Abstract
2-D Resistivity Survey was carried out in the Thata Island, one of the numerous circular islands in the Okavango Delta to investigate the mechanism governing the interactions between surface water, vegetation and groundwater. Seven profiles were laid across the island and the imaging results indicate that the centre of the island has very low resistivities (less than 10 ohm-m), while outside the island margins resistivity values increase laterally. This lateral resistivity zoning responds to shallow groundwater chemistry below the islands; high solutes load inside and the presence of fresh water outside the islands. Results of borehole to surface resistivity imaging in the island indicate a sinking blob of saline water to depths of 60 m. Groundwater salinities below the island range from 11.7g/l from outside the fringe to 122g/l at the centre of the island. Beyond the depth of 60m, the groundwater salinity drops to about 0.33 g/l at the centre of the island. Depth to water table in all the boreholes is less than 3 m below ground level. Results of the lateral and down-hole imaging as well as water salinity values show a migrating plume of high salinity groundwater from the surface of the island invading a relatively deeper low-density fresh groundwater environment.
| Original language | English |
|---|---|
| Title of host publication | Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007 |
| Subtitle of host publication | Geophysical Investigation and Problem Solving for the Next Generation |
| Pages | 385-398 |
| Number of pages | 14 |
| Volume | 1 |
| Publication status | Published - Dec 1 2007 |
| Event | 20th Symposium on the Application of Geophysics to Engineering and Environmental Problems: Geophysical Investigation and Problem Solving for the Next Generation, SAGEEP 2007 - Denver, CO, United States Duration: Apr 1 2007 → Apr 5 2007 |
Other
| Other | 20th Symposium on the Application of Geophysics to Engineering and Environmental Problems: Geophysical Investigation and Problem Solving for the Next Generation, SAGEEP 2007 |
|---|---|
| Country | United States |
| City | Denver, CO |
| Period | 4/1/07 → 4/5/07 |
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All Science Journal Classification (ASJC) codes
- Geophysics
- Geotechnical Engineering and Engineering Geology
- Environmental Engineering
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The applicability of dc resistivity imaging to investigating the feedback mechanism between water quality and transpiration beneath circular islands in the Okavango delta, Botswana : A Case study of Thata Island. / Molwalefhe, Loago N.; Shemang, Elisha M.
Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation. Vol. 1 2007. p. 385-398.Research output: Chapter in Book/Report/Conference proceeding › Conference contribution
TY - GEN
T1 - The applicability of dc resistivity imaging to investigating the feedback mechanism between water quality and transpiration beneath circular islands in the Okavango delta, Botswana
T2 - A Case study of Thata Island
AU - Molwalefhe, Loago N.
AU - Shemang, Elisha M.
PY - 2007/12/1
Y1 - 2007/12/1
N2 - 2-D Resistivity Survey was carried out in the Thata Island, one of the numerous circular islands in the Okavango Delta to investigate the mechanism governing the interactions between surface water, vegetation and groundwater. Seven profiles were laid across the island and the imaging results indicate that the centre of the island has very low resistivities (less than 10 ohm-m), while outside the island margins resistivity values increase laterally. This lateral resistivity zoning responds to shallow groundwater chemistry below the islands; high solutes load inside and the presence of fresh water outside the islands. Results of borehole to surface resistivity imaging in the island indicate a sinking blob of saline water to depths of 60 m. Groundwater salinities below the island range from 11.7g/l from outside the fringe to 122g/l at the centre of the island. Beyond the depth of 60m, the groundwater salinity drops to about 0.33 g/l at the centre of the island. Depth to water table in all the boreholes is less than 3 m below ground level. Results of the lateral and down-hole imaging as well as water salinity values show a migrating plume of high salinity groundwater from the surface of the island invading a relatively deeper low-density fresh groundwater environment.
AB - 2-D Resistivity Survey was carried out in the Thata Island, one of the numerous circular islands in the Okavango Delta to investigate the mechanism governing the interactions between surface water, vegetation and groundwater. Seven profiles were laid across the island and the imaging results indicate that the centre of the island has very low resistivities (less than 10 ohm-m), while outside the island margins resistivity values increase laterally. This lateral resistivity zoning responds to shallow groundwater chemistry below the islands; high solutes load inside and the presence of fresh water outside the islands. Results of borehole to surface resistivity imaging in the island indicate a sinking blob of saline water to depths of 60 m. Groundwater salinities below the island range from 11.7g/l from outside the fringe to 122g/l at the centre of the island. Beyond the depth of 60m, the groundwater salinity drops to about 0.33 g/l at the centre of the island. Depth to water table in all the boreholes is less than 3 m below ground level. Results of the lateral and down-hole imaging as well as water salinity values show a migrating plume of high salinity groundwater from the surface of the island invading a relatively deeper low-density fresh groundwater environment.
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M3 - Conference contribution
SN - 9781604239546
VL - 1
SP - 385
EP - 398
BT - Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007
ER -