1. Hydrogeological Aspects and Selection of Potential Sites
Ecological and Environmental Impacts of Large-scale Groundwater Development in the Table Mountain Group (TMG) Aquifer System
Scoping Workshop
Hydrogeological Aspects and Selection of Potential Sites
C.J.H. Hartnady
Umvoto
28 March 2003
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2. Objectives Introduce TMG aquifer definitions
Define target zones for CCT Project
Discuss groundwater target type settings
Provide hydrogeological background to scoping of potential impacts
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3. WRC Eco Project

4. TMG Groundwater
Aquifers and Aquitards
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5. TMG Groundwater Aquifers and Mountain Springs
Regolith (weathered-and-fractured) aquifer
Fractured-rock aquifer
Aquitard
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6. Groundwater Unconfined and Confined Aquifers
Unconfined aquifer – Aquifer overlain by an unsaturated (vadose) zone or a surface water body. Its upper surface is the water table
Confined (or artesian) aquifer – Aquifer overlain by a low-permeability unit (confining layer). A confined aquifer does not have a water table, only a potentiometric surface which is defined by water levels in boreholes under pressure.
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7. TMG Groundwater
Aquifers:
Confined / Unconfined
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8. TMG Groundwater re = 1.5 (Kt/Ss)1/2 Radius of influence (re)
for pumped well
independent of abstraction rate (Q)
depends only on:
hydraulic conductivity (K)
specific storage (Ss)
duration (t) of abstraction
re = 1.5 (Kt/Ss)1/2 re t

9. TMG Groundwater
Hermanus Development o o o o
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10. TMG Target Generation CCT Feasibility & Pilot Project
Southern Target Region
Target Zone K (Kogelberg)
Target Zone H (Hottentots-Holland)
Target Zone T (Theewaterskloof)
Target Zone B (Brandvlei – south)
Target Zone W (Wemmershoek)
Northern Target Region
Target Zone B (Brandvlei – north?)
Target Zone V (Voelvlei)
Target Zone A (Agter-Witzenberg ?)

11. Target Zone Definition: Southern Area
Faults
Fractures

12. Target Zone Definition: Northern area

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14. TMG Groundwater
Fluid Flow in Fractured Rock

15. WRC Eco Project

16. Brandvlei (B) Target Zone: Northern area
Goudini
Brandvlei
Potential targets ?

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18. W Target Zone: Wemmershoek-Berg River scheme links
Klein Drakenstein Fault ZS
La Motte Fault
ZS = Zachariashoek Syncline

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20. H Target Zone: Steenbras-Palmiet scheme conjunction
Possible deep flow-path to submarine discharge SS KA
SS = Steenbras Syncline
KA = Kogelberg Anticline

21. T Target Zone: Theewaterskloof scheme conjunction
Recharge
Steenbras-Brandvlei
Megafault
Discharge

22. WRC Eco Project

23. Voelvlei (V) Target Zone:
Waterval Syncline and faults

24. Thanks for your attention
Ecological and Environmental Impacts of Large-scale Groundwater Development in the Table Mountain Group (TMG) Aquifer System
Thanks for your attention
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25. WRC Eco Project

26. Exploratory Phase Drilling: Typical Set-up
DWAF Core Rig
City of Cape Town

27. Exploratory Phase Drilling: Typical Set-up
Air Percussion Rig at
Hermanus

28. Exploratory Phase Drilling: Typical Set-up
Air Percussion Rig at
Hermanus

29. Exploratory Phase Drilling: V-notch yield measurement during air-lift test

30. Exploratory Phase Drilling: Hermanus Magnetic Observatory site

31. Hermanus monitoring borehole: Final construction and site rehabilitation

33. Table Mountain Group (TMG) Superaquifer
Outcrop and subsurface extent

34. TMG Groundwater Fluid Flow in Fractured Rock Landsat 5 Band 347 (RGB)
composite

35. Hydrogeological Data Acquisition: 1:50 000 Digital Geology (CGS)
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