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Chapter 3: Engineered Water
WATER-SENSITIVE URBAN DESIGN
Cities of the future need to reduce water pollution and re-integrate the water
cycle back into town-planning. Current designs dominated by hard surfaces
and channelled storm water rush water and pollution out of the city and into
the nearest river or bay. ‘Greening’ the city with softer, living surfaces and
slowing down water to allow infiltration, helps to recharge local groundwater
and reduce pollution in rivers. Water sensitive cities encourage more recycling
and re-use of water. And they are greener and more pleasant places to live!
Perth and Philadelphia are examples of cities that have started using water
sensitive urban design.
37%
OF WATER IN OUR
URBAN PIPED WATER
SYSTEMS LEAKS OUT
OR IS USED ILLEGALLY
Addressing leakages and illegal off-takes
Research conducted by the Water Resource Partners (WRP) showed that the level
of leakages and illegal off-takes (non-revenue water) from our urban reticulation
systems averages 37%. This is fairly typical of leakage losses worldwide – especially
from ageing infrastructure.
If we could reduce this loss to those of a world leader like Denmark (5% leakages),
then we would be able to close the gap between supply and demand without
expensive investment in new infrastructure. A proactive investment in our existing
infrastructure, and programmes to reduce the leakages and illegal off-takes is
urgently required along the full cycle – from treatment plant to tap.
Towards this, the DWS is training 15,000 new plumbers in a dual attempt to
minimise losses and create jobs. In addition, South Africa needs to make use of
leading leakage detection technology on pressurised systems, which can rapidly alert
operators to leaks and breakages, and detect leaks in old, low-pressure reticulation
systems.
Turn-around
pressure-causing
leaks to generating
power
Power in the pipes
Some of our dams produce hydropower, but even small piped infrastructure with
water under pressure can form part of our renewable energy infrastructure.
Micro-turbines are placed into existing pipes with water under pressure to generate
a renewable energy source known as ‘conduit hydropower’. It is an exciting
development for the water sector that enables multiple users to generate hydroelectricity
for on-site use and, in some cases to supply energy to isolated electricity
demand clusters, as well as to the national electricity grid.
The largest present installation of this kind is from the Caledon-Bloemfontein
potable water supply system that supplies the majority of the water demand in
Bloemfontein. The water is supplied to the Brandkop Reservoir, and excess energy
is dissipated through pressure control valves before being discharged into the
reservoir. The system supplies 96kW/h of energy from a pressurised conduit, to
power up its operational facilities, with a full capacity of 360 kW/h.
There is potential for widespread implementation of this power generation source.
An added advantage is that the harnessing of water for power reduces the pressure
and associated leakage losses in our pipes.
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48 | Water Facts & Futures: Rethinking South Africa’s Water Future