Knowledge Exchange mission SUSWA project 30 November – 5 December 2014, Kajiado, Kenya Hydrogeological surveying and geophysics Case study group 1

1. GROUND WATER GEOPHYSICS
ORMELIAI

2. 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

3. 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)
Rsistivityohmm

4. 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
Ohmmeter

5. 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
Ohmmeter
A
B
C

6. • 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

7. 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

8. • 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

9. 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
•

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

11. THANK YOU