WATER RESOURCES AND WATER RESOURCE PLANNING
BACKGROUND INFORMATION FOR WSDP
NOVEMBER 2005
WATER RESOURCES AND WATER RESOURCE PLANNING
1.
INTRODUCTION
One of the major issues facing CCT in the future is the task to reduce water demand through
the implementation of water demand management initiatives in order to ensure a sustainable
supply of water for the future. The limited nature of the available water resources and the
shortage of raw water storage capacity has increased the risk of water shortages occurring in
the Cape Metropolitan Area prior to the construction of the Berg Water Project, which is
scheduled for completion by the end of 2007. Two successive years of well below the long term
average rainfall in 2003 and 2004 led to DWAF imposing restrictions on the users of water from
the Western Cape Water System in October 2004 (20% reduction in water demand required in
2004/2005). In order to understand the limitations of existing water resources a description of
the existing water resources are herewith provided. Future Water Resource planning is also
discussed.
2.
WATER RESOURCES
2.1
GROUNDWATER
The following groundwater resources exist within the Cape Metropolitan Area. (See figure 1).
-
Albion Springs
Atlantis Aquifer
Cape Flats Aquifer
Newlands Aquifer
Only two of the abovementioned ground water resources are currently being exploited, namely,
Albion Springs and the Atlantis Aquifers. The Table Mountain Group Aquifer (TMG) falls outside
the boundaries of the CMA.
2.1.1
Albion Springs
Water from Albion Springs is treated with chlorine and lime and then pumped directly into the
reticulation system of the City of Cape Town.
2.1.2
Atlantis
The Atlantis Supply Scheme comprises of two aquifers, one at Witzands and one at
Silwerstroom.
The number of boreholes and abstraction potential is listed below:
AQUIFER
Witzands
NO. OF BOREHOLES
(APPROXIMATE)
30
Silwerstroom
14
ABSTRACTION POTENTIAL
(MILLION m3/a)
5
The Altantis water supply scheme supplies the towns of Altantis and Mamre and is situated
within Blaauwberg Municipality.
2.2
FUTURE GROUND WATER RESOURCES
2.2.1
Cape Flats Aquifer
The sand deposits at the Cape Flats referred to as the Cape Flats Aquifer System constitute a
large water storage unit with the CMA.
The Cape Flat Aquifer has not yet been exploited. The storage capacity of the aquifer is
believed to be about 128 Mm 3 (million cubic meters), but the rate of natural recharge is
estimated at only 18 Mm3/annum.
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2.2.2
Newlands Aquifers
The aquifers at Newlands have also not yet been exploited. The estimated yield from this
source could be a much as 10 Mm 3/annum.
2.2.3
Table Mountain Group Aquifer
The TMG Aquifer Feasibility Study and Pilot Project was awarded to the TMG Aquifer Alliance
(TMGA Alliance) by the Executive Committee of the City of Cape Town on the 23 April 2002. The
primary objective of the Study is to determine the viability of the TMG aquifer as a potential future
water resource for the City of Cape Town. An incremental and precautionary approach has been
adopted in the Study as there is uncertainty regarding the potential environmental impacts of
abstracting water from the aquifer.
Due to the nature of the project , the Study was broken up into 4 discreet phases. This flexible
approach allows for a significant amount of interaction with the City of Cape Town and enables the
CCT to play a key role in the decision making process throughout the Study. Provision has been
made in the Project for the CCT to be able to terminate the project at the end of the Preliminary and
Exploratory Phases and during the Pilot Phase of the Study should it become evident after reviewing
the progress and the feasibility of the various phases that the desired outcomes will not be achieved.
The outcome of the Preliminary Phase was the identification of 26 potential target sites suitable for
exploratory drilling to gain a better understanding of the properties of the aquifer. These 26 target
sites have been subjected to an environmental scoping process and now require authorization from
the Department of Environmental Affairs and Development Planning (DEA&DP) prior to commencing
with exploratory drilling. The Preliminary Phase concluded that, based on a regional desktop
assessment of the Table Mountain Group Aquifer, that the TMG Aquifer would most likely be a viable
water resource that could significantly augment the City’s current water resources in the future.
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2.3
SURFACE WATER
2.3.1
Introduction
The CCT utilises water from various dams within the CMA and also from dams outside the
CMA. Some of the dams are operated and controlled by the CCT, whilst the other dams are
operated and controlled by the Department of Water Affairs and Forestry. The CCT obtains
approximately 70 to 75% of its raw water requirements from DWAF and the remainder from its
own sources. Approximately 15% of the raw water requirements are obtained from sources
within the CMA.
The following dams and rivers are utilised:
DAMS/RIVERS
OWNED
&
OPERAT
ED BY
APPROXIMATE%
OF TOTAL
SUPPLY
REQUIREMENTS
**
%
FIRM YIELD*
(1:50 YEAR)
M m3
DWAF
DWAF
48.3%
219
DWAF
23.2%
105
70.5
DWAF
5%
22,5
22.5
CMC
11.9%
54
54
CMC
8.8%
40
40
97.1%
440.5
Approx.
yields
305
CMC
0,4%
1,85
1.8
CMC
0,1%
0,5
1
CMC
0.88%
4
3.5
446.86
311.3*
Major Sources
Theewaterskloof
Dam/
Kleinplaas Dam
Voëlvlei Dam
Palmiet River
Wemmershoek
Dam
Steenbras Upper
and Steenbras
Lower Dam
Total
M m3
Minor Sources
Simon’s Town:
Lewis Gay Dam
Kleinplaas
Land en Zeezicht
Dam
(From Lourens
River)
Table Mountain:
Woodhead
Hely-Hutchinson
De Villiers Dam
Victoria Dam
Alexandra Dam
Grand Total
CCT
Registerd
Usaage
98.5*
118
3
*Excludes the Atlantis Aquifer and Albion Springs (approx. 6.5 Million m /a)
** Approximate % of total supply requirement and firm yield includes Agriculture and other Water Service Authorities.
The Berg River Dam and the Supplement Scheme (Skuifraam Dam and the Skuifraam
Supplement Scheme) are the next major water resource schemes to be constructed in the
Western Cape.
The major dams and rivers utilised by the CCT are shown in Figure 1.
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Further water augmentation schemes that could possibly be implemented in the short to
medium term include the Voëlvlei/Augmentation Scheme Phase I, the Table Mountain Group
Aquifer, the Cape Flats Aquifer, the Lourens River Diversion Scheme and the Eerste River
Diversion Scheme.
2.3.2
Theewaterskloof Dam/Kleinplaas Dam
Theewaterskloof Dam is part of the Department of Water Affairs and Forestry’s
Riviersonderend/Berg River Government Water Scheme.
This is a large inter-basin water transfer scheme that regulates the flows of the Riviersonderend,
the Berg (including its Wolwekloof and Banhoek tributaries) and Eerste Rivers for urban,
industrial and irrigation use. It consists, of the Theewaterskloof Dam on the Riviersonderend, a
tunnel through the Franshhoek Mountain Range to the Upper Berg River, and a siphon under
that river leading to another tunnel that passes under the Klein Drakenstein Mountains to a
balancing dam at Kleinplaas on the Jonkershoek tributary of the Eerste River. A third tunnel
leads from the dam to an outlet close to Stellenbosch. Diversion works on the Banhoek and
Wolwekloof rivers allow surplus winter flows to be diverted and conveyed through the tunnel
system into Theewaterskloof Dam where the water is stored. In summer it can be released
back through the tunnel system to outlets on the Berg River, the Eerste River at Kleinplaas
Dam, the Stellenbosch tunnel Outlet, and an outlet from a branch tunnel at Dasbos.
The Theewaterskloof Dam has a total capacity of 480 Mm 3.
Water from Theewaterskloof can be treated at Faure, Blackheath and Wemmershoek Water
Treatment Plants.
Table 1 in Annexure “A” sets out the main characterics of Theewaterskloof and Kleinplaas
Dams.
2.3.4
Voëlvlei Dam
Voëlvlei Dam is owned by DWAF and supplies water to the CCT, and other Water Services
Authorities in the immediate area as well as irrigation. Voëlvlei Dam has a full supply capacity
of 172 Mm3. The dam, which is not fed directly by any river and receives little run-off from its
31 km2 natural catchment, relies upon diversion works in the Klein Berg, Leeu and 24 Rivers for
its water supply. The canal from the Klein Berg river is 8 km long and has a maximum capacity
of 20 m3/s while that of the 24 Rivers is 29 km long and has a maximum capacity of 34 m 3/s.
The CCT’s Voëlvlei Water Treatment Plant is situated along the banks of the dam.
The CCT receives an annual allocation of 70,3 Mm 3 of water. This includes an allocation of
4 Mm3 of water for supply to Krantzkop.
Table 2 in Annexure “A” sets out the main characteristics of the Voëlvlei Dam.
2.3.5
Wemmershoek Dam
The Wemmershoek Dam was completed in 1957 and is owned and operated by the Cape
Metropolitan Council. The dam is situated on the Wemmershoek River in the mountains near
Franschhoek and has a capacity of 58,6 Mm 3. The dam has a gravel and boulder embankment
with a sloping clay core.
The Wemmershoek Water Treatment Plant is situated at the base of the dam wall.
Wemmershoek Dam has a yield of 51 Mm 3/annum at 99% assurance of supply. When
Wemmershoek Dam was constructed a compensation agreement involving an exchange of
water rights for agricultural use, between Wemmershoek Dam and the RSE scheme was made
and a 10 Mm3 annual release is made into the Berg River from the RSE Scheme in lieu of
that from the Wemmershoek Dam.
Table 3 in Annexure “A” sets out the main characteristics of the Wemmershoek Dam.
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2.3.6
Steenbras Upper and Lower Dams
The construction of Steenbras Lower Dam was completed in 1921. In 1928 the dam wall was
raised by 12,29 m and then raised again to its present height. The capacity of Steenbras Lower
Dam is 36,2 Mm3.
Steenbras Upper Dam was completed in 1977 and is situated 5 km upstream of Steenbras
Lower Dam. Steenbras Upper Dam was constructed for a dual purpose of providing an upper
reservoir for the City of Cape Town’s Steenbras Pumped Storage Scheme and for supplying
water for domestic/industrial use to Cape Town. The capacity of Steenbras Upper Dam is
31,7 Mm3. Both Steenbras Upper and Lower Dams are owned and operated by the CCT.
Steenbras Water Treatment Plant is situated on the Western side of the Hottentots Holland
Mountains and receives its water via a 752 m long tunnel from Steenbras Lower Dam.
Steenbras Upper Dam is also an integral part of the Palmiet Phase 1 system and stores water
transferred via a canal from the Palmiet River.
Table 4 in Annexure “A” sets out the main characteristics of Steenbras Upper and Lower Dams.
The combined historic firm yield of both dams together is approximately 38 x 10 6 m3.
2.3.7
Kleinplaas and Lewis Gay Dams
Kleinplaas and Lewis Gay Dams are both situated on the Woel River and have storage
capacities of 1,36 Mm 3 and 0,18 Mm3 respectively. Water is also pumped into Kleinplaas Dam
from the small Rawson Reservoir in the adjacent Klawer River catchment. In 1996 the yield of
the system was estimated to be 1,85 Mm 3/annum at 96% assurance. The dams are owned by
the CCT and water from the two dams is treated at Brooklands Water Treatment Plant.
Figure 2 shows the locality plan of the dams.
Table 5 in Annexure “A” sets out the main characteristics of the dam.
2.3.8
Table Mountain Dams
There are 5 dams utilised for water supply which are situated on the top of Table Mountain. All
these dams are owned and operated by the CCT. Figure 3 shows the locality plan of the
dams.
Woodhead Dam and Hely-Hutchinson Dam
The construction of Woodhead Dam was completed in 1897. The dam is on the Disa River and
has a capacity of 0,955 Mm3. The dam is a stone faced structure of cement mortar, and rubble
fill.
Hely-Hutchinson Dam was completed in 1904. The dam also lies on the Disa River and acts as
an extension to the Woodhead Dam. The dam has a capacity of 0,927 Mm 3. The outlet works
on the Woodhead Dam feeds the water back into the Disa Gorge en route to the Twelve Apostle
tunnel. Both dams are owned by the CCT and their water is treated at Kloof Nek Water
Treatment Plant.
Table 5 in Annexure “A” sets out the main characteristics of the dams.
De Villiers Dam, Victoria Dam and Alexandra Dam
The Victoria Dam was completed in 1895 and has a capacity of 0,128 Mm 3. Alexandra Dam
was completed in 1903 and has a storage capacity of 0,126 Mm 3. The De Villiers Dam was
completed in 1910 and holds 0,243 Mm 3 of water. All three dams are located on the Disa River,
with water from Victoria Dam being discharged into the Alexandra Dam as the levels in that dam
dropped, and from there into the De Villiers Dam.
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Water leaving the De Villiers Dam is fed back into the Disa Stream and then diverted into a
1,5 km pipeline that delivers it to the Constantia Nek Water Treatment Plant .
Table 5 in Annexure “A” sets out the main characteristics of the dams.
2.3.9
Land-en-Zeezicht Dam
Land-en-Zeezicht Dam is an off-channel storage dam that stores water supplied from the
Lourens River. The dam is situated in the Helderberg Nature Reserve in Somerset West and
supplies the Somerset West Water Treatment Plant. The dam is an earth fill dam with a
capacity of 0,45 Mm 3. The dam is owned by CCT.
Table 6 in Annexure “A” sets out the main characteristics of the dam.
2.3.10
Lourens River
The Lourens River supplies water to the Somerset West and Strand Water Treatment Plants.
Water from the Lourens River (and adjacent boreholes) can be fed either directly into the
Somerset West Treatment Works or stored in the off-channel Land-on-Zeezicht Dam (full supply
capacity of 0,451 Mm 3) until required. The water treatment plants are currently owned by the
CCT.
Palmiet Phase I
Water supply to the CMA is also supplemented by water transferred from the Palmiet River to
the Steenbras Upper Dam. Water from the Palmiet River is impounded in Kogelberg Dam and
then transferred to Rockview Dam by means of Eskom’s Palmiet Pumped Storage Scheme.
This water is then released via an aqueduct from Rockview Dam to Steenbras Upper Dam. Both
Kogelberg Dam is then released via an aqueduct from Rockview Dam to Steenbras Dam. Both
Kogelberg Dam and Rockview Dam are owned by DWAF. The Palmiet water in Steenbras
Upper Dam is further transferred to the City of Cape Town’s Electricity Department’s Steenbras
Lower Reservoir by means of the Steenbras Pumped Storage Scheme. The water is then
pumped from Firlands pump station to the Faure Water Treatment Plant.
The CCT’s allocation of water from the Palmiet River is approximately 22,5 Mm 3. The quantity
of water that will be transferred to Steenbras Upper Dam each year will be reviewed annually
and will be dependent on the rainfall in the Palmiet Catchment area.
2.4
FUTURE WATER RESOURCES
Implementation and financing of the Berg Water Project (BWP), which comprises a dam on the
farm Skuifraam, a supplemental scheme and ancillary works, was approved by National
Cabinet on 30 April 2002. The City’s increasing demand for water, although significantly
tempered by a successful Water Demand Management Policy and Strategy, requires the urgent
implementation of Cabinet’s decision if the City is not to be compromised with regard to future
water supply and exposed to possible more severe water restrictions in the short to medium
term.
The Minister of Water Affairs and Forestry has directed the Trans-Caledon Tunnel Authority
(TCTA) to finance and implement the BWP in terms of Section 103(2)(b) of the National Water
Act. TCTA will own the land and infrastructure until the loans raised by TCTA have been
redeemed, whereafter the land and infrastructure will revert back to the Department of Water
Affairs and Forestry (DWAF). It is intended that users of the water will fund the BWP which in
today’s terms will cost between R1,4 billion and R1,5 billion. Other users who are allocated
water from the BWP will pay a third party capital charge, based on their water allocation and the
CCT will receive a credit from DWAF for this amount. See Table 7 for provisional characteristics
of the dam.
It is important to note that the Department of Water Affairs and Forestry only approved the
implementation of the Berg Water Project when they were satisfied that the City had made
progress with respect to the implementation of water demand management (WDM). The
construction of the Dam was to proceed as a parallel process to the City implementing WDM.
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The Department of Water Affairs and Forestry is currently in the process of reviewing and
updating the Western Cape Systems Analysis (WCSA). This "Reconciliation" Study will reassess all the water resource options available for the City of Cape Town, neighbouring local
authorities and the agricultural sector. The Study will utilize information from the City’s
“Integrated Water Resource Planning Study” and the City’s “Review of Long term Urban Water
Demand Study” as well as other studies which DWAF has undertaken in the Breede Valley and
Lower Berg River Area. Effluent re-use schemes are also becoming an important consideration.
The Study will also compare the latest current information on desalination to all the other water
resource options available to DWAF and the City. The outcome of the Reconciliation Study will
be a shortlist of
options to be studied at Feasibility level, and associated with each will be a
legal requirement to undertake an Environmental Impact Assessment
process. The Reconciliation Study will also develop a strategy to guide future water resource
development for the City of Cape Town (CCT), surrounding local authorities and agriculture.
Assuming the City of Cape Town achieved its WDM objective, it is then anticipated that a new
water resource, after the Berg Water Project, will only be required in approximately 2013. It is
imperative that planning commences at an early stage as the lead time to implement a water
resource scheme is approximately 6 to 7 years.
Further water augmentation schemes that could possibly be implemented in the short- to
medium term include the Voëlvlei/Augmentation Scheme Phase I, the Table Mountain Group
Aquifer, the Cape Flats Aquifer, the Lourens River Diversion Scheme and the Eerste River
Diversion Scheme.
There are a number of factors which could bring forward the timing of new water augmentation
schemes eg possible climate change, decrease in system yield due to environmental reserve
requirements. Given the abovementioned factors, the Mayoral Committee of the City of Cape
Town resolved to follow a “precautionary and conservative” approach to water resource
planning and implementation in order to ensure that water restrictions are not unnecessarily
imposed on the water consumers within the Cape Metropolitan Area.
3.
WATER RESOURCES PLANNING MODEL
The results of the WCSA are based on static demands and given levels of reliability (or yields)
from the various sub-systems. In the real world water demands and infrastructure development
are dynamic components. Ninham Shand therefore developed the Water Resources Planning
Model (WRPM) which could take into account varying demands, changing infrastructure and the
implications of imposing various levels of water restrictions.
The Water Resources Planning Model is utilitsed at least twice a year, at the onset of the winter
rain (June) and at the end of the hydrological year (end October).
Based on the result of the WRPM, the CCT and DWAF operate their infrastructure/resources so
as to maximise the waste resource situation by the end of winter each year. In other words
those water resources that are most likely to spill are more heavily utilised in order to
ensure that the optimum available amount of water is available prior to the start of the dry
summer season. Similarly, in summer those resources which are not under a “stress” situation
are first utilised.
The results of the stochastic analysis carried out by the WRPM also inform DWAF and the
CCT of the probability of any potential shortfall in the water resources in the summers to come.
The WRPM indicates what level of water restriction would have to be applied each year to all
users of those water resources in order to ensure the sustainability of the water resource in the
long-term.
The WRPM also:
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provides information regarding the dates when a pre-defined acceptable risk of having to
impose restriction is exceeded.
*
provides information when the next augmentation scheme has to be implemented in order
not to exceed a certain risk of having to impose water restrictions.
page
5.
*
indicates the annual volume of inter sub-system support required to balance the risk of water
shortages across the total system and
*
indicates the level of restrictions required in a particular year to avoid failure of the total
system in the short term.
LONG-TERM URBAN DEMAND
In 1998/99 the Department of Water Affairs and Forestry (DWAF) commissioned Ninham
Shand together with sub-consultants Palmer Development Group (PDG) and the Institute of
Futures Research (IFR) to analyse the past-, present- and future urban demand for water in the
Cape Metropolitan Area. In order to better assess and understand current and future demand,
this study was updated in 2003/2004 by the City of Cape Town. Based on the potential
economic growth and population growth it is estimated that the unconstrained water demand
growth in the City will vary between 2,7% and 3,7% per annum.
6.
RAINFALL/EVAPORATION AND WATER USAGE
The following information is tabulated in Annexure “B”.
-
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Table 8:
Table 9:
Table 10:
Yearly Resource Supply Figures
Monthly Consumption Figures
Yearly Rainfall Figures
page
ANNEXURE “A”
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Riviersonderend/Berg River Government Water Scheme
STORAGE RESERVOIRS
Name of Dam
Theewaterskloof
Kleinplaas
Nearest Town
Villiersdorp
Stellenbosch
Distance (km)
10
8
DWAF
DWAF
1980
1981
Riviersonderend
Jonkershoek
500
31
Earthfill
Composite concrete gravity/rockfill
Wall Height (m)
37,5
21,5
Crest Length (m)
646
345
Uncontrolled side channel
Uncontrolled overflow
480.406
0,376
0,358
Surface area at FSC (ha)
480,19
432,176 (above tunnel outlet)
5082
Reduced level of FSL (m)
308,5
267,0
Owner
Completion Date
River
Catchment area
(km 2)
Type of Wall
Spillway Type
Full supply capacity
Active capacity
(m 3
(m 3
x
x
106)
106)
Outlet works
1.
7,6
Octagonal reinforced
concrete tower and pipe and
culvert under embankment
Concrete inlet/outlet structure
to tunnel system
2.
Outlet works in concrete wall
comprising two river discharges
and a connection to a conduit
leading to the Stellenboschberg
Tunnel Portal.
DIVERSION WEIRS
Name of Weir
Wolwekloof
Banhoek
8,7 m
11,5 m
335,5 m
434,0 m
Diameter of shaft to tunnel system
4,0 m
Length of Shaft
70 m
1,8 (Upper 80 m)
8,0 (lower 80 m)
160 m
22,0 m3/s
16,4 m3/s
Maximum Height of Weir
Spillway crest level
Diversion capacity of Shaft with
water weir FSL
TUNNELS
Name of Tunnel
Length (km)
Internal dimensions
Design capacity
(m3/s)
PIPELINES
Franschhoekberg
Jonkershoek
Dasbos
12,0
22,6
4,8
5,0
3,95 x 4,27 m
horseshoe
33,5
4,3 and 3,5 m
diameter
27,4 and 13,3
3,5 m diameter
3,5 diameter
14,1
15,7
BERG RIVER SIPHON
STLLENBOSCHBERG/
BLACKHEATH
Length
200 m
17,8 km
Diameter
3,5 m
1,5 m
Capacity
Stellenboschberg
33,5
m3/s
5,15
m3/s
STELLENBOSCHBERG
OUTLET/FAURE
(PROPOSED)
12 km
1,8 m/1,7 m
11,6 m3/s
TABLE 1
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VOëLVLEI DAM AND DIVERSION WORKS
DAM
Name of Dam
Voëlvlei
Nearest Town
Gouda
Distance (km)
7
Owner
DWAF
Completion Date
Raised 1970
River
Off channel storage
Catchment area (km 2)
31
Type of Wall
Earth embankment
Wall Height (m)
9,7
Crest Length (m)
2905 m (north embankment)
1073 (south embankment)
None
Spillway Type
Full supply capacity (m 3 x 106)
Active Capacity
(m 3
x
172,168
106)
164,095
Surface area at FSC (ha)
1573
Reduced level of FSL (m)
79,33
Outlet Works
Outlet Capacity
DIVERSION WORKS
Weir Type
Rectangular reinforced concrete outlet tower and
2 m diameter concrete lined tunnel
Limited by delivery pipeline (273 Mℓ/day
Klein Berg River
Twenty-four Rivers
Hollow buttress
Mass gravity
Max. Height of overflow section (m)
4,1
5,9
Structure Length (m)
126
90
Canal Type
Concrete lined parabolic
Concrete lined trapezoidal
Length (km)
8,2
29,0
20,0
34,0
Capacity
(m3/s)
TABLE 2
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WEMMERSHOEK DAM
NAME OF DAM
WEMMERSHOEK
Nearest Town
Franschhoek
Distance (km)
15
Owner
Cape Town
Completion Date
1957
River
Catchment area
Wemmers
(km 2)
84,2
Type of Wall
Earthfill
Wall Height (m)
55
Crest Length (m)
518
Spillway Type
Full Supply Capacity
Gate-controlled discharge with chute
(m 3
x
106)
58,863
Active Capacity
(m3 x 106)
Surface Area at FSC (ha)
58,776
Reduced Level of FSL (m)
296,7
Outlet Works
296
Circular reinforced concrete tower with two 1067 mm
diameter outlet pipes and one 1067 mm diameter
scour pipe in a culvert through the right flank of the
dam.
TABLE 3
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STEENBRAS SCHEME DAMS
NAME OF DAM
STEENBRAS LOWER
STEENBRAS UPPER
Nearest Town
Gordon’s Bay
Gordon’s Bay
Distance (km)
9
13
1921, 1928*, 1954*
1977
Steenbras
Steenbras
68,6**
29,7
Concrete gravity/arch
Earthfill
Wall Height (m)
28
34
Crest Length (m)
389
Uncontrolled Overflow
550 & 390
(Two embankments)
Uncontrolled Overflow
Full Supply Capacity
(m3 x 106)
Active capacity (m 3 x 106)
33,725
31,770
33,725
26,26
Surface area at FSC (ha)
370
263
Reduced level of FSL (m)
346,5
370,0
Completion Date
River
Catchment Area
(km 2)
Type of Wall
Spillway Type
Outlet Works
*
**
Octagonal concrete tower located
700 m from the dam wall. One 610
mm dia and two 762 mm dia
scours are located in the dam
wall. An 813 mm dia cement
mortar lined steel pipe runs from
the outlet tower through a tunnel
to the treatment plant.
1. Concrete outlet tower with
1 225 mm dia cement mortar
lined steel pipe encased in
reinforced concrete passing
beneath the embankment.
2. Pumped storage scheme tunnel
intake consisting of 19 m x 9 m
screened bellmouth leading to
a control tower with a 3 m x
4,4 m gate at the entrance to
the 4,5 m diameter, 850 m long
low pressure tunnel. This tunnel
discharges to a high pressure
shaft, tunnel and penstock
leading to the power station
turbines.
Dam Raised
Includes Catchment of Steenbras Upper
TABLE 4
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TABLE MOUNTAIN AND SOUTHERN PENINSULA DAMS
NAME OF DAM
HELY HUTCHINSON
DE VILLIERS
VICTORIA
ALEXANDRA
WOODHEAD
KLEINPLAAS
LEWIS GAY
Nearest Town
Cape Town
Cape Town
Cape Town
Cape Town
Cape Town
Simon’s Town
Simon’s Town
Distance (km)
6
4
4
4
6
4
4
City of Cape Town
City of Cape
Town
910
City of Cape
Town
1896
City of Cape
Town
1903
City of Cape Town
1897
Simon’s Town
Municipality
1970
Simon’s Town
Municipality
1951
1896
1903
Disa
Woel
Woel
0,41
0,28
2,61
2,43
1,30
Owner
Completion Date
1904
River
Disa
Catchment area
(km2)
Type of Wall
2,13
Original Disa of
p 15
0,69
Masonry Gravity
Masonry Gravity
Masonry Gravity
Masonry Gravity
Masonry Gravity
Earth
Wall Height
16
28
6
12
38
13
Concrete arch/
gravity
17
Crest Length (m)
532
118
124
173
25
480
160
Overflow (Ogee)
Overflow (Ogee)
Overflow (Ogee)
Overflow (Ogee)
Overflow (Ogee)
0,925
0,243
0,128
0,126
0,954
Uncontrolled
side channel
1,368
Uncontrolled
ogee
0,182
16
4
5
3
10
748,12
654,34
717,46
711,67
732,06
Spillway Type
Full supply
capacity (Mm2)
Surface area at
FSC (ha(
Reduced level of
FSL (m)
TABLE 5
116101684
page
4
265,9
198,86
LAND-EN-ZEEZICHT DAM, SOMETSET WEST
NAME OF DAM
LAND-EN-ZEEZICHT
Nearest Town
Somerset West
Distance (km)
3
Owner
Somerset West
Completion Date
1976
River
Catchment are
Off-channel supplied from Lourens River
(km2)
0,17
Type of Wall
Earthfill
Wall Height (m)
14
Crest length (m)
800
Spillway Type
Uncontrolled earth side channel on left flank
Full Supply Capacity (m 3 x 106)
Active Capacity
(m 3
x
0,451
106)
0,451
Surface Area at FSC (ha)
6
Reduced Level of FSL (m)
105,5
Outlet Works
Outlet box and reinforced concrete encased pipe
under embankment with downstream control valve
TABLE 6
116101684
page
MAIN FEATURES OF THE PROPOSED SKUIFRAAM DAM
Gross storage capacity (million m 3)
126,4
Net storage capacity after allowance for
sedimentation and dead storage (million m 3)
Full supply level (FSL) m
124,4
RL 250
Water surface area at FSL (ha)
525
Lowest drawdown level (m) (pump station)
RL 213
Lowest river outlets (m)
RL 206
Dead storage volume (million
m 3)
Provision for sedimentation (million
1,4
m 3)
0,6
Non overspill crest level (m)
RL 254
Area at non overspill crest level (ha)
558
Design high flood level at dam (m)
RL 251,75
River bed level (m)
RL 195
Lowest foundation level (m)
RL 185
Maximum height of wall above river bed level (m)
59
Length of dam wall (m)
990
Length of spillway crest (m)
150
Rated total capacity of outlet works for damage
control IFR (m3/s)
Gross catchment area (km 2)
160
77,03
Mean annual precipitation over catchment area
2 462
Gross natural mean annual runoff (million m 3)
139
Gross present day mean annual runoff (million m 3)
1:50 firm yield to CCT (million m3)
115,6
81
TABLE 7
116101684
page
ANNEXURE “B”
116101684
page
SUPPLY (Continued)
YEAR
ALBION
SPRING
TABLE
MOUNTAIN
STEENBRAS
Ml
Ml
Ml
WEMMERS/
HOEK
FAURE
EX
FIRLANDS
VoëLVLEI
Ml
Ml
Ml
RIVIERSONDEREND
WEMMERS/
HOEK
BLACK/
HEATH
FAURE
Ml
Ml
Ml
BROOK/
LANDS
SILVER/
STREAM
WITZANDS
Ml
Ml
Ml
STRAND
S/WEST
Ml
1982
1964
3451
32586
57329
68041
488
4966
1983/84
1644
5968
43014
104434
66684
638
48275
1984/85
1615
3399
30223
79917
42937
0
22665
1985/86
1122
3325
34062
69263
44673
0
47373
1986/87
1485
4577
36093
67447
43130
0
51635
1987/88
1443
4205
36258
69508
38050
0
64516
1988/89
1461
4005
34067
62421
49196
225
73112
1989/90
1167
3650
33755
66916
48431
1332
75204
1990/91
605
2915
39183
71266
51853
6806
87329
1991/92
515
4428
37327
66871
60320
3043
81905
1992/93
270
5290
34541
77787
57369
1522
85340
1993/94
0
3713
38291
59941
71489
13616
89603
2623
1994/95
355
3472
30576
61837
78217
13086
61783
47838
1995/96
867
3773
32790
57529
63212
13857
64022
48433
1996/97
1195
4764
30698
58960
56445
11079
80735
38644
1997/98
999
4688
36019
73033
61582
7829
63724
54487
1222
1693
3007
974
1998/99
673
4069
37373
41493
28778
53053
30849
75989
48014
1227
1471
2588
1866
1999/2000
725
3273
34095
64768
24882
55218
14262
86291
48206
937
819
1350
1159
2000/2001
547
3093
30113
49794
30815
45560
22233
58634
47356
780
74
4467
1167
2001/2002
143
4223
29086
64351
31012
52076
13326
59580
38427
2156
689
5048
1220
2002/2003
2418
3405
31944
63378
17234
45842
10962
64686
55588
1181
653
5558
9398
2003/2004
101
3320
32748
37707
23933
51471
34384
83406
41276
8307
733
5827
6899
2004/2005
9368
4432
30366
47532
45040
46868
18845
57033
23924
1249
479
6013
5882
TABLE 8
116101684
page 23
MONTH
2003/2004
JULY
AUGUST
SEPTEMBER
OCTOBER
NOVEMBER
DECEMBER
JANUARY
FEBRUARY
MARCH
APRIL
MAY
JUNE
TOTAL
SUPPLY
A: MONTHLY CONSUMPTION
DAILY AVG.
MONTH
Ml
Ml/day
2004/2005
21776
702 JULY
20338
630 AUGUST
21494
716 SEPTEMBER
25689
829 OCTOBER
30705
1023 NOVEMBER
30493
984 DECEMBER
32498
1048 JANUARY
31805
1136 FEBRUARY
30598
987 MARCH
23772
792 APRIL
24797
780 MAY
21908
730 JUNE
315873
865 TOTAL
Ml
21825
21754
23609
23742
26069
27722
26677
23904
25287
21767
20737
19301
282394
DAILY AVG.
Ml
704
707
787
766
769
894
860
854
816
726
669
644
774
TABLE 9
116101684
page 24
RAINFALL
B: ANNUAL
RAINFALL
1981
VOEL/
VLEI
STEEN/
BRAS NO 1
WEMMERS/
HOEK NO 1
WOOD/
HEAD
NEWLANDS
WYNBERG
MTN NO 1
mm
560.2
mm
1153.3
mm
1000.7
mm
1469.0
mm
1451.0
mm
1347.0
1982
673.4
760.4
838.4
1391.1
1310.0
1278.7
1983/84
940.6
1687.1
1776.4
2643.9
2606.1
2515.6
1984/85
661.3
1024.3
1182.0
1526.5
1704.6
1558.8
1985/86
519.8
999.7
1027.5
1609.7
1693.6
1623.4
1986/87
530.1
1083.5
1017.8
2331.6
1954.6
1844.7
1987/88
575.4
988.8
805.9
1806.1
1761.7
1595.2
1988/89
618.8
1142.4
961.6
1407.7
1509.0
1290.9
1989/90
699.4
1222.7
1158.3
1662.5
2144.2
1528.0
1990/91
492.4
916.1
1174.0
1341.3
701.8
1259.0
1991/92
696.5
1179.8
1396.4
1777.5
2144.6
1775.9
1992/93
634.2
1330.2
1112.5
1542.8
1777.3
1950.7
1993/94
538.5
923.6
1161.5
1417.2
1853.0
1474.0
1994/95
399.5
803.6
539.5
1181.0
1055.5
1009.8
1995/96
654.1
1126.0
1198.9
1476.0
1743.0
1428.8
1996/1997
681.2
1191.9
1117.0
1979.0
2006.0
1668.6
1997/1998
454.3
913.0
676.3
1747.6
1579.6
1618.4
1998/1999
463.0
906.0
706.7
1462.4
1279.3
1281.7
1999/2000
405.2
843.3
769.6
1354.5
1503.0
1291.7
2000/2001
465.3
889.9
749.8
1485.7
1520.0
988.8
2001/2002
1809.7
1405.2
1351.6
2646.1
2570.6
1536.8
2002/2003
375
798.3
711.3
1827.5
997.5
787.7
2003/2004
404.7
841.6
685.8
2195.8
1634.5
892.4
2004/2005
551.7
1122.3
903.1
1837
1969.7
1288.3
TABLE 10
116101684
page 25