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; 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

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

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

Natural Occurance of Seawater Intrusion Dr. Ahmet Dogan

Wedge Dr. Ahmet Dogan

Seawater intrusion due to over pomping Dr. Ahmet Dogan

Dr. Ahmet Dogan

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

Dr. Ahmet Dogan

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

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

Goksu Delta Setting 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 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

A A Dr. Ahmet Dogan

Hydrogeologic Section A-A’ Dr. Ahmet Dogan

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

Chloride versus TDS Concentrations in Water from Deep Wells Average TDS= 759 mg/l Average Cl=210mg/l Dr. Ahmet Dogan

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

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

Observed TDS Concentrations in Section A-A’ Dr. Ahmet Dogan

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

Equivalent Freshwater Heads in the Surficial Aquifer Dr. Ahmet Dogan

TDS Concentrations in the Surficial Aquifer Dr. Ahmet Dogan

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

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

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

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

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

Conceptual Hydrologic Cross-Section Dr. Ahmet Dogan

Discretization and Boundary Packages in Layer 1 Dr. Ahmet Dogan

Distribution of Observation Wells in the Basin Dr. Ahmet Dogan

Recharge zones in Layer 1 Dr. Ahmet Dogan 32

Discretization and Boundary Packages in Column 23 Dr. Ahmet Dogan

Observed vs Calculated Heads Observed vs Calculated TDS Dr. Ahmet Dogan

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

Simulated TDS Concentration in Column 23 Dr. Ahmet Dogan

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

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

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

Scenarios About the Expected Climate Change Temp. Increase C Sea Level Rise m Recharge mm/d B1 (avrg) 1.8* 0.25* -0.00005 (%17) B1 (max) and A1FI (avrg) 4.0* 0.38* -0.00012 (%45) A1FI (max) 6.4* 0.59* -0.00021 (%97.4) * IPCC, 2007. Climate Change 2007: The Physical Science Basis. Summary for Policymakers. WGI Dr. Ahmet Dogan

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

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

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

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

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

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

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

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 Dr. Ahmet Dogan

Artificial Recharge Helps to Stop Saltwater Intrusion Dr. Ahmet Dogan

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

Acknowledgments 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 Dr. Ahmet Dogan

THANK YOU Dr. Ahmet Dogan