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Iceberg proposal as a new water source for Cape Town

28 June 2018
Iceberg proposal as a new water source for Cape Town

Using icebergs as a water source sounds like something from a sci-fi movie, but it is more of a reality than most of us would think

South African marine salvage expert Nick Sloane, who sprang to international fame when he refloated the massive Costa Concordia wreck in the Mediterranean in 2013, is hatching a plan to tow icebergs to Cape Town to ease the city's water crisis. It may sound off the wall, but Sloane says the iceberg proposal has generated enough interest among experts for him to hold a seminar on the project in Cape Town in mid-May.

Engineers and University of Cape Town academics have assessed it

Dr Chris von Holdt from Aurecon's advisory practice, who has done a technical assessment and economic evaluation of the iceberg proposal, said: "I believe it has sufficient technical feasibility and economic merit to be considered seriously as a supply option for filling the supply gaps during periods of drought."

Sloane, from Cape Town, with the two other members of his Southern Ice team, French engineer Georges Mougin and Norwegian glaciologist Dr Olav Orheim, will be joined by global experts at the seminar to decide: "Is the iceberg project a 'Go' or a 'No-Go'?"

"I am driving the campaign - mainly due to our water crisis - and the fact that now these icebergs are tracked and found about a third of the distance to Antarctica, only around 1 200 nautical miles away," Sloane said. Although the City has projects underway to increase Cape Town's water supply, Sloane says these will still leave a gap of around 100 million litres a day.

Not just any old iceberg

Estimates are that more than 2 000 billion tons of icebergs break off the Antarctic ice-shelf every year and drift with ocean currents until they melt in warmer water. The Southern Ice team hopes to capture icebergs that have drifted northward to Gough Island, about 2 700 km south west of Cape Town. Not just any iceberg will do. Orheim, who was the director of the Norwegian Polar Institute from 1993 to 2005, has analysed 271 000 icebergs, of which only 7% would be suitable. The shape must be tabular, with a flat top and steep sides, and a thickness of 200 to 250 metres. Once a suitable iceberg has been assessed, it can be "captured".

Two tugs are used to encircle the iceberg, pulling an enormous piece of geotextile material to form a "skirt" around it that reaches down the sides of the ice beneath the water level.

A third tug stands by as back up. A tanker will then tow the iceberg, with the distance between the tanker and the ice about 1.5 kilometres. The two tugs will steam alongside, ensuring the iceberg stays on its course. The destination will be Cape Columbine north of Saldanha Bay. Because of its big draught, the iceberg cannot go close inshore but will "anchor" itself on the seabed about 40km offshore.

It will then be moored using a system similar to that used by specific offshore oil rigs.
Orheim said getting the iceberg into a useable form of water was still "part of the unknowns", but some ideas have been proposed.

One proposal is for helicopters to lift machinery from a barge onto the iceberg, where it will be assembled and used to "mine" the ice similar to open cast mining. The harvested ice would result in a pool of melted ice inside the saucer-like "mine", which would be pumped into tankers and taken to a discharge point on shore. The team says the iceberg would supply 55 million kilolitres a year, more than 150 million litres a day. Orheim estimates about 30% of the iceberg would melt during the towing.

Cheaper than desalination

Orheim said an advantage of the iceberg scheme is that that it could be used when there was a need for water, and stopped when there was not. Sloane said the latest price for water from a permanent desalination plant in Cape Town was around R20 a kilolitre.

"We are looking to deliver pure Antarctic water for less than R30 a kilolitre. The advantage of iceberg over desalination is that long-term desalination projects require a 20-year commitment to repay the R10bn needed to fund it before one drop of water is produced. And this is without the high Eskom tariff risks, and the environmental damage caused by millions of litres of brine into the ocean every day," Sloane said.

UCT academic Dr Kevin Winters of the Future Waters Institute said a range of scientists and engineers had become involved in the iceberg proposal.

"I love it. The narrative we have at the moment about icebergs as a water source is that they are too far away, it's too expensive, too complicated - it's all about the 'cants'. So this proposal challenges that narrative and let's find out more," winter said.

Asked to comment, the city council said it would not consider the iceberg proposal as a new water supply because of the "risks, complexities and expense involved in such operations".

Water the lifeblood of agriculture in the Eastern Cape

It is not only parts of the Western Cape that require relief from a water shortage. Most of the Eastern Cape has a severe water shortage at present, and there is no immediate relief from the current drought which poses a huge risk on agriculture in the Eastern Cape.

Will this iceberg proposal become a feasible alternative to desalination for the Eastern Cape? Alternative water sources need to found not only for the immediate future but also to bring relief of future water shortages, as this will become a regular, if not a permanent problem with the current population growth. This will continue to create challenges for the agricultural sector.