Mapping Of A Groundwater Aquifer Using Geophysical Methods In Telok Datok Area, Selangor
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Date
2002-03
Authors
Ibrahim, Abdi Nouh
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Abstract
Rapid development of Selangor has resulted in an increase of demand for water supply
in recent years. Existing dams can no longer cope with such high demand, and this has lead to
the construction of new dams. Alternative sources of water were also sought, among them is
groundwater. The presence of detectable and significant contrasts in the physical properties of
the subsoil was found in Telok Datok, Selangor, thus allowing the use of an integrated
geophysical investigation technique. An integrated geophysical survey containing 2-D
resistivity imaging and seismic refraction data obtained along 24 lines and 3-D visualization
based on 2-D resistivity imaging are carried out as part of groundwater study at three sites in
Telok Datok. Most of the surveys were made at nearby boreholes for comparison. The principal
goals of this survey are to define the thickness of groundwater aquifer, the water table and the
depth of bedrock as well as suitable sites for wells.
The results of 2-D resistivity imaging reveal that resistivity imaging is an effective tool
for defining the thickness of groundwater aquifer at these sites. It is also an effective method in
mapping bedrock. The results clearly show the thickness of aquifer is about 10 to 30 meters and
in some exceptional cases up t6 40 meters depending upon the thickness of all the deposits as
well as the nature of the bedrock (fracture zone). The depth to the bedrock estimated from 2-D
resistivity imaging data at Site-l and Site-3 generally vary from 30 meters to up 65 meters.
Depth to the bedrock estimated at Site-2 ranges from 50 meters to up 65 meters. The bedrock
relief is relatively flat and gently undulates along most of the lines.
The 3-D visualization of the bedrock shows that southern part of Site-l is characterized
by very deep bedrock and increased thickness of saturated layer, which given that site higher
priority for proposed well site.
The results of seismic refraction also show the water table is about 3 meters at Site-l
and is slightly deeper at about 5 meters at Site-2. The difference in the depth of the water table
at these two sites could be due to the difference in location of the aquifer from recharge of the
Langat River. This research has shown that both of the thickness of aquifer and the depth of
bedrock can be accurately mapped by 2-D electrical imaging surveys and the water table can
also be accurately mapped by seismic refraction, while the suitable site of well can be
accurately located by 3D visualization.
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Keywords
Groundwater Aquifer , Using Geophysical Methods