Luận văn Thạc sĩ CHLB Đức _ Matriculation no.11074596

IMPROVEMENT OF WATER SUPPLY FOR AGRICULTURAL
PRODUCTION THROUGH OPERATION AND MANAGEMENT
BY CONSIDERING SALINITY INTRUSION ADAPTATION
≥ 0.8‰

Measuring of salt concentration

Salt concentration

< 0.8‰

1 hour

1 hour

1 hour
Last point

< 0.8‰

Pump


MASTER THESIS – TERMA VIETNAM
Cologne University of Applied Science – Institute for Technology and Resources
Management in the Tropics and Subtropics
and
Vietnam Academy for Water Resources – Center for Training and International
Development

IMPROVEMENT OF WATER SUPPLY FOR AGRICULTURAL PRODUCTION

THROUGH OPERATION AND MANAGEMENT BY CONSIDERING SALINITY
INTRUSION ADAPTATION
CASE STUDY: TU CAU IRRIGATION SYSTEM, VU GIA_ THU BON RIVER BASIN,
VIETNAM

Viet Nguyen Duc
2011


TERMA VIETNAM
Cologne University of Applied Sciences
Vietnam Academy for Water Resources
ITT - Institute for Technology and Resources Management
in the Tropics and Subtropics

Improvement of water supply for agricultural production through operation
and management by considering salinity intrusion adaptation
Case study: Tu Cau Irrigation System, Vu Gia_Thu Bon river basin, Vietnam
Thesis to Obtain the Degree of
MASTER OF SCIENCE
“TECHNOLOGY AND RESOURCES MANAGEMENT IN THE TROPICS AND
SUBTROPICS”
DEGREE AWARDED BY COLOGNE UNIVERSITY OF APPLIED SCIENCES

PRESENTS:
VIET DUC NGUYEN
SUPERVISOR OF THESIS ITT
PRO. DR. SABINE SCHLÜTER
SUPERVISOR IN VIETNAM
DR. PHONG NGUYEN TUNG

DATE OF SUBMISSION
13.09.2011
presented by
Viet Duc Nguyen Student no:11074596 Email:
en.wikipedia.org/ FH_Koeln_IWZ_from_NordenG


“Water is the key for life and production activities of human, not only in the present but
also for the future…”

Flood and Salinity Management the Mekong Delta, Vietnam 2008


TABLE OF CONTENT

13 September 2011

TABLE OF CONTENTS
LIST OF TABLES................................................................................................................8
LIST OF FIGUGES..............................................................................................................9
LIST OF ACRONYMS........................................................................................................11
ACKNOWLEDGEMENTS.................................................................................................12
ABSTRACT........................................................................................................................13
KEYWORDS......................................................................................................................13
SOFTWARE USED............................................................................................................13
CHAPTER I.

INTRODUCTION..................................................................................15

1.1.

BACKGROUND.......................................................................................................15

1.2.

PROBLEMS STATEMENT......................................................................................17

1.3.

1.4.

1.2.1.

Tu Cau irrigation system..............................................................................17

1.2.2.

Operation and management (O&M) at Tu Cau irrigation system................17

1.2.3.

Impact of salinity intrusion to agricultural production..................................18

OBJECTIVES..........................................................................................................19
1.3.1.

Objective......................................................................................................19

1.3.2.

Specific objective.........................................................................................19

APPROACH AND METHODOLOGY......................................................................19
1.4.1.

Approach......................................................................................................19

1.4.2.

Methodology.................................................................................................20

CHAPTER II.
2.1.

LITERATURE REVIEWS......................................................................21

SALINITY INTRUSION IMPACT ON AGRICULTURAL PRODUCTION................21
2.1.1.

Definition of the salinity intrusion.................................................................21

2.1.2.

Previous studies on salinity intrusion adaptation through O& M.................21

2.1.3.

Impact of salinity on agricultural production in Vietnam..............................23

CHAPTER III.
3.1.

3.2.

STUDY AREA......................................................................................26

NATURAL CONDITIONS.........................................................................................26
3.1.1.

Terrain of irrigation area...............................................................................26

3.1.2.

Soil types......................................................................................................28

3.1.3.

Land use.......................................................................................................29

CLIMATE..................................................................................................................31

Master Thesis| Cologne University Applied Sciences


3.3.

3.4.

3.5.

HYDROLOGY AND VINH DIEN RIVER..................................................................32
3.3.1.

Location........................................................................................................32

3.3.2.

Topography of Vinh Dien River....................................................................32

3.3.3.

Hydrology.....................................................................................................32

3.3.4.

Water quality................................................................................................33

3.3.5.

Tides regime.................................................................................................34

SOCIO – ECONOMIC CONDITIONS.....................................................................36
3.4.1.

Population....................................................................................................36

3.4.2.

Economic......................................................................................................36

3.4.3.

Culture - Society...........................................................................................37

AGRICULTURAL PRODUCTION............................................................................37
3.5.1.

Cultivated area and main crops in the year.................................................37

3.5.2.

Rice schedule and varieties.........................................................................38

3.5.3.

Cultivation technique....................................................................................38

3.5.4.

Others production.........................................................................................39

3.6. SALINITY INTRUSION IMPACT ON AGRICULTURAL PRODUCTION IN THE
STUDY AREA.................................................................................................................40
3.6.1.

Damages of area..........................................................................................40

3.6.2.

Damages on crop productivity.....................................................................41

CHAPTER IV.
4.1.

4.2.

4.3.

TUCAU IRRIGATION SYSTEM...........................................................42

HEAD WORK – TU CAU PUMPING STATION......................................................42
4.1.1.

Pump units and electric equipments............................................................42

4.1.2.

Problems of the machines and equipments................................................43

CANAL AND HYDRAULIC WORKS IN THE CANAL.............................................43
4.2.1.

Main canal....................................................................................................43

4.2.2.

Primary and secondary canal......................................................................45

4.2.3.

Check regulator............................................................................................45

4.2.4.

Temporary pumping station..........................................................................46

OPERATION AND MAINTENANCE........................................................................47
4.3.1.

O&M of Tu Cau pumping station..................................................................47

4.3.2.

Some shortcomings in O&M........................................................................50

CHAPTER V.

RESULTS AND DISCUSSIONS..........................................................51


5.1.

5.2.

RESULTS.................................................................................................................51
5.1.1.

Mapping damage due to salinity intrusion...................................................51

5.1.2.

Water balance calculations in the system...................................................58

DISCUSSIONS........................................................................................................65
5.2.1.

Approach and methodology to adapt the impacts of salinity intrusion........65

5.2.2. Proposed alternatives of O&M for water supply to adapt salinity
intrusion 66
5.2.3.

Proposal O&M framework in adaptation of salinity intrusion.......................74

5.2.4.

Initial benefit analyses..................................................................................75

CHAPTER VI.

CONCLUSIONS AND RECOMMENDATIONS...................................77

6.1.

CONCLUSIONS......................................................................................................77

6.2.

RESULTS AND LIMITATION OF RESEARCH........................................................77

6.3.

RECOMMENDATIONS...........................................................................................78

6.4.

FURTHER NEED OF RESEARCH.........................................................................78

BIBLIOGRAPHY................................................................................................................79
APPENDIX.........................................................................................................................83


LIST OF TABLES
Table I-1: Relationship between rice schedule and operating time of Tu Cau pumping
station.................................................................................................................................18
Table II-1: Global area is salinity or affected by salinity....................................................24
Table III-1: Monthly rainfall figures in Da Nang station in period 2004 – 2008.................31
Table III-2: Location and characteristics of Vinh Dien River.............................................32
Table III-3: Number of diurnal tidal days in a month over the years at stations...............34
TableIII-4: Cultivated area in the study area in the period 2008 – 2010...........................37
Table III-5: Statistics on livestock in the study area in 2011.............................................39
TableIII-6: Statistic table of reduced productivity in 2011 against that in 2010.................41
Table IV-1: Statistics of length of the primary canal at Tu Cau (unit: m)..........................45
Table V-1: Statistic table of mapping damage in Summer- Autumn crop, 2011...............52
Table V-2: Climate in Da Nang station in period 1971 – 2000..........................................58
Table V-3: Average monthly rainfall in Da Nang station in period 1971-2008.................59
Table V-4: Length stage of two main rice crops in Tu Cau irrigation area........................59
Table V-5: Monthly irrigation coefficient for Winter-Spring crop.......................................60
Table V-6: Monthly irrigation coefficient for Summer – Autumn crop...............................60

Table V-7: Discharge of water demand at Tu Cau (Winter -Spring crop).........................61
Table V-8: Discharge of water demand at Tu Cau (Summer-Autumn crop).....................61
Table V-9: Actual discharge supplied by Tu Cau irrigation system in Winter - Spring
crop relating salt concentration..........................................................................................63
Table V-10: Actual discharge supplied by Tu Cau irrigation system in Summer Autumn crop relating salt concentration............................................................................63
TableV-11: Test results of salt concentration after diluting water at Tu Cau pumping
station, Dien Ngoc commune in year 2011........................................................................68
Table V-12: Total water volume permitted to be pumped into the regulating reservoir
corresponding to each salt concentration level.................................................................69
Table V-13: Total water volume obtained when applying new O&M................................73
Table V-14: Total water volume permitted to be pumped into the regulating reservoir
............................................................................................................................................75



LIST OF FIGUGES
Fig I-1: Problem statement tree of salinity intrusion to Tu Cau irrigation system.............16
Fig I-2: Tu Cau Pumping station – Dien Ngoc commune.................................................17
Fig I-3: Suction chamber of Tu Cau pumping station........................................................17
Fig II-1: Generic approach to determining climate change impacts and agricultural
adaptation strategies..........................................................................................................22
Fig II-2: Salinity intrusion in some provinces in the South Central Coast - VN................25
FigIII-1: Vu Gia - Thu Bon River Basin Map......................................................................32
Fig III-2: The curve reflecting the tide level inflection from June 15 th, 2011 to July2nd,
2011 in Da Nang estuary....................................................................................................35
Fig III-3: The curve reflecting the tide level inflection from July2 nd, 2011 to July17th,
2011 in Da Nang estuary....................................................................................................35
Fig III-4: Drough at Đien Ban district – Quang Nam province, 2010................................40
Fig III-5: Drough atHoa Quy ward – Danang city, 2010....................................................40
Fig III-6: Statistics of rice cultivation area of years 2008, 2009, 2010 and 2011..............41

FigIV-1: O&M house of Tu Cau pumping station..............................................................42
Fig IV-2: Electric pumps....................................................................................................43
FigIV-3: Electrical equipments...........................................................................................43
Fig IV-4: Map of Tu Cau irrigation scheme.......................................................................44
Fig IV-5: Main canal in position +712m.............................................................................44
Fig IV-6: Main canal in position +2,272m..........................................................................44
Fig IV-7: Check regulator in the main canal......................................................................45
Fig IV-8: Outlets in inter - farm canal................................................................................45
Fig IV-9: Pump to cope with drought at Sen lake.............................................................46
FigIV-10: Pump from Sen lake into the main canal..........................................................46
Fig IV-11: Organization chart of Tu Cau irrigation system................................................47
Fig IV-12: Diagram of operation procedure of Tu Cau pumping station...........................49
Fig IV-13: Measuring salinity at Tu Cau Irrigation management unit...............................50
Fig IV-14:Listing the salt concentration result at Dien Ban Sub- IME..............................50


Fig V-1: Relationship between water demand for rice and actual discharge supplied
by Tu Cau irrigation system under impacts of salinity intrusion in Summer - Autumn
crop in 2011........................................................................................................................64
Fig V-2: Diagram calculation of volume of water shortage at the study area...................65
Fig V-3:Taking water sample of Vinh Dien River...............................................................68
Fig V-4: Measuring the salt concentration........................................................................68
Fig V-5: Temporal relationship between salt concentration at Tu Cau pump station
and tide amplitude at Da Nang estuary on 08 July 2011 (semi- diurnal tide)...................70
Fig V-6: Temporal relationship between salt concentration (at Tu Cau pump station)
and tide amplitude (at Da Nang estuary) on 08 August 2011 (diurnal tide)......................70
Fig V-7: Diagram of the new changing in O&M relating tide amplitude............................71
Fig V-8: Relationship between total water storage volume after changing O&M and
total volume of water shortage in the Summer – Autumn crop, 2011...............................73
Fig V-9: Proposal on new operating procedure relating tidal amplitude...........................74

ACKNOWLEDGEMENTS

16 August 2011


ACRONYMS

13 September 2011

LIST OF ACRONYMS
GOVN

Government of Vietnam

MARD

Ministry of Agriculture and Rural Development

DARD

Department of Agricultural and Rural Development

FAO

Food and Agricultural Organization

IPCC

Intergovernmental Panel on Climate Change

NGOs

Non – Government Organizations

IMC

Irrigation Management Company

IME

Irrigation Management Enterprise

O& M

Operation and Management

UBND

People’s Committee

UNDP

United Nations Development Program

VND

Vietnam Dong (exchange rate: US$ 1.00 = 20.570 VND)

WUOs

Water Users Organizations

QWD

Discharge of water demand by rice (m3/h)

QWD_SA

Discharge of water demand for Summer - Autumn crop (m3/h)

QWD_WS

Discharge of water demand for Winter - Spring crop (m3/h)

Qwsl

Actual discharge of water supplied for Tu Cau irrigation system (m3/h)

Qp

Actual discharge pump for Tu Cau pumping station (m3/h)

Qlw

Discharge of water shortage per hour of Tu Cau irrigational system (m3/h)

Wlw

Total volume of water shortage of Tu Cau irrigational system (m3)

Wrl

Total additional water volume pumped into regulation reservoirs (m3)

Wtide

Total water volume which is additionally pumped based on tide amplitude
(m3)


ACKNOWLEDGEMENT

13 September 2011

ACKNOWLEDGEMENTS
This thesis could not have been completed without the help, encouragement and
support from a number of people who all deserve my sincerest gratitude and
appreciation.
First of all, I am heartily thankful to my German supervisor, Prof. Dr. Sabine
Schluter, Center for Natural Resources and Development (CNRD) and the Institute for
Technology and Resources Management in the Tropics and Subtropics (ITT) – Cologne
University of Applied Sciences, for her constant guidance and constructive criticism with
encouragement throughout the study period.
It is an honor for me to thank my Vietnamese supervisor, Dr. Phong Nguyen Tung,
Director of Center for Training and International Cooperation (CTIC) – Vietnam Academy
for Water Resources (VAWR), for his experience support and materials on the adaptation
of operation and maintenance to improve water supply of agricultural production
considering salinity intrusion in Vietnam.

I also would like to acknowledge my old colleagues at the Institute for Water and
Environment (IWE), my teachers and Mrs. Ha Nguyen Viet who is a classmate at
TERMA Master Program, staffs of Center for Training and International Cooperation
(CTIC) – Vietnam Academy for Water Resources (VAWR) and staffs of Dien Ban Branch
of Irrigation Enterprise for their supports and encouragements during my study.
Finally, grateful acknowledgements are extended to my family for constant
encouragement and moral support. A special thank to my wife for her dedication and for
taking good care of the family during my study and during the stressful time of writing this
thesis.

Ha Noi, Vietnam, September 2011
Viet Nguyen Duc


ABSTRACT AND KEYWORDS

13 September 2011

ABSTRACT
Location and features of topography make Vietnam is one of the most disaster–
prone countries in the world. Vietnam is threatened by hurricanes, floods, droughts and
salinity intrusion, landslides, forest fires, in which storms occur frequently and most
destructive. In the past decade, damages resulting from disasters seriously increasing
and this trend shall continue for according to forecast, climate change shall continuously
change extremely and danger of sea – level rise, salinity intrusion. Most of Vietnamese
land used for agricultural production shall be flooded.
Vu Gia – Thu Bon river basin is one of the largest river systems of Vietnam with
total area of the basin of around 10,000km2 with great value on water resource, traffic
and irrigation. However, due to adverse effects of global climate change, water sources
upon Vu Gia - Thu Bon Rivers also gradually reduce, severe shortage of water and

salinity intrusion deeply encroaching on river mouths increasingly.
Problem is to raise capacity of water supply for the irrigation system serving
agricultural production under impact of salinity intrusion. In order to resolve this problem,
in addition to determination of salinity intrusion reasons in researching area and propose
the reconstruction and improvement solutions, need to have new approaches, which are
alternative to irrigation system modernization including works, operation and
management.

KEYWORDS
Adaptation, salinity intrusion, water supply, operation and management, Tu Cau
irrigation system, Vinh Dien river.

SOFTWARE USED
1.

Office suite of Microsoft Office Excel 2007;

2.

Software for map analysis and development Arc GIS 9.3.1, MapInfo 10.5;

3.

Adobe Photoshop 10.0;

4.

Design and construction software AutoCad 2008;

5.

Geographic coordinate and satellite image software: Google Earth 6.0;

6.

Software of Project manager 2007;

7.

Tide analysis and forecast software WXTide_32 version 4.7.


INTRODUCTION

16 August 2011

12


CHAPTER I: INTRODUCTION

CHAPTER I.
I.1.

13 September 2011

INTRODUCTION

BACKGROUND

Population in the world will soon be approximately seven billions and expect to
increase to nine billions in 2050 as UNDP report in 2010. Climate change and global
warming will make glacier melted quickly. According to scientific research, the Earth’s
temperature will increase about 3oC in 2050 and 4oC in 2070 (Futuretimeline.net 2011).
Glacier melted leads to the rising of seawater level. As results is the widespread salinity
intrusion of seawater into the coastal production areas. Therefore, food security
becomes a serious issue in the society at present.
In Viet Nam, in order to adapt the negative impacts of salinity intrusion in
agricultural production, the Government has implemented a national target program in
agricultural and rural development such as improving, constructing new or upgrading
irrigation systems. However, difficulties are to find the financial source from the
Government or Non-Governmental Organizations (NGOs) because this process requires
such great amount of capital. Solutions for modernization in management and operation
of existing irrigation systems are rather cheaper than construct a new works or upgrade
them.
Dien Ban district in Quang Nam province, (a coastal district of Vu Gia – Thu Bon
river system - in South Central region of Viet Nam) has low topography, spreads on a
wide area. One of the most serious impacts of climate change to Dien Ngoc commune,
Dien Ban district is salinity on a wide area in a long time with frequent rate has impacted
on the lives and economic activities of the local people, especially in the agricultural
production.
Vu Gia – Thu Bon river basin is one of the largest river systems of Vietnam with
total area of the basin around 10,000km 2, Vu Gia – Thu Bon river consists of two main
branches: Vu Gia river and Thu Bon river.
At Vinh Dien town, a part of Thu Bon river water is drained into Vinh Dien tributary
and then this flow is combined with Vu Gia river, finally is Da Nang estuary. In other
words, Vinh Dien river is the middle flow, connecting Vu Gia and Thu Bon rivers.
Tu Cau pumping station has been constructed and operated since 1977. It is
located on the bank of Vinh Dien river to ensure irrigation water for 600 ha of rice. The
main water resource of this pumping station is from Vinh Dien river.

In recent years, Vinh Dien river water was salinity intrusion from Da Nang estuary.
Before 2004, the salt concentration was low (<2‰), but since 2005, it has been often
above 5‰. With the effect of sea level rise, salinity intrusion might frequently occur with
the higher concentration in dry season. The problem of salinity intrusion in Tu Cau
pumping station is illustrated in Figure 1-1.


The global climate change
has warmed
Climate
changeby an average of 0.74oC during 1906 – 2005 periods. Temperature in contin

Comparing
period
1980-1999
sea level
in Vietnam
could go up about 30cm to 70 cm by the mid and the end o
Sea leveltorise
andofdecline
of water
from
upstream

In the
dry season
in 2011,
concentration
of Vinh
Dien

river up to 10.2‰, it is also impact of water supply
Salinity
intrusion
in Vu
Gia –salt
Thu
Bon and Vinh
Dien
river

Not enough water to supply for cultivation area and reducing operation capacity of Tu Cau ir

Reduce water supply of Tu Cau irrigation system

of crop and impact
on food security at Dien Ngoc, Dien Ban district, Quang
Shortage of waterDrought,
supplyfailure
for agricultural
production

Fig I-1: Problem statement tree of salinity intrusion to Tu Cau irrigation system

Therefore, the purpose of the Master’s thesis is to propose appropriate
solutions on operation and management of Tu Cau irrigation system, Dien Ngoc
commune, Dien Ban district, Quang Nam province adapt to salinity intrusion, and
consideration for the criteria of reliability, flexibility and equity of irrigation service
[ CITATION Thi07 \l 1033 ].
This research finding is expected to be practical solutions and can be applied
in operation and management of this system. Besides, improving the reasonable

exploitation and efficiency of using water resource in Dien Ban district in particular
and in the Vu Gia – Thu Bon river basin in general.


I.2.

PROBLEMS STATEMENT

Main issues in Tu Cau irrigation system include the deteriorated works, irrational
O&M and strongly affected by global climate change, especially specific salinity intrusion
as follows:
I.2.1. Tu Cau irrigation system
At first, Tu Cau pumping station has 6 pump units, total discharge is about
3,600m3/h. Task of this pumping station is to ensure water supply for 600 ha rice area.
Currently, after 33 years, it is facing degradation of both house station and pump units,
namely discharge was decreased to 2,400 m3/h for nearly 300 ha cultivation area.
Total main canal length is 5,310m, in which concreted line is about 3,657m
(approximately 69%).
Total primary canal and over level- canal are 8,900m, in which concreted line is
2,845m (approximately 32%)
Total inter-farm canal is about 15,210m, but only 2,000m canal length is concreted
line. Inter- farm canal mostly is earth canal.
Concrete canal rate is low that lead to lack of water. Efficient use of canal system
is about 60%. Erosion, sedimentation, coastal grassing are also causes of water loss.

Fig I-2: Tu Cau Pumping station – Dien Ngoc
commune

Fig I-3: Suction chamber of Tu Cau pumping
station

I.2.2. Operation and management (O&M) at Tu Cau irrigation system
Quang Nam IMC in charge of operating main canal and check regulators provide
water based on requirement contract with WUOs.
Tu Cau pumping station is only operated when salt concentration content
(measure every fourth times one hour) less than 0.8‰.
According to WUO Dien Ngoc I (2005 – 2010) salinity intrusion was increased.
Due to impact of salinity intrusion, discharge of water supply for agricultural production is


always less than discharge of water demand. Therefore, it cannot ensure the process of
taking water for irrigation.
Table I-1: Relationship between rice schedule and operating time of Tu Cau pumping station
Month

Ja
n

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep
t

Oct

Nov

Dec

Winter– Spring
crop
Summer–
Autumn crop
Operating time
of Tu Cau
pumping station

Due to low efficiency (50 to 60%) of pump units, operation time must be increased;
leading to the electric consumption is also high.
In researching area, there are some large reservoirs such as Sen lake and Cung
lake. But now, they have not been used efficiently to add water resources for Tu Cau
irrigation system during salinity intrusion time.
Impact of salinity intrusion is more and more increasing and extended, but Dien
Ban IME has not have any operating procedure of Tu Cau pumping station.
I.2.3. Impact of salinity intrusion to agricultural production
Under impact of salinity intrusion is more and more increasing, cultivation area has
been decreased over the years, from 600 ha in 1997 to nearly 250 ha in 2011.
Salinity intrusion affects growth of rice, making rice production is also decline. For

example in 2011, production of Winter – Spring crop has been reduced by 1.500kg/ha.
Especially since 2009, almost Summer – Autumn crop has been quite loss.
According to Quang Nam IMC, Summer – Autumn crop in 2009 and 2010, salinity
intrusion has caused damage to hundreds tons of rice (approximately 4 billion VND) and
threaten seriously to food security in the study area.


I.3.

OBJECTIVES

I.3.1. Objective


To enhance the water supply efficiency and propose possible solutions to adapt
impact of climate changes to irrigation systems.

I.3.2. Specific objective


To access impact of salinity intrusion to the ability of water supply and O&M of Tu
Cau irrigation system for agriculture production.


I.4.

To propose solutions and changes in O&M to adapt salinity intrusion;
APPROACH AND METHODOLOGY

I.4.1. Approach

 To assess Tu Cau irrigation system under impact of salinity intrusion;
1. Tu Cau irrigation system (pump units, intake, canal, etc) 6. Propose models O&M to adapt salinity intrusion

2. Assess status of Tu Cau irrigation system by salinity intrusion.
5. Concentrate to study solutions on Operation & Management

3. Calculate water shortage for agricultural production
4. Determine causes of water shortage corresponding salinity intrusion.

Oriented research
Application


To determine volume of water shortage in agricultural production at researching
area, through water balance calculations;



To determine cause of problems that need to resolve water shortage of Tu Cau
irrigation system;



To access operating procedure of Tu Cau irrigation system, to propose changes of
O&M base on salinity intrusion to ensure water supply for agriculture production;



To apply these changes above on the irrigation system, from feedback of irrigation
system, will continuously change the options for suitability.

I.4.2. Methodology


To determine volume of water demand via water balance calculations of Tu Cau
irrigation system by CropWAT 8.0 software;



To access status of Tu Cau irrigation system via data collection;



To calculate volume of water supply ability of Tu Cau irrigation system by
analyzing status of works such as: pump units, canals, intakes, check regulator,
etc. and time of salinity intrusion upon Vinh Dien river;



To identify problem: determine volume of water shortage by comparison volume of
water demand with volume of water supply of Tu Cau irrigation system;



To propose solutions O&M to resolve problems above, these solutions base on
local conditions such as salinity, tide regime;



Summarize factors above to develop works of Tu Cau irrigation system become
an

irrigation modernization

gauging stations upon main canal.

[ CITATION Dan05 \l 1033 ] with water


CHAPTER II: SALINITY INTRUSION CONCEPT

CHAPTER II.
II.1.

13 September 2011

LITERATURE REVIEWS

SALINITY INTRUSION IMPACT ON AGRICULTURAL PRODUCTION

II.1.1. Definition of the salinity intrusion
According to Abdul Rahim S of School of Environment and Natural Resources and
Abdul Ghani R of ScienceUniversity Kebangsaan (Malaysia), salinity intrusion is defined
as follows:
“In

general, salinity intrusion is the movement of salt

water into fresh water aquifer or intrusion of salt water into

river estuaries”.
Salinity intrusion into river estuaries depends on many factors:


Water amount from upstream: the less its volume is, the more deeply salt water
intrudes into inland.



Tide range at river estuary: salinity intrusion occurs at the stage of high tide.



Terrain: plain terrain is a favorable condition for salinity intrusion.



Meteorological factors: wind from the sea moving inland, high temperature, low
rainfall, etc are causes of salinity intrusion proceeding to inland.



Economic activities of human: use of large amount of water in dry season (both
surface water and underground water) leads to more serious salinity intrusion.
Salt water flows from the sea to the river that prevent fresh water (flows from

upstream to the sea) make water flow back toward upstream. In contrast, at the period of
low tide, salt water draw out toward the sea, addition force of fresh water make velocity
of tide flow draw out more quickly.
Actually, salinity intrusion is natural phenomenon that occurs frequently at coastal

areas and estuaries. However, under impact of climate change, sea level rise has made
salinity intrusion becomes extreme phenomenon that strongly affect on society security
and economic sectors.
II.1.2. Previous studies on salinity intrusion adaptation through O& M of hydraulic
works
FAO (2010), looking at irrigated agriculture in more detail, the options for
adaptation to salinity intrusion at farm level can be considered in the following terms:




Manipulation of crop selection and cropping calendar;



Reduce rice production on highly permeable soils to conserve water and
minimize salinity, preferably through reasonable incentives and removal of
perverse incentives;



Improved water management technologies and techniques for cropping.

Fig II-4: Generic approach to determining climate change impacts and agricultural
adaptation strategies
(Source: Climate Change and Adaptation in Agriculture - East Asia and the Pacific, 2011)

In report of Oxford about “Proceedings of the Oxford Symposium”, (April 1980)
has been studied control of salinity intrusion in estuaries by means of a dual-purpose
reservoir. The solution mentioned here is: one-dimensional mathematical model of

salt-water intrusion is used to develop a methodology to assist the operators of a
reservoir with planning the release of water down the river to control the salinity in the
estuary.
In Viet Nam, there are some studies related to access impact of salinity
intrusion to agriculture production, such as:
Hoang (1994) research and evaluation on salinity intrusion upon river systems
in Long An province, Viet Nam. In this study has outlined the proposal to implement
salinity intrusion prevention by operating culvert regulator on small rivers.
Anh (2011) integrated for water resources management in Mekong Delta in
context of climate change-sea level rise, the author proposed a "operating procedure
the irrigation system under impact of salinity intrusion." The main content of this
proposal: closed costal culvert to prevent salinity intrusion in the dry season, when
salt concentration up to 4 ‰.


Besides, there are also many studies assessing in salinity intrusion process
from estuary into river such as:
San (2009) used observed and calculated incoming water data from 1979 to
2008 by NAM mathematical model to establish the operation procedures for Dau
Tieng reservoir in the case of with and without supply water from Phuoc Hoa
reservoir, and then he applied MIKE 11 to identify minimum quantity of fresh water
released from Dau Tieng reservoir to push seawater toward downstream in the dry
season [ CITATION San \l 1033 ].
Sam (2006) has described the actual state of saltwater intrusion in the
Vietnamese Mekong Delta (VMD). This publication has synthesized situations of
salinity intrusion, salty levels of water and its impacts on cultivating and planting
agriculture products for different areas in the VMD such as Ben Tre, Kien Giang, Ca
Mau, and Tu Giac Long Xuyen.
Institute of Geography (2010) had some study access the relationship between
sea level rise and salinity intrusion at coastal area in Quang Nam province (Case

study: Thu Bon – Vu Gia river basin).
The results of studies above mainly consider how to solve O&M problems as a
macro-problem as operation procedures of reservoirs or running the model Mike,
NAM to assess the impact of salinity intrusion process into the river flows. Currently,
there is not any specific research on O&M of irrigation system under impact of salinity
intrusion for an irrigation system.
II.1.3. Impact of salinity on agricultural production in Vietnam

II.1.3.1. Impact of salinity on agricultural production
Food security has become a significant problem in the current society;
however, irrigation solutions have improved 20% agricultural cultivated land in the
world[ CITATION Hof \l 1033 ]. In the 20th century, the global agricultural cultivated
land has increased over 500%, from 40 to 270 million ha irrigated land. This is an
important factor for prompting and supply enough food for rapidly increasing
population.
Another concern is the rising temperature. According to report of
Intergovernmental Panel on Climate Change (IPCC) in 2007, the global average
temperature increased about 0.74oC during 1906 – 2005 periods and the
temperature of recent 50 years has raised twice as much as the previous 50 years. In
addition, temperature in continents increased faster than in the ocean[ CITATION
JAr07 \l 1033 ].