Desalination & Reuse Handbook - Flipbook - Page 11
THE YEAR IN SCARCITY
Tariffs
Cape Town (South Africa)
The cost of combined water and wastewater services for a
benchmark monthly consumption of 15 m3 rose by almost
380% in Cape Town between 2017 and 2018, mostly due
to punitive rates for higher usage intended to reduce
demand. The unit cost of water increases significantly at
each threshold, with block four usage (>20 m3/month)
costing over ten times block one (0-6 m3/month). Rate
increases and water usage restrictions have dramatically
reduced the number of users consuming water at higher
levels.
Legend
Fixed charges per month
Water: $0.00
Wastewater: $0.00
Sales tax
Water: 0.14
Wastewater: 0.14
Volumetric charges: increasing
Water: Block (m3)
0.0-6.0
6.0-10.5
10.5-20.0
>20.0
$/m3
1.91
3.34
7.26
21.79
Wastewater: Block (m3)
0.0-4.2
4.2-7.4
7.4-14.0
>14.0
$/m3
1.63
2.83
6.25
7.63
Benchmark tariff (15 m3/month)
Variable water costs
Variable wastewater costs
Water sales tax
Wastewater sales tax
$7.19/m³
3.94
0.55
2.36
0.33
Source: Global Water Leaders Group
Unlike previous years, changes in agricultural water use did not exceed allocated quantities. The release of 10 million m3 of
water from an agricultural reservoir to the city was a significant contributing factor in Day Zero projections being pushed
from April to May in early February, 2018.
A side effect of the City’s dramatic demand management has been a reduction in tariff income, which had previously
relied on higher volume users to subsidise loss-making lower usage bands. Following a collapse in higher-volume domestic
usage, the City is re-evaluating its tariff structure to ensure full cost recovery across all usage bands, with some exceptions
for the lowest income households.
The City also upgraded its monitoring and regulation of water pressure, piloting an advanced pressure management
technology in 15 sections of its distribution network to reduce pressure by around 25% at critical points. In the network
overall, total water losses have decreased less quickly than total water running through the network, resulting in a slight
increase in losses as a percentage. The City attributed an average of 55,000 m3/d in water savings to pressure management.
Supply augmentation had a limited impact on Cape Town’s ability to last the summer: just three desalination facilities
with a combined capacity of 15,000 m3/d were completed, and delays in procurement and commissioning meant that
these came online only after the worst of the crisis had passed. It was a clear demonstration that the relatively drawn-out
procurement process and costly product water make desalination a poor short-term solution to water scarcity. The City
of Cape Town sees 300–350,000 m3/d of supply augmentation as necessary to avoid dams falling to restriction levels
at the end of summer, which is set to come from 100,000 m3/d in additional groundwater abstraction, 70,000 m3/d in
wastewater reuse capacity, and 120–150,000 m3/d in desalination capacity.
Best-case scenario planning delayed the procurement of a large desalination plant in 2015, when it was decided that the
water would not be necessary until after 2020. The worst-case scenario projections of Day Zero may have overplayed the
likelihood of water supplies running out, but the pivot to a more precautionary approach to water supply and sustainability
is one that drought-stricken regions worldwide can learn from.
Water Supply Augmentation in Cape Town: Having weathered several years of drought, Cape Town is committed to
augmenting its water supply by 350,000 m3/d. Assessment of potential water sources’ drought vulnerability, implementation
speed, and cost led the city to deprioritise seawater desalination due to high water costs and a projected 36 month
development period. Wastewater water reuse for groundwater recharge is seen as being cheaper and faster than desalination,
and is effective in maximising existing water supplies. Surface water is the cheapest option, but vulnerable to drought and
slow to augment. Abstraction of additional groundwater resources - which currently goes largely untapped - represents the
city’s cheapest and fastest source of short-term water supply augmentation.
New water sources to be tapped in Cape Town (projected cost)
100,000 ($0.47/m3)
120,000 ($0.81-$2.44/m3)
70,000
($0.51/m3)
60,000
($0.34/m3)
Groundwater abstraction
Seawater desalination
Wastewater reuse
Surface water
abstraction
Source: City of Cape Town
3
