Geophysical Investigations for Groundwater Potential Assessment of Volcanic Plain, Mermero Area, Borena Zone
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Date
2015-06-06
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Addis Ababa University
Abstract
Geophysical investigation methods of Vertical Electrical Sounding and magnetic prospecting
were used to investigate groundwater potential zones of Mermero area, Borena zone, Southern
Ethiopia. The main objective of this study is to determine the depth of groundwater table, to
locate the groundwater potential areas and to identify the subsurface layers.
The data acquired from twenty eight (28) Vertical Electrical Sounding points and 663
magnetic data points, which were interpreted both qualitatively and quantitatively in order to
understand the lithostratigraphic section at the specific locality and identify aquifer bearing
horizons.
The qualitative analysis of Vertical Electrical Sounding data were performed by using pseudo
depth sections and geo-electric section and different apparent resistivity maps. Similarly, the
qualitative interpretations of magnetic data were performed by total magnetic variation plot
and different magnetic anomaly maps.
Finally, the qualitative interpretation was done by all the above results together with the
geologic, topographic maps and borehole information. From the analysis result, geologic
structures and groundwater potential zones are identified.
The quantitative interpretations of the Vertical Electrical Sounding data were conducted by
modeling the sounding data using Ip2win and Win Resist modeling software and constructing
geoelectric sections along selected survey lines, using the result from individual Vertical
Electrical Sounding point interpretations.
The depth and lithologic units from the boreholes were used to fix parameters during the
modeling of Vertical Electrical Sounding data. The geoelectric sections enabled to identify the
overburden thickness and the depth to the aquifer along survey lines whereas the magnetic
method complemented the finding of the other geophysical methods regarding structural
indication such as faults, fractures and lithologic contacts.
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Keywords
Magnetic Anomalies, Pseudo–Depth Section, Geoelectric Section, Magnetic and Electrical Properties of Earth Materials, Mermero, Borena