Browsing by Author "Midzi, Vunganai"

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    A comparison of crystalline basement aquifers and Kalahari aquifers in exploration of groundwater occurrence in Zimbabwe
    (2016-07) Chuma, Constant; Hlatywayo, Dumisani J.; Midzi, Vunganai; Gumbo, Mervyn; Muchingami, Innocent; Mashingaidze, Robin T
    Exploration of groundwater occurrence becomes complex if there is inadequate information to explain the its dynamics. The paper compares the major aquifers found in Zimbabwe in order to maximise the exploration of groundwater in the semi-arid regions. Geophysical and geospatial tools have proved to be useful tools in divining for groundwater in different geological settings. Crystalline basement aquifers are characterised by impervious rock which confines water in the upper layers whilst Kalahari sands provide high yielding unconsolidated aquifers. Transmissivity and conductivity decreases with depth in crystalline whilst the reverse is true for Kalahari sands.
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    Modelling the Subsurface Geology and Groundwater Occurrence of the Matsheumhlope Low Yielding Aquifer in Bulawayo Urban, Zimbabwe
    (Canadian Center of Science and Education, 2013-08) Chuma, Constant; Hlatywayo, Dumisani J.; Zulu, Joseph; Muchingami, Innocent; Mashingaidze, Robin T.; Midzi, Vunganai
    This study is focused on determining the nature, extend and spatial variation of the subsurface and groundwater in the Matsheumhlope low yielding aquifer so as to improve the understanding of groundwater occurrence within Bulawayo Metropolitan area. The abstraction and utilisation of groundwater from crystalline basement complexes have often been hampered by the high rate of borehole failure. For instance, borehole failure in the Matsheumhlope wellfield that characterises the greater part of Bulawayo City, Zimbabwe, is often ascribed to many factors which are yet to be investigated locally and regionally. The electrical resistivity method was used to establish the depth, thickness and sequence of geological units in the low yielding aquifer. Satellite data were used to delineate the lineaments and assess the topographic features of the area. Geological samples obtained from boreholes were correlated with the geophysical pseudo sections to give a better view of the subsurface and groundwater occurrence in the area. Geographic Information Systems (GIS) was used to model the geophysical characteristics of the subsurface giving the potential groundwater occurrence in the area. The study confirmed that the Matsheumhlope aquifer is a heterogeneous unconfined aquifer with a shallow depth to the basement rock in highlands of the study area. The results also showed high spatial variation of subsurface formations and groundwater potential over short distances, thereby indicating the complex nature of mapping basement aquifers. Borehole failure in the area was attributed to the occurrence of shallow depth of the bedrock underlying some parts of the aquifer. Therefore the results of the study recommended that the structural and geodynamic analysis of the fractures of the whole Matsheumhlope aquifer should be done using both structural mapping and geophysical methods.
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    Modelling the subsurface geology and groundwater occurrence of the Matsheumhlope low yielding aquifer in Bulawayo urban, Zimbabwe
    (Canadian Center of Science and Education., 2013-08-19) Chuma, Constant; Hlatywayo, Dumisani J.; Zulu, Joseph; Muchingami, Innocent; Mashingaidze, Robin T.; Midzi, Vunganai
    This study is focused on determining the nature, extend and spatial variation of the subsurface and groundwater in the Matsheumhlope low yielding aquifer so as to improve the understanding of groundwater occurrence within Bulawayo Metropolitan area. The abstraction and utilisation of groundwater from crystalline basement complexes have often been hampered by the high rate of borehole failure. For instance, borehole failure in the Matsheumhlope wellfield that characterises the greater part of Bulawayo City, Zimbabwe, is often ascribed to many factors which are yet to be investigated locally and regionally. The electrical resistivity method was used to establish the depth, thickness and sequence of geological units in the low yielding aquifer. Satellite data were used to delineate the lineaments and assess the topographic features of the area. Geological samples obtained from boreholes were correlated with the geophysical pseudo sections to give a better view of the subsurface and groundwater occurrence in the area. Geographic Information Systems (GIS) was used to model the geophysical characteristics of the subsurface giving the potential groundwater occurrence in the area. The study confirmed that the Matsheumhlope aquifer is a heterogeneous unconfined aquifer with a shallow depth to the basement rock in highlands of the study area. The results also showed high spatial variation of subsurface formations and groundwater potential over short distances, thereby indicating the complex nature of mapping basement aquifers. Borehole failure in the area was attributed to the occurrence of shallow depth of the bedrock underlying some parts of the aquifer. Therefore the results of the study recommended that the structural and geodynamic analysis of the fractures of the whole Matsheumhlope aquifer should be done using both structural mapping and geophysical methods.
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    Seismic hazard assessment in Eastern and Southern Africa.
    (ANNALI DI GEOFISICA,, 1999-12) Midzi, Vunganai; Hlatywayo, Dumisani J.; Chapola, Lostina S.; Kebede, Fekadu; Atakan, Kuvvet; Lombe, Daniel K.; Turyomurugyendo, Gadi; Tugume, Fred Alex
    Seismic hazard assessment for the Eastern and Southern Africa region was done using the probabilistic approach. Seismic hazard maps for 10% exceedance in 50 years, 10% exceedance in 100 years, as well as for 50 and 100 years return periods were prepared using the FRISK88M software. The area involved covers a wide region bounded by latitudes 400 S-25°N and longitudes 100E and 55°E. Input parameters for the computations were obtained using the recent earthquake catalogue compiled by Turyomurugyendo. The catalogue which covers the time period 627-1994, contains earthquakes within the area bounded by 400 S-25°N and 100 E-55°E, with homogeneous magnitudes (M). Since a Poisson model of earthquake occurrence is assumed, dependent events were cleaned from the catalogue. Attenuation relations for the Eastern and Southern Africa region based on the strong motion data are virtually non-existent. However, attempts have been made recently by Jonathan 'and Twesigomwe to establish an average attenuation relation for the region. These relations were used in the computations. Possible uncertainties in the attenuation relations were accounted for using the logic-tree formalism. The results are presented in seismic hazard maps in terms of Peak Ground Acceleration (PGA) for the mean and the 85th percentile. The distribution ofPGA values indicate relatively high hazard along the EastAfrican rift system. In the northern segments of the rift system, they exceed 250 gals for 10% probability of exceedence in 50 years.