dry season, the total monthly average rainfall is 958 mm, take the other 30% of total amount The average number of rainy day in the plain region is 200-220 days and in mountainous area is 150-170 days

0 500 1000 1500 2000 2500 3000 3500 4000

hue a luoi nam

dong

thuong nhat

phu oc binh dien co bi ta luong

Annual Rainfall

(mm/year)

Stations

Figure 3.3: Monthly average rainfall of observed stations

3.2.5 Hydrology conditions

The average annual runoff of Bo River is approximately 56.0m3/s and Huu Trach River has annual discharge of 41.1m3/s The runoff is unevenly distributed during months in the year, it is divided into floods season from September to November and low flow season from January to September Often, in flood season, the average annual runoff occupies about 69.1% in Bo River, 66% in Huu Trach River and 64%

in Ta Trach River of the total annual inflow In low flow season, the average annual discharge is about 30% in Bo River, 34% in Huu Trach River and 36% in Ta Trach River of the total annual runoff

The annual average surface water inflow of the basin is approximately 6258 MCM/a in the period of 1977-2010 Overall, the total annual inflow of this area witnesses a significant increase