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Investigation

Simulation of 3-D Groundwater Flow and Seawater Intrusion Along the Mediterranean Coast of Turkey. Investigation. Develop simulation and optimization models for a coastal aquifer: Characterize the hydrogeology of the Goksu Delta;

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Investigation

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  1. Simulation of 3-D GroundwaterFlowandSeawaterIntrusionAlong 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 intofreshwater aquifers under the influence of groundwaterdevelopment. (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. NaturalOccurance of SeawaterIntrusion Dr. Ahmet Dogan

  6. Wedge Dr. Ahmet Dogan

  7. Seawater intrusion due to over pomping Dr. Ahmet Dogan

  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. SYSTEM Outputs Response Effect Uncontrollable Inputs Excitation Cause Undesirable Controllable Desirable Detection Identification Prediction 1 2 3 Groundwater System • Uncontrollable Inputs: • Natural Recharge fromprecipitation • Evapotranspiration • Controllable Inputs: • Pumpingandinjectionschedules • Artificialrecharge • 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 parametersusing 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: 15000 ha (land) , 7 615 ha (water) • Population: 30 112 • Precipitation : 55cm/yr • Evapotranspiration : 56.3cm/yr • Irrigation from River: Area Irrigated: 5565 ha Irrigation Rate: 1.84 m/yr Irrigation Volume :102 x 106 m3/yr Goksu River: Q = 110 m3/sec (3.47 x 109 m3/yr) • Groundwater Pumpage: 69 920 m3/day (25.5 x 106 m3/yr) Dr. Ahmet Dogan

  14. A A Dr. Ahmet Dogan

  15. Hydrogeologic Section A-A’ Dr. Ahmet Dogan

  16. Piezometric Surface in Goksu Delta Aquifer in July 2008 Dr. Ahmet Dogan

  17. Chloride versus TDS Concentrations in Water from Deep Wells n= 344 r 2=0.987 Average TDS= 759 mg/l Average Cl=210mg/l Dr. Ahmet Dogan

  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’ Dr. Ahmet Dogan

  21. Observed TDS Concentrations at -45 m, msl (Layer 5) Dr. Ahmet Dogan

  22. Equivalent Freshwater Heads in the Surficial Aquifer Dr. Ahmet Dogan

  23. TDS Concentrations in the Surficial Aquifer Dr. Ahmet Dogan

  24. Advection-Dispersion Equations for Heterogeneous Flow • Variable-Density Groundwater Flow Equation: • Solute Transport Equation: • Darcy’s Equation: Dr. Ahmet Dogan

  25. Advection-Dispersion Equations for Heterogeneous Flow • Groundwater Velocity: • Concentration and Density: • Five Equations, Five Unknowns: Dr. Ahmet Dogan

  26. Equivalent Freshwater Head • Head in aquifer: • Equivalent Freshwater Head: • Conversion Between Model Results and Field Data: Dr. Ahmet Dogan

  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 Dr. Ahmet Dogan

  29. Conceptual Hydrologic Cross-Section Dr. Ahmet Dogan

  30. Discretization andBoundaryPackages in Layer 1 Dr. Ahmet Dogan

  31. Distribution of Observation Wells in the Basin Dr. Ahmet Dogan

  32. Recharge zones in Layer 1 Dr. Ahmet Dogan 32

  33. Discretization and Boundary Packages in Column 23 Dr. Ahmet Dogan

  34. Observed vs CalculatedHeads Observed vs Calculated TDS Dr. Ahmet Dogan

  35. Simulated Heads in Layer 5 (-45 m, msl) Dr. Ahmet Dogan

  36. Simulated TDS Concentration in Column 23 Dr. Ahmet Dogan

  37. Simulated TDS Concentrations in Layer 5 (-45 m, msl) Dr. Ahmet Dogan

  38. The Ghyben-Herzberg relation states that a one-meterheight of freshwater above sea level assures 40 meters of freshwater below sea level. Likewise, a 0.5m rise in sea level due to climate change would cause a 20 m reduction in thefreshwater thickness. That eventually causes more seawater intrusion. Dr. Ahmet Dogan

  39. 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 * IPCC, 2007. 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

  42. 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. RESULTS Dr. Ahmet Dogan

  43. HOW CAN SALTWATER INTRUSION BE AVOIDED? • WHAT TO DO? • WHAT NOT TO DO? Dr. Ahmet Dogan

  44. Seawater Intrusion Coastal Aquifer - No Pumping Water Table Equilibrium Sea Level Ocean Fresh Water Brackish Water Dr. Ahmet Dogan

  45. Seawater Intrusion Coastal Aquifer - With Pumping Water Table Sea Level Ocean Fresh Water Brackish Water Dr. Ahmet Dogan

  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 Dr. Ahmet Dogan

  48. 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 Dr. Ahmet Dogan

  49. Artificial Recharge Helps to Stop Saltwater Intrusion Dr. Ahmet Dogan

  50. Conclusions / Recommendations Dr. Ahmet Dogan 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 andupconing but safe yield pumping rate regulations should enforced strickly to assess the potential salinity impacts causedby 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 50

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