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

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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 languageEnglish
Title of host publicationEnvironmental and Engineering Geophysical Society - 20th, SAGEEP 2007
Subtitle of host publicationGeophysical Investigation and Problem Solving for the Next Generation
Pages385-398
Number of pages14
Volume1
Publication statusPublished - Dec 1 2007
Event20th 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 2007Apr 5 2007

Other

Other20th Symposium on the Application of Geophysics to Engineering and Environmental Problems: Geophysical Investigation and Problem Solving for the Next Generation, SAGEEP 2007
CountryUnited States
CityDenver, CO
Period4/1/074/5/07

Fingerprint

Botswana
transpiration
Transpiration
water quality
feedback mechanism
Water quality
Groundwater
electrical resistivity
Feedback
Imaging techniques
ground water
salinity
Boreholes
groundwater
Water
Zoning
Saline water
boreholes
Surface waters
borehole

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geotechnical Engineering and Engineering Geology
  • Environmental Engineering

Cite this

Molwalefhe, L. N., & Shemang, E. M. (2007). 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. In Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation (Vol. 1, pp. 385-398)
Molwalefhe, Loago N. ; Shemang, Elisha M. / 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. Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation. Vol. 1 2007. pp. 385-398
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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.",
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Molwalefhe, LN & Shemang, EM 2007, 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. in Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation. vol. 1, pp. 385-398, 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, 4/1/07.

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 proceedingConference contribution

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Molwalefhe LN, Shemang EM. 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. In Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation. Vol. 1. 2007. p. 385-398