Sourcebook of Alternative Technologies for Freshwater Augumentation in Small Island Developing States


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PART B - ALTERNATIVE TECHNOLOGIES

4. TECHNOLOGIES APPLICABLE TO SMALL ISLANDS WITH SPECIFIC PROBLEMS OR CIRCUMSTANCES

4.1 Freshwater Augmentation Technologies

4.1.1 Importation Using Sea Transport/Barging

Where there is insufficient water resources on an island to meet its demands, freshwater may have to be imported to supplement available supplies. Barging of water and submarine pipeline have been identified as systems of importing freshwater. Water can also be conveyed to water-poor areas from water-rich areas by overland pipelines (inter-basin transfers). This is common practice, well-documented in standard textbooks, and not discussed further in this volume. A fourth option, also not discussed further in this book, is the importation of bottled water, primarily for drinking water.

Technical Description

Barging of water involves transportation of water from one location to another by sea, using an ocean-going vessel or barge. The barge should contain storage tanks of adequate size to make transportation cost-effective. Often the barge is towed by another vessel, such as a tug boat, but can be self-propelled. Ships have also been used to transport water; e.g., in Nauru, the ships used to carry phosphate off-island, carry water back to the island as return cargo. Once the vessel arrives at a suitable port, the storage tanks must be emptied by pumping into stationary or mobile storage tanks on land prior to distribution.

Extent of Use

Except in the Bahamas, and at some small island resorts (e.g., in Fiji), barging is rarely used except during emergency periods. In the Bahamas, barging is used more frequently, and facilities have been developed to efficiently load, transport (using contract ships), and discharge freshwater. In Fiji, water is transported by barge to the outer islands, at various times on an "as needed" basis. During periods of water shortage, barging of water is used extensively in SIDS.

Operation and Maintenance

Efficient operation is required to minimise the cost of barging. The costs include suitable loading and unloading facilities as well as the cost of a suitably-sized barge. Maintenance includes regular inspection and cleaning of barge tanks to minimize contamination of the water. Once unloaded, the water must be stored, reticulated, or trucked to the consumer. Pumps are required for off-loading the water, but gravity-feed can be used to transfer water to the barge at the loading point if the storage tank is located at an higher elevation than the barge.

Level of Involvement

Barging requires qualified and skilled personnel to operate, load, and unload the barges.

Costs

Barging water is a very expensive method of providing freshwater to islands. The main component of the cost is the transportation cost. For , in the mid-1980s, the cost of transporting water from Dominica over distances of 100 km to 1 000 km varied from about $1.40/m3 to $5.70/m3. The cost of water transported over a distance of about 100 km between Puerto Rico and St. Thomas, in the early 1980s, was $7.65/m3. This service was provided using small tankers and barges (UNESCO, 1991). In Fiji, the total budgeted provision for emergency water supply in 1996 was $285 000, which included the cost of trucking emergency water to and from the loading docks as well as barging.

Effectiveness of the Technology

To be effective, a suitably-sized barge is required to minimise shipping costs, and proper loading and unloading facilities are necessary in the ports of embarkation and off-loading. The expenditures required for establishing such an extensive infrastructure can only be justified if barging is a normal means of supplying water, as in the Bahamas.

Suitability

This technology is suitable for use in most geographic areas where there are suitable berthing facilities for the barges and infrastructure to store the water after it is unloaded and while it is being distributed the water to the consumers. The transport of water by barge is also acceptable during and following emergency situations, such as during severe droughts and following hurricanes, as a means of supplementing other water sources.

Advantages

Barging can provide emergency freshwater supplies to islands during droughts or other emergencies.

Disadvantages

Barging incurs an high cost, and, because it depends on sea conditions, can be very unreliable. It also depends on availability of suitable barges or tankers, and requires efficient loading/unloading and adequate storage facilities. The major disadvantage of this technology is the high cost of transportation which generally precludes its use except in times of emergency.

Cultural Acceptability

Reliance on water from off-island sources, particularly if those sources are from a different country, may be source of concern.

Further Development of the Technology

This technology is already well known, and there is no need for further development.

Information Sources

Bradanovic, J.Z. 1980. Overview: Certain Considerations and Criteria in Marine Barging of Water. In: P. Hadwen (Ed.), Proceedings of the United Nations Seminar on Small Island Water Problems, United Nations Development Programme, New York. pp. 556-583.

Meyer, T.A. 1987. Innovative Approaches to Transportation of Water by Tanker. In: Non-Conventional Water Resources Use in Developing Countries, United Nations Natural Resources/Water Series No. 22, 119-135.

Rogers, M. 1989. The Public Water Supply in Antigua. APUA Review, 1(3).

UNDTCD [United Nations Department of Technical Cooperation and Development] 1985. The Use of Non-conventional Water Resources in Developing Countries. United Nations Natural Resources/Water Series No. 14.

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.

Woodroffe, M. 1992. The General Manager Says ..... APUA Review, 1(1).

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