Jemias Mazibuko | University of the Free State (original) (raw)

Videos by Jemias Mazibuko

Field demonstration for Electromagnetic Frequency Method for groundwater exploration using MAXMIN... more Field demonstration for Electromagnetic Frequency Method for groundwater exploration using MAXMIN I-10 equipment.

2 views

Papers by Jemias Mazibuko

Conference Presentations by Jemias Mazibuko

The climate of Botswana is primarily semi-arid, with annual open water evaporation in the order o... more The climate of Botswana is primarily semi-arid, with annual open water evaporation in the order of 2,000 mm exceeding average rainfall in all months of the year. This creates a situation where in the absence of recharge, Kalahari aquifers are prone to salinization due to evapo-transpiration and downward leakage of freshwater from the productive near surface Kalahari aquifers. The delineation of fresh water aquifers in semi-arid climate becomes complex and difficult for convectional DC resistivity techniques. Airborne and ground-based electromagnetic methods are a viable and efficient tool for mapping groundwater quality variations and has been used extensively to explore the fresh water aquifers and establish salinization boundaries in Kalahari sediments. Interpretation of existing airborne electromagnetic resistivity data and data acquisition of ground transient electro-magnetic (TEM) soundings was used to define the lateral and depth extents of the fresh water aquifers in Komana and Mababe villages located in the lower Okavango delta of Botswana. The shallow Kalahari Beds form the main aquifer units around Komana and Mababe villages. Airborne electromagnetic AEM data shows that in Komana area the fresh water aquifers are mainly developed along the Nhabe River Channel while in Mababe area fresh water occurs only in the river channels and flood plains of the Khwai and Mogogelo Rivers. These fresh water aquifers are underlain by brackish/ saline water aquifer and surrounded by brackish/ saline water aquifers away from the river channels. The thickest fresh water aquifers are indicated as high resistance zones (> 180 milli-Ohms) on AEM map, which are represented as 10 to 30 Ωm resistivity on ground TEM. In these zones the depth to the base of the fresh water aquifer is interpreted as 16 to >120 m from ground TEM soundings data.

Keywords
Airborne electromagnetic (AEM), ground transient electromagnetic (TEM), Salinization, freshwater aquifers, Okavango Delta

Thesis Chapters by Jemias Mazibuko

Estimation of hydraulic parameters in heterogeneous aquifers require high resolution measurement ... more Estimation of hydraulic parameters in heterogeneous aquifers require high resolution measurement of characteristic parameters to infer groundwater flow pattern. The common practice is to measure drawdown on few boreholes during pumping test. The information obtained from pumping test has limited spatial representation of hydraulic conductivity. A complementary, approach is to measure streaming potentials during pumping and recovery phases to provide additional spatially dense data. Streaming potential method is a passive, non-invasive geophysical approach and its signals are generated by groundwater flow through electro-kinetic coupling. Interpretation of streaming potential data in terms of groundwater flow parameters is facilitated by a coupled flow relationship which links streaming potential gradient to hydraulic gradient through a constant of proportionality called the electro-kinetic coupling coefficient. This paper demonstrates the applicability of estimating the hydraulic conductivity using streaming potentials in fractured and porous Karoo aquifers. Field experiments were conducted on the Campus and Krugersdrift test sites in Bloemfontein. The Campus test site is a fractured aquifer with hydraulic conductivity values between 1.1 to 2 m/d. Krugersdrift test site is a porous aquifer with hydraulic conductivity values between 9.9 to 11 m/d. The electro-kinetic coupling coefficient was determined by correlating streaming potentials near observation boreholes with the hydraulic head. Measured streaming potentials formed a positive anomaly around the pumping borehole, mirroring the hydraulic head cone of depression. Hydraulic conductivity values estimated from streaming potential field analytical solution for transient mode were in the same order as values determined through analytical analysis of drawdown data with relative error of 0.2.

Key words: Passive geophysics, streaming potential, hydraulic conductivity, pumping test

Field demonstration for Electromagnetic Frequency Method for groundwater exploration using MAXMIN... more Field demonstration for Electromagnetic Frequency Method for groundwater exploration using MAXMIN I-10 equipment.

2 views

The climate of Botswana is primarily semi-arid, with annual open water evaporation in the order o... more The climate of Botswana is primarily semi-arid, with annual open water evaporation in the order of 2,000 mm exceeding average rainfall in all months of the year. This creates a situation where in the absence of recharge, Kalahari aquifers are prone to salinization due to evapo-transpiration and downward leakage of freshwater from the productive near surface Kalahari aquifers. The delineation of fresh water aquifers in semi-arid climate becomes complex and difficult for convectional DC resistivity techniques. Airborne and ground-based electromagnetic methods are a viable and efficient tool for mapping groundwater quality variations and has been used extensively to explore the fresh water aquifers and establish salinization boundaries in Kalahari sediments. Interpretation of existing airborne electromagnetic resistivity data and data acquisition of ground transient electro-magnetic (TEM) soundings was used to define the lateral and depth extents of the fresh water aquifers in Komana and Mababe villages located in the lower Okavango delta of Botswana. The shallow Kalahari Beds form the main aquifer units around Komana and Mababe villages. Airborne electromagnetic AEM data shows that in Komana area the fresh water aquifers are mainly developed along the Nhabe River Channel while in Mababe area fresh water occurs only in the river channels and flood plains of the Khwai and Mogogelo Rivers. These fresh water aquifers are underlain by brackish/ saline water aquifer and surrounded by brackish/ saline water aquifers away from the river channels. The thickest fresh water aquifers are indicated as high resistance zones (> 180 milli-Ohms) on AEM map, which are represented as 10 to 30 Ωm resistivity on ground TEM. In these zones the depth to the base of the fresh water aquifer is interpreted as 16 to >120 m from ground TEM soundings data.

Keywords
Airborne electromagnetic (AEM), ground transient electromagnetic (TEM), Salinization, freshwater aquifers, Okavango Delta

Estimation of hydraulic parameters in heterogeneous aquifers require high resolution measurement ... more Estimation of hydraulic parameters in heterogeneous aquifers require high resolution measurement of characteristic parameters to infer groundwater flow pattern. The common practice is to measure drawdown on few boreholes during pumping test. The information obtained from pumping test has limited spatial representation of hydraulic conductivity. A complementary, approach is to measure streaming potentials during pumping and recovery phases to provide additional spatially dense data. Streaming potential method is a passive, non-invasive geophysical approach and its signals are generated by groundwater flow through electro-kinetic coupling. Interpretation of streaming potential data in terms of groundwater flow parameters is facilitated by a coupled flow relationship which links streaming potential gradient to hydraulic gradient through a constant of proportionality called the electro-kinetic coupling coefficient. This paper demonstrates the applicability of estimating the hydraulic conductivity using streaming potentials in fractured and porous Karoo aquifers. Field experiments were conducted on the Campus and Krugersdrift test sites in Bloemfontein. The Campus test site is a fractured aquifer with hydraulic conductivity values between 1.1 to 2 m/d. Krugersdrift test site is a porous aquifer with hydraulic conductivity values between 9.9 to 11 m/d. The electro-kinetic coupling coefficient was determined by correlating streaming potentials near observation boreholes with the hydraulic head. Measured streaming potentials formed a positive anomaly around the pumping borehole, mirroring the hydraulic head cone of depression. Hydraulic conductivity values estimated from streaming potential field analytical solution for transient mode were in the same order as values determined through analytical analysis of drawdown data with relative error of 0.2.

Key words: Passive geophysics, streaming potential, hydraulic conductivity, pumping test