scoping workshop hydrogeological aspects and selection of potential sites c.j.h. hartnady umvoto
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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. - PowerPoint PPT PresentationTRANSCRIPT
Ecological and Environmental Impacts of Large-scale
Groundwater Development in the Table Mountain Group
(TMG) Aquifer System
Scoping WorkshopScoping Workshop
Hydrogeological Aspects and Hydrogeological Aspects and Selection of Potential SitesSelection of Potential Sites
C.J.H. HartnadyC.J.H. Hartnady
UmvotoUmvoto
28 March 200328 March 2003
Scoping WorkshopScoping Workshop
Hydrogeological Aspects and Hydrogeological Aspects and Selection of Potential SitesSelection of Potential Sites
C.J.H. HartnadyC.J.H. Hartnady
UmvotoUmvoto
28 March 200328 March 2003 WRC Eco Project
WRC Eco Project
Objectives
Introduce TMG aquifer definitionsIntroduce TMG aquifer definitions
Define target zones for CCT ProjectDefine target zones for CCT Project
Discuss groundwater target type settingsDiscuss groundwater target type settings
Provide hydrogeological background to Provide hydrogeological background to scoping of potential impactsscoping of potential impacts
WRC Eco Project
TMG GroundwaterAquifers and Aquifers and AquitardsAquitards
WRC Eco Project
TMG Groundwater
Fractured-rock Fractured-rock aquiferaquifer
AquitardAquitard
Regolith (weathered-and-Regolith (weathered-and-fractured) aquiferfractured) aquifer
Aquifers and Mountain Aquifers and Mountain SpringsSprings
WRC Eco Project
GroundwaterUnconfined and Confined Unconfined and Confined AquifersAquifers•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 Confined (or artesian) aquifer – – Aquifer overlain by a low-permeability unit Aquifer overlain by a low-permeability unit (confining layer). A confined aquifer does (confining layer). A confined aquifer does not have a water table, only a not have a water table, only a potentiometric surfacepotentiometric surface which is defined by which is defined by water levels in boreholes under pressure.water levels in boreholes under pressure.WRC Eco Project
TMG Groundwater
Aquifers: Aquifers:
Confined / Confined / Unconfined Unconfined
WRC Eco Project
Radius of influence (rRadius of influence (ree))
for pumped wellfor pumped well
independent of abstraction rateindependent of abstraction rate (Q) (Q) depends only on:depends only on:
hydraulic conductivityhydraulic conductivity (K (K))
specific storage (Sspecific storage (Sss) )
durationduration (t) of abstraction(t) of abstraction
rre e == 1.5 (Kt/S1.5 (Kt/Sss))1/21/2
TMG Groundwater
rree
tt
WRC Eco Project
TMG GroundwaterHermanus Hermanus DevelopmentDevelopment
oo
oo
oooo
TMG Target Generation
Southern Target Region Southern Target Region Target Zone K (Kogelberg)Target Zone K (Kogelberg) Target Zone H (Hottentots-Holland)Target Zone H (Hottentots-Holland) Target Zone T (Theewaterskloof)Target Zone T (Theewaterskloof) Target Zone B (Brandvlei – south)Target Zone B (Brandvlei – south) Target Zone W (Wemmershoek)Target Zone W (Wemmershoek)
Northern Target Region Northern Target Region Target Zone B (Brandvlei – north?)Target Zone B (Brandvlei – north?) Target Zone V (Voelvlei)Target Zone V (Voelvlei) Target Zone A (Agter-Target Zone A (Agter-
Witzenberg ?)Witzenberg ?)
Southern Target Region Southern Target Region Target Zone K (Kogelberg)Target Zone K (Kogelberg) Target Zone H (Hottentots-Holland)Target Zone H (Hottentots-Holland) Target Zone T (Theewaterskloof)Target Zone T (Theewaterskloof) Target Zone B (Brandvlei – south)Target Zone B (Brandvlei – south) Target Zone W (Wemmershoek)Target Zone W (Wemmershoek)
Northern Target Region Northern Target Region Target Zone B (Brandvlei – north?)Target Zone B (Brandvlei – north?) Target Zone V (Voelvlei)Target Zone V (Voelvlei) Target Zone A (Agter-Target Zone A (Agter-
Witzenberg ?)Witzenberg ?)
CCT Feasibility & Pilot CCT Feasibility & Pilot ProjectProject
Target Zone Definition: Southern Area
FaultsFaults FracturesFractures
Target Zone Definition: Northern area
WRC Eco Project
TMG GroundwaterFluid Flow in FracturedFluid Flow in Fractured
RockRock
WRC Eco Project
Brandvlei (B) Target Zone: Northern area
Potential targets ?Potential targets ?
GoudiniGoudini
BrandvleiBrandvlei
WRC Eco Project
W Target Zone:Wemmershoek-Berg River scheme links
La Motte FaultLa Motte Fault
Klein Klein Drakenstein FaultDrakenstein Fault
ZSZS
ZS = ZS = Zachariashoek Zachariashoek SynclineSyncline
WRC Eco Project
H Target Zone: Steenbras-Palmiet scheme conjunction
KAKA
SSSS
SS = Steenbras SynclineSS = Steenbras SynclineKA = Kogelberg AnticlineKA = Kogelberg Anticline
Possible deep flow-path to submarine dischargePossible deep flow-path to submarine discharge
T Target Zone: Theewaterskloof scheme conjunction
RechargeRecharge
DischargeDischarge
Steenbras-BrandvleiSteenbras-BrandvleiMegafaultMegafault
WRC Eco Project
Voelvlei (V) Target Zone:Waterval Syncline and faults
WRC Eco Project
Thanks for Thanks for your your
attentionattention
Thanks for Thanks for your your
attentionattention
Ecological and Environmental Impacts of Large-scale Groundwater Development in the Table Mountain Group (TMG) Aquifer System
WRC Eco Project
City of Cape Town
Exploratory Phase Drilling: Typical Set-up
DWAF Core RigDWAF Core Rig
Exploratory Phase Drilling: Typical Set-up
Air Percussion RigAir Percussion Rigatat
HermanusHermanus
Exploratory Phase Drilling: Typical Set-up
Air Percussion RigAir Percussion Rigatat
HermanusHermanus
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) SuperaquiferOutcrop and subsurface Outcrop and subsurface
extentextent
TMG GroundwaterFluid Flow in FracturedFluid Flow in Fractured
RockRock
Landsat 5Landsat 5Band 347 (RGB)Band 347 (RGB)
compositecomposite
Hydrogeological Data Acquisition: 1:50 000 Digital Geology (CGS)
WRC Eco Project