Develop simulation and optimization models for a
coastal aquifer:
•
Characterize the hydrogeology of the Goksu Delta;
•
Model three-dimensional variable-density groundwater flow
and seawater intrusion using SEAWAT;
•
Use groundwater simulation model to develop response
matrices for heads and chlorides for the optimization model;
•
Maximize groundwater pumping subject to drawdown and
chloride constraints, water demands, and pumping
constraints; and
•
Relate chloride concentrations and maximum pumping rates
using GAMS (General Algebraic Modeling System).
Dr. Ahmet Dogan
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Definition of Salt water intrusion
Salt water intrusion is the migration of
saltwater into freshwater aquifers under
the influence of groundwater
development. (Freeze and Cherry, 1979).
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



Generally, Salinisation process is a result of
human activities.
In addition, a relative sea level rise of 0.5 m
per century will intensify the salinisation
process in all low-lying areas of the world.
Saltwater intrusion is a problem for every
coastal region.
Therefore, we should be very careful to protect
freshwater resources all over the world!!!
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Wedge
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Seawater intrusion due to over pomping
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Upconing Due to Pumping
Pumping causes water table drawdown...
…and seawater intrudes into well due to upconing.
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Uncontrollable
Controllable
Inputs
Excitation
Cause
SYSTEM
Detection
Identification
1


Uncontrollable Inputs:
◦ Natural Recharge from
precipitation
◦ Evapotranspiration
Controllable Inputs:
 Pumping and injection
schedules
 Artificial recharge
Outputs
Response
Effect
Undesirable
Desirable
Prediction
2
3

Desirable Outputs:

Undesirable Outputs:
◦ Reduction in Subsurface
Outflow
◦ Drying of a wetland
◦ Seawater Intrusion
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1-Detection problem
Determination of some of the unknown input parameters
using both the responses of the system and the system
outputs, e.g. (Recharge and leakage estimations)
2-The identification (Calibration) problem
Determining the aquifer parameters, e.g. transmissivity and
the storage coefficient. Identification is an extremely
important problem in groundwater hydraulics.
3-The prediction problem
Solving the prediction (forecasting) problem means solving a
model in order to obtain the future responses of an aquifer to an
anticipated natural replenishment or to any planned schedule of
future pumping and artificial recharge in a proposed
management scheme.
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•
Area: 15 000 ha (land) , 7 615 ha (water)
Population: 30 112
•
Precipitation : 55 cm/yr
•
Evapotranspiration : 56.3 cm/yr
•
Irrigation from River:
•
Area Irrigated: 5565 ha
Irrigation Rate: 1.84 m/yr
6
3
Irrigation Volume : 102 x 10 m /yr
3
9
Goksu River: Q = 110 m /sec (3.47 x 10
m /yr)
Groundwater Pumpage: 69 920 m3/day (25.5 x
106 m3/yr)
3
•
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A
A
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1800
Adedi = 344
Örnek
n= 344
katsayısı (r) = 0.987
Korelasyon
2
1500
r =0.987
Cl, mg/l
1200
900
600
Average
mg/l
759 mg/l
TDS =759
OrtalamaTDS=
Average
Cl=210mg/l
Ortalama Cl = 210 mg/l
300
0
0
500
1000
1500
2000
2500
3000
3500
4000
TDS, mg/l
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July 2008 Chloride Concentration vs Na/Cl ratios
Temmuz 2008
2.5
0.557
Na/Cl
2.0
1.5
1.0
0.5
0.0
0
200
400
Cl
600
800
1000
Four wells near the coast line have saltwater intrusion
whereas two of them are under risk.
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July 2008 Chloride Concentration vs Mg/Cl ratios
Temmuz 2008
0.8
Mg/Cl
0.6
0.4
0.2
0.0
0
200
400
Cl
600
800
1000
Mg/Cl ratio of 0.05 and over indicates saltwater intrusion.
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•
Variable-Density Groundwater Flow Equation:
•
Solute Transport Equation:
•
Darcy’s Equation:
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•
Groundwater Velocity:
•
Concentration and Density:
•
Five Equations, Five Unknowns:
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•
•
Head in aquifer:
•
Conversion Between
Model
Results and Field Data:
Equivalent Freshwater
Head:
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



SEAWAT is based on the
concept of equivalent
freshwater head in a
saline ground-water
environment
Piezometer A contains
freshwater
Piezometer B contains
water identical to that
present in the saline
aquifer
The height of the water
level in piezometer A is
the freshwater head
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•
•
Combines MODFLOW and MT3DMS.
Solves Coupled Flow and Solute-Transport Equation
Implictly ( and C from same time step)
Explicitly ( calculated using C from previous
time step)
MODFLOW Packages:
Basic
Block-Centered Flow
Well
•Link Package: LKMT3D
Drain
River
Evapotranspiration
General-Head Boundary
Recharge
Solvers
Time-Variant Constant
Head
MT3DMS Packages:
Basic Transport
Advection
Dispersion
Source/Sink Mixing
Reaction
Generalized Conjugate
Gradient Solver
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Distribution of Observation Wells in the Basin
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Recharge zones in Layer 1
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32
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4.0
Simulated TDS (g/l)
Simulated head (m, msl).
3.0
2.0
1.0
3.0
2.0
1.0
1:1 Line
1:1 Line
0.0
0.0
0.0
1.0
2.0
Observed head (m, msl)
Observed vs Calculated Heads
3.0
0.0
1.0
2.0
3.0
4.0
Observed TDS (g/l)
Observed vs Calculated TDS
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The Ghyben-Herzberg relation
states that a one-meter height of
freshwater above sea level assures
40 meters of freshwater below sea
level.
Likewise, a 0.5 m rise in sea level
due to climate change would cause
a 20 m reduction in the freshwater
thickness. That eventually causes
more seawater intrusion.
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

In the last century average temperature of the earth rose
0.6C. (IPCC, 2001).
Last 30 years’ heating trend seems worse than that of last 100
years.
It is estimated that the temperature of the earth will rise about
1.4 to 5.8C due to green house effect.
Temperature-Recharge Relationship
0.0008
y = 0.0009-0.000033x
R2 = 0.809
0.0007
Recharge, mm/day

0.0006
0.0005
0.0004
0.0003
0.0002
0.0001
0.0000
0
5
10
15
20
25
30
35
Temperature, oC
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Scenarios About the Expected Climate Change
Temp. Sea Level
Recharge
Rise
Scenarios Increase
mm/d
m
C
-0.00005
1.8*
0.25*
B1 (avrg)
(%17)
B1 (max)
-0.00012
4.0*
0.38*
and
(%45)
A1FI (avrg)
-0.00021
A1FI (max)
6.4*
0.59*
(%97.4)
* IPCC, 2007. Climate Change 2007: The Physical Science Basis. Summary for Policymakers. WGI
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CLIMATE CHANGE AND SALTWATER INTRUSION?
Change of saltwater/freshwater interface caused by sea level rise (Liu, 2003).
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RESULTS

The SEAWAT model simulated the Göksu Delta
succesfully
which will help us understanding the
hydrogeology of the region accurately. In addition the
location of saltwater/freshwater interface was determined
by means of the model.

Effects of the probable pumping schemes on
saltwater intrusion were succesfully tested by
means of the model.
Effects of the climate change on saltwater intrusion
mechanism were also investigated by means of the
model.

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 HOW
CAN SALTWATER
INTRUSION BE AVOIDED?
 WHAT
 WHAT
TO DO?
NOT TO DO?
Dr. Ahmet Dogan
Coastal Aquifer - No Pumping
Water Table
Equilibrium
Sea Level
Ocean
Fresh
Water
Brackish
Water
Dr. Ahmet Dogan
Coastal Aquifer - With Pumping
Water Table
Sea Level
Ocean
Fresh
Water
Brackish
Water
Dr. Ahmet Dogan
Coastal Aquifer - Intrusion Advancing
Water Table
Sea Level
Ocean
Brackish
Brackish
Water Water
Fresh
Fresh Water
Water
Dr. Ahmet Dogan
Coastal Aquifer - Pumping and Injection
Water Table
Sea Level
Ocean
Brackish
Brackish
Water Water
Fresh
Fresh Water
Water
Dr. Ahmet Dogan
Coastal Aquifer - Pumping and Injection
Water Table
Sea Level
Ocean
Brackish
Brackish
Water Water
Fresh
Fresh
Water
Dr. Ahmet Dogan
Stranded
Brackish
Water
(Saline
Water
Plume)
Artificial Recharge Helps to Stop Saltwater Intrusion
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Conclusions / Recommendations





Saltwater Intrusion can not be stopped but it can be
CONTROLLED.
SEAWAT type of models can be very useful in determining
aquifer characteristics and saltwater intrusion mechanism to
determine safe yield pumping rates in coastal aquifers.
Luckily, there is a growing awareness of salt water intrusion
and upconing but safe yield pumping rate regulations should
enforced strickly to assess the potential salinity impacts
caused by pumping.
Uncontrolled water pumpage should be prevented by law or
local authorities strickly.
Remediation procedures and measures should be
implemented based on the type of saltwater intrusion
problem at coastal regions immediately
Dr. Ahmet Dogan
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•
State Hydraulic Works (DSI), Republic of Turkey
•
Scientific and Technical Research Council of Turkey (TUBITAK)
•
•
•
Research Foundation (No. MMF.2000.13), Cukurova University,
Adana, Turkey
Society for the Protection of Nature (DHKD), Turkey
Mersin Directorate, Authority for the Protection of Special Areas,
Ministry of the Environment
•
National Science Foundation, U.S.A.
•
University of Florida, Gainesville, Florida, U.S.A.
•
Suleyman Demirel University, Isparta, Turkey
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THANK YOU
Dr. Ahmet Dogan
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