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Transporting Potable Water by Sea

iceberg
Image courtesy USCG

By Harry Valentine 09-22-2020 03:48:34

The combination of occasional drought conditions in some regions and excess rainfall in other regions invites exploration into moving massive volumes of potable water between nations. Such movement would require exploration of suitable maritime technologies by which to undertake the task.

A combination of factors - including changing weather patterns - produce changing volumes of rainfall in many locations. For example, at the moment the reservoirs that hold potable water for City of Cape Town, South Africa are at the brink of overflowing. Three years ago, the same region faced a severe drought that practically emptied all of its water storage. While there was much discussion about water desalination and treatment of sewage water for re-use, present rainfall conditions would have resulted in idled desalination plants - which would have been built at very high cost.

In the Gulf region, ongoing desalination of seawater has steadily increased salinity, thereby increasing the energy required for more desalination. It led to one of Emirate nations even considering the potential of towing an iceberg from the Antarctic into the Gulf to provide potable water. 

These examples highlight the potential attractiveness and economics of bulk transportation of potable water from regions that have an abundance to regions of occasional drought and increasing seawater salinity. 

The Iceberg Option

The combination of winds, ocean currents and tidal currents provide propulsion for icebergs that gouge the seafloor while sometimes entering into bays and inlets in Eastern Canada, where they slowly melt. Most often, the presence of an iceberg either impedes the movement of fishing vessels or providing a local tourist sightseeing attraction. Teams of tugs are often dispatched to redirect icebergs that would otherwise enter North Atlantic shipping lanes, using extended length steel cables to gently readjust the iceberg’s direction. Future trans-Arctic commercial shipping would likely require tug teams to move icebergs from shipping lanes. 

The biggest tanker ships can carry two million barrels (400 million liters) of liquid. Prior to the drought that recently ended, Cape Town’s population of over four million used some 500 million liters of potable water per day. Had the drought lasted longer, Cape Town would have required mega-size tanker ships delivering potable water every day. 
A single iceberg would hold the equivalent water capacity of several hundred tanker ships - hence the attractiveness of towing an iceberg into a bay, where it could melt and be broken up to provide enough potable water for several weeks to several months.

Water from Icebergs

Icebergs entering bays and inlets could provide a future basis by which to obtain potable water for transport. Future technology will need to devise methods to harvest the ice, such as using steam jets to carve manageable chunks from the trapped icebergs. Floating cranes could transfer blocks of ice to barges to inflatable floating reservoirs to prevent or minimize seawater contamination. While hydraulic pumps could transfer potable water into tanker ships, cranes could transfer small blocks of ice into the hold of bulk carrier ships modified to carry either liquid or non-liquid bulk cargo.

While several suitable bays and inlets are available in Eastern Canada for catching Arctic ice, the western coasts of the South Orkney Islands, South Sandwich Island and Prince Edward Island have potential to function as capture areas for icebergs that originate from the Antarctic. The Emirates would be among the prime destinations for potable water originating from the Antarctic region. Recent droughts in South Africa and Brazil could make their ports potential destinations for Antarctic potable water. The volume of water that would need to be transported would require new research and new development into future bulk carrier technology.

Excess Water Regions

Toward the end of the northern winter over the past five years, water levels in North America’s Great Lakes and along the Upper St. Lawrence River have risen to near-record levels, with some officials even considering the situation as a new normal. During this seasonal period, plentiful potable water flows into the ocean from several major rivers. On previous occasions when seasonal water levels were high, entrepreneurs negotiated with relevant authorities to load tanker ships with potable water to be transported to regions experiencing water shortages, but political activists opposed such plans. 

During the southern winter, abundant rainfall occurs over the watershed regions of the Amazon and Congo Rivers, as well as over Indonesia and Malaysia. During the northern summer, abundant rainfall occurs over much of southern Asia between the Arabian Sea and South China Sea. On a seasonal basis and where authorities would allow, there would be potential to transport tanker loads of potable water from regions of seasonal water abundance to regions experiencing full or partial drought. The sheer volume of water requiring seasonal transportation would require development of new mega-capacity maritime tanker transportation technology.

The Flexible Vessel

In response to oil shortages during the 1970s, a group of maritime designers theorized a flexible and inflatable bulk liquid tanker built using the methods of automotive tire construction. Since that period, advances have been made in the development of super-high-strength woven fabric materials made from Kevlar and fiberglass, which could be embedded with a water-proofing compound. Such a raft-like vessel would offer the prospect of construction to extreme length and cross-section dimensions.

An alternative ocean-going, extended-length liquid bulk carrier could combine a series of rigid tanker hulls linked by flexible, inflatable sections. This combination could deliver an exceptional vessel length of perhaps 12,000 feet and a draft of 75 to 90 feet. Such a vessel could transport a massive volume of potable water from a region with an abundance to a region experiencing drought, with Emirates nations being a potential destination.

Conclusion

The combination of excess water in some regions and drought in other regions that usually experience precipitation increases the attractiveness of transporting massive volumes of water by sea. It could be a lower cost alternative to building desalination plants that could remain idle for years at a time and only used during drought.  

Harry Valentine is a regular contributor to The Maritime Executive.

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.