The Atlantis Water Supply Scheme
“Witzands Aquifer: the value of
ecosystem services”
A case study of integrated water resource
management : highlighting the value of
ecosystem services & management issues
Atlantis
Water Supply
Scheme
ATLANTIS AQUIFER
T MG AQUIFER
STUDY AREA
SITUATED IN THE
MOUNTAIN CHAIN
NEWLANDS AQUIFER
CAPE FLATS
AQUIFER
Wz
WTP
Atlantis Water Supply Scheme
Vvlei
WTP
Ss
WTP
Industrial users
Residential users
Domestic
WWTW
Residential
SW
Industrial
WWTW
Industrial
SW
Pond 6
Bholes
Recharge
P12
Natural
Recharge
Recharge
P7
Coastal
Recharge
Aquifer
Sea
Weir
Bholes
Environmental Services: – identified value
benefits to the Atlantis Water Supply
Scheme
The groundwater flow through the aquifer sands results in reduction,
adsorbtion and elimination of pathogens as well as chemical
stabilisation- this is a vital risk elimination control
Wetlands remove unwanted gross pollutants and nutrients from
entering the groundwater
The white dunes and protected natural area provide for unpolluted
natural recharge of the aquifer
Ponds provide a flow attenuation for storm flows and retention time
which enhances water quality and recharge into the aquifer
The aquifer provides a large reserve storage without the
disadvantages of a surface water impoundment
Active environmental management enhances the groundwater quality
Atlantis Water Supply Scheme
Ecosystem management issues
Purpose – Municipal supply
Resources –
Groundwater quality –
Neutral pH, hard, moderate TDS
Spring, groundwater and transferred
municipal supply, recycled SW & WW
Iron clogging – Frequent &
Aquifers – 2 Primary unconfined
Boreholes – 32 Production
Recharge – Natural & managed
Declining borehole yield –
SW detention ponds – 4 residential, 4
industrial , 1reception & diversion
Recharge basins – 2 for aquifer and 4
for sea water barrier
Treated domestic WW – to aquifer
Treated industrial WW – to sea water
Groundwater treatment –
Hardness removal, blending with
stabilised municipal supply
problematic
Due to clogging and borehole
construction
Borehole rehabilitation –
Sporadic to maintain yield
Management initiatives –
Monitoring monthly, borehole step
drawdown tests & CCTV camera
logging, Atlantis Aquifer Management
Committee, Atlantis Aquifer
Protection Zones
Challenges – operational & policy
Optimal management of the resource groundwater abstraction and
storage and water balance
Management and control of individual borehole yields and control of
iron related clogging, rehabilitation scheduling
Optimised monitoring of aquifer condition
Improved coordination between City role players and interested and
affected parties – city services, consumers, industry, para-statal
bodies, governmental organs
Establishment of aquifer protection zone – land use planning
Community awareness of resource and vulnerability to pollution –
informal housing, backyard dwellings, street littering
Access and control into the natural recharge areas
Control and prevention of vandalism
Management Initiatives
Ecosystem management issues
Aquifer levels & water
balance
Pump yield monitoring and
optimization
Water quality control tests
Drawdown management
Routine maintenance review
and improvement
Staff training & operating
rules
Aquifer protection zone and
land use rules
Witzands Nature Reserve
(proposed proclamation)
Borehole design review &
improvement
Clogging control
CCTV inspections
Step drawdown pumping
tests
Rehabilitation plan
Pumping equipment review &
improvement.
Multi-disciplinary team
management
Atlantis Aquifer protection zones
The zones are based on the surface and basement topography as
well as the likely travel time for pollutants to reach the wellfields
How is this a “Local Sustainablity Solution” ?
What are the ecosystem benefits ?
Groundwater is a potentially
significant renewable resource
in Africa
Aquifer sustainability can be
enhanced by artificial recharge
Stormwater and treated effluent
can be safely used at relatively
low cost
Water can be stored and losses
to evaporation can be
minimised.
Optimisation of water use
Water stress due to climatic
variations can be buffered
A drought reserve can be
maintained
Technology can range from
simple ( recharge ponds ) to
complex treated effluent reuse.
Artificial recharge can be used
to improve public environmental
awareness and understanding
of how to cope with climate
variability and stresses.
Recharge areas can be
integrated into nature reserves
Wetlands could generate
economic benefits and crops,
maintain biodiversity
The Benefits and Cautions
Improved assurance of
water supply
A water in the bank
approach
Lower energy utilisation
than desalination
Low carbon footprint
potential
Economic and ecological
sustainability benefits
Requires careful
management and
operation to maintain
contamination barriers and
controls
Aquifer monitoring costs
Retro-fitting not cheap,
greenfield infrastructure
most cost effective
Will not work everywhere
SCHEMATIC OF THE ATLANTIS WATER RESOURCE MANAGEMENT SCHEME
11
5
1st FLUSH
TO LAND
RESIDENTIAL
AREA
1
3
2
6
4
DOMESTIC
WASTE WATER
TREATMENT PLANT
(DWWTP)
Semi-noxious trade area
INDUSTRIAL AREA
Noxious trade area
9
10
OPEN LAND
DONKERGAT
RIVER
ARTIFICIAL
RECHARGE
BASIN 12
INDUSTRIAL
WASTE WATER
TREATMENT PLANT
(IWWTP)
ARTIFICIAL
RECHARGE
BASIN 7
MELKBOS
PIPELINE
WATER TREATMENT
& SOFTENING PLANT
Catchment , Stormwater &
Roads Management
Potable water
4
COASTAL
RECHARGE
BASINS
WITZAND WELLFIELD
Environmental
Resource
Management
Stormwater
detention
basin/pond
Treated effluent ex DWWTP &
higher quality stormwater runoff
Proposed re-routing
Bulk Water
Treated effluent ex IWWTP,
diluted softening brines & poorer
quality stormwater runoff
Proposed re-routing
Waste Water
Raw waste water
Responsibility
area
Witzands wellfield water levels
Showing the recovery of the aquifer storage due to
artificial recharge – data from CSIR aquifer monitoring
Pond 3 –residential area stormwater
The stormwater is detained in this pond to attenuate peak storm
flows
Pond 6 – combined SW +WWTE
This is the reception pond for all the stormwater from the
residential area and the domestic wastewater treated effluent. The
integral reed-bed attenuates the stormwater quality and traps
debris. Periodic cleaning is carried out
Pond 9 – industrial area stormwater
This receives polluted runoff and has an oil barrier at the inlet for
periodic cleaning and pollution minimisation
Flow splitter box – into recharge ponds
This device has two outgoing pipes to direct the flow into the
recharge ponds to 7 (underflow weir – low flow) and 12 (overflow
weir – storm flow).
P12
P7
Pond 7 - combined recharge SW + WWTE
This receives the base flow stormwater and first flush during
rainfall. Water quality is generally saline with bacteria count higher
than wastewater treated effluent
Coastal ponds P1 &P2 –combined recharge SW
+WWTE
The industrial area noxious stormwater and wastewater treated
effluent in directed to these ponds to provide an intermediate
salinity barrier against sea water intrusion into the low salinity
aquifer
Thank you
Any Thank
Questions
?
you
Cape Town : Groundwater
Challenges and Hurdles
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Public suspicion of Government regulating landowner’s “own free
water”
Inadvertent or careless pollution of superficial aquifer difficult to
control – informal housing , garden fertilisers, informal industries
Lack of resources to control and monitor – reliant on public
cooperation and awareness
Poverty, squalor and lack of basic services together with rapid
urbanisation
Acquiring and focusing adequate funding for GW protection
Cape Town: Groundwater Protection
Initiatives currently in place
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Identification and initiation of the Atlantis Aquifer protection
Zones
Atlantis aquifer monitoring since 1975
Regulatory monitoring required for waste sites for operational and
closed facilities. So far about 37 sites identified, but not all are
being monitored
Limited GW monitoring associated with some watercourses and
waterbodies – City of CT has limited database for river catchment
management
TMG hydrocensus, baseline, near-field & far-field protocol and
database under development
DWAF monitors sites and receives data from site licensees