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 WRC Eco Project
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
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TMG Groundwater Aquifers and Aquitards WRC Eco Project
TMG Groundwater Aquifers and Mountain Springs Regolith (weathered-and-fractured) aquifer Fractured-rock aquifer Aquitard WRC Eco Project
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
TMG Groundwater Aquifers: Confined / Unconfined WRC Eco Project
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
TMG Groundwater Hermanus Development o o o o WRC Eco Project
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 ?)
Target Zone Definition: Southern Area Faults Fractures
Target Zone Definition: Northern area
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TMG Groundwater Fluid Flow in Fractured Rock
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Brandvlei (B) Target Zone: Northern area Goudini Brandvlei Potential targets ?
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W Target Zone: Wemmershoek-Berg River scheme links Klein Drakenstein Fault ZS La Motte Fault ZS = Zachariashoek Syncline
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H Target Zone: Steenbras-Palmiet scheme conjunction Possible deep flow-path to submarine discharge SS KA SS = Steenbras Syncline KA = Kogelberg Anticline
T Target Zone: Theewaterskloof scheme conjunction Recharge Steenbras-Brandvlei Megafault Discharge
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Voelvlei (V) Target Zone: Waterval Syncline and faults
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 WRC Eco Project
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Exploratory Phase Drilling: Typical Set-up DWAF Core Rig City of Cape Town
Exploratory Phase Drilling: Typical Set-up Air Percussion Rig at Hermanus
Exploratory Phase Drilling: Typical Set-up Air Percussion Rig at Hermanus
Exploratory Phase Drilling: V-notch yield measurement during air-lift test
Exploratory Phase Drilling: Hermanus Magnetic Observatory site
Hermanus monitoring borehole: Final construction and site rehabilitation
Table Mountain Group (TMG) Superaquifer Outcrop and subsurface extent
TMG Groundwater Fluid Flow in Fractured Rock Landsat 5 Band 347 (RGB) composite
Hydrogeological Data Acquisition: 1:50 000 Digital Geology (CGS) WRC Eco Project