3/26/2011

Climate Change:
Are Small Islands ‘Drowning’?
2nd WEPA International Workshop

Ahmad Zaharin Aris and Sarva Mangala Praveena
Universiti Putra Malaysia
zaharin@env.upm.edu.my1

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OutlineWhat to be covered?

o Climate changeo Small Islando Climate change in small islando Impact – groundwater quality23/26/2011

Climate change: scourges of thetwenty first century3

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Climate change: Global concern

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Threaten the very existence ofmankind

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temperature rises

Global Temperature Anomalies (°C)

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frequent and abnormal

rainfall pattern7

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climate variability

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floods9

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droughts

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coastlines being washed away11

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agricultural areas
turned into desert

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reduction of food supply

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shortage of water supply

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deteriorated
water quality15

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and many more…….

(UNEP, 2009)16

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great risk from climate change impacts

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3/26/2011(mindmapart)18

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SMALL
ISLANDS

Possible climate change‐related impacts in Tropical Asia

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physical, demographic and economic features20

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Outstanding
touristdestinations

Economic
growthBalanced
betweenrecharge &outflows

Extractions,evapotranspiration,discharge andmixing of seawater

Experiencing water
stress due togroundwater extraction

Easilyoverexploited

Vulnerable toclimate change

Pressure of island
resources and impactsof freshwater resources21

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SEAWATERINTRUSION

Natural stresses- Sea level rise
- Climate change

Artificial stresses- Overpumping

Irreversible deteriorations ofgroundwater quality223/26/2011

5 mm/yr by 2100

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Typical small island freshwater lens that always in danger.

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AB(EPA, 1989)25

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WET CLIMATEDRY CLIMATESEA LEVELTHICK FRESHWATER LENS

THIN FRESHWATER LENS26

3/26/201127

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ImpactImpact on groundwatero South Asia is the largest user of groundwater– 1/4 of the total use
o The effects of climate change and over use isdisastrous combinationo Impactso Drying up of wells/bore wells
o Poor quality of groundwatero Saline water intrusion28

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limited alternatives todevelop their freshwater
resources

depends on recharge,quantity and surfacestorage

Small islands

may easily beoverexploited or polluted
due to dense
development

distort the natural
recharge-dischargeequilibrium29

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Study area
Island:Manukan(Tunku Abdul Rahman Park)Area:
206 000 m2
Population:
Inhabitants (challets)
Maximum altitude:
80 m

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Manukan Island features31

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The sediment of the island is loose, not cemented and act as goodwater storage
Small area and low elevations – limited water storage32

3/26/2011••

Climate in this region– Warm and wet throughout
the year
Water resources– Dominated by rainfall
recharge

Average monthly rainfall distribution for study area from 1995 to 200733

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34

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3/26/2011‐ No surface water‐ Rely heavily on its groundwater‐ Tourism with tourist increased 400% (1997‐2004)

A total of 8 wells have been closed, and only ONE WELL
is operating

Seawater intrusion is taking place at the beneathof pumping well with mixing ratio of 14.6%

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Objectives
Aim of this study
STUDY themovement ofsaline solutes intothe aquifer(current scenario)

Objectives

SIMULATE seawaterintrusion underselected scenariosof varying recharge(climate impact) andpumping rates

PREDICT seawater
intrusion underselected scenarios
for TWO years373/26/2011

Experimental
Experimental phases in this study

Observation
wells

GeneralHydrochemistry
SurveyTransport
Modeling

Experimental Phases38

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5.9762
PK 1

5.976

PK 2

PK 6

5.9758PK 7

PK 3

5.9756

PK 8

PK 4

PK 9
PK 5

116.0066

116.0064

116.0062

116.006

116.0058

116.0056

116.0054

5.9754116.005239

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Observation wells
Observation wells constructed for simulation modelling• Over a distance of 80 m fromcoastline40

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Geochemical Model Setup41

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Numerical Model Setup
The groundwater flow and transport model for
Manukan island aquifer implemented using 3D
finite‐difference model SEAWAT‐2000.

SEAWAT‐2000 is the latest modelingsoftware available in groundwatermodeling that couples flow and transport
together (Guo and Langevin, 2002).

SEAWAT 2000

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Numerical Model Setup
Wells and Boreholes data (hydrauliclevels and chloride concentrations
Boundary condition
Soil physical parameters
Surface elevation modelThree dimensional model using SEAWAT‐200043

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Parameter
Hydraulic conductivity (Kx, Ky & Kz)
Layer 1
Layer 2
Layer 3Layer 4 (sedimentary rock)Molecular diffusion
Freshwater density
Seawater density
Total porosity
Specific storage
Specific yield
Longitudinal dispersivity
Horizontal transverse dispersivity
Vertical transverse dispersivity
Recharge
Evapotranspiration

Constant head
Recharge concentration
Constant head concentration
Initial Concentration (mg/L)
Initial head (m)Hydraulic heads (m)B1-B9W1, W2, W3, W4, W5, W7
Chloride concentration (mg/L)
B1-B9
W1, W2, W3, W4, W5, W7
Pumping rate at W6Value
6.49E-4, 2.4E-5, 1.5E-5
5.75E-4, 3.5E-5, 1.3E-5
7.17E-4, 1.3E-5, 1.2E-5
5.4E-7, 1E-5, 1E-5
1.0E-9 m2/s
1000.0 kg/m3
1025.0 kg/m3
0.49
0.0014
0.35
1.5 m
1. m
0.01 mmm/yearRecharge data in 2009
mm/year
Evapotranspiration data in 2009 calculated using
Penman method
16 m0 mg/l
19999 mg/l
Based on Jan 2009
Based on Jan 2009

Numerical model of Manukan Island

Monthly samplings in 2009
Monthly samplings in 2009

Monthly samplings in 2009
Monthly samplings in 2009
72 m3/dayGoverning equation

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Groundwater Major Ions Composition
PatternGeneral Patterno Results and Discussion

CationNa > Ca > Mg > KAnion
Cl > HCO3 > SO445

2++C lPresent study
Ca4SO2+• Major cation – Na &Ca

2+g+M

ANATION
EXPLANATION
undwater(1996)
Groundwater(1996)
Groundwater(2006-2007)
undwater(2006-2007)
Seawaterawater2-

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2-Mg

SO4

• Major anion – Cl &HCO3• Alkalis > Alkaline
earth metals• Strong acids > WeakacidsCa2++Na + K+2--

CO3 + HCO3

• Na-Cl typed
dominated-Cl46

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Water Chemistry at the Seawater/ Freshwater
Mixing Zone

FM
SSalinity
Intermediate salinity (0.90 – 4.60 ppt)
pHF<M<S47

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Groundwater Chloride and Salinity• Intruded by seawater up to 80 m andcan be reached further up to 100 mfrom coastline• Brackish water (300 – 10 000 mg/l); Cl
concs. Ranged from 591 to 3716 mg/l

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Groundwater Chloride and Salinity

The lowest; 78 m

• Intruded by seawater up to 80 m andcan be reached further up to 100 mfrom coastline• Brackish water (300 – 10 000 mg/l); Cl
concs. Ranged from 591 to 3716 mg/l
• Cl – decreased with distance• Thereby constitute an important
additional mechanism for thetransport of seawater into the aquifer.

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Chromatographic Ion Exchange Pattern Na + Ca‐X Na‐X + Ca+22+

Ca2+ + Mg‐X2 Mg2+ + Ca‐X2

0.800
0.700

Ca0.600

β0.500
0.400
0.300
0.200

Na
0.100
0.000
0102030

40

50

60

70

80

90100

Distance From Coast (m)50

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180

Concentration (mmol/l)

1601401201008060402000102030405060708090100

Distance From Coast (m)NaMg

CaK*10Cl

HCO33 *10HCO3 – increases with the flow path (towards further inland). The increasing of HCO3is partly due to sulfate reduction process. The highest value ( ~ 70 above) suggestthat the area are still not impacted with seawater chemistry value51

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180

Na‐ClConcentration (mmol/l)

160

Ca‐Cl

140
120
1008060
402000102030405060708090100

Distance From Coast (m)NaMg

CaK*10Cl

HCO33 *10Na, K and Mg – decreased at around 40 m from the coastline following thedecreased in Cl which indicates that a major part of the cation distribution are due toadvective transport. The water shifted from Na‐Cl to Ca‐Cl at this distance. The shifts
clearly indicate the ion exchange by the decrease in Na, increase in Ca concs.

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Conceptual model
Using SEAWAT‐2000

o The transient simulation model (SEAWAT‐2000) with
12 total periods was performed from January 2009‐
December 2009 with each stress period
representing 1 month of simulation month.
o Model calibration is achieved through trial and error
method using observed data of groundwater
hydraulic heads and chloride concentrations.
o Scenarios selected are as follows:53

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Climate change scenario
To mimic the climate variability impacto Climate change scenarios for Malaysia
Scientific Report 2001‐2099 concluded that
there will be a reduction in the annual rainfall
in East Malaysia that will affect the recharge
rate with the impact of an El Niño event.
Malaysia Meteorological Department, 200954

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Scenarios
Scenarios selectedScenario
AScenario
BScenario
CScenario
DScenario
ECurrent pumping rate
Current recharge rate
Reduction pumping
rate (-25%)
Reduction recharge
rate (-10%)
Artificial rate (+40%)

climate impact55

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Water Balance
Calculated water balance for low‐lying are of Manukan Island

The recharge rate is about 1.9% of the total inflows, whereas the ET and pumping areabout 1.2 and 15% of the total outflows, respectively.

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Current situation
The inconsistency in the recharge rate

ooThe inconsistency in the recharge rate in the current scenarion is a prove of
climate change and abnormal precipitation pattern.
It indicates that the small islands, particularly their recharge rates, are sensitive toclimate changes.

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Simulation
Simulation of freshwater seawater mixing
Seawater‐freshwater mixing concentration of 1.4% was chosen in this simulation toindicate that the mixing concentration exceeds the maximum chloride concentrationlevel reported by USEPA (1972).

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Seawater‐freshwater mixing ratio of 1.4%
Scenario A
The seawater-freshwater mixing
ratio moves landwards after twoyears of simulation in Scenario 1.

Scenario A

Overpumping causes irreversibledeteriorations of groundwater
quality due to drawdown of watertable or upconing of the saltwaterinterface (Praveena et al., 2010).

Simulated extent of seawater intrusion for low lying area of Manukan Island shown bya solid line in 2009.
Extent of seawater intrusion for next two years after December 2009 by a dashed line59

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Scenario B
Overpumping has indicatedin Scenario 1.
Scenario 2 has resulted inbackward movement of the1.4%
seawater‐freshwater
mixing ratio towards the coast
after two years of prediction.

Scenario B

Thus, a reduction in pumpingrate can be used to control theseawater intrusion problem.

Simulated extent of seawater intrusion for low lying area of Manukan Island shown bya solid line in 2009.
Extent of seawater intrusion for next two years after December 2009 by a dashed line60

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Scenario C
Seawater intrusion will be more
severe with an impact of El‐Nino
events on groundwater resources
depletion

Scenario C has resulted ininward movement of the 1.4%
seawater‐freshwater
mixingratio towards land after twoyears of prediction.

Scenario C

Simulated extent of seawater intrusion for low lying area of Manukan Island shown bya solid line in 2009.
Extent of seawater intrusion for next two years after December 2009 by a dashed line

When the pumping rate is larger
thanrecharge
rate,overexploitation
will cause
seawater intrusion in the study
area.

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Scenario D

Reductions of pumping andrecharge rates (Scenario D) haveworsened the current seawater
intrusion phenomenon

Scenario D

Indicated by further movement of
1.4% seawater‐freshwater mixing
ratio.

Simulated extent of seawater intrusion for low lying area of Manukan Island shown bya solid line in 2009.
Extent of seawater intrusion for next two years after December 2009 by a dashed line62

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Scenario E

It has resulted in movement of
1.4% seawater‐freshwater mixing
ratio towards the coast in twoyears after December 2009.

Scenario E

Simulated extent of seawater intrusion for low lying area of Manukan Island shown bya solid line in 2009.
Extent of seawater intrusion for next two years after December 2009 by a dashed line63

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ImpactGroundwater quality deteriorated with climate change impact

Chlorideconcentration at
beneath of pumping
well (W6)

Scenario

Scenario
AScenario
BScenario
CScenario
D

Scenario
E

Chlorideconcentration(mg/L)

1889.91812.7

1895.7

2003.31552.264

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Conclusions
Is there any impact?
There is definitely some impact of rainfall on groundwater. In
normal condition, impact will be visible in a decade but due toover use of the resource in on part and under use in other part,
it is difficult to assess the impacts

In case of groundwater, anthropogenic conditions override

Climate change is a natural and frequently occurring and theanthropogenic factors are hastening this change at an alarmingrate.
Climate change will worsen the ecosystem of small islands. This
study revel conclusively that the small islands are very
vulnerable to future sea level rise and climate change.

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3/26/2011> Acknowledgements

MINISTRY OF SCIENCE, TECHNOLOGY &INNOVATION(SCF04‐010‐SF0065)

MINISTRY OF HIGHER EDUCATIONMALAYSIA(FRG0050‐ST‐1/2006)66

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THANK YOU !

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