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Newsletter and Technical Publications

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


PART D - ANNEXES

Annex 3

Cost Comparisons

Introduction

Details of costs for different methods of water resources development are not readily available in the published literature. This type of information is generally contained in unpublished reports and files. Thus, while the cost details below should be considered only indicative of the full range of costs, they reflect costs incurred over a wide range of conditions and provide an idea of the relative costs of water resources development on small islands. Two sets of comparisons are given in this section. Firstly, the costs of alternative water source developments from feasibility studies are considered for selected cases. Secondly, costs of present (or recent) water production on a small number of islands are considered. Because these costs are indicative only, no general conclusions can be drawn. Each small island or group of small islands will have its own particular conditions which influence costs of the various alternatives.

Home Island, Cocos (Keeling) Islands

Cost comparisons for a number of water supply options were undertaken for Home Island in 1988 (Falkland, 1988) and were summarised by UNESCO (1991). These costs were based on estimated capital and recurrent costs of supplying water at the rate of 115 m3/day to the Home Island community, and are expressed in Table 15 as 1995 costs.

TABLE 15. Approximate Unit Costs of Alternative Freshwater Augmentation Technologies.

Alternative Unit cost ($/m3)
Groundwater supply plus emergency rainwater $ 1.20
Desalination by reverse osmosis $ 8.60
Importation by piping from South Island $ 2.90
Importation by barging from West island $ 4.30
Rainwater collection $ 12.10

The groundwater alternative required conversion of existing wells to galleries, but no further infrastructural development. The two importation alternatives required groundwater extraction on other islands on the atoll (Figure 49) and transportation of the water to Home Island. Rainwater collection was the most expensive option due to the need for very large storages and catchment areas should rainwater be used as the sole (rather than a supplementary) source of freshwater.

Subsequently, these costs were refined in 1994 (Falkland, 1994) on the basis of additional information and operational experience. The refined costs were based on supplying an additional 100 m3/day to Home Island. These costs, converted to 1995 costs, are shown in Table 16.

Figure 49

Figure 49. Map of South Keeling atoll, Cocos (Keeling) Islands, Indian Ocean.

TABLE 16. Refined Costs of Freshwater Augmentation Technologies.

Alternative Unit Cost ($/m3)
Desalination by reverse osmosis $ 6.30
Importation by piping from South Island $ 5.40
Importation by barging from West island $ 6.00

From the above data, the costs of supplying water based on groundwater development using infiltration galleries is the least costly option. After this, importation from other parts of the island, using groundwater abstracted from infiltration galleries, is the next most costly option.

Kiritimati (Christmas Island), Kiribati

Cost comparisons for a number of water supply options were undertaken for Kiritimati in 1983 (Falkland, 1983,1984), and were also summarised by UNESCO (1991). These options were based on supplying water at the rate of 50 m3/day to the population of London (Ronton). The unit costs shown in Table 17 are expressed as 1995 costs.

TABLE 17. Approximate Unit Costs of Alternative Freshwater

Alternative Unit cost ($/m3)
Groundwater supply from Decca lens $ 5.00
Desalination by reverse osmosis $ 8.60
Solar distillation $ 5.80
Rainwater collection >$27.00
Importation by barge from Washington Island (Teraina) $12.50

As for Home Island, but even more so, rainwater collection was the most expensive option due to the need for very large storage and catchment areas if rainwater is used as the sole (rather than a supplementary) source of water. Similarly, the costs of supplying groundwater from infiltration galleries is the cheapest option.

Costs

Table 18 shows the unit cost of water production for a number of small islands. The marked differences in the unit costs of production are not only due to the lack of local water resources but are also to the efficiency of development.Costs shown are mid-1980s costs and reflect both production costs and consumer costs as noted

Information Sources

Falkland, A.C. 1983. Christmas Island (Kiritimati) Water Resources Study. Australian Department of Housing and Construction Report No. HWR83/03, Australian Development Assistance Bureau, Canberra. 425 pp. + appendices.

Falkland, A.C. 1988. Cocos (Keeling) Island Water Resources and Management Study. ACT Electricity and Water Report No. HWR88/12, ACT Electricity and Water, Canberra, Australia. 211 pp. + appendices.

Falkland, A.C. 1994. Home Island Water Supply Options. ACT Electricity and Water Report No. HWR94/05, ACT Electricity and Water, Canberra.

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. 435 pp.

TABLE 18. Unit Costs of Water Production for Some Small Island States.

Island/Country Water Source Unit Cost
($ per m3)
Reference
Anguilla Desalination (brackish RO) 5.80 Wright (1984a)
Bahamas 0.37 Dabbagh and Al-Saqabi (1989)
Barbados 0.34 Dabbagh and Al-Saqabi (1989)
Bermuda Groundwater extraction (and pumping to reservoir, not including treatment) 0.55
Desalination (RO) 1.10
Canary Islands Groundwater extraction (Gran Canaria) 0.50 - 1.20
Groundwater extraction (Tenerife) 0.20 - 0.40
Groundwater extraction (Gran Canaria) 0.20 - 0.30
Desalination - seawater (cost) 1.50 -3.00
Desalination (consumer charges) 1.10 - 2.00
Reused Wastewater (cost to farmers) 0.05
Cape Verde 4.65 Dabbagh and Al-Saqabi (1989)
Cayman Islands Groundwater extraction 2.50
Desalination 4.00 - 4.81
Rainwater 26.00
Imported bottled water 240 - 320
Cook Islands 0.40 Dabbagh and Al-Saqabi (1989)
Fiji Importation (from main islands) 6.00
Malta Groundwater extraction (boreholes and tunnels or galleries) 0.29 Spiteri Staines
Groundwater (boreholes only) 0.22
Desalination (MSF distillation) 1.17
Desalination (RO) 1.20
Mauritius 0.29 Dabbagh and Al-Saqabi (1989)
St. Thomas, USVI Bulk importation (From Puerto Rico) 4.65 Brewster and Buros (1985b)
Seychelles 0.60 Dabbagh and Al-Saqabi (1989)
Singapore 0.24 Dabbagh and Al-Saqabi (1989)
Taeawa, Kiribati Groundwater extraction 1.00 Metutera (1989)
Tonga 0.80 Dabbagh and Al-Saqabi (1989)
Western Samoa 0.09 Dabbagh and Al-Saqabi (1989)
Caribbean islands Bulk importation (from Puerto Rico) 1.50 - 5.70 de Hahn (1987)

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