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Scoping Workshop Hydrogeological Aspects and Selection of Potential Sites C.J.H. Hartnady Umvoto

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. WRC Eco Project. Objectives.

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Scoping Workshop Hydrogeological Aspects and Selection of Potential Sites C.J.H. Hartnady Umvoto

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  1. 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 WRC Eco Project

  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 WRC Eco Project

  3. WRC Eco Project

  4. TMG Groundwater Aquifers and Aquitards WRC Eco Project

  5. TMG Groundwater Aquifers and Mountain Springs Regolith (weathered-and-fractured) aquifer Fractured-rock aquifer Aquitard WRC Eco Project

  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. WRC Eco Project

  7. TMG Groundwater Aquifers: Confined / Unconfined WRC Eco Project

  8. TMG Groundwater • 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 WRC Eco Project

  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

  13. WRC Eco Project

  14. TMG Groundwater Fluid Flow in Fractured Rock

  15. WRC Eco Project

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

  17. WRC Eco Project

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

  19. WRC Eco Project

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

  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

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

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

  34. Hydrogeological Data Acquisition: 1:50 000 Digital Geology (CGS) WRC Eco Project

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