GROUND WATER GEOPHYSICS

ORMELIAI

Introduction

• The study area was carried out around Ormeliai borehole

• Three VES were carried out by the consultant

• The team carried out one VES and one profiling in the area

VES

1 10 100 1000

10

100

1000

ORMELIAI borehole siting VES measurements

VES nr.1

VES nr 2

VES nr.3

AB/2 (m)

Rs

isti

vit

y o

hm

m

Profile

0 200 400 600 800 1000 1200 1400

0

50

100

150

200

250

300

350

400

450

Wenner a=50 Ormeliai

Kolom E

Distance meter

Oh

mm

ete

r

Interpretation

0 200 400 600 800 1000 1200 1400

0

50

100

150

200

250

300

350

400

450

Wenner a=50 Ormeliai

Kolom E

Distance meter

Oh

mm

ete

r

AB

C

• A, B and C are the low resistivity points along the profile

• B has the lowest resistivity of around 120 ohms which was at the black cotton soil or a possible fracture

VES

• VES 4 was carried out at point B of the profile and interpretation is as shown in the model below.

1 10 100 L/2

10

1e+2

1e+3

Rho

• From the graph, there are more than one solution. eg whether Rho is 1000, 5000 or 10000, the model fit does not change.

Rho Depth Bore hole log

12.83 1.70 Red sandy soil

356.32 26.59 Highly weathered basement

42.65 46.11 Clayey formation

1000.00 Highly weathered basement

Drillers log, VES & profile

• The borehole log has highly fractured zones at the same depth as the VES and the profile.

• Borehole log matches the information from the VES in the first three layers.

• The low Rho along the profile where the VES 4 was taken matches with the drillers log which has highly weathered and fractured gneiss

•

Recomendation

• VES 3 gives the best choice to drill as it has a thicker weathered layer providing a deeper Aquifer.

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