Groundwater exploration by using electrical resistivity survey
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Date
2018-06
Authors
Muhamad Syahizat Abdul Razak
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Abstract
In this project, geophysical method of electrical resistivity survey is used for
subsurface groundwater mapping in Lafarge Cement Plant, Langkawi, Kedah. Generally,
the geology of Langkawi is mainly overlying by limestone and unconsolidated soil. This
project is conducted to determine the presence of the groundwater so that prevention step
can be taken to prevent disasters such as sinkholes. Water is essentially important in human
life. Groundwater is one of main water supply for drinking and industry. However, should
the groundwater are excessively extracted, it will lower the water table and could cause
sinkhole formation. Three different electrode array which are Wenner Alpha array, Wenner
Schlumberger array and dipole-dipole array were used. All of the method have their
advantages and disadvantages. Six survey line of interest which located at critical point of
the quarry were established. Line 1 and Line 2 has the lowest resistivity values at just
around 0.5Ω to 50Ω. Line 3 and Line 4 gives moderately high resistivity values at around
200Ω to 500Ω. While Line 5 exert the highest resistivity values which around 5000Ω to
15000Ω. Line 6 which located further from the other 5 lines exert moderate values within
500Ω to 1000Ω. This conclude that the area which convey low resistivity value are the
zone that covered or has large quantity of water in the soil while the high resistivity area are
the area underlain by limestones/ soil rocks. For this survey project, groundwater has been
detected at depth below 10 meter level. There are specific drawback occur during the
project such as damaged cables and the method cannot show the clear image of boundaries
of soil and rock zones. For recommendation, this project can be further enhanced by
incorporating seismic refraction and borehole to get a better and more accurate result.