Water and power

2012-07-14 09:48

Some time ago, Yolandi Groenewald, commissioned by Greenpeace, wrote a well-balanced article headlined “Coal’s hidden water cost to South Africa”.

Following this well-researched but potentially sensational account, Greenpeace charged: “The impact of new coal-fired power stations on a future water crisis hasn’t been adequately taken into account.”

Greenpeace repeated the urban legend that as a result of water supply to Eskom, the country will have a water shortfall of 17% by 2030. This is not true.

Water is unevenly spread throughout the country and statements like this are not properly contextualised.

Such predictions can only materialise if nothing is done to develop and manage our water resources to maintain a positive balance of available water with the projected increase in demand.

Eskom has been putting the theory of efficient water use into practice for many years.

In South Africa, a “once-through” cooling system using large quantities of water was never applied, but the evaporation process of “wet-cooling” was adopted.

With each new power station that was built, better processes were used and the amount of water required for the generation of a unit of electricity decreased.

The most significant initiative by Eskom was to implement dry-cooling. Kendal and Matimba power stations were built as dry-cooled stations, and will now be joined by Medupi and Kusile.

Coal-based impact on water use comes from environmental legislation that forces Eskom to clean its emissions to decrease its impact on air quality. This uses water.

Eskom is looking at alternative technologies that use less water, but some alternative methods to generate power also require comparative amounts of water. Concentrated solar power plants convert the sun’s energy to steam and need cooling.

Nuclear power stations at the coast could use sea water for cooling and will not impact on scarce freshwater resources.

We have also conducted reconciliation studies on the use of water by all Eskom power stations and the associated use by coal mines, including the future use of the Kusile power station.

Main measures that need to be implemented are eradication of unlawful use by irrigators; implementation of water saving by the urban sector of 15%; the treatment and reuse of acid mine water; and the building of phase two of the Lesotho Highlands Water Project in the Vaal water supply system.

With all of these measures in place by 2020, there will be sufficient water in the system to well after 2040.

The implementation of these strategies is being monitored on a six-monthly basis by a strategy steering committee.

Although Eskom accounts for only 2% of total water use in the country, the 2012 figures for the Vaal River system constitutes about 9%.

The use for Kusile will be about 16 million cubic metres a year, which will increase the Eskom use from this system by about 5%, but will only increase the total demand in the system by 0.4%.

Eskom use will peak in 2022 and decrease to between 250 million and 290 million cubic metres in years to follow. Even with Kusile operating, Eskom will by 2030 use less water.

The reconciliation strategy for the Crocodile (west) addressed the future water requirements for the coal-based developments on the Waterberg coalfields.

This potential water use could all be supplied from purified water from the growing northern areas of Gauteng that drain into the Crocodile River, and none of the existing water rights for other users out of the system would be jeopardised.

»Molewa is the minister of water and environmental affairs

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