Peter Johnston, a climate scientist at the University of Cape Town, reports that while city officials are not currently considering the plan, he thinks it could be worth a shot. As he says, an iceberg about 100 million tons (91 million metric tons) in size, could ideally be found within a thousand miles (1,610 kilometers) of Cape Town. The iceberg, according to the plan, would be harnessed with a big belt and slowly towed by tanker, aided by ocean current and, perhaps, kite sails. Once the iceberg was moored offshore, a lattice steel structure lined with plastic would capture fresh water, pumping it into pipes that would carry the water to shore. After filtering, it could be channeled into the parched city's water supply system at, according to Sloane, an overall expense that would be half the cost of desalinization.
"If we did get one of these medium-sized icebergs, we're looking at supplying about 20 percent of the city's water needs per day at a cost of about a dollar per each 100 gallons (378 liters)," Johnston says.
A similar proposal about a year ago by an Abu-Dhabi-based firm, suggested relieving water shortages in the United Arab Emirates by towing an iceberg holding 20 billion gallons (76 billion liters) of fresh water to the coast of Fujairah, on the east coast of the Gulf of Oman. According to the firm, once anchored here, the iceberg could meet the needs of a million people for five years, as well as offer a tourist attraction and change the local climate to spur more rainfall. Here's a video presentation outlining the proposal:
But run an iceberg-towing scheme by a glaciologist and you're likely to have some very cold water splashed on your face.
"The scale is just really daunting," says Ted Scambos, lead scientist at the National Snow and Ice Data Center at the University of Colorado at Boulder. "Even tiny little icebergs are huge and most of the mass is below the water. It dwarfs the ship, so the idea of dragging it seems unrealistic."
In fact, there are Canadian companies that specialize in moving icebergs away from offshore platforms where they might strike and damage facilities. But those efforts, which use massive cables that are then nearly eaten away by friction, involve smaller-sized icebergs and the distances they are towed are miniscule compared with the distance that icebergs would need to be hauled to relieve areas with water shortages.
The shape of the iceberg is another factor. As Grant Bigg, a professor of Earth systems at Sheffield University in the U.K. and author of the 2015 book, "Icebergs", points out, an irregularly shaped iceberg "might roll over or break up," so you'd be better off selecting a tabular-shaped iceberg, with vertical sides and a flat top, like the ones more commonly found in the Southern Ocean.