Evaluation of DC Electrical Resistivity Survey for Identifying Saltwater/ Freshwater Interface in the Young Kwang Coastal Region, South-Korea

Dr. Muhammad Farooq

Department of Earth Sciences

COMSATS Institute of Information Technology Abbottabad

Dr. Samgyu Park

Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resource, South Korea

Quran & WaterSoorat al-Furqaan

25:53

And he has set free the two seas; one is fresh and palatable and the other is salty and bitter; and he has built between them a formidable, inviolable barrier.

Soorat ar-Rahman 55:19-20

He let free the two seas, they meet together; he has built a barrier between them, they do not transgress

Geography of South Korea Located in East Asia

Land border with North Korea

Coast line along three seas: 2413 kms

Land mass is approx= 100,032 sq kms

Geology of South Korea Most rocks are of Precambrian age

Isolated Pockets of Paleozoic, Mesozoic

& Cenozoic

Baekdu & Hallasan mountain have

crater lakes

Hot springs indicate volcanic activity are widespread throughout Peninsula

Topography & Drainage Tallest mountain is Hallasan (1950

m)

Volcanic formation constituting

Jeju Island

Geologially stable

(no active volcanoes & Earth

quake)

Aprrox. 30 % of the area consists

of lowlands

Aprrox. 70 % of the area consists

of uplands / mountains

Three important river, Nakdong

(521 kms), Han river (514 kms)

and

Geum river (401 kms)

Saltwater IntrusionSaltwater Intrusion

The movement of saline (salty) water into a freshwater aquifer

If source is marine water, the process is known as Seawater Intrusion

primary mechanisms of saltwater intrusion

Subsurface seawater movement (lateral large scale intrusion)

Seepage from tidal canals and streams

Connate upward movement from lower formations

(well withdrawals)

Factors controlling the extent of Salt Intrusion

Rate of withdrawal vs. freshwater recharge

Distance of stress from saltwater source

Geologic structure

So, why is this a problem? Saltwater unfit for human consumption, other anthropogenic uses Reduces fresh groundwater storage Abandonment of supply wells Coastal ecosystems sensitive to salinity changesRed tides, fish kills, loss of sea grass habitat, destruction of coral reef

Alluvium

Granodiorite

FG- Muscovite Granite

Porphytitic Biotite Granite

Biotite Granite

Geology of the area

aIV 2/

Electrical Resistivity (ER)Electrical Current is induced

into the ground through two current electrodes.

Voltage drop is measured across potential electrodes.

Electrode array is expanded to increase depth of penetration.

Resistivity of formation/fluids measured in ohm-meters (Ω-m).

Modern systems use multi electrodes with automated switching.

0 2 Km

VES 5 VES 6 VES 7

VES 8

VES 9

VES 10

VES 1 VES 2

VES 3

VES 4

VES 11

BH-01

BH-02

A

A`

Vertical Electrical Sounding Data Acquisition layout

VES 5 VES 6

VES 7 VES 8

VES 11VES 9

Curve Matching Technique in Vertical Electrical Sounding

Litho- Resistivity Stratigraphic Column

Litho- Resistivity Stratigraphic Cross Section

Litho- Resistivity Stratigraphic Cross Section

0 2 Km

VES 5 VES 7

VES 8

VES 9

VES 10

VES 1VES 2

VES 3

VES 4

VES 11

BH-01

BH-02

A

A`

VES 6

Brine water Brackish water

Litho- Resistivity Stratigraphic Cross Section

Conclusions

Saline water intrusion has been taken placeDepth of intrusion increased as moved toward

coastal area.It is important to monitor sea water intrusion

with the help of geophysical techniqueGeophysical technique helps us to minimize the

cost and understand problem in better wayRecommendations Regulatory (legislative) approachesScientific monitoring/assessment

Thank You!

Question????????