Newsletter and Technical Publications
<Sourcebook of Alternative Technologies for
in Small Island Developing States>
PART B - ALTERNATIVE TECHNOLOGIES
4. TECHNOLOGIES APPLICABLE TO SMALL ISLANDS WITH SPECIFIC PROBLEMS
4.1 Freshwater Augmentation Technologies
4.1.2 Submarine Pipelines
Submarine pipelines are pipes installed underwater and used to import
water to small islands from nearby continents or larger islands with
available water. Conveyance of water may be by gravity flow or by pumping.
Extent of Use
Because of the high cost and maintenance difficulties, this technology
is only used to supply those islands close to continents or larger
islands. Examples include the Seychelles, where five small islands are
supplied through submarine pipelines of up to 5 km in length; Manono,
Western Samoa, which was supplied with water through a submarine pipeline
until the pipeline was damaged during a storm; Fiji, where several small
islands with tourism resorts are supplied through submarine pipelines;
Hong Kong Island, where 50% of the potable water requirement is supplied
by gravity flow from China through twin
1 000 mm diameter, 1.3 km long
steel submarine pipelines with a combined design capacity of 180 000 m3/d,
and 25% of the requirement is piped from nearby Lantau Island (Lamma and
Ma Wan islands, Hong Kong, also receive water by submarine pipeline);
Penang, Malaysia, which receives some of its water supply from the
Malaysian peninsula via twin 3.5 km long, 900 mm diameter submarine
pipelines; and, Xiamen Island, China, which receives about 50% of its
water from surface water storages in the adjacent Fujian Province of
mainland China via a 50 km pipeline and 2.3 km submarine crossing (UNESCO,
Operation and Maintenance
This technology has no special operational requirements. However,
periodic inspection of submarine pipelines is recommended, especially
after storms, to ensure the integrity of the pipelines. Specially-designed
anchor blocks are needed to ensure that the pipeline is not damaged by
tidal flows and storms. In the Solomon Islands, fish have been known to
attack underwater pipelines.
Level of Involvement
The investigation, design, and construction of submarine pipelines
require highly-specialized engineering inputs, and use of this technology
should be based upon favourable feasibility studies that have given
consideration to the pipeline route, water depth, sea floor conditions,
and oceanic currents.
Submarine pipelines are economically feasible only on a small percentage
of islands located close to (not more than a few kilometres from) other
land masses with surplus water resources. Submarine pipelines are
expensive due to their high costs for engineering and construction
Effectiveness of the Technology
Submarine pipelines may be very effective under favourable conditions.
Investigations and feasibility studies are necessary to determine the
costs and risks involved.
This technology is only suitable for small islands close to continents
or larger islands with a surplus of water, and when others alternatives
are severely limited.
This technology incurs minimal operational costs if operated with a
gravity-fed supply. It also permits diversion of water from water-rich
areas to water-poor areas.
This technology incurs very high engineering and construction costs, and
is susceptible to damage due to heavy seas and tidal flows.
Reliance on water from off-island, particularly if those sources are in
a different country, may be a cause of concern.
Further Development of the Technology
Further research into improved pipe materials and installation
techniques might be a consideration.
Lee, Yow Ching 1989. Development of Water Supply in Penang Island,
Malaysia. In: Proceedings of the Seminar on Water Management in Small
Island States, Commonwealth Engineers Council, London. pp. 38-43.
Little, M.J. 1986. New Pipelines on Land and Across Victoria Harbour,
Hong Kong. Journal of the Institution of Water Engineers and
UNESCO [United Nations Education Scientific and Cultural Organization]
1991. Hydrology and Water Resources of Small Islands, A Practical
Guide. Studies and Reports on Hydrology No. 49, UNESCO, Paris.
Zhang, Zongwang and Liang Zhixin 1988. Study of Water Supply to Xiamen
Island. In: Proceedings of the Southeast Asia and the Pacific Regional
Workshop on Hydrology and Water Balance of Small Islands,
UNESCO-ROSTSEA, Nanjing, China. pp. 134-140.