i
INTEGRATED MODELLING FOR COASTAL ALLUVIUM AQUIFER AT
KG. TEKEK, TIOMAN ISLAND
LIEW KUET FAH
A project report submitted in partial fulfillment
of the requirements for the award of the degree of
Master of Engineering (Civil - Hydraulics and Hydrology)
Faculty of Civil Engineering
Universiti Teknologi Malaysia
NOVEMBER, 2006
iii
To my beloved parents and family
iv
ACKNOWLEDGEMENTS
For the accomplishment of this master project, I would like to take this
opportunity to express my deepest appreciation to my supervisor, Assoc. Prof. Dr.
Norhan Abd. Rahman, for his enthusiastic effort, suggestions, advices and guidance
during the preparation of this report. Appreciations are also dedicated to my cosupervisor, Professor Toshiharu Kojiri of Water Resources Research Centre, D.P.R.I
Kyoto University for his willingness to comment and provide suggestions for
improvements on the results of this project.
I also gratefully acknowledge the panels of my project presentation,
consisting of Dr. Noor Baharin, Dr. Supiah Shamsudin, Ir. Ahmad Kamal and Prof.
Narayanan for their comments, opinions and suggestions to produce a better report.
I would like to extent my appreciation to my friends especially Siti, Shah,
Kamarul, Zulkifli and Hakim for their supports, cooperation and assistances during
my studies in Master program.
Last but not least, deepest thanks are expressed to my beloved parents and
family members for their moral support on my decision to further study. Without
them, I would not have been able to complete my course.
v
ABSTRACT
Sufficient water supply plays an important role in busting the continuous growth of
tourism industry for an island. Tioman Island as one of the well-known marine
tourism attraction in Malaysia still highly relies on the limited surface water source
to supply water for the local residents and tourists. Thus, exploration for the
groundwater source is essential as an supplement for the existing water supply
system to cater for the increasing water demand in the future. Utilization of surface
water and groundwater will prevent the total reliance on a single resource which
avoids the water scarcity problem during drought seasons and also occurrence of
groundwater overdraft. Groundwater modellings in this study are developed with
MODFLOW2000 based on the available data to determine the hydraulic heads and
drawdowns of groundwater due to different pumping rates and saline intrusion
effects are simulated with the SEAWAT2000 model. The linear optimization
problem is solved with GAMS to maximize the rate of pumping for groundwater to
fulfill the quantity and quality requirements. The aquifer system would be capable to
support withdrawal of groundwater up to 5.8 MLD and cater for water demand till
year 2015. The hydraulic drawdown has greater influence for the optimization of
pumping rate compared to saline intrusion effects. With additional supply from
surface water source of 4 MLD, the combination system could cater for the water
demand up to year 2025.
vi
ABSTRAK
Bekalan air yang mencukupi memainkan peranan penting bagi perkembangan
industri perlancongan yang berterusan di sebuah pulau. Pulau Tioman sebagai salah
satu tumpuan perlancongan marin yang terkenal di Malaysia masih bergantung
kepada sumber air permukaan yang terhad untuk membekalkan air kepada penduduk
tempatan dan pelancong. Dengan itu, penerokaan sumber air bumi adalah penting
sebagai sumber tambahan bagi sistem bekalan air yang sedia ada untuk menampung
keperluan air yang semakin meningkat pada masa depan. Penggunaan air permukaan
and air bumi akan mengelakkan masalah kekurangan air pada musim kemarau dan
berlakunya pengepaman air bumi yang berlebihan. Model MODFLOW2000 telah
digunakan dalam kajian ini untuk membentuk model simulasi berdasarkan kepada
data yang sedia ada untuk menentukan turus hidraulik air bumi disebabkan oleh
pengepaman pada kadar alir yang berbeza. Model SEAWAT2000 pula menganalisa
kesan pencerobohan air masin pada setiap kadar pengepaman. Masalah penyelesaian
linear diselesaikan dengan GAMS untuk memperolehi kadar pengepaman yang
maksimum dan memuaskan syarat kuantiti dan kuality. Hasil kajian menunjukan
sistem akuifer mampu mengeluarkan air bumi sebanyak 5.8 MLD dan menampung
keperluan air sehingga tahun 2015. Penurunan turus hidraulik menunjukkan
pengaruh yang lebih besar berbanding dengan pencerobohan air masin dalam proses
mengoptimumkan kadar pengepaman. Dengan bekalan tambahan sebanyak 4 MLD
daripada sumber air permukaan, sistem kombinasi dapat menampung bekalan air
sehingga tahun 2025.
vii
TABLE OF CONTENTS
CONTENTS
PAGE
DECLARATION OF ORIGINALITY AND EXCLUSIVENESS
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
CONTENTS
vii
LIST OF TABLES
xi
LIST OF FIGURES
xii
LIST OF APPENDICES
xv
CHAPTER 1
INTRODUCTION
1
1.1
1
CHAPTER 2
Background of the study
1.2 Objectives of study
2
1.3
Scope of study
3
1.4
Importance of study
3
LITERATURE REVIEW
5
2.1
Groundwater Hydrology
5
2.1.1
Groundwater and Hydrologic Cycle
5
2.1.2
Groundwater Movement
7
2.1.3
Groundwater Recharge and Discharge
8
2.1.4
Aquifer and Confining Beds
8
2.2
Groundwater Quality
10
2.2.1
11
Saline Intrusion in Coastal Zones
viii
2.3
Type of Groundwater Models
2.4
Historical Review of Groundwater Modelling
in Malaysia
2.4.1
15
Historical Review of Previous Studies of
Alluvial Aquifer in Tioman Island
2.5
15
Historical Review of Groundwater
Modelling in Kelantan
2.4.2
13
17
Historical Review of MODFLOW and SEAWAT
Application for Tymbaki Aquifer, South Central
Crete, Greece (2005)
20
2.5.1
Site Description and Basin Hydrogeology
21
2.5.2
Simulation Models
23
2.5.3
Discretization, Boundary Condition and
2.5.4
2.6
2.7
Aquifer Parameters
23
Simulation Results and Conclusion
25
Optimization Modelling
27
2.6.1
28
Linear Programming
Historical Review of GAMS Application for
Groundwater Management in the Goksu Delta
2.8
CHAPTER 3
At Silifke, Turkey (2001)
30
2.7.1
Objective Function and Constraints
31
2.7.2
Results and Discussion
34
Summary
36
METHODOLOGY AND STUDY AREA
37
3.1
Modelling of Groundwater and Optimization
37
3.2
Description of the study area
37
3.2.1
Geology and Hydrogeology
42
3.2.2
Climate
44
3.2.3
Topography
44
3.2.4
Water Resources of Study Area
46
3.2.5
Hydrology
46
ix
3.3
Groundwater Modelling
46
3.3.1
MODFLOW2000
47
3.3.1.1
Spatial and Time Discretization
49
3.3.1.2
Governing Equation
50
3.3.2 SEAWAT2000
51
3.3.2.1
Temporal Discretization
53
3.3.2.2
Head and Equivalent Freshwater
54
Head in SEAWAT2000
3.3.2.3
Variable-Density Groundwater
55
Flow Equation
3.4
3.5
Simulation Setup
56
3.4.1
Simulation Time Steps
58
3.4.2
Boundary Condition
58
3.4.3
Data Input Parameters
58
3.4.4
Model Assumptions
59
Optimization Model
3.5.1
CHAPTER 4
59
General Algebraic Modeling Systems
(GAMS)
60
3.5.2
Objective Function
60
3.5.3
Constraints
60
3.5.4
Water Consumption Projection
63
3.6 Integrated Modelling Approach
63
RESULTS, ANALYSIS AND DISCUSSIONS
66
4.1
Introduction
66
4.2
Simulation Results for MODFLOW2000
67
4.2.1 Calibration Process
67
4.2.2
70
4.3
4.4
Simulation Analysis
Simulation Results for SEAWAT2000
79
4.3.1 Calibration and Validation Process
79
4.3.2
81
Simulation Analysis
Optimization Results
94
x
CHAPTER 5
CONCLUSIONS AND RECOMMENDATIONS
97
5.1
Conclusions
97
5.2
Recommendations
98
REFERENCES
99
APPENDICES
102
xi
LIST OF TABLES
TABLE NO.
2.1
TITLE
PAGE
Application of groundwater modelling at
Tioman Island
20
2.2
The calibrated model parameters
24
2.3
Application of groundwater management and
Optimization modelling in coastal aquifer of Malaysia
28
3.1
Processes and Packages of MODFLOW-2000
48
3.2
Projected water consumption for Kg. Tekek
63
4.1
Values for constant parameters
67
4.2
Cases considered for the calibration process
68
4.3
Calibration analysis results for Case (1)
69
4.4
Calibration analysis results for Case (2)
70
4.5
The aquifer influence coefficients of drawdown
for TEK1
76
4.6
Calibration results for SEAWAT2000
80
4.7
Validation results for SEAWAT2000
80
4.8
Calibrated parameters for SEAWAT2000 model
81
4.9
Optimization results for pumping well TEK1
95
4.10
Water supply for combine system
96
xii
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
1.1
Location of Tioman Island
4
2.1
Hydrological Cycle
6
2.2
Flow paths associated with local, intermediate
and regional flow systems
7
2.3
The aquifer and the confining beds
9
2.4
Saltwater intrusion occurrence due to pumping well
12
2.5
Location map of the Tymbaki and Mesara basin
21
2.6
Geological map of Tymbaki basin
22
2.7
Geological cross section of Tymbaki basin
22
2.8
Rainfall and streamflow infiltration recharge zone
25
2.9
Simulated extent of seawater intrusion into the
Tymbaki aquifer at various depth
2.10
Seawater intrusion along section C1 at the end of
120th stress period
2.11
26
26
Seawater intrusion along section C1 at the end of
240th stress period
26
2.12
The Goksu Delta
31
2.13
Correlation between simulation model results and
optimization model results for hydraulic heads
2.14
Correlation between simulation model results and
optimization model results for chloride concentrations
2.15
3.2
35
Trade-off curves between maximum pumping rate
and chloride concentration limit
3.1
34
35
Groundwater simulation and optimization model
for the study
38
Methodology Flow Chart
39
xiii
3.3
Groundwater modelling process flow chart
40
3.4
Location of Kg. Tekek in Tioman Island
41
3.5
Geologic map for Tioman Island
42
3.6
Geological cross section for Kg. Tekek aquifer system
43
3.7
Topography map for Tioman Island
45
3.8
Finite difference grid
50
3.9
Simulation modes available with the
SEAWAT2000 programme
3.10
53
Horizontal plane and vertical section of the
Groundwater models
57
3.11
Input and output for integrated modelling
65
4.1
Hydraulic conductivity zoning plan for
Kg. Tekek (isotropic heterogeneous)
68
4.2
Location of pumping wells at Kg. Tekek
69
4.3
Hydraulic head contour due to pumping of 1 MLD
71
4.4
Hydraulic head contour due to pumping of 2 MLD
72
4.5
Hydraulic head contour due to pumping of 3 MLD
73
4.6
Hydraulic head contour due to pumping of 4 MLD
74
4.7
Hydraulic head contour due to pumping of 5 MLD
75
4.8
Hydraulic head at TEK1
77
4.9
Hydraulic head at TEK3 and TEK4
78
4.10
Relationship between hydraulic drawdown
and pumping rate at TEK1
4.11
Concentration contour (saline intrusion) on
horizontal plane due to pumping of 0.5 MLD
4.12
85
Concentration contour (saline intrusion) on
horizontal plane due to pumping of 1.5 MLD
4.16
84
Concentration contour (saline intrusion) on
vertical section due to pumping of 1 MLD
4.15
83
Concentration contour (saline intrusion) on
horizontal plane due to pumping of 1 MLD
4.14
82
Concentration contour (saline intrusion) on
vertical section due to pumping of 0.5 MLD
4.13
79
Concentration contour (saline intrusion) on
86
xiv
vertical section due to pumping of 1.5 MLD
4.17
Concentration contour (saline intrusion) on
horizontal plane due to pumping of 2 MLD
4.18
92
Concentration contour (saline intrusion) on
vertical section due to pumping of 3 MLD
4.23
91
Concentration contour (saline intrusion) on
horizontal plane due to pumping of 3 MLD
4.22
90
Concentration contour (saline intrusion) on
vertical section due to pumping of 2.5 MLD
4.21
89
Concentration contour (saline intrusion) on
horizontal plane due to pumping of 2.5 MLD
4.20
88
Concentration contour (saline intrusion) on
vertical section due to pumping of 2 MLD
4.19
87
93
Relationship between saline intrusion length
and pumping rate
94
xv
LIST OF APPENDICES
APPENDIX
A1
PAGE
Analysis results of groundwater in Kg Tekek
103
(source : ALS Technichem (M) Sdn. Bhd. 28 March 2003)
A2
Analysis results of groundwater in Kg. Tekek
104
(source : ALS Technichem (M) Sdn. Bhd. 28 March 2003)
(continue)
A3
Analysis results of groundwater in Kg. Tekek
105
(source : FELDA AGRICULTURAL SERVICES SDN. BHD.
8 July 2004)
A4
Analysis results of groundwater in Kg. Tekek
106
(source : FELDA AGRICULTURAL SERVICES SDN. BHD.
8 July 2004)(continue)
A5
Water Quality Monitoring (6 June- 7 June 2004)
107
by Universiti Teknologi Malaysia
A6
Water Quality Result During Pumping Test In Kg. Tekek
108
by Universiti Teknologi Malaysia
A7
Water Quality Result During Pumping Test In Kg. Tekek
109
by Universiti Teknologi Malaysia. (continue)
A8
Analysis results of groundwater in Kg Tekek
110
(source : ALS Technichem (M) Sdn. Bhd. 31 December 2003)
A9
Analysis results of groundwater in Kg. Tekek
111
(source : ALS Technichem (M) Sdn. Bhd. 31 December 2003)
A10
Analysis results of groundwater in Kg. Tekek
112
xvi
(source : ALS Technichem (M) Sdn. Bhd. 31 December 2003)
A11
Analysis results of groundwater in Kg. Tekek
113
(source : ALS Technichem (M) Sdn. Bhd. 31 December 2003)
A12
Analysis results of groundwater at various depths in Kg. Tekek
114
(source : Department of Environment 2001 - 2005)
A13
Analysis results of groundwater at various depths in Kg. Tekek
115
(source : Department of Environment 2001 - 2005)
B1
Constant Discharge Pump Test Record (Tek 1)
116
B2
Constant Discharge Pump Test Record (Tek 3)
117
B3
Constant Discharge Pump Test Record (Tek 4)
118
B4
Recovery Test (Tek 1)
119
B5
Recovery Test (Tek 3)
120
B6
Recovery Test (Tek 4)
121
B7
Recovery Test (Piez 7)
122
B8
Constant Discharge Pump Test Record (Piez 1)
123
B9
Constant Discharge Pump Test Record (Piez 2)
124
B10
Constant Discharge Pump Test Record (Piez 3)
125
B11
Constant Discharge Pump Test Record (Piez 4)
126
B12
Constant Discharge Pump Test Record (Piez 5)
127
B13
Constant Discharge Pump Test Record (Piez 6)
128
B14
Constant Discharge Pump Test Record (Piez 7)
129
C
Optimization Model
130 - 132
1
CHAPTER 1
INTRODUCTION
1.1
Background of the Study
Tioman Island, as one of the marine tourism destination in Malaysia, is
located in the South China Sea, 56 km off Mersing. The island having a total area of
about 131 km2, spanning about 11 km from west to east and 20 km from north to
south, is the largest among a group of 64 volcanic islands in the South China Sea.
Noted for its crystal clear water and marine life, the island in the vicinity of 2°43’00”
to 2°54’00” N latitude and 104°06’00” to 104°12’30” E longitude, have attracted
many tourists both local and abroad annually. In addition to fishing activities,
tourism has become a very important income generating activity on the island.
Due to the importance of water as the basic criteria for the development of
tourism, many studies have been carried out to determine the water availability on
the island. Based on this purpose of study, Nazan Awang (1988) had suggested Kg.
Tekek and Kg. Juara to be the potential areas for surface water and groundwater
extraction on the island. The study also explored into annual water yield from surface
as well as groundwater sources in Kg. Tekek by using simulation model based on the
site collected data.
Presently, the limited availability of surface water sourced from the river
system serves as the main source of water supply in the vicinity for domestic and
tourism demands. Groundwater utilization is only available in certain parts of the
2
area on the island in the form of individual wells. Groundwater system for public
water supply is still virtually non-existent. The government’s intention to promote
Tioman Island as a tax-free tourist based island will further burden the water stress.
Thus exploration for new reliable water sources is essential to cater for the increasing
water demand due to population and tourist growth.
The extraction of available groundwater will be the best solution for the water
crisis problem on Tioman Island other than water transfer from the mainland. The
main concern for groundwater aquifer to be developed as public water supply will be
the maximum yield available. Pumping of groundwater may cause deleterious side
effects if proper management and water conservation aspects are neglected. For
coastal aquifer system, water quality degradation due to saline intrusion effects may
limit the application of groundwater, therefore careful study should be carried out on
groundwater aquifer to ensure a sustainable water supply of the area.
1.2
Objectives of Study
The objectives of this study include:
a. To predict the available yield of the groundwater flow system due to different
pumping rate on Tioman Island.
b. To study the saline intrusion effects under different pumping rate.
c. To study the maximum pumping rate of groundwater for optimization.
3
1.3
Scope of Study
The study on groundwater aquifer system at Tioman Island involves scopes
as listed below:
a. The study will focus on the groundwater system in Kg. Tekek, Tioman Island
(Figure 1.1).
b. The simulation process involves groundwater numerical models, which
include MODFLOW for groundwater flow and SEAWAT for saline intrusion
effects.
c. The optimization of pumping rate that involves application of simulated
results into linear programming for GAMS.
1.4
Importance of Study
As the basic human need, water is an essential criterion that enables the
continuous growth in tourism industry of Tioman Island. The analytical data in 1999
provided by Hassan indicated that the surface runoff is limited and inconsistent, with
fluctuating water amount following the annual climatic changes. In order to ensure
continuous availability of water supply to local residents and tourists, alternative
water sources will be required to supplement or replace diminished surface water
supplies. Groundwater resources available in several areas on the island will be a
potential option to the solution of the crisis, but extensive studies are still required to
determine the advantages and disadvantages of implementation.
4
Figure 1.1: Location of Tioman Island.
5
CHAPTER 2
LITERATURE REVIEW
2.1
Groundwater Hydrology
Groundwater is commonly understood as water that occupies all the voids
within a geologic stratum. Groundwater is an important natural resource, especially
in countries that are having limited surface water sources.
As defined by the U.S. National Research Council (1991), hydrology is the
science that treats the waters of the Earth, their occurrence, circulation and
distribution, their chemical and physical properties and their reaction with the
environment, including the relation to living things. The domain of hydrology
embraces the full life history of water on Earth.
As a whole, groundwater hydrology may be defined as the science of the
occurrence, distribution and movement of water below the surface of the earth.
2.1.1
Groundwater and the Hydrologic Cycle
The hydrologic cycle can be thought as a series of reservoir, or storage areas
and a set of processes that cause water to move between those reservoirs.
Groundwater is part of this continuous cycle as water evaporates, forms clouds and
6
returns to earth as precipitation. The hydrologic cycle begins with the water
evaporation from the soil, plant and water surfaces to form water vapor. The vast
majority of evaporation occurs from the oceans. The continuous processes of the
hydrological cycle are shown in Figure 2.1.
Figure 2.1: Hydrological Cycle (Source: http://techalive.mtu.edu.htm)
Water vapor is drawn into the atmosphere by temperature gradients. When
water vapor cools, it condenses to form clouds. As water condenses within clouds,
water droplets increase in size until they fall to the earth’s surface as precipitation
such as rainfall. The water that falls to the earth’s surface and enters into the soil can
become groundwater but most of it will evaporate or is used by vegetation. Water
that passes through the root zone may continue to move downward to reach the
groundwater. Once passed the root zone, water enters the unsaturated zones which
are soil and geologic materials located between the land surface and the saturated
zone. In the unsaturated zone, the voids are filled with a combination of air and water.
After a significant rain, the zone may be almost saturated, but may be almost dry
after a long dry spell.
After the water requirements for plant and soils are satisfied, any excess
water will infiltrate to the water table. The entire region below the water table is
called the saturated zone with all the voids filled with water that moves slowly
7
through the aquifer to streams, springs or wells from which the water is being
withdrawn.
2.1.2
Groundwater Movement
The groundwater flow system comprises the subsurface water, the geologic
(porous) media containing the water, the flow boundaries, the sources and the sinks.
Water flows through and is stored within the groundwater system. Groundwater flow
is very slow compared to surface water movement. Under natural condition, the
travel time of groundwater can range from less than a day to more than a million year.
Flows within groundwater systems can be on a local, intermediate and
regional basis as illustrated in Figure 2.2. The recharge and discharge areas in a local
system of groundwater flow are adjacent to each other. The recharge and discharge
in an intermediate groundwater flow system are separated by one or more
topographic high and low. In regional groundwater flow systems, recharge areas are
along groundwater divides and discharge areas are located at the bottom of major
drainage divides.
Figure 2.2: Flow paths associated with local, intermediate and regional flow systems
8
2.1.3
Groundwater Recharge and Discharge
Recharge is the process by which groundwater is replenished. A recharge
area is where water from precipitation is transmitted downward to an aquifer. Most
areas, unless composed of solid rock or covered by development, allow a certain
percentage of total precipitation to reach the water table. However, in some areas
more precipitation will infiltrate than in others. Areas which transmit the most
precipitation are often referred to as "high" or "critical" recharge areas.
The amount of water that infiltrates into soil depends on vegetation cover,
slope, soil composition, depth to the water table, the presence or absence of
confining beds and other factors. Natural vegetation cover, flat topography,
permeable soils, a deep water table and the absence of confining beds increase the
recharge rate.
Discharge areas are the locations at which ground water leaves the aquifer
and flows to the surface. Groundwater discharge occurs where the water table or
potentiometric surface intersects the land surface. Springs or seeps are usually found
in the intersection area. Springs and seeps may flow into fresh water bodies, such as
lakes or streams, or they may flow into saltwater bodies.
Under the force of gravity, groundwater generally flows from high areas to
low areas. Consequently, high areas, such as hills or plateaus, are typically where
aquifers are recharged and low areas, such as river valleys, are the discharge points.
However, aquifers occur beneath river valleys in many instances, so river valleys can
also be important recharge areas.
2.1.4 Aquifer and Confining Beds
An aquifer is a geologic unit that can store and transmit water at rates fast
enough to supply reasonable amounts of water to wells. A confining bed or aquitard
is a geologic unit which is relatively impermeable and restricts movement of
groundwater into and out of adjacent aquifers. Aquifers may be classed as
9
unconfined or confined depending on the presence or absence of a water table, while
a leaky aquifer represents a combination of the two types. (Figure 2.3)
Figure 2.3: The Aquifer and the Confining Beds
(Source: http://www.usgs.gov/)
Unconfined aquifer has no confining bed above it and is usually open to
infiltration from the surface. The upper groundwater surface in an unconfined aquifer
is called the water table. The depth to the water table varies according to factors such
as the topography, geology, season and tidal effects and the quantities of water being
pumped from the aquifer. Unconfined aquifers are usually recharged by rain or
stream water infiltrating directly through the overlying soil.
Confined aquifers are permeable rock units that are usually deeper under the
ground than unconfined aquifers. They are overlain by relatively impermeable rock
or clay. Groundwater in a confined aquifer is under pressure and will rise up inside a
borehole drilled into the aquifer. The level to which the water rises is called the
potentiometric surface. Confined aquifers may be replenished, or recharged through
cracks or openings in impermeable layers above or below them. Confined aquifers in
complex geological formations may be exposed at the land surface and can be
directly recharged from infiltrating precipitation. For a adjacent highland area such
10
as a mountain range, water can infiltrate through the fractured rock in the mountain
to flow downward and then move laterally into confined aquifers.
The most productive aquifers, whether confined or unconfined, are generally
in sand and gravel deposits. The aquifers tend to have large void spaces for holding
water. Rocks with large openings such as solution cavities or fractures can also be
highly productive aquifers. Generally, the smaller grain size or the less fracturing
less water and aquifer will produce. This is because there are fewer void spaces for
holding water.
2.2
Groundwater Quality
Groundwater quality is a consequence of the natural physical and chemical
state of the water as well as any alterations that may have occurred as a result of
human activities. Groundwater quality is determined by the solutes and gases
dissolved in the water, as well as the matter suspended in the water. The quality
required of a groundwater supply depends on its purpose, therefore the standard
requirements for drinking water, industrial water and irrigation water vary widely.
The natural quality of groundwater varies substantially from one place to
another. Natural groundwater generally acquires dissolved constituents by
dissolution of aquifer gasses, minerals and salts. Consequently, soil zone and aquifer
gases and the most soluble minerals and salts in an aquifer generally determined the
chemical composition of groundwater in an aquifer.
The suitability of groundwater usage for different purposes can be assessed
through sampling for key indicators which include:
a. General parameters, (electric conductivity, pH, alkalinity)
b. Major cations (calcium, magnesium, sodium, potassium, iron and manganese)
c. Major anions (chloride, suphate, nitrate and phosphorus)
d. Biological indicators (Faecal coliforms)
e. Biocides (pesticides, herbicides and insecticides)
11
2.2.1
Saline Intrusion in Coastal Zones
Alluvium groundwater aquifers at coastal regions are usually encountered
with saline intrusion problem. Intrusion of saline water occurs where saline water
displaces or mixes with freshwater is an aquifer. The phenomenon can occur in deep
aquifer with the upward advance of saline waters of geologic region, in shallow
aquifers from surface waste discharges and invasion of seawater in coastal aquifers.
Saltwater intrusion into fresh groundwater formations generally results inadvertently
from human activities. The saline intrusion commonly occurs due to groundwater
pumping that causes local decline of groundwater levels in the vicinity of pumped.
Some coastal wells in Washington, USA are now functioning properly due to
saltwater intrusion problem and the situations are particularly obvious in coastal
areas with high population growth that results in increasing water demand.
Freshwater is less dense than saline water and tends to flow on top of the
surrounding or underlying saline groundwater. Under natural conditions, the
boundary between freshwater and saltwater maintains at stable equilibrium as shown
in Figure 2.4a. The boundary is typically not sharp and distinct, but rather is a
gradation from fresh to saline water known as the zone of diffusion, zone of
dispersion or the transition zone. When water is pumped from an aquifer that
contains or is near saline groundwater, the boundary for saltwater and freshwater will
move in response to this pumping. If the boundary moves far enough, some wells
become saline, thus contaminating the water supply as illustrated in Figure 2.4b. The
location and magnitude of the groundwater withdrawals with respect to the location
of saline water will determines the rate of saltwater intrusion.
12
Figure 2.4: Saltwater Intrusion Occurrence due to Pumping Well
(Source: http://www.usgs.gov/)
The physical formulations of saltwater intrusion were made by Badon (1889)
and Ghyben-Herzberg (1901). They derived analytical solution to approximate the
intrusion behaviour, which are based on a number of assumptions that do not hold in
all field cases. Due to the development in technology, the higher computing power
allowed the use of numerical methods, usually finite differences or finite elements
that required less assumptions and can be applied more generally. Thus, many
models have been developed as tool to aid in the study and proposal for management
plans.
The solute transport models, suitable for the simulation of saltwater intrusion
and commercially available include SUTRA (Voss, 1984), FEFLOW, HST3D and
SEAWAT. These models provide solutions of two simultaneous, non-linear, partial
differential equations that describe the “conservation of mass of fluid” and
“conservation of mass of salt” in porous media.
Even so, the modelling of saltwater intrusion is considered difficult for the
typical difficulties arise, which include:
a. The possible presence of fissures and fractures in the aquifer, whose precise
positions are unknown but have great influence on the development of the
saline water intrusion.
13
b. The possible presence of small scale heterogeneities in the hydraulic
properties of the aquifer, which are too small to be take into account by the
model but may also have great influence on the development of the saline
water intrusion.
c. The change of hydraulic properties by the saltwater intrusion. A mixture of
saltwater and freshwater is often under-saturated with respect to calcium,
triggering dissolution of calcium in the mixing zone and changing hydraulic
properties.
d. The non-equilibrium state of saline intrusion makes it harder to model.
Aquifer dynamics tend to be pretty slow and it takes the intrusion cone a long
time to adapt to changes in pumping schemes, rainfall and others. Therefore,
the situation in the field can be significantly different from the expectation
based on sea level and pumping scheme.
e. For long-term models, the future climate change forms a big unknown. Model
results often depend strongly on sea level and recharge rate.
2.3
Types of Groundwater Models
Several types of groundwater models have been developed for the purpose of
groundwater flow systems study. The groundwater model can be divided into three
broad categories (Herbert, 1982): sand tank models, analog models, including
viscous fluid models and electrical models, and mathematical models, including
analytical and numerical models. A sand tank model consists of a tank filled with an
unconsolidated porous medium through which water is induced to flow. A major
drawback of sand tank models is the problem of scaling down a field situation to the
dimensions of a laboratory model. Phenomena measured at the scale of a sand tank
model are often different from conditions observed in the field, and conclusions
14
drawn from such models may need to be qualified when translated to a field situation
(Herbert, 1982).
The groundwater flow can be described by differential equations derived
from basic principles of physics. Other processes, such as the flow of electrical
current through a resistive medium or the flow of heat through a solid, also operate
under similar physical principles. In other words, these systems are analogous to the
groundwater system. The two types of analogs used most frequently in groundwater
modelling are viscous fluid analog models and electrical analog models (Herbert,
1982).
Viscous fluid models are known as Hele-Shaw or parallel plate models
because a fluid more viscous than water (for example, oil) is made to flow between
two closely spaced parallel plates, which may be oriented either vertically or
horizontally. Electrical analog models were widely used in the 1950’s before highspeed digital computers became available. These models consist of broads wired
with electrical networks of resistors and capacitors. They work according to the
principle that the flow of groundwater is analogous to the flow of electricity. This
analogy is expressed in the mathematical similarity between Darcy’s law for
groundwater flow and Ohm’s law for the flow of electricity. Changes in voltage in an
electrical analog model are analogous to changes in groundwater head. A drawback
of an electrical analog model is that each one is designed for a unique aquifer system.
When a different aquifer is to be studied, an entirely new electrical analog model
must be built (Herbert, 1982).
A mathematical model consists of a set of differential equations that are
known to govern the flow of groundwater. Mathematical models of groundwater
flow have been in use since the late 1800s. The reliability of predictions using a
groundwater model depends on the efficiency of model to approximate the field
situation. Assumptions simplification must always be made to construct a model
because the field situations are too complicated to be simulated exactly. Usually the
assumptions necessary to solve a mathematical model analytically are fairly
restrictive. For example, many analytical solutions require that the medium be
homogenous and isotropic. To deal with more realistic situations, it is usually
15
necessary to solve the mathematical model approximately using numerical
techniques. Since the 1960s, when high-speed digital computers became widely
available, numerical models have been the favored type of model for studying
groundwater (Herbert, 1982).
2.4
Historical Review of Groundwater Modelling in Malaysia
Water supply system in Malaysia mainly depends on surface water, except
for Kelantan that rely heavily on groundwater water sources, contributing 70% of the
state total water supply. Therefore, Kelantan state is the main concentration for
groundwater modellings study in Malaysia. Groundwater studies and modellings
were also actively carried out for Tioman Island since 1988 with groundwater flow
and contamination transport as the main purpose of the studies.
2.4.1
Historical Review of Groundwater Modelling in Kelantan
In Kelantan, the first evaluation was conducted in 1974 at the northern part of
the state which includes Kota Bahru, Pengkalan Chepa, Bachok and Pasir Puteh.
Several groundwater models were developed in those areas to study and forecast
groundwater flow and contaminant transport (Kuan, 2003).
In 1989, Hossain used the runoff analysis method and groundwater model
developed by Rushton (1975) and Ismail (1979) to simulate a conjunctive model for
surface and groundwater management in North Kelantan. However, the modelling
works for groundwater contamination started only after the groundwater flow and
management systems have been explored for a long time in Northern Kelantan
(Kuan, 2003).
Environmental assessment for impact of water supply by groundwater source
in North Kelantan was conducted by a consultancy firm, Sepakat Setia Sdn. Bhd.
16
under Public Work Department (JKR), Kelantan in 1990. This model is based on an
existing suite of programs developed by Howard Humphreys and Partners Ltd. From
the original codes produced by Prickett and Lonnquist in 1971. The model can be
developed either in steady state or transient flow, which then needs to be calibrated
by a calibration tool. The programs were adopted to develop the groundwater
management systems in the studied area. The model was then calibrated against
actual river, groundwater level and climatic data available from 1970’s till to date.
Saim (1996) then developed the regional well head protection areas
(WHPAs) simulation to help minimize the effect and protect the resources for further
contamination, which covered most of the area in Northern Kelantan. In his study,
groundwater model was developed using Arc View GIS (version 3.1) together with
the MODFLOW model to simulate the groundwater flow and pollutant transport. In
his model, several detected pollutants in Northern Kelantan such as nitrates,
ammonium, pesticides, and mircorbial have been considered in this model (Nadia,
2004).
Department of Environment Malaysia has assigned BW Consultants Sdn.
Bhd. to evaluate the groundwater quality system in Northern Kelantan in 1997. The
groundwater model was developed in a local scale and was applied to evaluate the
simulated mercury plume in the Panji landfill.
In this study, the information
available from the site was insufficient to provide data on the vertical and horizontal
hydraulic conductivity values directions of groundwater flow and subsurface
geology. Therefore, the flow and transport model was not properly calibrated as only
two well pairs were available at the site. Since lacking of site-specific data for model
parameters, sensitivity analyses were conducted to evaluate the effects of uncertainty
in model parameters on plume migration (Samira, 2001).
Visual MODFLOW and MT3D model have also been applied by Samira
(2001), to develop a 3-dimensional groundwater model. The model was then
simulated and calibrated in steady-state and transient to simulate and predict the flow
and contaminant transport of Kg. Puteh well field. The aquifer was simulated in a
single layer with covered area of 4200 m x 4200 m. The calibrated model in transient
flow was used to predict the concentration plumes of nitrate at recharge
17
concentration of 100, 200, 400 mg/L. The result of simulation of 20 years showed
that the highest designate recharge concentration of contaminant might contaminate
the wellfield and the estimated range of nitrate plume is low if compared with the
allowable value of 45 mg/L (Kuan, 2003).
In 2002, Faizal used Aquifer Simulation Model to predict the level of
groundwater at local scale for well field in Kg. Puteh, Kelantan which are influenced
by the recharge, leakage from surface water and changes in the pumping rate. The
result from his study show that groundwater heads in wellfield area ranges from 2.45
to –6.56 m below mean sea level (Nadia, 2004).
Suhana (2002) also used ASMWin to give an overview of groundwater level
in Kota Bahru until year 2020. The study predicts the maximum groundwater
capacities for the wellfield in Kota Bahru, Kelantan. The result shows that
groundwater level at Kg. Puteh wellfield area ranges from –2.3 m to –2.55 m from
mean sea level. The simulation results shows that the maximum pumping rate that
can be done at Kg. Puteh wellfield until 2020 is between 7197 m3/day to 7776
m3/day.
Harun (1998) studied about the variations of groundwater electrical
conductivity in the sandy aquifer of Pulau Manukan, Sabah by using SUTRA.
Skimming of fresh phreatic water were carried out through dug well and to evaluate
the current electrical conductivities (EC) of phreatic water and dug well water. From
his study, the groundwater EC of lowland-sandy aquifer varies with rainfall seasons.
Rainwater plays a significant role in recharging such aquifer and sustains its
groundwater freshness.
2.4.2
Historical Review of Previous Studies of Alluvial Aquifer in Tioman
Island
Nazan Awang (1988) from Geological Survey Department Malaysia (Jabatan
Penyiasatan Kajibumi Malaysia) has studied the groundwater yield in Kg. Tekek and
18
Kg. Juara using water balance approach since 1988. This study was based on the
available rainfall data for Kg. Tekek (11 years) and Kg. Juara (9 years) respectively.
The result of the study has shown that the groundwater yield in Kg. Tekek and Kg.
Juara could achieve rate of withdrawal at 2,270 m3/day and 310 m3/day respectively
(Kuan, 2003).
The groundwater yield study in Tioman Island was continued in 1991 (Nazan
Awang). Geological Survey Department conducted site investigations on the
groundwater yield in Kg. Tekek, Kg. Juara, Kg. Salang, Kg. Genting and Kg. Mukut.
According to their investigations, only Kg. Tekek and Kg. Juara showed a good
potential for exploitation of groundwater. Therefore, two well-point fields were
constructed each in Kg. Tekek and Kg. Juara to abstract water. The results have
shown that 6 wellpoints in Kg. Tekek were capable to withdraw water at 696 m3/day
(Kuan, 2003).
Modelling of Kg. Tekek aquifer started since early 90’s by Mohammed Hatta
(1991) from Geological Survey Department using 2 dimensional numerical models
‘FLOWPATH’. This model was used to simulate the aquifer as shallow unconfined
aquifer in Kg. Tekek and was calibrated at steady state. The result showed that the
aquifer in Kg. Tekek could supply groundwater at pumping rate of 2400 m3/day
without any undesirable effect to the aquifer system and to the consumers.
In 2001, Hasan (2001) continued the study on the aquifer in Kg. Tekek. His
study focused on Kg. Tekek to assess the maximum annual yield of groundwater
from the aquifer. He used a numerical model of Kg. Tekek aquifer using ASM
(Aquifer Simulation Model) to simulate and the model was calibrated in steady state.
The result showed that the Kg. Tekek aquifer could be exploited by maximum
pumping rate of 6000 m3/day.
Following Hasan, Rahim (2002) also studied on the Kg. Tekek aquifer using
numerical model but with different modelling tool, Visual MODFLOW. The
parameters adopted by Rahim referred to the calibrated model developed by Hasan
(2001). His study also included the pollutant (nitrate) transport using the calibrated
model developed by Hasan. His study also included the pollutant (nitrate) transport
19
using the calibrated model at different pumping rate and recharge concentration. The
result of his study showed that the contaminant, nitrate concentration comply with
WHO drinking water standard.
Kuan (2003) continued the study on the aquifer in Kg. Tekek and Kg. Juara.
His study focuses on the drawdown of water table at different mode of pumping rate
and pumped wells distribution and potential point source contaminant migration at a
given pumping rate of different recharge concentration and distribution coefficient,
kd. From his study, the flow analytical results have showed that both aquifers are
sufficient to pump at the rate of 4000 m3/day and 300 m3/day in Kg. Tekek and Kg.
Juara respectively. In pollutant transport modelling, resultant migration path of
contaminant resultant headed towards South China Sea in steady state. While the
estimate concentration of contaminant, nitrate in the pump well in transient state due
to withdrawal at a given pumping rate and recharge concentration is generally low
and complied with World Health Organization (WHO) drinking water standard.
Nadia (2004) continued the study on the aquifer in Tioman Island that
concentrates on groundwater flow system to predict the available yield of the alluvial
aquifer in the island by studying the drawdown of water table at different mode of
pumping rate. Aquifer Simulation Model for Windows (ASMWin) is used to
simulate the groundwater flow of the aquifer in Kg. Tekek, Kg. Juara, Kg. Salang
and Kg. Paya based on the available data. The groundwater simulation results
showed that the alluvial aquifer at Kg. Tekek is sufficient to pump at 10 MLD and 3
MLD at Kg. Paya and Kg. Salang. The aquifer in Kg. Juara is only sufficient to
pump at 0.4 MLD. The quality of groundwater in Kg. Tekek, Kg. Paya and Kg.
Salang also complies with World Health Organization (WHO) drinking water
standard. The application of groundwater modellings at Tioman Island are tabulated
in Table 2.1.
20
Table 2.1: Application of groundwater modelling at Tioman Island
Groundwater Modelling at Tioman Island
Year User
Models
Location
1991 Mohamad
FLOWPATH Kg. Tekek
Scopes Of Study
Groundwater Flow
Hatta, JBA
Pahang
2001 Hasan Basyri, ASMWin
Kg. Tekek
Groundwater Flow
Kg. Tekek
Groundwater Flow and
UTM
2002 Rahim
(MSc), UTM
2003 Kuan
Visual
MODFLOW
Contaminant Transport
Visual
Kg. Tekek and
Groundwater Flow and
MODFLOW
Kg. Juara
Contaminant Transport
ASMWin
Kg. Tekek, Kg.
Groundwater flow based on with
Adillah
Paya, Kg. Juara
pumping/no pumping under
(MSc), UTM
& Kg. Salang.
steady state
Kg. Tekek
Saltwater intrusion
(MSc), UTM
2004 Nadiatul
2005 Norasman bin SUTRA
Othman
(MSc), UTM
2.5 Historical Review of MODFLOW and SEAWAT Application for Tymbaki
Aquifer, South Central Crete, Greece (2005)
The apparent importance for the regional economy of both Tymbaki and the
adjoining Mesara basins had prompted the Food and Agriculture Organization (FAO)
of the United Nations Development Programme to conduct a comprehensive
investigation on the hydrogeology and water resources of the area during 1967-1970.
However the potential seawater intrusion into the Tymbaki aquifer was not taken into
consideration in the investigation. Thus, Savvas N. Paritsis had conducted a study in
year 2005 on behalf of the Department of Management of Water Resources of the
region of Crete regarding the saltwater intrusion into the Tymbaki aquifer.
21
2.5.1. Site Description and Basin Hydrogeology
The Tymbaki aquifer comprises the alluvial fill of the 50 km2 coastal
Tymbaki basin that was morphologically differentiated by subsequent blockfaulting
into a coastal plain to the west and a hilly area to the east. The basin is located by the
south western tip of the Heraklion prefecture in Central Crete and represents a
westwards tectonic extension of the larger alluvial plain of Mesara (Fig 2.5).
Figure 2.5: Location map of the Tymbaki and Mesara Basin
The basin is filled with Pleistocene to Holocene alluvial deposits and is fault
bound to the north and south by Neogene aquitards and to the east by Mesozoic
aquifuge flysch. The alluvial sediments are underlain by Neogene sediments and at
the eastern tip of the basin, by the Mesozoic flysch. The alluvial deposits fill erosion
troughs within the Lower Pleistocene and comprise upper Pleistocene reddish and
brown clay, silt, and gravel beds and grey Holocene deposits of gravel, sand, silt and
clay, often with organic matter. (Figure 2.6 & 2.7) At the Geropotamos river, the
alluvial deposits extend from a few hundred metres in the east to about 1.5 km in the
22
west and their corresponding thickness increases from about 60 m in the east to
around 100 m in the west.
Figure 2.6: Geological map of Tymbaki Basin
Figure 2.7: Geological cross section of Tymbaki Basin
23
Groundwater level maxima are observed around May and minima during
October –November. There is usually a 5 month time lag between maximum rainfall
and the maximum ground water level. Hydraulic gradients in the basin are of the
order of 2.5 to 3.5 %. Transmissivity values in the alluvium exceed 1 x 10
-1
m2 /s.
Storage coefficient values are on average around 10 % and in coarser grained layers
probably reach 15% or more. Transmissivities for the Lower Pleistocene range from
5 x 10- 3 to 4 x 10-2 m2/s, Storage coefficients are estimated to be around 6 %. Well
yields in the alluvium can exceed 300m3/h with a drawdown of a few metres. The
pumping levels range between 3 and 7m above sea level.
2.5.2
Simulation Models
For the constant-density groundwater flow simulations the widely accepted
by the modelling community program MODFLOW (McDonald and Harbaugh, 1988)
was used whereas the variable density simulations were carried out with SEAWAT.
The source code for SEAWAT was developed by combining MODFLOW and
MT3DMS into a single program that solves the coupled flow and solute-transport
equations.
2.5.3
Discretization, Boundary Condition and Aquifer Parameters
To simulate the groundwater – seawater interaction in the Tymbaki basin, a
regularly spaced, finite-difference model grid was constructed so that the y-axis is
roughly parallel the coast so that numerical dispersion problems resulting from
solving the transport equation are minimized. Each cell is 250 by 250 m in the
horizontal plane. The grid consists of 30 rows and 47 columns with the top of layer 1
is apatially variable and corresponds to the land-surface elevation derived from a
1:50000 scale topographic contour map.
24
The simulation is divided into 240 monthly stress periods from October 1968
to September 1987. For each stress period, the average hydrologic conditions are
assumed to remain constant. Further temporal discretization is introduced in the form
of transport steps. For the regional scale model, 10 transport steps were required for
each stress period.
No flow cells represent the Mesozoic aquifuge and Neogene aquitards which
bound and underlie the aquifer. At block 1, no flow cells are assigned at depths
below -160, at block 2, below -110, at block 3, below -50 and at block 4, below -10.
Time Variant Constant Head and Constant-Concentration cells represent the sea with
head value set to 0 and constant salt concentration set to 35000 mg/L. The General
Head Boundary cells extent down to depth 30m below sea level and posseses the
hydraulic parameters of block 1. The recharge from rainfall and streamflow
infiltration is distributed according to Figure 2.8. The calibrated model parameters
for the study are summarized in Table 2.2:
Table 2.2: The calibrated model parameters
Calibrated parameters
Hydraulic Conductivity (m/s)
Value
Block 1: Kx=Ky=Kz = 0.0001
Block 2: Kx=Ky=Kz = 5E-6
Block 3: Kx=Ky=Kz = 5E-7
Block 4: Kx=Ky=Kz = 5E-7
Specific yield
Uniform value Sy=0.2
Effective Porosity
Uniform value 0.15
Total Porosity
Uniform value 0.3
Dispersivity (m)
Uniform value αL=10
Uniform value αT=0.1
25
Figure 2.8: Rainfall and streamflow infiltration recharge zone.
2.5.4
Simulation Results and Conclusion
The extent of the simulated seawater intrusion into the Tymbaki aquifer at
various depths (500 mg/L salt contour at 38, 78, 118 and 158 meters below sea level),
at the end of the last stress period (20th year), is depicted in Fig. 2.9. It is apparent
that for southern end of the coast by the Geropotamos alluvium, the toe of the
saltwater intrusion front lies 550 to 600 m from the coastline. For the northern end of
the coast at the Makrymaliana area, the toe of the saltwater intrusion front is located
1500m from the coastline.
26
Figure 2.9: Simulated extent of seawater intrusion into the Tymbaki aquifer at
various depth
The extent and pattern of the seawater intrusion along the section C1 on the
10th and 20th year of simulation are depicted in Figure 2.10 and 2.11.
Figure 2.10: Seawater intrusion along section C1 at the end of 120th stress period
Figure 2.11: Seawater intrusion along section C1 at the end of 240th stress period
27
According to the model results, the toe of the saltwater intrusion front lies
550 to 600 m from the coastline at the southern end of the coast. At the northern end
of the coast (Makrymaliana area), the toe of the saltwater intrusion front is located
1500 m from the coastline. This apparent differential behavior of seawater intrusion
between the southern and northern part of the coast, is attributed to the effects of the
Geropotamos infiltration recharge. With replenishment amounting on average 4 Mm3,
36% of the total recharge, Geropotamos is by the far the most important water
supplier to the Tymbaki aquifer.
2.6
Optimization Modelling
Optimization theory is an analytical analysis to determine the best solution
from a series of alternatives without evaluating all the options available.
Optimization models are used extensively in almost all areas of decision-making
such as engineering design, and financial portfolio selection.
Knowledge in basic vector matrix, linear algebra and calculus are required for
the optimization theory. Most of the optimization problems involve a large amount of
mathematical calculations, therefore computer software is usually used to assist for
the solution. The types of optimization models for solving problems are linear
programming, non-linear programming and dynamic programming. A mathematical
optimization model consists of an objective function and a set of constraints
expressed in the form of a system of equations or inequalities. The basic goal of the
optimization process is to find values of the variables that minimize or maximize the
objective function while satisfying the constraints. The result is called an optimal
solution.
The objective function is a mathematical (i.e., analytical) model that
describes the behavior of the measure of effectiveness or the quantity that required to
be maximize or minimize. The objective function must capture the relationship
between the effectiveness measure and those variables that cause it to change.
System variables can be categorized as decision variables and parameters. A decision
28
variable is a variable that can be directly controlled by the decision-maker. There are
also some parameters which the values might be uncertain for the decision-maker. In
practice, mathematical equations rarely capture the precise relationship between all
system variables and the measure of effectiveness. This mathematical relationship is
the objective function that is used to evaluate the performance of the system being
studied.
Constraints are relations between decision variables and the parameters. A set
of constraints allows some of the decision variables to take on certain values, and
exclude others. Constraints are not always essential. In fact, the field of
unconstrained optimization is a large and important one for which a lot of algorithms
and software are available. In practice, answers that make good sense about the
underlying physical or economic problems, cannot often be obtained without putting
constraints on the decision variables. The applications of groundwater optimization
modelling in Malaysia are presented in Table 2.3.
Table 2.3: Application of groundwater management and optimization modelling for
coastal aquifer in Malaysia
Groundwater Management and Optimization Modelling in Malaysia
Year User
Models
1989 Afzal Hossain Parametric
(Ph D)
2001 Mohd.
Location
Scopes Of Study
North Kelantan
Optimization on conjunctive use
of surface water and groundwater
Dynamic
Faisal GAMS
Kota Bharu
(Ph D), UTM
2.6.1
of
groundwater
of
groundwater
hydraulic head.
(MSc), UTM
2001 Mohd. Harunl SUTRA
Optimization
Pulau Manukan, Optimization
Sabah
extraction.
Linear Programming
Linear programming is the most widely used method for solving optimization
problems. Linear programming deals with a class of optimization problems, where
29
both the objective function to be optimized and all the constraints, are linear in terms
of the decision variables. The linear programming problem is solved by using
Simplex algorithm, an algebra method introduced by Dantzing (1963). The linear
programming utilized the combination of simultaneous concept and other method
like Simplex method to check for the optimum solution.
Linear programming able to check all the possible solution for a problem and
give the best and appropriate solution based on the objective function which must be
stated specifically and comprehensively. The objective function and constraints set
for the linear programming must be specified in the form of linear equation.
Objective function is stated in linear equation to maximize or minimize the required
parameters. Linear constraints are the requirements for the solution of optimization
problems. The general form of linear programming must fulfill the following
requirements:
¾ Contain only equality for the main constraints
¾ Contain non-negative variables only
¾ Contain objective function and constraints which are written in simple form
where variables on the left-side of equation and constant on the right side.
The standard format of linear programming with m constraints and n
variables is represented as follows:
Maximum or minimum,
Z = C1X1 + C2X2 + ………………CnXn`
(2.1)
Referring to constraint set,
a11X1 + a12X2 + ………………..a1nXn = b1
(2.2)
a21X1 + a22X2 + ………………..a2nXn = b2
(2.3)
am1X1 + am2X2 + ………………..amnXn = bm
(2.4)
X1 > 0, X2 > 0, ………………..Xn > 0
(2.5)
until,
where,
30
b1 > 0, b2 > 0, …………………bn > 0
(2.6)
Inequity of the constraint set can be changed to equation with the introduction
of slack variables. The slack variables shall be added or deducted for the inequity
that involves ≤ and ≥ respectively.
2.7
Historical Review of GAMS Application for Groundwater Management
in the Goksu Delta at Silifke, Turkey (2001)
The Goksu Delta (also known as the Silifke Plain), which is located in south
central Turkey on the Mediterranean Sea, was chosen as the study area (Figure 2.12).
An optimization model was developed to manage the supplemental use of
groundwater in the coastal aquifer subject to saline intrusion problem of the study
area. The response of the aquifer system was linked to the optimization model using
the response matrix method. The aquifer response coefficients at specific well
locations were obtained through execution of a calibrated groundwater simulation
model using SUTRA (Saturated-Unsaturated Transport). It was assumed that
pumping occurs from two wells and linear optimization model was constructed under
steady-state condition to maximize the total pumping rates from the two wells
subject to water demands and chloride concentration and drawdown limitations. The
GAMS model was used to execute the optimization model.
31
Figure 2.12: The Goksu Delta
2.7.1
Objective Function and Constraints
The objective of the optimization model was to maximize the total pumping
rate from the two wells located in Bahce and Kurtulus town, while meeting the
demands of five municipal areas that were reduced to two demand areas in the
optimization model. Besides that, the chloride concentrations must be maintained
equal to or less than specified level in the optimization model since the water will be
used for drinking and irrigation purpose. The objective of the model is:
Max
∑ QT j
j
where: QTj
=
the pumping rate at well j (m3/s)
(2.7)
32
Seven observation nodes were considered in this study to calculate and
constrain the aquifer drawdown and chloride concentrations. The following
drawdwon constraint for each observation node includes a linear superposition of
aquifer responses to the wells:
si =
∑αijQT j
(2.8)
j
where si
αij
=
drawdown at observation node I (m)
=
aquifer influence coefficient describing the change of head at
node i with respect to change in pumping rate at well j
The hydraulic heads at an observation node were estimated by subtracting the
drawdown at node i from the initial hydraulic head:
H i = ( H 0 )i − si
where Hi
(H0)i
=
hydraulic head at node i (m)
=
initial hydraulic head at node i (m)
(2.9)
The linear superposition of aquifer responses in terms of chloride
concentration to the pumping wells gives the change in chloride concentration at
each node as follows:
Ci =
∑ βijQT j
(2.10)
j
where Ci
=
change in chloride concentration (mg/L)
βij
=
aquifer influence coefficients describing chloride
concentration change at node i due to a change in the pumping
rate at well j
The final chloride concentration at a node was estimated by adding the
change in chloride concentration to the initial concentration, which was obtained
from the calibrated groundwater simulation model such that:
CCi = (CC0 )i + Ci
where CCi
=
(CC0)i =
chloride concentration at each node i (mg/L)
initial chloride concentration at node i (mg/L)
(2.11)
33
Since the water pumped in the field is used for drinking and irrigation
purposes, the chloride concentration was limited at each well by taking the average
of the chloride concentrations of the nodes assigned to each well.
CC j ≤ CL
(2.12)
where CCj
=
chloride concentration at well j (mg/L)
CL
=
chloride concentration limit (mg/L)
∑ CCn
CC1 =
Well 1
n
3
CC2 =
Well 2
where n
m
n = 1, 2, 3
(2.13)
∑ CCm
m
4
=
the nodes assigned for well 1
=
the nodes assigned for well 2
m = 1, 2, 3, 4
(2.14)
In addition to the drawdown and concentration constraints the model was
subject to the following constraints as well:
(a)
Water demand limitations:
∑ Q jk ≥ Dk
(2.15)
j
where Qjk
=
pumping rate of well j supplying water for
demand area k (m3/s)
Dk
=
the amount of water required for demand area k
(m3/s)
(b)
Distribution of water from pumping wells to the demand areas:
QTi =
∑ Q jk
(2.16)
k
(c)
Well capacity limitations:
QTi ≤ CAPQ j
where CAPQj =
maximum capacity of well j, (m3/s)
(2.17)
34
(d)
Avoidance of dewatering the well nodes:
H i ≥ Bi + 1.0
where Bi
=
(2.18)
bottom elevation of the aquifer at node i below
mean sea level (m)
(e)
Non-negativity constraints:
QTi , QT jk , CCi ≥ 0
2.7.2
Results and Discussion
The model was solved for five levels of chloride concentrations. Each
solution sought an optimal pumping strategy for the different chloride concentration
limits. The optimal pumping strategies determined by the optimization model were
incorporated into the groundwater simulation model to verify the optimization model.
The correlation of aquifer responses between the simulation model estimates and the
optimization model results for hydraulic heads and chloride concentration were
shown in Figure 2.13 and 2.14.
Figure 2.13: Correlation between simulation model results and optimization model
results for hydraulic heads
35
Figure 2.14: Correlation between simulation model results and optimization model
results for chloride concentrations
The results of the optimization model were expressed in the form of a tradeoff curve as illustrated in Figure 2.15 to assist the water resource managers in
evaluatig different management scenarios. The curve relates the chloride
concentration to the maximum pumping rate for each well. The optimization model
tends to maximize the pumping rate at well 2, which is farther from the saltwaterfreshwater interface until the chloride concentratins reach 100 mg/L. After this point,
the influence that pumping from well from well 2 has on the well 1 becomes
significant and then the optimization model begins to maximize the pumping rates
for both wells.
Figure 2.15: Trade-off curves between maximum pumpng rate and chloride
concentration limit
36
2.8
Summary
Groundwater serves as an important alternative source of the water supply
system to meet the water demand, especially for regions with limited catchment area.
During dry weather season, water shortage is an issue that usually occurs for area
depending on surface water. Extraction of groundwater thus can supplement the
surface water source in water supply system.
Tioman Island with its potential continuous growth in tourism industry
required sufficient water for the tourists and local residents. Groundwater studies had
been carried out since year 1988 for Tioman Island to determine the suitability of
groundwater extraction to supply water in the future to cater for the increasing water
demand. The studies focused on groundwater flow and groundwater quality by
developing various types of groundwater numerical models as mentioned in the
previous section. However, the groundwater flow and quality issues were studied
separately without consideration of the relationship between the two aspects. Thus
this study involved the application of integrated numerical models that simulate
simultaneously to predict the groundwater drawdown and quality. Savvas N. Paritsis
(2005) had implement the same approach in his study on saline intrusion for
Tymbaki Aquifer, South Central Crete, Greece.
In order to fulfill the requirement of quantity and quality, optimum pumping
rate was determined in this study for management purpose. Linear programming of
optimization modelling provides the best solution from a series of constraints based
on the simulation results and site collection data. Nevertheless, optimization model
was not widely applied for groundwater management in Malaysia. The application of
optimization model for groundwater extraction was presented by F. Gordu, R. Yurtal
and L.H. Motz (2001) to optimize the pumping rate for aquifer system in Goksu
Delta at Silifke, Turkey.
37
CHAPTER 3
METHODOLOGY AND STUDY AREA
3.1
Modelling of Groundwater and Optimization
The study of the groundwater condition in Tioman Island involves the
groundwater flow, solute transport and optimization modelling. In order to satisfy
both water demand and water quality requirements, the simulation models results are
integrated to obtain optimum solution through linear programming. The groundwater
numerical models for the simulation process consist of MODFLOW and SEAWAT,
whereas GAMS will be utilized for the optimization purpose. The methodology
applied for this study as shown in Figure 3.1, Figure 3.2 and Figure 3.3 will be
further discussed in this chapter.
3.2
Description of the Study Area
Well-known for its scenic and natural beauty, Tioman Island is one of the
main marine tourism destinations in Malaysia. The island with total area of about
131 km2, has 6 main villages namely Kg. Genting, Kg. Paya, Kg. Tekek, Kg. Salang,
Kg. Mukut in the west coast and Kg. Juara in the east coast. The study will focus on
Kg. Tekek which encompasses area between X:684200 to 686200 and Y:311000 to
313000 is shown in Figure 3.4.
38
Figure 3.1: Groundwater Simulation and Optimization Model for the Study
39
Study Area:
The study will focus on Kg. Tekek on Tioman Island.
Collection of data:
(a) Existing and projection of water demand
(b) Hydrology data including historical rainfall data and flow for modelling
(c) Groundwater and surface water level and parameter values of aquifer (T, K, S)
MODFLOW2000 Simulation Modelling
• Determine nodal drawdown
• Determine the minimum hydraulic head
• Groundwater flow equation (Finite Difference Method)
∂ ⎛
⎜K
∂x ⎝
•
•
•
xx
∂h ⎞
∂
⎟+
∂x ⎠ ∂y
⎛
⎜⎜ K
⎝
yy
∂h
∂y
⎞
∂ ⎛
⎟⎟ +
⎜K
⎠ ∂z ⎝
zz
∂h ⎞
∂h
⎟+W = Ss
∂z ⎠
∂t
Calibration – Steady State (without pumping)
o Based on data collected on 4th June 2004 to determine the best value of k.
Calibration – Unsteady State (with pumping)
o Based on pumping test data on 4th June 2004 after pumping for 1 day.
Case Analysis – Unsteady State
o Run pumping from 1MLD to 5 MLD in 1, 3, 7, 15 and 31 days.
SEAWAT2000 Simulation Modellling
• Determine the saline intrusion due to groundwater pumping.
• Finite Difference Method
• Conservation of mass fluid
∂ ερ
= −∇ (ερ V ) + Q
∂t
p
•
Conservation of mass of solute
•
Calibration – Unsteady State (with pumping)
o Based on pumping test data on 4th June 2004 after 1 day of withdrawal.
Validation – Unsteady State (with pumping)
o Based on pumping test data on 8th July 2004 after 1 day of withdrawal.
Case Analysis - Unsteady State
o Run pumping from 1MLD to 3 MLD in 1, 3, 7, 15 and 31 days.
•
•
[
]
∂ (ε C )
= −∇ (ε VC ) + ∇ ε D ij • ∇ C + Q p C
∂t
OPTIMIZATION
• GAMS numerical Model
• Linear programming
o Z = C1X1 + C2X2 + ...CnXn
• To maximize the pumping rate, Q
• Constraint set
o am1X1 + am2X2 +…amnXn = bm
RESULTS, DISCUSSIONS AND CONCLUSIONS
Figure 3.2: Methodology Flow Chart
40
Groundwater Numerical Models
MODFLOW2000
SEAWAT2000
Discretization and Boundary Conditions Specification
•
Numbers of columns and rows with spacing
•
Numbers of layers with thickness
•
No flow cell
•
Time stepping for the simulation
Calibration and Validation of Model
•
Constant and calibrated parameters
•
Validation of Model
Model Simulations
•
Different pumping rates
Simulations Results
•
Hydraulic drawdown and concentration contours for each time step
•
Hydraulic head profile in vertical section for each time step
Figure 3.3: Groundwater modelling process flow chart
41
Figure 3.4: Location of Kg. Tekek in Tioman Island
42
3.2.1
Geology and Hydrogeology
Tioman Island is made up of mainly Triassic granite with Permian volcanic at
the eastern part of the island. In low lying areas such as Kg. Tekek, they are
generally made up of thin layers of alluvium consisting silt, sand and gravel with
some clays and corals. The aquifer in the study area is classified as an unconfirmed
aquifer which comprise mainly of about 12 m thick medium to coarse sand with
coral along the coast. Gravity method was used for the geophysical investigation and
the over all coral thickness is found to be within 7 to 20 m. The geologic map for
Tioman Island and geological cross section for Kg. Tekek aquifer system are
indicated in Figure 3.5 and Figure 3.6 respectively.
Figure 3.5: Geologic map for Tioman Island
43
Figure 3.6: Geological Cross Section for Kg. Tekek Aquifer System
Hydro-geological factors, comprising of the permeability and porosity of the
rocks and sediments, and the presence as well as distribution of small cave system
and solution cavities, have a major influence on the distribution of groundwater on
an island. Surface water resources prevail only on islands with relatively low
permeability. Groundwater resources are most abundant on small islands with
moderate to high permeability and porosity.
The geology of Tioman Island is well described by Bean (1972). This island
is underline mainly be granite rock/hard rocks which mean it has the least
groundwater potential and a thin narrow belt of metamorphosed volcanic and
sedimentary rocks along the north and east coast of the island. Meanwhile the
alluvium which has a better prospect for groundwater development were found only
on the limited areas, patches along coastlines at low-lying area such as Kg. Tekek,
Kg. Salang, Kg. Juara, Kg. Paya, Kg. Genting and Kg. Mukut.
44
3.2.2
Climate
The study area has a tropical climate characterized by uniformly high
temperature and high relative humidity. As the location of Tioman Island within the
Asian monsoon regime, the climate is modified by the monsoon effects. As the effect
of the northeast monsoon, the rainy season in Kg. Tekek falls between July and
January whereas the dry season occurs from February to June.
3.2.3
Topography
Tioman Island is a volcanic island covered in rainforest. It is fairly rugged, with
little flat land, mainly limited to the coast. Much of its terrain is more or less steeply
sloping and there are several large and often spectacular rocky outcrops. There is a
series of peaks and ridges running along the central spine of the island, of which
Gunung Kajang is the highest point with altitude 1038 m. Other peaks that are able to
be seen are Gunung Rombin Tioman (976 m), Gunung Seperak (958 m), and Bukit
Nenek Semukut (766 m). There are many small rivers, and the largest river is Sungai
Mentawak (about 5.5 km). Size, shape and topography of a small island are major
influences on the occurrence of both surface and groundwater resources. The
topography map for Tioman Island is illustrated in Figure 3.7.
10
0
45
200
100
Kg. Salang
10
0
100
0
40
Kg. Penuba
Kg. Air Batang
20
0
100
0
30
0
20
20
0
200
30
0
0
30
Lapangan
Terbang
0
10
0
20
30
0
300
Kg. Tekek
0
10
500
0
30
Kg. Juara
200
Kg. Paya
10
0
ROMPIN
300
100
500
100
0
70
300
0
80
200
300
Kg. Genting
0
30
200
300
600
0
60
0
10
50
0
200
500
700
0
10
0
30
80
0
Kg. Nipah
600
10
50
0
40
0
0
300
400
600
0
10
Batu
Sirau
0
10
100
Nenek
Si-Mukut
0
20
Kg. Mukut
100
Kg. Asah
100
Figure 3.7: Topography map for Tioman Island
46
3.2.4
Water Resources of Study Area
Water resources for the study area can be divided into surface water and
groundwater resources. The water supply system still depends on the surface water to
cater for the water demand for local residents and tourists. Untreated water is supply
directly form small collecting dam, which was constructed on the hilly terrain at the
upstream of the catchment. In Kg. Tekek, the surface water for domestic uses is
obtained mainly from Sg. Ayer Besar. Based on the study done by Awang and
Loganathan (1991), the aquifer in Kg. Tekek has good potential of groundwater
resource and is able to produce water of 1368 m3/day.
3.2.5
Hydrology
Kg. Tekek is covered with a limited catchment area of approximately 6 km2.
The recorded average annual precipitation between year 1975 and 1985 for Kg.
Tekek was 2,912.7 mm/year, which means a total amount of water rainfalls annually
equilibrium to 17.48 x 106 m3/year. The evapotranspiration on the other hand
resulted in total water losses of 7.63 x 106 m3/year, therefore the surface water runoff
and groundwater recharge is 9.85 x 106 m3/year. With the groundwater runoff of 7.42
x 106 m3/year, surplus groundwater recharge that can be exploited is 2.43 x 106
m3/year or 6,658 m3/day.
3.3
Groundwater Modelling
In this study, the simulation for groundwater flow will involve application of
two numerical models for different purposes. In order to determine the optimum
solution for the adverse effects of groundwater pumping to the hydraulic heads and
saline intrusion must be identified. Therefore, MODFLOW simulation model will be
utilized to predict the available yield of the groundwater flow system due to different
pumping rate, whereas study on saline intrusion effects will depends on SEAWAT.
47
Both the numerical models of MODFLOW2000 and SEAWAT2000 are included in
the package of Groundwater Vista
3.3.1
MODFLOW2000
MODFLOW is a computer program that simulates three-dimensional
groundwater flow through porous medium by using a finite-difference method.
MODFLOW was designed to have a modular structure that facilitates with objectives
of ease understanding and enhancing. MODFLOW was originally documented by
McDonald and Harbaugh (1984) and underwent several overall updates. Although
MODFLOW was originally designed to facilitate change, solving equations other
than groundwater flow equation were not included in the design concepts. Therefore,
the latest version of MODFLOW-2000 has been developed to facilitate the addition
multiple types of equations with ease of understanding still remains as an objective
of the design.
The MODFLOW2000 computer programme is divided into a main program
and a series of independent subroutines called modules. The modules are grouped
into packages that deal with a single aspect of the simulation. The packages are listed
and briefly described in Table 3.1. Individual packages may or may not be required,
depending on the problem being solved.
48
Table 3.1: Processes and Packages of MODFLOW-2000
Processes
Packages
GWF1- Groundwater Flow Process
BAS6- Basic Package
SEB1- Sensitivity Process
BCF6-Block-Centered Flow
OBS1-Observation process
LPF1-Layer-Property Flow Package
PES1-Parameter-Estimation Process
RIV6-River Package
DRN6-Drain Package
WEL6-Well Package
GHB6-General Head Boundary Package
RCH6-Recharge Package
EVT6-Evapotranspiration Package
CHD6-Time-Variant Specified-Head Package
HFB6-Horizontal Flow Barrier Package
SIP5-Strongly Implicit Procedure Package
SOR5-Slice Successive Over-Relaxation Package
PCG2-Version 2 of Preconditioned Conjugate
Gradient Package
DE45-Direct Solver
STR6-Streamflow-Routing Package
ADV2-Advertive-Transport Observation Package
RES1-Reservoir Package
FHB1-Flow and Head Boundary Package
IBS6-Interbed Storage (Subsidence) Package
HUF1-Hydrogeologic-Unit Flow Package
LAK3-Lake Package
ETS1-Evapotranspiration
with
a
Segmented
Function Package
DRT1-Drains with Return Flow Package
MODFLOW2000 can simulate steady and unsteady flow in an irregularly
shaped flow system in which aquifer layers can be confined, unconfined or a
combination of confined and unconfined. Flow from external stresses, such as flow
to wells, area recharge, evapotranspiration, flow to drains and flow through river
beds can be simulated. The hydraulic conductivities or transmissivities for any layer
49
may differ spatially and be anisotropic, and the storage coefficient may be
heterogeneous. Specified head and specified flux boundaries can be simulated, as can
a head-dependent flux across the model’s outer boundary, which allows water to be
supplied by a boundary block in the modelled area at a rate proportional to the
current head difference between a source of water outside the modelled area ant the
boundary block. MODFLOW-2000 has been expanded to simulate solute transport
and parameter estimation.
3.3.1.1 Spatial and Time Discretization
The physical size of the finite difference grid is provided through input to the
program. In all version of MODFLOW, the finite difference grid is assumed to be
rectangular horizontally and can be distorted vertically as illustrated in Figure 3.8.
The horizontal grid dimensions are specified by the cell widths DELR and DELC.
Columns are numbered starting from the left side of the grid and rows are numbered
starting from the upper edge of the grid. All cells in a column have the same width
and all cells in a row have the same width. Layers are numbered starting from the
top layer down. The elevation of the top of Layer 1 and the bottom elevation of each
layer for each cell are used to determine the thickness of each cell. A confining bed
through which only vertical flow exists can be simulated below each layer except
the bottom layer. This simulation of confining bed is referred to as the quasi-threedimensional (quasi-3D) approach.
50
Figure 3.8: Finite Difference Grid (Harbaugh et al., 2000)
3.3.1.2 Governing Equation
The partial-differential equation of groundwater flow used in MODFLOW is
(McDonald and Harbaugh),
∂ ⎛
⎜K
∂x ⎝
xx
∂h ⎞
∂
⎟+
∂x ⎠ ∂y
⎛
⎜⎜ K
⎝
yy
∂h
∂y
⎞
∂ ⎛
⎟⎟ +
⎜K
⎠ ∂z ⎝
zz
∂h ⎞
∂h
⎟+W = Ss
∂z ⎠
∂t
(3.1)
51
where,
Kxx, Kyy and Kzz are values of hydraulic conductivity along the x, y and z
coordinates axes which are assumed to be parallel to the major axes of
hydraulic conductivity [L/T]
h is the potentiometric head [L]
W is a volumetric flux per unit volume representing sources and/or sinks of
water with W < 0.0 for flow out of the groundwater system and W > 0.0 for
flow in [T-1]
Ss is the specific storage of the porous material [L-1]
t is time [T]
When Equation 3.1 combined with boundary and initial conditions, it
describes the transient three-dimensional groundwater flow in a heterogeneous and
anisotropic medium, provided that the principal axes of hydraulic conductivity are
aligned with the coordinate directions. The Groundwater Flow Process solves
Equation 3.1 using the finite-difference method in which the groundwater flow
system is divided into a grid of cells as shown in Figure 3.4. The head at a node is
calculated for each cell.
3.3.2
SEAWAT2000
The SEAWAT2000 programme is designed to simulate variable-density
groundwater flow and solute transport in three dimensions. SEAWAT2000 was
designed by combining a modified version of MODFLOW-2000 and MT3DMS into
a single computer program. The code was developed using the MODFLOW-2000
concept of a process, which is defined as “part of the code that solves a fundamental
equation by a specified numerical method. SEAWAT2000 contains all of the
processes distributed with MODFLOW2000 and also includes the Variable-Density
Flow Process. Processes may be active or inactive, depending on simulation
objectives, however, not all processes are compatible.
52
The processes in SEAWAT-2000 can be used in many different combinations,
called modes. Figure 3.9 illustrates all the possible modes in SEAWAT-2000. The
files types listed in the name file determine the active mode for the simulation. Four
simulation modes are available for constant-density simulations without solute
transport (Figure 3.9a). These four simulation modes correspond with the modes
available in the standard version of MODFLOW-2000.
Four simulation modes are available for constant-density groundwater flow if
solute transport is included (Figure 3.9b). The OBS, SEN and PES process are
currently not compatible with the IMT process, but they can be used with the GWF
Processes.
Only two simulation modes are available for variable-density
groundwater flow without transport. The two simulation modes in Figure 3.9c are
new features in SEAWAT-2000 provide advantage that a variable-density flow
simulation can be performed without simulating solute transport. The modes allow
for relatively quick simulations but the application of these modes should be avoided
if the fluid density will change in response to the imposed hydrologic stresses.
For the two simulation modes in Figure 3.9d, flow and transport are
uncoupled, meaning that the flow solution is affected only by the specified density
array. Therefore the flow field is not affected by the solute concentration simulated
with the IMT Process. The simulation of coupled variable-density flow and solute
transport can be carried out with the two modes in Figure 3.9e. The fluid density is
calculated by using an equation of state and the simulated solute concentration. For
problem involving coupled flow and transport, the computer run-times may be
exceedingly long because time step lengths are subjected to stability criteria, which
are necessary for accurate transport solution.
53
Figure 3.9: Simulation Modes Available with the SEAWAT-2000 programme
3.3.2.1 Temporal Discretization
The time discretization used in SEAWAT-2000 depends on the active
simulation mode. For the simulation modes without solute transport (Figure 3.9a, c),
time discretization follows the standard MODFLOW approach. The simulation is
divided into stress periods, and each stress period may be divided into flow time
steps. The flow time step lengths can be increased according to a geometric series,
which results in shorter flow time steps at the beginning of the stress period.
54
For the simulation modes that include solute transport (Figure 3.9b, d, e),
flow time steps are further divided into transport time steps. Lengths of transport
time steps are calculated according to stability criteria. In SEAWAT-2000, the flow
and transport equations are both solved for each transport time step. Solutions to both
flow and transport are required for each transport time step because changes in solute
concentration can affect flow patterns. In a constant-density system, however, flow
time steps may be much longer than transport time steps because ground-water flow
patterns are unaffected by solute concentrations.
3.3.2.2 Head and Equivalent Freshwater Head in SEAWAT2000
The Variant-Density Flow Process in SEAWAT2000 uses equivalent
freshwater head as the dependent variable in the variable-density ground-water flow
equation. By using equivalent freshwater head rather than pressure, the
MODFLOW2000 structure and subroutines can be used with few modifications to
solve the variable-density ground-water flow equation. The concept of equivalent
freshwater head is best explained by using water levels measured in a well.
Consider a monitoring well with a short screened opening in a saline aquifer.
The water level in the well is a measurement of head, h, in terms of aquifer water. If
the saline water within the well were replaced with freshwater, the water level in the
well would be higher because more freshwater would be required to equal the weight
of the saline aquifer water. The new water level in the well would be a measurement
of head in terms of freshwater, called the equivalent freshwater head, h f.
Conversions between h and h f can be made using the following equations
(Guo and Langevin, 2002):
hf =
and
ρ −ρ
ρ
h−
ρf
ρf
f
Z
(3.2)
55
h=
ρ
f
ρ
hf −
ρ −ρ
ρ
f
Z
(3.3)
f
where
ρ is the density of the native aquifer water [ML -3 ]
ρ f is the density of freshwater[ML -3 ]
Z is the elevation at the measurement point [L]
3.3.2.3 Variable-Density Groundwater Flow Equation
Guo and Langevin (2002) derive the governing equation for variable-density
ground-water flow, in terms of equivalent freshwater head, as:
⎛ ∂h f ρ − ρ f ∂Z ⎞ ⎤ ∂ ⎡
⎛ ∂h f ρ − ρ f ∂Z ⎞ ⎤
∂ ⎡
⎟⎥ +
⎟⎥
⎢ ρ K fα ⎜
⎢ ρ K fβ ⎜
+
+
⎜ ∂α
⎟
⎜
⎟⎥
∂
∂
ρ
α
β
β
ρ
β
∂α ⎢
∂
∂
⎥
⎢
f
f
⎝
⎠⎦
⎝
⎠⎦
⎣
⎣
+
⎛ ∂h f ρ − ρ f ∂Z ⎞⎤
∂h f
∂ρ ∂C
∂ ⎡
⎟⎥ = ρS f
⎢ ρK fγ ⎜
+
+θ
− ρ s qs
⎜ ∂γ
⎟
∂γ ⎢
∂
∂
ρ
γ
t
∂
C
∂
t
⎥
f
⎝
⎠⎦
⎣
(3.4)
where
α, β, γ are orthogonal coordinate axes, aligned with the principal directions of
permeability;
K f is equivalent freshwater hydraulic conductivity [LT -1]
S f is equivalent freshwater specific storage [L -1]
t is time [T]
θ is effective porosity [dimensionless]
C is solute concentration [ML -3]
ρs is fluid density source or sink water [ML -3]
qs is the volumetric flow rate of sources and sinks per unit volume of aquifer
[T -1 ]
56
The VDF Process in SEAWAT2000 has two different options for treating the
density terms in Equation 3.4. The simplest option and would result in the fastest
computer runtimes is specification of a fluid density array by user. The fluid density
can also be calculated by using the equation of state and solute concentrations from
the IMT Process. With this type of simulation, flow and transport are coupled and
thus the lengths of time steps may be subjected to stability criteria. For a coupled
variable-density flow and solute-transport simulation, fluid density is assumed to be
a function only of solute concentration, the effects of pressure and temperature on
fluid density are not considered. A linear equation of state is used to represent fluid
density as a function of solute concentration:
ρ =ρ
3.4
f
+
∂ρ
C
∂C
(3.5)
Simulation Setup
The groundwater numerical models were developed for both horizontal and
vertical section. The discretization of vertical section was done for the purpose of
SEAWAT2000 simulation. The horizontal plane was discretized into grid of 80 rows
and 80 columns with uniform spacing of 25m. The vertical section of the aquifer was
divided into 12 layers with thickness of 5m for layer 1 and 1m for layer 2 to 12 as
shown in Figure 3.10. The aquifer system was assumed to have a constant thickness
of 16m with the bottom elevation of the unconfined aquifer is 12m below the sea
level.
57
LEGEND:
Well Location
A
A
Constant Head &
Concentration
Representing Sea
Constant Head &
Concentration
Representing
River
No Flow Cell
Figure 3.10: Horizontal plane and vertical section of the groundwater models
58
3.4.1
Simulation Time Steps
The simulations of groundwater flow for unsteady conditions involve one
stress period with 5 time steps which represent 1, 3, 7, 15 and 31 days after pumping
of groundwater. Each groundwater flow time steps is further divided into 5 transport
steps to simulate the saline water movement. The hydrologic conditions are assumed
to be constant within the stress period.
3.4.2 Boundary Condition
Model boundary are set in the groundwater flow simulations to coincide with
the aquifer hydrogeological boundaries such as impermeable hydraulic barriers and
areas that can be represented with a constant head or flux. The boundary conditions
that are applied for the groundwater models are as stated below:
(a)
No flow cells which represent aquitards that bound and underlie the
aquifer are assigned at depth 12 m below sea level within the whole
groundwater system.
(b)
Constant head and concentration represents the sea with hydraulic
head value set at 0m and constant salt concentration of 35 kg/m3.
(c)
The recharge rate due to rainfall infiltration is taken as 10% of the
average rainfall.
3.4.3
Data Input Parameters
For the simulation of MODFLOW2000 and SEAWAT2000, aquifer
parameters that pertain to groundwater flow and solute transport are required to be
assigned to the models. The parameters are classified into constant and calibrated
parameters where calibration and validation processes are carried out to obtain
calibrated parameters values that enable the model becomes a reasonable
59
representation of the physical system. The constant and calibrated parameters are as
follow:
3.4.4
(a)
Constant parameters
1.
Freshwater Density
2.
Seawater Density
3.
Seawater Concentration
4.
Seawater hydraulic head
5.
Porosity
(b)
Calibrated parameters
1.
Hydraulic conductivity (horizontal and vertical)
2.
Longitudinal dispersivity
3.
Transverse dispersivity
4.
Molecular diffusivity
Model Assumptions
In this study, model assumptions were made based on the limited data
collected from previous study and field works, which include:
a. The aquifer is assumed to be unconfined.
b. Single layer unconfined aquifer with a bottom layer defined by the position
granitic bedrock.
c. Recharge rate is assumed to be constant within the study area.
3.5 Optimization Model
With the objectives of satisfy both quantity and quality requirements for the
extraction of groundwater, optimization modelling is applied to obtain the best
solution available. The simulated results from the groundwater modellings of
60
MODFLOW2000 and SEAWAT2000 are applied for the development of
optimization model.
3.5.1
General Algebraic Modeling System (GAMS)
The General Algebraic Modeling System (GAMS) is specifically designed
for modelling linear, non-linear and mixed integer optimization problems. The
system is especially useful with large, complex problems. GAMS structures good
modeling habits itself by requiring concise and exact specification of entities and
relationships. The GAMS language is formally similar to commonly used
programming languages, therefore it is familiar to anyone with programming
experience.
3.5.2
Objective function
The objective of the optimization model is to maximize the total pumping
rate from three wells in Kg. Tekek, consisting of TEK1, TEK3 and TEK4, in order to
meet the water demands within the study area. Therefore the objective function of
the model can be written as:
Maximize Q
(3.6)
where,
Q
3.5.3
=
Total pumping rate of wells
Constraints
The water demand and saline intrusion due to groundwater pumping will act
as constraints for the optimization model. The withdrawal of groundwater must be
able to cater for the water demand based on the projection done by Uni-Technologies
61
in year 2003. The quantity of water supply only based on the groundwater draft to
study the capability of the groundwater to support the water demand when surface
water source is not considered. Thus the water demand limitation:
QT ≥ DT
(3.7)
where
QT
= The total pumping rate (m3/s)
DT
= The total water demand (m3/s)
As mentioned earlier, the pumping activities will be carried out for three
existing wells in Kg. Tekek and the total pumping rate is distributed equally among
the wells in this study. The distribution of water from pumping wells is:
QT =
∑Qi
(3.8)
where
Qi
= The pumping rate of each well (m3/s)
i
= 1, 2, 3.
The hydraulic drawdown which relates to the aquifer yield is essential to be
determined to avoid overdraft of groundwater. The simulation of MODFLOW2000
will enable a development of relationship between hydraulic drawdown and pumping
rates and obtain an aquifer influence coefficient. In this study, only the pumping well
that produced maximum drawdown will be considered for the constraint. The
maximum hydraulic drawdown is defined as the sum of hydraulic drawdowns for
each pumping rate at pumping well. The maximum hydraulic drawdown must be
compared with the well screen level of the pumping well as the benchmark.
S max =
∑α jQ j
S max ≤ WSL
min
where
Smax = The maximum drawdown of the well (m)
α
= The aquifer influence coefficient describing the change of
drawdown with respect to pumping rate
WSLmin = Minimum screen level of well
j
= 1, 2, 3, …n
(3.9)
(3.10)
62
Besides the maximum drawdown, the hydraulic drawdowns at the location
25m and 50m from pumping well are also been monitored.
∑ α k Qk
S 50 = ∑ α l Ql
S 25 =
(3.11)
(3.12)
where
S25
= The drawdown at location 25m from pumping well (m)
S50
= The drawdown at location 50m from pumping well (m)
k, l
= 1, 2, 3, …n
Since the withdraw water will be supply for drinking purpose, the water
quality problem related to saline intrusion must also be taken into consideration
besides the hydraulic drawdowns. The groundwater simulation model of
SEAWAT2000 was executed for several pumping rates in order to develop a
relationship between pumping rate with saline intrusion length. Before the pumping
activities, a certain level of concentration can be traced at the study area. The
drinking water quality standard limits a maximum total dissolved solid concentration
of 1000mg/L in order for the water to be considered safe for drinking purpose. The
simulation of SEAWAT2000 model was carried out to determine the saline intrusion
length under non-pumping condition and pumping condition with different rates. The
pumping well that is constructed at a location nearest to the coastline is chosen as the
reference point for water quality monitoring.
Lint = βQT + L0
(3.13)
Lint ≤ L min
(3.14)
where
Lint
= The length of saline water intrusion (m)
L0
= The lenght of saline water intrusion before pumping activities (m)
Lmin = The minimum distance between pumping well and coast line (m)
β
= The aquifer influence coefficient describing the change of
saline intrusion length with respect to pumping rate
63
3.5.4
Water Consumption Projection
Long term projection of water demand is essential to forecast whether the
existing water supply would be capable to support the increase water demand. In
year 2003, Uni-Technologies Sdn. Bhd. had prepared a report on 5-year interval
water demand projection for Kg. Tekek from year 2001 to year 2025. The projection
basically concentrated on the growth of local residents and tourists as shown in Table
3.2.
Table 3.2: Projected water consumption for Kg. Tekek
Type of Demand
MLD, million liters per day
2001
2005
2010
2015
2020
2025
Local Residences
0.41
2.12
2.12
3.25
5.06
6.45
Tourists
1.45
1.78
2.11
2.43
2.67
2.84
Total
1.86
3.90
4.23
5.68
7.73
9.29
3.6
Integrated Modelling Approach
MODFLOW2000 and SEAWAT2000 are included in the whole package of
Groundwater Vistas. Groundwater Vistas is a unique modelling environmental for
Microsoft Windows that couples a powerful model design system with
comprehensive graphical analysis tools. The MT3DMS computer program (Zheng
and Wang, 1999), which normally runs as a separate program from MODFLOW2000,
was integrated directly into SEAWAT2000 and this new capability is called the
Integrated MT3DMS Transport (IMT) Process. The main purpose for integrating
MT3DMS directly into SEAWAT2000 is for variable-density simulations where
flow and transport are coupled processes, and thus, the flow and transport equations
must be solved sequentially (explicit) or simultaneously (implicit) for each time step.
The IMT process was created for SEAWAT2000 by adding the subroutines from the
MT3DMS programme directly to MODFLOW2000. Minor modifications were
required for the MT3DMS source code to integrate the programme directly into
64
SEAWAT2000. The data requirements for both groundwater models are similar
which will be discussed in the later section.
The IMT process simulates advective and dispersive transport and simple
chemical reactions for multiple species. The IMT Process solves the following form
of the advection-dispersion equation (Zheng and Wang, 1999):
(
)
∂ θC K
∂
=
∂t
∂xi
K
⎛
⎜ θ Dij ∂C
⎜
∂x j
⎝
⎞ ∂
⎟−
θv C K + q z C Ks +
⎟ ∂x i
⎠
(
)
∑R
n
(3.15)
where
C κ is dissolved concentration of species κ [ML -3]
Dij is the hydrodynamic dispersion tensor [L 2 T -1]
vi is seepage or linear pore water velocity [LT -1]
Csk is concentration of the source or sink flux for species κ [ML -3]
Rn is the chemical reaction term [ML -3 T -1]
One of the potential limitations of the SEAWAT2000 program is that the
dispersive term in the transport equation for variable-density ground-water flow
should contain a density gradient term. This term is only necessary for dense brines
and has not been incorporated into the transport equation because it would require
extensive modifications to the MT3DMS subroutines.
Comparing to the groundwater models that were already integrated through
IMT process in Groundwater Vistas package, the integration between groundwater
models and optimization model was carried out manually with application of
simulation results from groundwater models. The simulation results were utilized to
define the aquifer influence coefficients for groundwater drawdown (α) and saline
intrusion length (β) under different pumping rates. The influence coefficients were
applied for developing the constraints of linear programming optimization model.
65
Groundwater Model (Groundwater Vista)
MODFLOW2000
Input:
a)
b)
c)
d)
e)
Hydraulic Conductivity
Constant Head of Sea and River
Recharge Rate
Porosity
Top & Bottom Elevation
Output / Input of SEAWAT2000:
a) Hydraulic Head
b) Groundwater Drawdown
SEAWAT2000
Input:
a) Freshwater Density
b) Seawater Density
c) Slope of Density over
Concentration
d) Seawater Concentration
e) Longitudinal and Transverse
Dispersivity
f) Molecular Diffusivity
Optimization Model (GAMS)
Input:
a) Aquifer Influence Coefficient for
Hydraulic Drawdown, α
b) Aquifer Influence Coefficient for
Saline Intrusion Length, β
c) Minimum Screen Level of Well
d) Minimum Distance between Well
and Coastline
e) The Length of Saline Intrusion
Without Pumping Activities
f) Total Projected Water Demand
Output:
a) Optimum Flow Rate
Output:
b) Saline Intrusion Concentration
Figure 3.11: Input and output for integrated modelling
66
CHAPTER 4
RESULTS, ANALYSIS AND DISCUSSIONS
4.1
Introduction
MODFLOW2000 and SEAWAT2000 are numerical models that are included
in the package of Groundwater Vista, thus the models have a same presentation of
the simulation results. The hydraulic head and concentration are presented as contour
line on horizontal and vertical section.
In order for the numerical models to represent the physical system reasonably,
calibration processes were carried out to adjust the input parameters. For this study,
calibration was achieved by adjusting the input parameters for the model within a
reasonable range until simulated results of head and position of the saltwater
interface show approximate values with the observed data. MODFLOW2000 model
was calibrated for both steady and unsteady condition, whereas calibration for
SEAWAT2000 only involved unsteady condition. However, additional process of
validation for SEAWAT2000 was executed to validate the calibrated values with
water quality data collected under unsteady state condition.
The calibrated models were executed for several pumping rates to determine
the relationship between pumping rate with hydraulic drawdown and saline intrusion
length. The numerical models simulation results were applied to the optimization
models for optimization purpose. The results of groundwater simulations and
optimizations will be presented in detail in this chapter.
67
4.2
Simulation Results for MODFLOW2000
MODFLOW2000 was developed to simulate the groundwater flow system in
this area and predict the available yield due to different pumping rate. The simulation
results will provide information on hydraulic head and drawdown at different
location under unsteady state condition. The constant parameters that were applied to
the groundwater model are listed in Table 4.1.
Table 4.1: Values for constant parameters
Constant Parameters
Recharge Rate (R)
Porosity (θ)
Values
255 mm/year
0.3
Freshwater Density (ρf)
1,000 kg/m3
Seawater Density (ρs)
1,025 kg/m3
Slope of density over concentration (∂ρ / ∂C )
Seawater Concentration (C)
4.2.1
0.7143
35 kg/m3 = 35,000 mg/L
Calibration Process
The purpose of MODFLOW2000 calibrated was to determine the best value
of hydraulic conductivity, K. The calibration process involved both steady and
unsteady state condition with consideration of two cases. The aquifer system is
considered to be isotropic homogeneous in Case (1), whereas in Case (2), the
hydraulic conductivity varies in certain area (isotropic heterogeneous). The
calibrations were carried out based on the observed head data on 4th June 2004. The
initial hydraulic head is taken as the water level of Sg. Air Besar on the considered
day which range from 1.11m to 2.20m.
For aquifer as isotropic homogeneous, the value of hydraulic conductivity
was taken as 31 m/day based on Kuan research on year 2002. In Case (2), Kg. Tekek
is divided into 2 areas with hydraulic conductivity of K1 = 25 m/day and K2 = 10.9
68
m/day respectively as illustrated in Figure 4.1. The values of hydraulic conductivity
taken into consideration for the calibration purpose are summarized in Table 4.2.
Case study with isotropic heterogeneous aquifer was considered because the
pumping test results on 4th June 2004 indicated that pumping well TEK4 showed
lower hydraulic drawdown although the groundwater was pumped at higher rate
compare to the other two wells. Furthermore, the geological cross section for Kg.
Tekek also showed varies composition of soil at the area where well TEK1 and
TEK3 are located. The calibrated results for both cases were compared with the
observed hydraulic head at the three pumping wells, which are TEK1, TEK3 and
TEK4 (Figure 4.2).
Table 4.2: Cases considered for the calibration process
Case
Anisotropy and
Hydraulic Conductivity
Heterogeneity
Values
Case I
Isotropic homogeneous
K = 31 m/day
Case II
Isotropic heterogeneous
K1 = 25 m/day
K2 = 10.9 m/day
Figure 4.1: Hydraulic conductivity zoning plan for Kg. Tekek (isotropic
heterogeneous)
69
Figure 4.2: Location of pumping wells at Kg. Tekek
From the calibration analysis, both cases (1) and (2) for steady state condition
showed results that range in small percentage of difference between simulation
results and observed data. However, when pumping activities were considered, Case
(2) showed better results compared to Case (1). The calibration analysis results for
Case (1) and Case (2) are stated in Table 4.3 and 4.4 respectively. Thus the calibrated
model will consider the aquifer system as isotropic heterogeneous.
Table 4.3: Calibration analysis results for Case (1)
Well
Steady State
Unsteady State (after 1 day with
pumping rate 4.428MLD)
Observed Calibration
%
Observed Calibration
%
Head
Results
Different
Head
Results
Different
TEK1
1.601
1.6322
1.95
-2.19
0.5098
123.28
TEK3
1.752
1.8352
4.75
-2.31
0.6039
126.14
TEK4
2.036
1.9409
4.67
-0.79
0.1467
93.67
70
Table 4.4: Calibration analysis results for Case (2)
Well
Steady State
Unsteady State (after 1 day with
pumping rate of 4.428MLD)
Observed Calibration
%
Observed Calibration
%
Head
Results
Different
Head
Results
Different
TEK1
1.601
1.5957
0.33
-2.19
-2.244
2.45
TEK3
1.752
1.8365
4.80
-2.31
-2.434
5.37
TEK4
2.036
1.9433
4.65
-0.79
-0.751
4.73
4.2.2
Simulation Analysis
The calibrated model was used to predict the hydraulic head and drawdown at
different location under unsteady state condition. Simulation runs were conducted
with pumping rate range from 1 MLD to 5 MLD. The total pumping rate was
distributed equally between the three pumping wells considered. The simulation
results were utilized to determine the aquifer influence coefficient of drawdown
against the pumping rate. The hydraulic head contours after 1 day till 31 days of
pumping for 1MLD to 5 MLD are shown in Figure 4.3 to Figure 4.7.
71
Figure 4.3: Hydraulic head contour due to pumping of 1 MLD
72
Figure 4.4: Hydraulic head contour due to pumping of 2MLD
73
Figure 4.5: Hydraulic head contour due to pumping of 3MLD
74
Figure 4.6: Hydraulic head contour due to pumping of 4MLD
75
Figure 4.7: Hydraulic head contour due to pumping of 5MLD
76
The simulation results indicated that pumping well TEK1 suffered greater
hydraulic drawdown compare to TEK3 and TEK4 (Figure 4.8 and Figure 4.9). Thus
well TEK1 was chosen to determine the aquifer influence coefficient that to be
applied to optimization model. The screen of well TEK1 was between 6.1m and
10.1m below the sea water level, thus the withdrawal of groundwater must not cause
drawdown greater than the minimum screen level. The relationship between
hydraulic drawdown and pumping rate at pumping well TEK1 and surrounding
location (25 m and 50 m from TEK1) is illustrated in Figure 4.10.
The groundwater drawdown at the pumping well TEK1 showed a non-linear
relationship with the pumping rate. Since the results required to be applied to linear
programming of GAMS, the aquifer influence coefficients were determined by
sections of the graph, which means the aquifer influence coefficients varies for each
pumping rate as shown in Table 4.5. In contrary, the groundwater drawdown at
location 25 m and 50 m from well TEK1 relate linearly with the pumping rates, thus
the aquifer influence coefficients are presented by the slope of graph. The aquifer
influence coefficients for drawdown at location 25 m and 50 m from TEK1 are
0.0003117 and 0.0001151 respectively.
Table 4.5: The aquifer influence coefficient of drawdown for TEK1
Pumping rate
Influence
Pumping rate
Influence
(MLD)
Coefficient, α
(MLD)
Coefficient, α
0 to 1
0.00081
5 to 6
0.005065
1 to 2
0.000915
6 to 7
0.010545
2 to 3
0.001169
7 to 8
0.02481
3 to 4
0.001686
8 to 9
0.065956
4 to 5
0.002749
9 to 10
0.19813
77
Hydraulic Head at TEK-01
3
2
1
0
-80
-60
Hydraulic head (m)
-100
-40
-20
0
20
40
60
80
100
-1
-2
-3
-4
-5
-6
No Pumping
1 MLD
2 MLD
3 MLD
4 MLD
5 MLD
-7
Distance (m)
Pumping
Rate
-100
-75
0 MLD
1 MLD
2 MLD
3 MLD
4 MLD
5 MLD
1.585
1.585
1.585
1.585
1.585
1.585
1.618
1.618
1.618
1.618
1.618
1.618
Location
-50
-25
TEK1
25
Hydraulic Head
1.561
1.569
1.59
1.608
1.444
1.257
0.78
1.207
1.3235
0.934
-0.141
0.784
1.196
0.594
-1.343
0.321
1.063
0.239
-3.046
-0.183
1.031
0.1062
-6.074
-0.393
Figure 4.8: Hydraulic Head at TEK1
50
75
100
1.636
1.352
1.056
0.731
0.382
0.268
1.673
1.389
1.093
0.768
0.422
0.2977
1.719
1.413
1.094
0.743
0.37
0.2
78
Hydraulic Head at TEK-03 and TEK-04
3
2
1
Hydraulic head (m)
0
0
50
100
150
200
250
-1
-2
No Pumping
1 MLD
2 MLD
3 MLD
4 MLD
5 MLD
-3
-4
-5
-6
Distance (m)
Pumping
Rate
0
25
50
0 MLD
1 MLD
2 MLD
3 MLD
4 MLD
5 MLD
1.723
1.706
1.687
1.665
1.642
1.63
1.747
1.747
1.747
1.747
1.747
1.747
1.779
1.779
1.779
1.779
1.779
1.779
Location
75
TEK3
125
150
TEK4
Hydraulic Head
1.801
1.835
1.877
1.913
1.944
1.506
1.035
1.531
1.666
1.532
1.201
0.135
1.126
1.473
1.099
0.882
-1.073
0.792
1.145
0.635
0.548
-2.561
0.388
0.863
0.13
0.4008
-4.794
0.148
0.6441
-0.2771
Figure 4.9: Hydraulic head at TEK3 and TEK4
200
225
250
275
1.983
1.838
1.691
1.539
1.386
1.232
2.038
2.038
2.038
2.038
2.038
2.038
2.071
2.071
2.071
2.071
2.071
2.071
2.109
2.107
2.079
2.076
2.072
2.086
79
Graph of Drawdown Vs Pumping Rate At TEK1
9
8
7
Drawdown (m)
6
5
Pumping well TEK1
4
25m from TEK1
50m from TEK1
Li
3
(25
f
2
1
0
0
1
2
3
4
5
6
Pumping Rate, Q (MLD)
Figure 4.10: Relationship between hydraulic drawdown and pumping rate at TEK1
4.3
Simulation Results for SEAWAT2000
SEAWAT2000 was carried out to simulate variable density flow of
groundwater. The numerical model present the dissolved solid movement through
concentration contours in horizontal and vertical section. The simulation results
enable the prediction of saline intrusion length due to pumping activity.
4.3.1
Calibration and Validation Process
For SEAWAT2000, the numerical model was calibrated for the aquifer
hydrogelogic parameters that relate to sediment transport, including longitudinal
dispersivity, transverse dispersivity and molecular diffusivity. The hydraulic
conductivity values as calibrated in MODFLOW2000 were applied to the
SEAWAT2000 model, so no further calibration on hydraulic conductivity value was
carried out for this model. The calibration process involved unsteady state condition
80
with comparison to the water quality data collected during the pumping test by Bina
Juta Construction on 4th June 2004. The measured concentrations of total dissolved
solid at the three wells were inserted as the initial concentration of SEAWAT2000
model. The initial concentration considered for TEK1, TEK3 and TEK4 are 80mg/L,
70mg/L and 40mg/L respectively. Table 4.6 stated the calibration analysis results for
SEAWAT2000 model.
Table 4.6: Calibration results for SEAWAT2000
Calibration Process
Well
Observed TDS
Calibration
Concentration
Results
TEK1
180.00
96.90
46.17
TEK3
80.00
68.50
14.38
TEK4
50.00
42.80
14.40
% Different
After the calibration process, validation of model was done to compare the
simulation results with water quality data during pumping test activity on 8th July
2004 by FELDA Agricultural Services Sdn. Bhd. The calibrated model was executed
for a time step of 30 hours. The validation results of SEAWAT2000 model is shown
in Table 4.7. The calibrated aquifer parameters that were applied to SEAWAT2000
model in this study are listed in Table 4.8
Table 4.7: Validation results for SEAWAT2000
Validation Process
Well
Observed TDS
Calibration
Concentration
Results
TEK1
97.00
126.76
30.68
TEK3
34.90
35.28
1.09
TEK4
20.40
19.37
5.05
% Different
81
Table 4.8: Calibrated parameters for SEAWAT2000 model
4.3.2
Calibrated parameters
Value
Longitudinal Dispersivity
αL = 0
Transverse Dispersivity
αT = 0
Molecular Diffusivity
Dc = 1.629 m2/day
Simulation Analysis
The calibrated SEAWAT2000 model was run for different pumping rates that
range from 0 MLD to 3 MLD in order to study the effects on saline intrusion length.
The simulation involved 25 time steps with total period of 31 days. The initial
concentration of the pumping well is taken as the observed total dissolved solid (TDS)
concentration on 4th June 2004.
Pumping well TEK1 is constructed at the location nearest to the coastline,
thus the well was chosen as the reference point for the monitoring of groundwater
quality. The distance between TEK1 and coastline is approximately 350m. The
concentration contours for horizontal plane and vertical section due to groundwater
pumping of 0.5 MLD to 3 MLD for 1, 3, 7, 15 and 31 days are shown in Figure 4.11
to 4.22.
82
Figure 4.11: Concentration contour (seawater intrusion) on horizontal plane due to
pumping of 0.5 MLD
83
Figure 4.12: Concentration contour (seawater intrusion) on vertical section due to
pumping of 0.5 MLD
84
Figure 4.13: Concentration contour (seawater intrusion) on horizontal plane due to
pumping of 1 MLD
85
Figure 4.14: Concentration contour (seawater intrusion) on vertical section due to
pumping of 1 MLD
86
Figure 4.15: Concentration contour (seawater intrusion) on horizontal plane due to
pumping of 1.5 MLD
87
Figure 4.16: Concentration contour (seawater intrusion) on vertical section due to
pumping of 1.5 MLD
88
Figure 4.17: Concentration contour (seawater intrusion) on horizontal plane due to
pumping of 2 MLD
89
Figure 4.18: Concentration contour (seawater intrusion) on vertical section due to
pumping of 2 MLD
90
Figure 4.19: Concentration contour (seawater intrusion) on horizontal plane due to
pumping of 2.5 MLD
91
Figure 4.20: Concentration contour (seawater intrusion) on vertical section due to
pumping of 2.5 MLD
92
Figure 4.21: Concentration contour (seawater intrusion) on horizontal plane due to
pumping of 3 MLD
93
Figure 4.22: Concentration contour (seawater intrusion) on vertical section due to
pumping of 3 MLD
Similar to MODFLOW2000 model, the simulation results were applied to
obtain a relationship between saline intrusion length and pumping rate as specified in
94
Figure 4.23.
Under the non-pumping situation, the saline intrusion length was
identified as 80m. The saline intrusion length relates linearly with the pumping rate,
thus the aquifer influence coefficient can be determined easily through the slope of
plotted graph. The value of aquifer influence coefficient for saline intrusion length is
0.0093.
Graph Of Intrusion Length Vs Pumping Rate
120
y = 9.2967x + 80
100
Intrusion Length, L (m)
80
60
40
20
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Pumping Rate, Q (MLD)
Figure 4.23: Relationship between saline intrusion length and pumping rate
4.4
Optimization Results
A groundwater management model was developed under unsteady state
condition with the objective to maximize the total pumping rate of the three wells
considered. GAMS was employed for the execution of the optimization model. The
simulation results of the groundwater numerical models, MODFLOW2000 and
SEAWAT2000, were applied to form the constraints of the model. Appendix C
shows the linear programming model that was developed from the simulated results.
95
In order to meet the increasing water consumption, the other source of water
supply was explored as an supplement for the surface water source currently rely on.
The groundwater management model provided an optimal solution that avoid
overdraft of groundwater and fulfill the water quality standard. Based on the
constraints that were developed from simulation results, the aquifer system in Kg.
Tekek would be able to support total pumping rate up to 5.8 MLD. The
maximum
hydraulic drawdown allowable for Kg. Tekek is 11.6 and it was noted that hydraulic
drawdown has greater influence in the determination of optimal solution. The saline
intrusion line is still far away from the pumping well when the hydraulic drawdown
had already reached it maximum value. The summarized results of the optimization
model are stated in Table 4.9.
Table 4.9: Optimization results for pumping well TEK1
Optimum Pumping
Distance from
Drawdown
Distance between
Rate, Qmax (m3/day)
well TEK1 (m)
(m)
saline intrusion and
well TEK1 (m)
5843.24
0
11.60
25
1.91
50
0.72
75
0.00
215.66
Without the consideration of surface water source, the groundwater aquifer
system in Kg. Tekek is capable to cater for the water demand up to year 2015, which
is 5.68 MLD. However, the surface water source is still available in the area even
during dry season for purpose of water supply. Table 4.10 illustrates the combination
of surface water and groundwater system that will enable the projected water demand
up to year 2025 to be catered.
Table 4.10: Water supply for combine system
96
Surface Water
Groundwater
Total Water
Year that water
Supply (MLD
Supply (MLD
Supply (MLD)
demand can be catered
0
5.8
5.8
2015
3
5.8
8.8
2020
4
5.8
9.8
2025
Based on the results as stated in Table 4.10, with the groundwater extraction
till maximum flow rate and supply of 4 MLD from surface water source, the
residents and tourists will still not facing water scarcity problem till year 2025. Thus,
the aquifer system in Kg. Tekek can be considered as a reliable water source to cater
for the water demand in the future. However, the surface water will still serve as the
main source of water supply and groundwater only function as the supplement source
when water shortage occurs during draught season.
97
CHAPTER 5
CONCLUSIONS AND RECOMMENDATIONS
5.1
Conclusions
The developed optimization model in this study integrated the simulated
results from MODFLOW2000 and SEAWAT2000 numerical models to provide the
maximum pumping rate. The optimal solution shows that the aquifer system in this
study area would be able to support water supply of 5.8 MLD. The water quantity
and quality were the main considerations in this study. The results highlighted that
hydraulic drawdown has greater influence to the determination of maximum
pumping rate comparing to saline intrusion effects. The intrusion length only
encountered minor changes with the increment of pumping rate.
The groundwater aquifer system alone would be able to support water
consumption up to year 2015. With the combination of surface water supply up to 4
MLD, the local residents and tourism industry in this study area will still relief from
water scarcity problem till year 2025. Therefore, the groundwater aquifer system
poses an good option for the supplement to surface water supply system especially
during dry season.
5.2
Recommendations
The total pumping rate considered in this study is distributed equally among
the three wells considered. However, the wells showed different hydraulic drawdown
for the same value of pumping rate. As mentioned in the previous section, the well
98
TEK4 suffered lower hydraulic drawdown comparing to the other wells although
higher pumping rate was applied to TEK4. Thus, the pumping rate may be adjusted
according to the rate of hydraulic drawdown for each pumping well instead of
applying the same pumping rate for all wells.
Currently on site, a constructed pumping well, TEK2 is abandoned for
application of pumping activity. Additional well, either well TEK2 or new
production well, can be considered to obtain a better value of optimum pumping rate.
99
REFERENCES
Christian D. Langevin (2001). “Simulation of Ground-Water Discharge to Biscayne
Bay, Southeastern Florida.” U.S. Geological Survey, Water-Resources
Investigation Report 00-4251.
Christian D. Langevin, Eric D. Swain, Harry L. Jenter and Raymond W. Schaffranek
(2001). “The Tides and Inflows in the Mangroves of the Everglades Project.”
Florida Bay Science Conference, Key Largo, Florida, 23 – 26 April.
Christian Langevin, Eric Swain, Melinda Wolfert (2004). “Simulation of Integrated
Surface-Water/Ground-Water Flow and Salinity for a Coastal Wetland and
Adjacent Estuary.” Journal of Hydrology 314, pg. 212-234
Eduardo Aguado, Irwin Remson (1974). “Ground-Water Hydraulics In Aquifer
Management.” Journal of The Hydraulics Division, pg. 103 – 117.
Eduardo Aguado, Irwin Remson, Mary F. Pikul, Will A. Thomas. “Optimal Pumping
For Aquifer Dewatering.” Journal of The Hydraulics Division, pg. 869 -877.
F. Gordu, R.Yurtal, L.H. Motz (2001). “Optimization of Groundwater Use in the
Goksu Delta at Silitke, Turkey.” First International Conference on Saltwater
Intrusion and Coastal Aquifers Monitoring, Modeling and Management, Morocco,
23-25 April.
Hasan Daulay, Norhan Abd. Rahman, Kamarul Azlan Mohd. Nasir (2000). “Aquifer
Simulation Model in Tioman Island.” Journal of Civil Engineering, Universiti
Teknologi Malaysia.
Http://techalive.mtu.edu/meec/module06/TheHydrologicCycle.htm
Http://www.usgs.gov/
100
Kuan Woei Keong (2003). “Simulation of Groundwater Flow and Pollutant
Transport for Alluvial Aquifer in Kg. Tekek and Kg. Juara, Tioman Island.”
Universiti Teknologi Malaysia. Master Project.
Langevin C.D., Swain E.D. and Wolfert M.A. (2002). “Numerical Simulation of
Integrated Surface-water/Groundwater Flow and Solute Transport in the Southern
Everglades, Florida.” Second Federal Interagency Hydrologic Modeling
Conference, Las Vegas, Nevada, 28 July – 1 August.
Mohamad Faizal Bin Tajul Baharuddin (2002). “Pengurusan Airbumi Untuk Akuifer
Cetek Persisir Pantai Di Kota Bharu.” Universiti Teknologi Malaysia. Master
Project.
Mohd. Harun Bin Abdullah (2001). “Penyairan Air Freatik Akuifer Cetek di Pulau
Bersaiz Kecil.” Universiti Teknologi Malaysia. Phd. Thesis.
Nadiatul Adilah Abd. Rahman. (2004). “Groundwater Study For Alluvial Aquifer in
Tioman Island.” Universiti Teknologi Malaysia. Master Project.
Nicholas Albergo, William C. Hutchings (2005). “Surface Water and Seawater
Interactions in the Coastal Environmental of Biscayne Bay, Southeast Florida.”
2005 Salt Lake City Annual Meeting (16-19 October). Paper 191-8.
Norasman bin Othman. (2005). “Simulation of Saltwater Intrusion in Alluvial
Aquifer at Kg Tekek, Tioman Island.” Universiti Teknologi Malaysia. Master
Project.
Savvas N. Paritsis (2005). “Simulation of Seawater Intrusion into the Tymbaki
Aquifer, South Central Crete, Greece.” Department of Management of Water
Resources of the Region of Crete. Technical Report.
101
Thorne D.T., Langevin C.D. and Sukop M.C. (2006). “MODFLOW/MT3DMS –
Based Simulation of Variable-Density Groundwater Flow with Simultaneous Heat
and Solute Transport.” Proceedings of the XVI International Conference on
Computational Methods in Water Resources, Denmark, 18 - 22 June.
102
APPENDICES
103
A1: Analysis Results Of Groundwater In Kampung Tekek (source : ALS Technichem (M) Sdn. Bhd. 28 March 2003)
TEK 01
Parameter
Unit
TEK 02
TEK 03
TEK 04
WHO Water
36
72
36
72
36
72
36
72
hours
hours
hours
hours
hours
hours
hours
hours
6.89
4.85
5.79
4.03
6.61
6.75
6.01
6.39
6.5 – 9.0
C
23.00
22.50
24.00
23.50
23.00
21.50
24.00
23.50
-
Dissolved Oxygen
mg/l
3.86
4.05
3.91
3.01
3.98
4.01
4.21
3.45
-
Color
Unit Hazen
28.00
25.00
33.00
28.00
25.00
10.00
15.00
10.00
15 TCU
Turbidity
NTU
18.10
14.90
23.40
23.80
26.20
4.01
5.50
1.80
5 NTU
TDS
mg/l
94.40
29.30
37.40
32.00
43.00
53.00
26.00
34.00
1000
Conductivity
uS
183.00
50.30
51.00
55.60
80.00
79.10
52.00
69.80
-
Chloride (Cl)
mg/l
15.70
16.40
14.30
15.00
13.00
15.00
16.00
16.00
250
Ammonia (NH4)
mg/l
< 0.10
< 0.10
< 0.10
< 0.10
< 0.10
< 0.10
< 0.10
< 0.10
15
Arsenic (As)
mg/l
< 0.05
< 0.05
0.05
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
0.05
Cadmium (Cd)
mg/l
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
0.003
Clacium (Ca)
mg/l
3.40
3.90
4.10
3.90
4.20
4.30
2.50
3.80
-
Aluminium (Al)
mg/l
0.05
0.22
0.08
0.08
0.05
0.04
0.05
0.22
0.20
Barium(Ba)
mg/l
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.7
Chromium (Cr)
mg/l
0.00
0.00
0.00
0.001
< 0.001
< 0.001
< 0.001
< 0.001
0.050
Copper (Cu)
mg/l
0.07
0.08
0.09
0.09
0.07
0.08
0.07
0.11
1.0
Cyanide (CN)
mg/l
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
0.07
Fluoride (F)
mg/l
0.12
0.15
0.07
0.08
0.07
0.09
0.04
0.04
0.5 – 0.7
pH
Temperature
0
Raw
104
A2: Analysis Results Of Groundwater In Kampung Tekek (source : ALS Technichem (M) Sdn. Bhd. 28 March 2003) (continue)
Parameter
Unit
TEK 01
TEK 02
TEK 03
WHO Water
TEK 04
36 hours
72 hours
36 hours
72 hours
36 hours
72 hours
36 hours
72 hours
Raw
Iron (Fe)
mg/l
8.660
12.850
6.780
6.400
11.220
10.230
4.570
7.230
0.3
Lead (Pb)
mg/l
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
0.10
Magnesium (Mg)
mg/l
1.40
2.30
1.00
0.90
1.50
1.50
11.40
0.70
150
Manganese (Mn)
mg/l
0.07
007
0.06
0.06
0.12
0.11
0.04
0.08
0.20
Mercury (Hg)
mg/l
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
0.002
Nickel (Ni)
mg/l
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
0.1
Nitrate (NO3)
mg/l
0.04
0.04
0.14
0.24
< 0.01
0.19
0.04
0.12
10
Phosphate (P)
mg/l
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
-
Silica (SiO2)
mg/l
17.60
18.70
15.00
14.90
20.20
20.20
16.40
15.90
-
Selenium (Se)
mg/l
< 0.1
< 0.1
< 0.01
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.05
Strontium (Sr)
mg/l
0.01
0.02
< 0.01
< 0.01
0.03
0.03
< 0.01
< 0.01
-
Potassium (K)
mg/l
1.90
2.30
1.30
1.40
1.90
1.90
1.0
1.40
-
Sodium (Na)
mg/l
14.10
25.40
1.00
6.90
8.90
9.20
1.80
4.50
-
Carbonate (C)
mg/l
< 0.1
< 1.0
< 0.1
< 0.1
< 1.0
< 1.0
< 1.0
< 1.0
-
Zinc (Zn)
mg/l
0.08
0.68
0.26
0.10
0.21
0.18
0.09
6.77
1.50
E. Coli
MPN/100ml
< 2.0
< 2.0
< 2.0
< 2.0
< 2.0
< 2.0
< 2.0
< 2.0
0 - 50
105
A3 : Analysis Results Of Groundwater In Kampung Tekek (source : FELDA AGRICULTURAL SERVICESS SDN.BHD. 8 July 2004)
Parameter
Unit
pH
TEK 01
TEK 03
WHO Water Raw
TEK 04
30 minutes
36 hours
30 minutes
36 hours
30 minutes
36 hours
4.3
4.3
5.3
5.1
5.2
5.5
6.5 – 9.0
Temperature
0
C
29.9
29.3
29.2
28.9
29.0
30.0
-
Dissolved Oxygen
mg/l
2.19
2.32
2.09
2.24
2.84
2.89
-
Color
Unit Hazen
175
100
150
125
125
100
15 TCU
Turbidity
NTU
80.1
48.2
37.7
55.9
31.6
34.3
5 NTU
TDS
mg/l
126.5
97.0
29.0
34.9
18.3
20.4
1000
Conductivity
uS
183.2
140.4
41.8
51.4
27.5
30.4
-
Chloride (Cl)
mg/l
N.D
21.2
7.3
9.2
5.8
5.9
250
Ammonia (NH4)
mg/l
3.81
10.90
8.17
5.31
2.59
6.13
15
Arsenic (As)
mg/l
N.D
N.D
N.D
N.D
N.D
N.D
0.05
Cadmium (Cd)
mg/l
N.D
N.D
N.D
N.D
N.D
N.D
0.003
Clacium (Ca)
mg/l
3.35
3.88
1.88
2.52
0.95
1.17
-
Aluminium (Al)
mg/l
N.D
N.D
N.D
N.D
N.D
N.D
0.20
Barium(Ba)
mg/l
0.06
0.05
0.06
0.05
0.02
0.02
0.7
Chromium (Cr)
mg/l
N.D
N.D
N.D
N.D
N.D
N.D
0.050
Copper (Cu)
mg/l
N.D
N.D
N.D
N.D
N.D
N.D
1.0
Cyanide (CN)
mg/l
0.015
0.016
0.008
0.004
0.008
0.005
0.07
Fluoride (F)
mg/l
N.D
N.D
N.D
N.D
N.D
N.D
0.5 – 0.7
106
A4 : Analysis Results Of Groundwater In Kampung Tekek (source: FELDA AGRICULTURAL SERVICESS SDN.BHD. 8 July 2004)
(continue)
Parameter
Unit
TEK 01
TEK 03
TEK 04
30 minutes
36 hours
30 minutes
36 hours
30 minutes
36 hours
WHO Water Raw
Iron (Fe)
mg/l
0.06
0.05
0.04
0.04
0.06
N.D
0.3
Lead (Pb)
mg/l
N.D
0.06
0.01
N.D
0.05
N.D
0.10
Magnesium (Mg)
mg/l
2.79
0.92
0.78
0.95
0.19
0.79
150
Manganese (Mn)
mg/l
0.17
0.18
0.11
0.14
0.04
0.06
0.20
Mercury (Hg)
mg/l
N.D
N.D
N.D
N.D
N.D
N.D
0.002
Nickel (Ni)
mg/l
N.D
N.D
N.D
N.D
N.D
N.D
0.1
Nitrate (NO3)
mg/l
0.11
0.09
0.10
0.11
0.12
0.09
10
Phosphate (P)
mg/l
0.41
0.50
0.82
0.69
0.23
0.69
-
Silica (SiO2)
mg/l
6.88
8.63
9.43
9.68
6.58
12.53
-
Selenium (Se)
mg/l
N.D
N.D
0.01
N.D
N.D
N.D
0.05
Strontium (Sr)
mg/l
N.D
N.D
N.D
0.09
0.03
0.05
-
Potassium (K)
mg/l
1.88
1.78
0.88
1.05
0.36
0.56
-
Sodium (Na)
mg/l
17.28
16.42
13.07
6.68
5.05
4.73
-
Carbonate (C)
mg/l
N.D
N.D
N.D
N.D
N.D
N.D
-
Zinc (Zn)
mg/l
0.10
0.09
0.03
0.10
0.07
0.08
1.50
E. Coli
MPN/100ml
-
-
-
-
-
-
< 2.0
107
A5 :Water Quality Monitoring (6 June 2004 - 7 June 2004) by Universiti Teknologi Malaysia , Skudai
Parameter
Stn.
pH
Cond. (µS/m)
Turb. (NTU)
DO (mg/L)
Temp.
Salinity (%)
TDS (g/L)
TKW 1
6.5
49
47
4.1
27.10
0
0.32
6-Jun-04
6.3
49
50
3.4
27.60
0
0.32
TKW 3
6.3
13
13
7.8
27.1
0
0.08
6-Jun-04
6.4
13
10
7.3
27.1
0
0.08
TKW 4
6.2
15
18
8.2
27.1
0
0.1
6-Jun-04
6.2
15
13
7.4
27
0
0.1
3:00 PM
3:00 PM
Upstream
6.3
0.42 (S/m)
48
9.3
27.2
0.2
2.6
6-Jun-04
6.3
0.41 (S/m)
48
9
27.2
0.2
2.6
TKW 1
6.1
52
74
8.5
28.1
0
0.33
7-Jun-04
6
52
74
7.5
28.2
0
0.33
Upstream
6.6
0.47 (S/m)
27
9.6
26.9
0.3
3.1
7-Jun-04
6.6
0.49 (S/m)
25
9.1
26.9
0.3
3.2
TKW 1
6.2
54
93
4.6
28.7
0
0.34
7-Jun-04
6.2
54
90
4.6
28.7
0
0.34
Upstream
6.1
0.87 (S/m)
22
8.8
26.8
0.3
4.2
7-Jun-04
6.2
0.67 (S/m)
18
8.8
26.8
0.3
4.6
3:00 PM
12.00pm
12.00pm
12.12 m
3:00 PM
3:00 PM
TKW 1
5.9
54
100
4.6
28.5
0
0.34
7-Jun-04
6.5
53
100
3.7
28.5
0
0.34
Upstream
6.4
0.69 (S/m)
38
8.8
26
0.4
4.8
7-Jun-04
6.4
0.73 (S/m)
41
8.4
26
0.4
4.7
6:00 PM
6:00 PM
108
A6 : Water Quality Result During Pumping Test In Kampung Tekek by Universiti Teknologi Malaysia
Location
Date
2004
Time
Hour
Time
am,pm
TK1
4-Jun
4-Jun
4-Jun
4-Jun
4-Jun
4-Jun
5-Jun
5-Jun
5-Jun
5-Jun
5-Jun
6-Jun
6-Jun
6-Jun
6-Jun
7-Jun
7-Jun
7-Jun
5-Jun
5-Jun
4-Jun
4-Jun
4-Jun
4-Jun
5-Jun
5-Jun
5-Jun
5-Jun
6-Jun
6-Jun
7-Jun
30 min
30 min
1hr45min
9.50am
9.50am
11.05am
12.20pm
3.20pm
9.20pm
3.20am
9.20am
12.20pm
3.20pm
9.20pm
3.20am
9.20am
3.20pm
9.20pm
3.20am
9.20am
3.20pm
9.20am
12.20am
9.50am
12.20pm
3.20pm
9.20pm
3.20am
9.20am
3.20pm
9.20pm
3.20am
9.20am
3.20pm
JMG
TK3
6hr
12hr
18hr
24hr
6hr
12hr
18hr
24hr
6hr
12hr
18hr
24hr
30min
6hr
12hr
18hr
24hr
6hr
12hr
18hr
24hr
6hr
JMG
pH
microS/m
Cond
mS/m
5.8
5.7
5.9
6.4
6
5.9
5.9
5.9
5.9
13
110-JMG
13
13
14
14
27
28
29
26
6.1
45
5.8
6.1
6.1
6
6
6
6.1
244
249
11
12
12
12
12
12
13
4
38
3
4
10
79
8
6.1
13
14
Turb
NTU
DO
temp
21
5.4
27.8
22
32
16
26
8
15
9
38
4.2
3.2
8
6.6
6.9
7.1
2.5
6.7
470
7
o/o
Sal
o/o
TDS
g/L
Qpam
m3/hr
0.08
51
51
51
51
51
51
51
51
51
51
27.6
27.6
27.6
27.6
27.6
27.6
27.6
27.6
0
0.04-JMG
0
0
0
0
0
0
0
0
0.08
0.09
0.09
0.09
0.17
0.18
0.19
0.17
27.6
0
0.29
6
2.4
7.5
4.8
4.7
5.5
6.6
27.1
27.6
27.1
27.2
27.3
27.1
27.1
0.12
0.12
0
0
0
0
0
0
0
0.07
0.08
0.08
0.08
0.08
0.08
0.08
3.5
27.3
0
0.08
54.5
54.5
54.5
54.5
54.5
54.5
109
A7 : Water Quality Result During Pumping Test In Kampung Tekek by Universiti Teknologi Malaysia (continue)
Location
TK4
Date
2004
4-Jun
4-Jun
4-Jun
4-Jun
5-Jun
5-Jun
5-Jun
5-Jun
6-Jun
6-Jun
6-Jun
6-Jun
7-Jun
7-Jun
7-Jun
7-Jun
8-Jun
u/stream
5-Jun
Time
Hour
30 min
6hr
12hr
18hr
24hr
6hr
12hr
18hr
24hr
6hr
12hr
18hr
24hr
6hr
12hr
18hr
24hr
Turb
NTU
20
DO
temp
5.8
microS/m
Cond
mS/m
7
6.1
12.20pm
3.20pm
9.20pm
3.20am
9.20am
3.20pm
9.20pm
3.20am
9.20am
3.20pm
9.20pm
3.20am
9.20pm
3.20pm
9.20pm
3.20am
6.4
6.1
5.8
6
5.9
6.1
7
7
7
7
8
8
23
35
23
5
86
13
6
11
12.20pm
6.1
1.5
Time
am,pm
9.50am
JMG
pH
26.5
o/o
Sal
o/o
0
TDS
g/L
0.04
6.9
7.8
6.8
7.4
5.3
6.8
26.5
26.5
26.5
26.5
26.7
26.8
0
0
0
0
0
0
0.04
0.04
0.05
0.05
0.05
0.05
10
5.2
26.8
0
0.07
11
5.8
28.1
0.9
9
JMG
16.8
5-Jun
6-Jun
4.30pm
9.20am
6
6.2
0.11
9
13
12
7.7
8.5
26.9
26.3
0.1
0
0.8
0.06
5-Jun
4.30pm
6
0.14
20
8.8
26.6
0.1
0.9
d/stream
Qpam
m3/hr
79
79
79
79
79
79
79
79
110
A8 : Analysis Results Of Groundwater In Kampung Paya (source : ALS Technichem (M) Sdn. Bhd. 31 Dec 2002)
Parameter
Unit
pH
PP02
PP03
PP07
PP08
PP10
WHO Water Raw
4.44
5.28
5.63
5.52
5.65
6.5 – 9.0
Temperature
0
C
23.00
22.00
22.50
22.00
24.00
-
Dissolved Oxygen
mg/l
6.31
6.62
5.76
6.21
6.68
-
Color
Unit Hazen
67.00
18.00
20.00
22.00
8.00
15 TCU
Turbidity
NTU
15.00
5.25
3.12
7.67
6.34
5 NTU
TDS
mg/l
10.00
10.00
190.00
80.00
20.00
1000
Conductivity
uS
43.20
35.00
179.60
152.10
39.20
-
Chloride (Cl)
mg/l
8.00
10.00
17.00
23.00
6.00
250
Ammonia (NH4)
mg/l
0.10
0.10
0.20
< 0.10
0.10
15
Arsenic (As)
mg/l
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
0.05
Cadmium (Cd)
mg/l
< 0.001
< 0.001
< 0.001
< 0.001
0.002
0.003
Clacium (Ca)
mg/l
1.50
1.60
14.30
8.00
3.00
-
Aluminium (Al)
mg/l
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
0.20
Barium(Ba)
mg/l
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.7
Chromium (Cr)
mg/l
< 0.001
< 0.001
< 0.001
< 0.001
0.013
0.050
Copper (Cu)
mg/l
0.03
0.06
0.11
0.04
0.04
1.0
Cyanide (CN)
mg/l
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
0.07
Fluoride (F)
mg/l
0.52
0.48
0.45
0.52
0.45
0.5 – 0.7
111
A9 : Analysis Results Of Groundwater In Kampung Paya (source : ALS Technichem (M) Sdn. Bhd. 31 Dec 2002) (continue)
Parameter
Unit
PP02
PP03
PP07
PP08
PP10
WHO Water Raw
Iron (Fe)
mg/l
2.120
0.570
< 0.001
< 0.001
0.020
0.3
Lead (Pb)
mg/l
< 0.05
< 0.05
< 0.05
< 0.05
< 0.05
0.10
Magnesium (Mg)
mg/l
0.5
0.5
6.0
4.2
0.9
150
Manganese (Mn)
mg/l
0.01
0.01
0.08
0.02
0.04
0.20
Mercury (Hg)
mg/l
< 0.001
< 0.001
< 0.001
< 0.001
< 0.001
0.002
Nickel (Ni)
mg/l
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
0.1
Nitrate (NO3)
mg/l
0.03
0.04
0.02
0.03
0.04
10
Phosphate (P)
mg/l
< 0.03
< 0.03
0.07
< 0.03
< 0.03
-
Silica (SiO2)
mg/l
18.00
18.20
46.00
50.70
16.30
-
Selenium (Se)
mg/l
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.05
Strontium (Sr)
mg/l
< 0.01
< 0.01
0.16
0.14
0.03
-
Potassium (K)
mg/l
1.00
1.40
4.00
2.70
1.60
-
Sodium (Na)
mg/l
6.80
6.30
19.80
19.00
4.70
-
Carbonate (C)
mg/l
<1.00
<1.00
<1.00
<1.00
<1.00
-
Zinc (Zn)
mg/l
0.02
0.04
0.04
0.02
0.01
1.50
E. Coli
MPN/100ml
< 2.00
< 2.00
< 2.00
< 2.00
< 2.00
0 - 50
112
A10 : Analysis Results Of Groundwater In Kampung Salang (source : ALS Technichem (M) Sdn. Bhd. 31 Dec 2002)
Parameter
Unit
pH
PS01
PS02
PS06A
WHO Water Raw
6.90
6.20
6.80
6.5 – 9.0
Temperature
0
C
22.50
22.50
22.50
-
Dissolved Oxygen
mg/l
6.00
6.15
6.80
-
Color
Unit Hazen
23.00
39.00
14.00
15 TCU
Turbidity
NTU
144.40
18.20
1.38
5 NTU
TDS
mg/l
610.00
160.00
280.00
1000
Conductivity
uS
283.00
274.00
442.00
-
Chloride (Cl)
mg/l
16.00
31.00
11.00
250
Ammonia (NH4)
mg/l
0.30
0.10
< 0.1
15
Arsenic (As)
mg/l
< 0.05
< 0.05
< 0.05
0.05
Cadmium (Cd)
mg/l
0.002
0.003
< 0.001
0.003
Clacium (Ca)
mg/l
53.20
40.00
93.70
-
Aluminium (Al)
mg/l
3.34
0.15
< 0.01
0.20
Barium(Ba)
mg/l
< 0.1
< 0.1
< 0.1
0.7
Chromium (Cr)
mg/l
0.010
0.002
0.002
0.050
Copper (Cu)
mg/l
0.03
0.05
0.06
1.0
Cyanide (CN)
mg/l
< 0.05
< 0.05
< 0.05
0.07
Fluoride (F)
mg/l
0.50
0.48
0.51
0.5 – 0.7
113
A11 : Analysis Results Of Groundwater In Kampung Salang (source: ALS Technichem (M) Sdn. Bhd. 31 Dec 2002
(continue)
Parameter
Unit
PS01
PS02
PS06A
WHO Water Raw
Iron (Fe)
mg/l
8.910
0.002
0.002
1.000
Lead (Pb)
mg/l
< 0.05
< 0.05
< 0.05
0.10
Magnesium (Mg)
mg/l
0.13
13.60
4.10
Manganese (Mn)
mg/l
0.13
0.08
0.24
0.20
Mercury (Hg)
mg/l
< 0.001
< 0.001
< 0.001
0.001
Nickel (Ni)
mg/l
< 0.01
< 0.01
< 0.012
Nitrate (NO3)
mg/l
0.04
0.02
0.03
Phosphate (P)
mg/l
< 0.03
0.04
0.11
Silica (SiO2)
mg/l
40.90
27.40
27.90
Selenium (Se)
mg/l
< 0.1
< 0.1
< 0.1
Strontium (Sr)
mg/l
0.86
0.08
1.70
Potassium (K)
mg/l
2.20
1.20
0.90
Sodium (Na)
mg/l
7.20
12.50
12.10
Carbonate (C)
mg/l
< 1.00
< 1.00
< 1.00
Zinc (Zn)
mg/l
0.06
0.04
0.05
1.50
E. Coli
MPN/100ml
< 2.00
< 2.00
< 2.00
0. - 50
0.01
114
A12 : Analysis Results of Groundwater at Various Depths In Kampung Tekek (source: Department of Environment 2001 - 2005)
NO. TELAGA
(MW (7)-)
C18-1-5.52 m
C18-1-5.52 m
C18-1-18.95 m
C18-1-18.95 m
LOKASI
TELAGA
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
TARIKH
SAMPEL
22-Feb-01
23-May-01
22-May-01
23-May-01
As
(mg/l)
0.0150
<0.0002
0.0010
0.0150
Hg
(mg/l)
<0.0001
<0.0001
<0.0001
<0.0001
Cd
(mg/l)
0.0030
0.0010
<0.0002
0.0030
Cr
(mg/l)
0.0010
<0.0002
0.0010
0.0010
Cu
(mg/l)
0.0110
<0.0003
<0.0003
0.0110
Fe
(mg/l)
4.2000
0.0020
0.1700
4.2000
Pb
(mg/l)
0.0090
0.0090
<0.0002
0.0090
Mn
(mg/l)
0.3000
<0.002
0.0380
0.3000
C18-1-5.52 m
C18-1-5.52 m
C18-1-18.95 m
C18-1-18.95 m
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
7-Aug-02
3-Oct-02
7-Aug-02
3-Oct-02
0.0030
0.0003
0.0002
0.0011
0.0001
0.0001
<0.0001
<0.0001
<0.0002
0.0006
0.0002
0.0097
<0.0002
<0.0002
<0.0002
0.0002
0.0017
0.0021
0.0016
0.0023
0.2669
0.0625
0.0422
0.2666
0.0014
0.0020
0.0018
0.0013
0.0291
0.0329
0.0047
0.0299
C18-1-5.52 m
C18-1-5.52 m
C18-1-18.95 m
C18-1-18.95 m
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
29-Apr-03
16-Sep-03
29-Apr-03
10-Jun-03
0.0004
0.0004
0.0010
0.0009
0.0006
0.0001
0.0005
0.0001
0.0002
0.0004
0.0003
0.0002
0.0012
0.0002
0.0009
0.0002
0.0007
0.0008
0.0006
0.0017
0.0667
0.0789
0.1194
0.1792
0.0011
0.0010
0.0008
0.0010
0.0041
0.0064
0.0143
0.0169
C18-1-5.52 m
C18-1-5.52 m
C18-1-5.52 m
C18-1-18.95 m
C18-1-18.95 m
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
8-Mar-04
1-Jun-04
21-Jul-04
1-Jun-04
21-Jul-04
<0.0002
0.0900
0.0003
0.005
0.0007
0.0001
<0.0001
<0.0001
<0.0001
0.0001
0.0002
<0.0002
0.0016
<0.0002
0.0016
0.0064
0.0010
0.0002
<0.0002
<0.0002
0.0023
0.0010
0.0031
0.002
0.0034
0.0323
34.0000
0.0770
0.2810
0.2510
0.0007
0.0040
0.0028
0.0010
0.0017
0.0049
3.1800
0.0037
0.0230
0.0137
C18-1-5.52 m
C18-1-5.52 m
C18-1-5.52 m
C18-1-18.95 m
C18-1-18.95 m
C18-1-18.95 m
C18-1-18.95 m
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
30-Mar-05
26-May-05
27-Jul-05
30-Mar-05
26-May-05
27-Jul-05
7-Sep-05
0.00010
0.00030
0.00030
0.00030
0.00060
0.00050
0.00060
0.00005
0.00005
0.00005
0.00005
0.00010
0.00005
0.00005
0.00080
0.00130
0.00060
0.00040
0.00090
0.00070
0.00040
0.00100
0.00010
0.00090
0.00200
0.00010
0.00060
0.00230
0.00015
0.00840
0.00160
0.00180
0.00530
0.00040
0.00040
0.02200
0.01800
0.01700
0.18700
0.15500
0.21600
0.20500
0.00280
0.00180
0.00130
0.00130
0.00350
0.00220
0.00050
0.01180
0.00340
0.01700
0.01720
0.01580
0.01300
0.01610
A13 : Analysis Results of Groundwater at Various Depths In Kampung Tekek (source: Department of Environmental 2001 - 2005)
115
(continue)
NO. TELAGA
(MW (7)-)
LOKASI
TELAGA
TARIKH
SAMPEL
Zn
(mg/l)
Se
(mg/l)
C18-1-5.52 m
C18-1-5.52 m
C18-1-18.95 m
C18-1-18.95 m
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
22-Feb-01
23-May-01
22-May-01
23-May-01
0.0150
<0.0002
0.0050
0.0150
<0.0005
0.0010
<0.0005
<0.0005
HARDNESS
(CaCO3)
(mg/l)
19.00
70.00
93.00
19.00
C18-1-5.52 m
C18-1-5.52 m
C18-1-18.95 m
C18-1-18.95 m
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
7-Aug-02
3-Oct-02
7-Aug-02
3-Oct-02
0.0492
0.0099
0.0242
0.0310
<0.0005
0.0006
<0.0005
<0.0005
C18-1-5.52 m
C18-1-5.52 m
C18-1-18.95 m
C18-1-18.95 m
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
29-Apr-03
16-Sep-03
29-Apr-03
10-Jun-03
0.0056
0.0038
0.0030
0.0098
C18-1-5.52 m
C18-1-5.52 m
C18-1-5.52 m
C18-1-18.95 m
C18-1-18.95 m
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
8-Mar-04
1-Jun-04
21-Jul-04
1-Jun-04
21-Jul-04
C18-1-5.52 m
C18-1-5.52 m
C18-1-5.52 m
C18-1-18.95 m
C18-1-18.95 m
C18-1-18.95 m
C18-1-18.95 m
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
Kg. Tekek
30-Mar-05
26-May-05
27-Jul-05
30-Mar-05
26-May-05
27-Jul-05
7-Sep-05
Cl
(mg/l)
NO3
(mg/l)
SO4
(mg/l)
SAL
(%)
TDS
(mg/l)
1.80
3.10
6.00
1.80
0.05
0.39
<0.1
0.05
0.48
0.00
0.00
0.20
0.00
50.0
4.2
190.0
50.0
150.00
120
33.00
55
5.10
19.00
14.00
5.50
0.08
6.40
0.56
<0.05
1.94
5.90
2.90
1.90
-
205.0
130.0
76.0
210.0
<0.0005
<0.0005
<0.0005
<0.0005
28.00
25.00
87.00
113.00
4.96
5.60
5.80
10.00
0.59
0.48
<0.05
0.11
3.05
3.29
2.98
2.71
-
60.0
53.0
200.0
190.0
0.0111
0.0820
0.0302
0.0100
0.0114
<0.0005
<0.0005
<0.0005
<0.0005
<0.0005
34.00
35.00
39.00
170.00
145.00
5.10
6.50
11.00
6.90
5.90
0.30
<0.05
15.00
0.10
0.10
2.60
2.70
2.90
3.10
3.50
-
84.0
62.0
44.0
202.0
191.0
0.01310
0.00880
0.00640
0.01350
0.01130
0.00400
0.00200
0.00025
0.00025
0.00025
0.00025
0.00025
0.00025
0.00025
36.0
20.0
36.0
73.0
150.0
145.0
140.0
8.8
10.0
14.0
5.3
33.0
6.6
4.0
30.0
1.3
10.0
2.5
0.2
0.1
0.5
9.4
4.9
4.3
4.4
3.6
3.6
3.3
-
121.0
66.0
117.0
199.0
200.0
195.0
220.0
116
Appendix B1
117
Appendix B2
118
Appendix B3
119
Appendix B4
120
Appendix B5
121
Appendix B6
122
Appendix B7
123
Appendix B8
124
Appendix B9
125
Appendix B10
126
Appendix B11
127
Appendix B12
128
Appendix B13
129
Appendix B14
Appendix C
130
*Optimization for pumping rate based on seawater intrusion
free variable Q "pumping rate"
positive variables
Q1 "pumping rate at Kg. Tekek",
Qcap "maximum capacity of pump",
Dw "Drawdown due to different pumping rate at TEK1",
D25 "Drawdown due to different pumping rate at 25m from TEK1",
D50 "Drawdown due to different pumping rate at 50m from TEK1",
Qa "Drawdown due to 1MLD",
Qb "Drawdown due to 2MLD",
Qc "Drawdown due to 3MLD",
Qd "Drawdown due to 4MLD",
Qe "Drawdown due to 5MLD",
Qf "Drawdown due to 6MLD",
Qg "Drawdown due to 7MLD",
Qh "Drawdown due to 8MLD",
Qi "Drawdown due to 9MLD",
Qj "Drawdown due to 10MLD",
Lint "Length of seawater intrusion";
equations
obj "max pumping rate",
pump1 "required water demand",
pump2 "maximum pump capacity",
pump3 "total pumping rate",
drawdown1 "maximum drawdown",
drawdown2 "total drawdown",
drawdown3 "drawdown at 25m from TEK1",
drawdown4 "drawdown at 50m from TEK1",
int1 "length of seawater intrusion",
int2 "maximum length of seawater intrusion",
131
con1 "condition 1",
con2 "condition 2",
con3 "condition3",
con4 "condition4",
con5 "condition5",
con6 "condition6",
con7 "condition7",
con8 "condition8",
con9 "condition9",
con10 "condition10";
obj..
Q1 =e= Q;
pump1..
Q1 =g= 5000;
pump2..
Q1 =l= 10000;
pump3..
Q1 =e= Qa+Qb+Qc+Qd+Qe+Qf+Qg+Qh+Qi+Qj;
drawdown1..
Dw =e= 0.00081*Qa+0.000915*Qb+0.001169*Qc+0.001686*Qd+0.002749*Qe
+0.005065*Qf+0.010545*Qg+0.02481*Qh+0.065956*Qi+0.19813*Qj;
drawdown2..
Dw =l= 11.6;
drawdown3..
D25 =e= 0.000317*Q1;
drawdown4..
D50 =e= 0.0001151*Q1;
int1..
Lint =e= 0.0093*Q1+80;
int2..
Lint =l= 355;
con1..
132
Lint =g= 0;
con2..
Qa =l= 1000;
con3..
Qb =l= 1000;
con4..
Qc =l= 1000;
con5..
Qd =l= 1000;
con6..
Qe =l= 1000;
con7..
Qf =l= 1000;
con8..
Qg =l= 1000;
con9..
Qh =l= 1000;
con10..
Qi =l= 1000;
model gw/all/;
solve gw using lp maximizing Q;