Cape Town Water Outlook 2018 Updated 20 May 2018 Department of Water and Sanitation City of Cape Town
Cape Town Water Outlook 2018
Updated 20 May 2018
Department of Water and Sanitation
City of Cape Town
What happened to Day Zero?
The level of water in the dams supplying Cape Town will not drop below 13.5% this year if restrictions are adhered to and assuming rainfall similar to last year.
Monitoring dam levels (inflow, evaporation and withdrawals) and managing withdrawals is key to maintaining the integrity of the system and getting through
the drought.
Day Zero calculation is based on conservative assumptions of consumption beyond the City’s control, including releases to agriculture, urban demand,
evaporation and rainfall. The projected Day Zero date is based on the previous weeks’ average volume extracted from the system, extrapolated into the
future to the intersection point of 13.5% dam level without adjusting for potential rainfall, reduction in demand etc. Unlike previous years, DWS stopped releases
to irrigation boards once allocations were reached late in January onwards thus dramatically reducing drawdown from the system. Furthermore, a sizeable
transfer was made by an adjacent catchment area in February, also reducing the drop in dam level. These two aspects, as well as a reduction in urban
demand led to the Day Zero date moving well beyond the anticipated start of the rainy season in 2018.
22 January 2018 - Projection of 13.5% dam level = 12 April
2018, Weekly drawdown = 1.4%, Agriculture : CCT, 48% : 47%
13 April 2018 - Projection of 13.5% dam level beyond July 2018,
Weekly drawdown = 0.5%, Agriculture : CCT, 15% : 76%
Cape Town’s water is part of an integrated system
Cape Town gets its water from a system of dams that supply agriculture and other urban areas. The current system is heavily dependent on rainfall. This complex system is managed by the national Department
of Water and Sanitation. About a third of the water in this system is used by agriculture and 7% by other urban areas (smaller towns).
2015
2016 2017
The National Department of Water and Sanitation
is responsible for planning and implementing
water resources schemes to meet water demand
for cities, industries, mining and agriculture.
The Department plans at a 1 in 50 year level of
assurance. This means that during droughts with a
severity of 1:50 years or more, restrictions need to
be imposed to reduce demand.
The current drought is much more severe than a 1
in 50 drought event. The best estimate of the
return interval of the meteorological drought in
the region of WCWSS dams is 311 years, with 90%
confidence that it actually falls between 105 and
1280 years1.
The next augmentation scheme for Cape Town
was planned for 2022/3 and is being accelerated
by the national Department. This scheme
(augmentation of Voelvlei Dam) is unlikely to be
ready before 2021.
Why is there a shortage of water in Cape Town?
Cape Town is experiencing an unprecedented multi-year
drought event.
Rainfall in the Cape Town area is variable. Wetter and drier years are common.
16 global climate models predict an overall decline in rainfall for Cape Town in the
future with more dry years and fewer wetter years.
A scenario in which it does not rain the future or in which it only rains at 2017 levels is
unrealistic.
Will it rain again? Yes.
Historical (grey) and predicted (pink) annual rainfall for Cape Town, according to
16 global climate models. Yellow dots below indicate rainfall incidents equal to or
lower than 2017 rainfall.
Sources: 1Facts are few, opinions plenty… on drought severity again (January 2018)
Is Cape Town’s drought the new normal? (1 November 2017)
Why Cape Town’s drought was so hard to predict (19 October 2017)
www.csag.uct.ac.za
284 329 368 361 275 184 125 77 83 94 136 201
1010 1100 1100 1218 1039 979 856 821 764 794 884 917
254 737 983 1028
846 451
55 28 27 27 28 136
0500
10001500200025003000
Nov
-17
Dec
-17
Jan-
18
Feb
-18
Mar
-18
Apr
-18
May
-18
Jun-
18
Jul-1
8
Aug
-18
Sep
-18
Oct
-18
Dai
ly c
on
sum
pti
on
ML
D
Evaporation - Maximum Urban (DWS average of last 5 years) Agriculture unrestricted
284 329 368 361 275 184 125 77 83 94 136 201 556 605 605 670 571 538 471 452 420 437 486 504 102 295 393 411
339 181
22 11 11 11 11 55
0500
10001500200025003000
Nov
-17
Dec
-17
Jan-
18
Feb
-18
Mar
-18
Apr
-18
May
-18
Jun-
18
Jul-1
8
Aug
-18
Sep
-18
Oct
-18
Dai
ly c
on
sum
pti
on
ML
D
Evaporation - Maximum 45% restricted Urban Agriculture 60% restricted
RESTRICT TO
Demand management through DWS restrictions
Demand management: Both the City, other urban and agriculture
must adhere to the restrictions imposed on the system
While Cape Town has significantly reduced its demand (measured here as production from the treatment works),
from a peak of 1200 Ml/day in 2015 down to nearly 500 Ml/day, a further reduction in demand is needed to below
450 Ml/day immediately due to not meeting the 500 Ml/day target since July 2017
For Cape Town, this means that demand must be
managed down to get below 450 Ml/day
Further measures are being put in place to reduce demand, including:
• punitive drought tariffs
• demand management devices & flow restrictors
• more aggressive pressure management
Demand reduction is saving >400 Ml/day Feb 2017 = 900 Ml/day Feb 2018 = 500 Ml/day
Demand management: Cape Town has done really well, but
we have to reduce to 450MLD
-
50
100
150
200
250
300
350
400
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
WaterintonetworkLitresperpersonperday(basedonpopulationinservicearea)
BuffaloCity
NelsonMandelaBay
Mangaung
EkurhuleniMetro
CityOfJohannesburg
CityOfTshwane
eThekwini
CapeTown
(Allmetros)
(based on litres per person per day, population in service area)
The drought affects the city’s finances in two primary ways: 1. Reduced sales means that city income is reduced because tariffs are volume based. 2. Additional expenditure is required to increase availability of water. New sources of water are more costly than the water obtained from the existing dams. This increases both capital and operating costs.
Demand management: Punitive tariff structure
Existing Restriction Water Tariffs 2017/18 (ex VAT)
Level 1 Level 2 Level 3 Level 4 Level 5 Level 6
Step 1 [0-6kl] 4.00 4.00 4.00 4.00 18.75 26.25
Step 2 [6-10.5kl] 15.57 15.57 15.57 15.57 26.25 46.00
Step 3 [10.5-20kl] 18.22 20.04 21.87 22.78 46.00 100.00
Step 4 [20-35kl] 26.99 32.65 36.43 38.32 100.00 300.00
Step 5 [35-50kl] 33.33 45.00 61.66 99.99 300.00 800.00
Step 6 [+50kl] 43.97 97.71 209.29 265.12 800.00 800.00
Commercial 19.63 21.59 23.55 24.54 37.50 50.00
Moving towards a resilient tariff means we need to:
1. Recover full costs including cost of water resilience program and adequate depreciation. It is a legal requirement to balance budget
2. Retain affordability for indigent and less affluent households and improve payment levels
3. Increase resilience of tariff to shocks (greater revenue stability in face of drought conditions)
4. Tariff reflects value of water and supports sustainability
Punitive tariffs discourage high water usage & support a sustainable water service
See Annexure B of Water Outlook for details on 2018/19 Tariff increase
Augmentation - considerations
Augmentation schemes are a far more
expensive source of water than runoff
from rainfall. The volume of runoff
cannot be easily augmented in short
time periods and is dependent on
rainfall patterns. Under poor rainfall
conditions like 2017 we would require
augmentation of ~770 MLD to match the
volume of runoff. Despite all
augmentation efforts, the supply scheme
is vulnerable to poor rainfall.
As can be seen the cost per kl of water
from other sources vary considerably.
The cost of bulk water, waste water and
reticulation is common so the costs can
be compared to the cost of runoff which
is ~R5.20/kl vs temporary desalination at
>R40/kl.
R 0 R 10 R 20 R 30 R 40 R 50
temporary desalination
temporary water re-use
groundwater extraction - TMG
permanent desalination
permanent re-use
groundwater extraction - sandy aquifer
treated surface water- historical Estimated cost ranges for treated water by source (R/kl)
0
200
400
600
800
2018
Pla
nned
augm
enta
tion
2019
Pla
nned
augm
enta
tion
500M
LD
2015
run
off
2016
run
off
2017
run
off
Ave
rage
run
off
Wet
win
ter
runo
ff
Equivalent annual inflow (millions of m3)
Augmentation - Advice from International Review (November 2017)
1. Assuming it will not rain again is not realistic
2. Prioritise ground water (Cape Flats Aquifer and Table Mountain Group Aquifer)
3. Do not pursue temporary desalination and reuse
4. Permanent Re-use is cheaper than desalination and may be quicker to execute
5. Plan and execute permanent desalination at an optimum scale
6. A turnkey approach for desalination with a water purchase agreement will yield
the lowest cost per unit of water
7. Do not delay decisions on permanent reuse and desalination.
Yield, cost, timing inform priorities
Indicativetargettime-framestoimplement
Timetoimplement(monthsfromafirmcommitmenttoproceed)
Yield(millionlitersperday)
0
100
200
300
0 12 24 36 48
Ground(100)
Reuse(70)
Desalination(120)
Surface(60)
0
5
10
15
20
0 100 200 300 400
TargetUnitCostsanduncertainty(Randperthousandliters)
Additionalsupply- Millionliters perday(MLD)
Ground
+100
Re-use
+70
Desalination
+120Surface
+60
+50%
+33%
+25%
+20%
• Surface water is least costly, but not resilient to drought;
• Groundwater is more drought resilient, and quick to provide additional water into the system;
• Permanent Desalination is very costly and cannot be implemented quickly BUT it is the only unlimited
new source of water into the system not reliant on rainfall;
• Re-used water is less costly than desalination, and is necessary to maximize value from the diversified
supply mix which is considerably more expensive than single source surface water.
The New Water Program – long-term plan
• Current existing augmentation includes transfers, springs & rivers, existing groundwater (Atlantis) and temporary desalination; • TMG and CFA are both programmed to provide yield in terms of phase 1 license conditions but over a longer period than
previously reported. Groundwater planned for sustainable yield of more than 100MLD, able to provide ~3x more during drought; • Permanent desalination and re-use in planning, each in the order of 100MLD sustainable yield.
See Annexure A of Water Outlook for details of change in augmentation program
0
20
40
60
80
100
120
140
160
180
0
50
100
150
200
250
300
350
400
450M
ay-1
8
Jun-
18
Jul-1
8
Aug
-18
Sep
-18
Oct
-18
Nov
-18
Dec
-18
Jan-
19
Feb
-19
Mar
-19
Apr
-19
May
-19
Jun-
19
Jul-1
9
Aug
-19
Sep
-19
Oct
-19
Nov
-19
Dec
-19
Jan-
20
Feb
-20
Mar
-20
Apr
-20
May
-20
Jun-
20
Jul-2
0
Aug
-20
Sep
-20
Oct
-20
Nov
-20
Dec
-20
Jan-
21
Feb
-21
Mar
-21
Apr
-21
May
-21
Jun-
21
Jul-2
1
Aug
-21
Sep
-21
Oct
-21
Nov
-21
Dec
-21
Cum
ulat
ive
volu
me
(mill
ions
of c
ubic
met
ers)
Dai
ly a
ugm
enta
tion
(MLD
)
Provisional Future Augmentation Programme May 2018 - December 2021
Cumulative volume Springs & rivers Atlantis Emergency desalination
TMG Ground Water Atlantis & Silverstroom Add Permanent desalination Permanent re-use
BRVAS Cape Flats Aquifer Temporary re-use
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
JA
N-1
8
FE
B-1
8
MA
R-1
8
AP
R-1
8
MA
Y-1
8
JU
N-1
8
JU
L-1
8
AU
G-1
8
SE
P-1
8
OC
T-1
8
NO
V-1
8
DE
C-1
8
JA
N-1
9
FE
B-1
9
MA
R-1
9
AP
R-1
9
DA
M L
EV
EL
MO
DE
LLE
D
Restricted, 100% 2017 Restricted, 50% rainfall Restricted, Average rainfall
Average rainfall
The impact of rainfall is such that other sources are insignificant in the short term
2017 rainfall
50% of 2017 rainfall
Summary
1. Continue demand management to reduce dam drawdown (in line with NDWS restriction 450MLD required);
2. Manage and monitor dam behaviour;
3. Fast-track augmentation:
• Decisions under consideration by the City on optimal augmentation types, volumes, methods;
• Groundwater projects (Atlantis, Cape Flats and TMG Aquifers) have been prioritised;
• Aquifer recharge projects from treated wastewater under development;
• Long-term Permanent Re-use project under development;
• Long-term Permanent Desalination under evaluation in terms of siting, optimum yield & procurement method;
4. Manage financial impacts through appropriate adjustments to the tariff structure and level. There is a high degree of
uncertainty related to future tariff revenues as a result of significant shifts in demand patterns and a steeply inclining block
tariff;
5. Improve coordination and leadership within and between spheres of government;
6. Improve information flows and consistency of messaging; actively engage citizens and stakeholders to encourage
active citizenry and stakeholder partnerships to jointly solve problems.