Simulation of 3 d groundwater flow and seawater intrusion along the mediterranean coast of turkey
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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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Simulation of 3 d groundwater flow and seawater intrusion along the mediterranean coast of turkey

Simulation of 3-D GroundwaterFlowandSeawaterIntrusionAlong the Mediterranean Coast of Turkey


Investigation

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


Investigation

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


Investigation

  • 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

NaturalOccurance of SeawaterIntrusion

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Investigation

Wedge

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Seawater intrusion due to over pomping

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Investigation

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Upconing Due to Pumping

Pumping causes water table drawdown...

…and seawater intrudes into well due to upconing.

Dr. Ahmet Dogan


Investigation

Dr. Ahmet Dogan


Groundwater system

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


Groundwater systems and three unique problems

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


Goksu delta setting

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


Investigation

A

A

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Hydrogeologic section a a

Hydrogeologic Section A-A’

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Piezometric surface in goksu delta aquifer in july 2008

Piezometric Surface in Goksu Delta Aquifer in July 2008

Dr. Ahmet Dogan


Chloride versus tds concentrations in water from deep wells

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


Investigation

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


Investigation

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

Observed TDS Concentrations in Section A-A’

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Observed tds concentrations at 45 m msl layer 5

Observed TDS Concentrations at -45 m, msl (Layer 5)

Dr. Ahmet Dogan


Equivalent freshwater heads in the surficial aquifer

Equivalent Freshwater Heads in the Surficial Aquifer

Dr. Ahmet Dogan


Tds concentrations in the surficial aquifer

TDS Concentrations in the Surficial Aquifer

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Advection dispersion equations for heterogeneous flow

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 flow1

Advection-Dispersion Equations for Heterogeneous Flow

  • Groundwater Velocity:

  • Concentration and Density:

  • Five Equations, Five Unknowns:

Dr. Ahmet Dogan


Equivalent freshwater head

Equivalent Freshwater Head

  • Head in aquifer:

  • Equivalent Freshwater

    Head:

  • Conversion Between Model Results and Field Data:

Dr. Ahmet Dogan


Freshwater head

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

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

Conceptual Hydrologic Cross-Section

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Discretization and boundary packages in layer 1

Discretization andBoundaryPackages in Layer 1

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Investigation

Distribution of Observation Wells in the Basin

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Investigation

Recharge zones in Layer 1

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Discretization and boundary packages in column 23

Discretization and Boundary Packages in Column 23

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Investigation

Observed vs CalculatedHeads

Observed vs Calculated TDS

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Simulated heads in layer 5 45 m msl

Simulated Heads in Layer 5 (-45 m, msl)

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Simulated tds concentration in column 23

Simulated TDS Concentration in Column 23

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Simulated tds concentrations in layer 5 45 m msl

Simulated TDS Concentrations in Layer 5 (-45 m, msl)

Dr. Ahmet Dogan


Investigation

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


Investigation

  • 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.

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Investigation

Scenarios About the Expected Climate Change

* IPCC, 2007. Climate Change 2007: The Physical Science Basis. Summary for Policymakers. WGI

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Investigation

CLIMATE CHANGE AND SALTWATER INTRUSION?

Change of saltwater/freshwater interface caused by sea level rise (Liu, 2003).

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Investigation

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


Investigation

  • HOW CAN SALTWATER INTRUSION BE AVOIDED?

  • WHAT TO DO?

  • WHAT NOT TO DO?

Dr. Ahmet Dogan


Seawater intrusion

Seawater Intrusion

Coastal Aquifer - No Pumping

Water Table

Equilibrium

Sea Level

Ocean

Fresh

Water

Brackish

Water

Dr. Ahmet Dogan


Seawater intrusion1

Seawater Intrusion

Coastal Aquifer - With Pumping

Water Table

Sea Level

Ocean

Fresh

Water

Brackish

Water

Dr. Ahmet Dogan


Seawater intrusion2

Seawater Intrusion

Coastal Aquifer - Intrusion Advancing

Water Table

Sea Level

Ocean

Fresh

Water

Brackish

Water

Fresh Water

Brackish Water

Dr. Ahmet Dogan


Seawater intrusion3

Seawater Intrusion

Coastal Aquifer - Pumping and Injection

Water Table

Sea Level

Ocean

Fresh

Water

Brackish

Water

Fresh Water

Brackish Water

Dr. Ahmet Dogan


Seawater intrusion4

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


Investigation

Artificial Recharge Helps to Stop Saltwater Intrusion

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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


Acknowledgments

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


Investigation

THANK YOU

Dr. Ahmet Dogan


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