1. Simulation of 3-D Groundwater Flow and Seawater Intrusion Along the Mediterranean Coast of Turkey

2. Investigation 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

3. 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).
Dr. Ahmet Dogan

4. 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!!!
Dr. Ahmet Dogan

5. Natural Occurance of Seawater Intrusion
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6. Wedge
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7. Seawater intrusion due to over pomping
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8. Dr. Ahmet Dogan

9. Upconing Due to Pumping
Pumping causes water table drawdown...
…and seawater intrudes into well due to upconing.
Dr. Ahmet Dogan

10. Dr. Ahmet Dogan

11. Groundwater System Uncontrollable Inputs: Desirable Outputs:3
SYSTEM
Inputs
Excitation
Cause
Outputs
Response
Effect
Undesirable
Desirable
Uncontrollable
Controllable
Detection
Identification
Prediction 1 2
Uncontrollable Inputs:
Natural Recharge from precipitation
Evapotranspiration
Controllable Inputs:
Pumping and injection schedules
Artificial recharge
Desirable Outputs:
Reduction in Subsurface Outflow
Undesirable Outputs:
Drying of a wetland
Seawater Intrusion
Dr. Ahmet Dogan

12. Groundwater Systems and Three Unique Problems
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.
Dr. Ahmet Dogan

13. Goksu Delta Setting Area: 15 000 ha (land) , 7 615 ha (water)
Population:
Precipitation : 55 cm/yr
Evapotranspiration : cm/yr
Irrigation from River:
Area Irrigated: ha
Irrigation Rate: m/yr
Irrigation Volume : 102 x 106 m3/yr
Goksu River: Q = 110 m3/sec (3.47 x 109 m3/yr)
Groundwater Pumpage: m3/day (25.5 x 106 m3/yr)
Dr. Ahmet Dogan

14. A A
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15. Hydrogeologic Section A-A’
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16. Piezometric Surface in Goksu Delta Aquifer in July 2008
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17. Chloride versus TDS Concentrations in Water from Deep Wells
Average TDS= 759 mg/l
Average Cl=210mg/l
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18. July 2008 Chloride Concentration vs Na/Cl ratios
0.557
Four wells near the coast line have saltwater intrusion whereas two of them are under risk.
Dr. Ahmet Dogan

19. July 2008 Chloride Concentration vs Mg/Cl ratios
0.14
0.05
Mg/Cl ratio of 0.05 and over indicates saltwater intrusion.
Dr. Ahmet Dogan

20. Observed TDS Concentrations in Section A-A’
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21. Observed TDS Concentrations at -45 m, msl (Layer 5)
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22. Equivalent Freshwater Heads in the Surficial Aquifer
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23. TDS Concentrations in the Surficial Aquifer
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24. Advection-Dispersion Equations for Heterogeneous Flow
Variable-Density Groundwater Flow Equation:
Solute Transport Equation:
Darcy’s Equation:
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25. Advection-Dispersion Equations for Heterogeneous Flow
Groundwater Velocity:
Concentration and Density:
Five Equations, Five Unknowns:
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26. Equivalent Freshwater Head
Head in aquifer:
Equivalent Freshwater
Head:
Conversion Between Model Results and Field Data:
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27. Freshwater Head
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
Dr. Ahmet Dogan

28. SEAWAT Combines MODFLOW and MT3DMS.
Solves Coupled Flow and Solute-Transport Equation
Implictly ( and C from same time step)
Explicitly (r calculated using C from previous time step)
MODFLOW Packages:
Basic
Block-Centered Flow
Well
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
Link Package: LKMT3D
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29. Conceptual Hydrologic Cross-Section
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30. Discretization and Boundary Packages in Layer 1
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31. Distribution of Observation Wells in the Basin
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32. Recharge zones in Layer 1
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33. Discretization and Boundary Packages in Column 23
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34. Observed vs Calculated Heads Observed vs Calculated TDS
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35. Simulated Heads in Layer 5 (-45 m, msl)
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36. Simulated TDS Concentration in Column 23
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37. Simulated TDS Concentrations in Layer 5 (-45 m, msl)
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38. 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.
Dr. Ahmet Dogan

39. Last 30 years’ heating trend seems worse than that of last 100 years.
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.
Dr. Ahmet Dogan

40. Scenarios About the Expected Climate Change
Temp.
Increase C
Sea Level Rise m
Recharge
mm/d
B1 (avrg)
1.8*
0.25*
(%17)
B1 (max)
and
A1FI (avrg)
4.0*
0.38*
(%45)
A1FI (max)
6.4*
0.59*
(%97.4)
* IPCC, Climate Change 2007: The Physical Science Basis. Summary for Policymakers. WGI
Dr. Ahmet Dogan

41. CLIMATE CHANGE AND SALTWATER INTRUSION?
Change of saltwater/freshwater interface caused by sea level rise (Liu, 2003).
Dr. Ahmet Dogan 41 41

42. 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.
Dr. Ahmet Dogan

43. HOW CAN SALTWATER INTRUSION BE AVOIDED?
WHAT TO DO?
WHAT NOT TO DO?
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44. Seawater Intrusion Coastal Aquifer - No Pumping Water Table
Equilibrium
Sea Level
Ocean
Fresh
Water
Brackish
Water
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45. Seawater Intrusion Coastal Aquifer - With Pumping Water Table Ocean
Sea Level
Ocean
Fresh
Water
Brackish
Water
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46. Seawater Intrusion Coastal Aquifer - Intrusion Advancing Water Table
Sea Level
Ocean
Fresh
Water
Brackish
Water
Fresh Water
Brackish Water
Dr. Ahmet Dogan

47. Seawater Intrusion Coastal Aquifer - Pumping and Injection Water Table
Sea Level
Ocean
Fresh
Water
Brackish
Water
Fresh Water
Brackish Water
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48. Stranded Brackish Water (Saline Plume)
Seawater Intrusion
Coastal Aquifer - Pumping and Injection
Water Table
Sea Level
Ocean
Stranded Brackish Water (Saline Plume)
Brackish
Water
Fresh
Water
Fresh Water
Brackish Water
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49. Artificial Recharge Helps to Stop Saltwater Intrusion
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50. 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 50 50

51. Acknowledgments State Hydraulic Works (DSI), Republic of Turkey
Scientific and Technical Research Council of Turkey (TUBITAK)
Research Foundation (No. MMF ), 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
Dr. Ahmet Dogan

52. THANK YOU
Dr. Ahmet Dogan