Browsing by Author "Makoba, Edikafubeni"

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    Delineation of the shallow stratigraphy and assessment of groundwater potential using resistivity method in the Northern part of Soga basin, Coast Region, Tanzania
    (University of Dar es Salaam, 2005) Makoba, Edikafubeni
    A geoelectric survey was conducted in the northern part of the Soga basin in order to establish the shallow stratigraphy of the basin and delineate aquiferous formation. It was conducted in the dry season using ABEM Terramiter SAS 4000 and in the rain season using SYSCAL R1 plus. A total of fifty four Vertical Electrical Soundings (VES) were conducted in the area utilizing Schlumberger array, with a maximum of current electrode spacing ranging from 400 t0 600 m. the data from the electrical resistivity survey were first interpreted by the classical partial curve matching and then by the computer modeling and inversion techniques using the Geoelectric Kurven Fehler (GKF2) program. Interpretation of resistivity data has revealed three main geoelectric layers. The uppermost layer has a thickness ranging between 0.1 and 5 m, characterized by resistivity values between 20 and 100 ohm-m in some parts which are rich in clays whereas in other areas the resistivity values range from 100 t0 400 ohm-m. the second layer is also thin with thickness ranging from 0.1 to 5 m. it is characterized by higher resistivity values, averaging at about 2000Ωm which are possibly due to dry silts and sands. The third layer is generally a low resistivity layer, extensively thick and appears to be shallow at a depth of about 6 m below the ground surface. It is dominated by resistivity values between 4 and 10 Ωm which may be attributed to the presence of clay formation or rock formation with saline water. Therefore, it is recommended that; integrated geophysical methods such as the use of resistivity and induced polarization (IP) should be done simultaneously so as to differentiate clays and saline water. However, in some few parts, the resistivity values ranging from 10-22 ohm-m were obtained; these values are possibly due to freshwater bearing formations. The existence of both freshwater and saline water was confirmed using water samples collected from the existing shallow wells.