Sourcebook of Alternative Technologies for Freshwater Augmentation in Small Island Developing States (UNEP-IETC, 1998, 230 p.): Part A - Introduction: 3. Structure of the source book

Sourcebook of Alternative Technologies for Freshwater Augmentation in Small Island Developing States (UNEP-IETC, 1998, 230 p.)

Part A - Introduction

		1. Background
		2. Purpose of the source book
		3. Structure of the source book
		4. How to use the source book
		5. Methodology for the identification and classification of small islands
		6. Results of the discussions at the workshop on augmenting freshwater resouces
		Information sources

3. Structure of the source book

The Source Book is in three major parts:

- Part A provides an introduction to freshwater augmentation: what it is and why it is necessary. Part A also outlines the purpose of the Source Book; reviews the methodology used in this Source Book for the classification of "small islands"; and, presents an overview of how to use the Source Book.
- Part B briefly describes a series of alternative technologies available and used in Small Island Developing States (SIDS), and presents a consistent and comparable set of data about the technologies which can be used to compare their relative advantages for maximizing water-use efficiency and augmenting existing water supplies in small island states. The objective of these technology profiles is to provide a reasonably comprehensive inventory, summarised in Table 1, that water resources professionals can use when planning water development projects on SIDS.
- Part C comprises case studies that highlight specific technologies that have been adopted in the region, and summarizes the experiences gained from their implementation.

For the purpose of this Source Book, the technologies applicable to Small Island Developing States, discussed in Part B, are divided into four subsections:

- The first subsection reviews those technologies that are generally applicable to small islands regardless of their geological and topographical configuration. These include technologies such as alternative (dry) sanitation, water quality improvement, irrigation systems, and water conservation and groundwater assessment technologies.
- The second subsection reviews those technologies applicable to very small, low coral islands. These include technologies such as rainwater harvesting and groundwater abstraction techniques such as dug wells and infiltration galleries, as these islands are not likely to have surface water resources and moderate to low availability of groundwater resources.
- The third subsection reviews those technologies applicable to small, high volcanic islands which are likely to have greater options for water resources development. These include technologies for the development of rainwater, surface water and groundwater resources.
- The fourth subsection covers islands where specific problems or circumstances make it necessary to pursue alternative (and not so commonly used) technologies. These include technologies such as desalination, dual water distribution systems, importation, and wastewater reuse.

TABLE 1. Summary of Freshwater Augmentation Technologies Applicable to Small Island Developing States.

TECHNOLOGY	EXTENT OF USE	SUITABILITY	ADVANTAGES	DISADVANTAGES	REMARKS
RAINWATER HARVESTING	Most SIDS	Suitable for very small islands without other options Suitable for islands where rainfall is evenly distributed throughout the year	Provides an additional source of water at the point of use Owner operated and managed Provides supplemental water source Water quality may be better than groundwater	Rainfall dependent Water can be contaminated within the catchment area Drought management may be required	On small coral islands, rainwater harvesting is often used to supplement groundwater sources
RAPID SAND FILTRATION	Mauritius, Seychelles	Suitable for larger urban water supply systems	Improved water quality Smaller land requirement than slow sand filtration	High capital cost Pretreatment required Trained operators required
SLOW SAND FILTRATION	Urban and rural water supply systems in Seychelles, Western Samoa, Cook Islands, and French Polynesia	Suitable for urban and rural water supply systems using surface water resources	Low construction cost Low operation and maintenance costs Energy source not required Improved water quality Unskilled labour can be used in operation and maintenance of units	Requires large land area Sensitive to certain toxins and high concentrations of colloids
DISINFECTION	Widely used throughout SIDS	Suitable for most water supply systems	Reduced occurrence of disease vectors Generally, easy to apply	Testing for residual chlorine concentrations is recommended Sodium hypochlorite is not always readily available Special care and handling of chlorine and chlorine compounds is required
ALTERNATIVE (DRY) SANITATION	Limited use in Kiribati and Federated States of Micronesia	Suitable for use on small, low islands where water is scarce and groundwater is sensitive to contamination	Conserved water Protects groundwater quality Produces compost for gardening use	Toilet bins are located above-ground Potential health hazard if not properly operated Can attract insects if not properly maintained Expensive	Should be used in conjunction with groundwater development projects on small coral islands Case Study included in Part C
WATER CONSERVATION	Widely used in SIDS	Suitable for all public water supply systems	Reduced water consumption Improved water quality Increased revenue Improved knowledge of system operations	Added cost Unpopular with consumers Meters require maintenance	Water conservation programmes should be integrated into all public water supply system operations
GROUNDWATER ASSESSMENT	Most SIDS	Suitable for assessing community water supply requirements Essential for small coral islands with limited groundwater resources	Contributes to sustainable use of groundwater Provides information necessary to optimally site wells and/or infiltration galleries	High cost of investigations, especially if drilling is required	See also Annex 4, Part D
IRRIGATION SYSTEMS	Limited to a few SIDS	Suitable for use on islands with adequate and sustainable water resources	Increased crop production	Increased water consumption Potential to contribute to water quality degradation
DUG WELLS	Most SIDS	Especially suitable for use on small, low islands	Simple to construct and use Provides water during dry periods Provides supplemental water resource	Potential water quality problems due to surface and subsurface contamination
INFILTRATION GALLERIES	Marshall Islands, Kiribati, Cook Islands, Cocos (Keeling) Islands, and Barbados	Most suitable for use in community water supply systems on small, coral sand islands	Improved water quality (lower salinity) without decreased yield Drilling may not be required Little maintenance required	Initial construction costs may be higher than those of dug or drilled wells Greater land area required
HAND PUMPS	Most SIDS	Suitable for use in abstracting water from shallow wells	No operational cost Low maintenance cost Minimal risk of overpumping aquifer Protects well from surface pollution Maintenance can be performed by users	Spare parts are required
SOLAR PUMPS	Islands in the Straits of Torres (Australia/New Guinea), Federated States of Micronesia, French Polynesia, and Kiribati	Suitable for use on islands where adequate solar energy is available, and where sufficient clear space exists for erection of solar panels	No on-going fuel costs Little maintenance required Quiet, pollution-free operation	High initial cost If used with back-up battery systems, problems may occur with battery maintenance in tropical conditions	See Case Study, Part C
HYDRAULIC RAM PUMPS	Limited to a few SIDS: Solomon Islands and Vanuatu	Suitable only for use on high islands with perennial, steeply sloping water courses	Low operating cost Minimal environmental impact Little maintenance required May be manufactured locally Automatic, continuous operation	Use limited to small-scale operations in hilly areas with suitable surface water resources Pumps a small proportion of the available water to higher elevations High capital costs Specialised design skills are required
BOREHOLES	Extensively used on high islands	Suitable for use on islands with adequate groundwater resources	Produces water of reliable quality and quantity	Requires skilled drill operators and technicians May have high construction costs May have high operating and maintenance costs Spare parts are required
RUNOFF COLLECTION USING IN-STREAM STRUCTURES	Used on most small islands with surface water resources	Suitable for use on islands with perennial streams	Diversion is less expensive than pumping Limited operating and maintenance requirements Can be operated by unskilled labourers	May be an unreliable source of supply May need pretreatment if used for potable purposes Moderate to high risk of contamination exists
RUNOFF COLLECTION USING SURFACE STRUCTURES	Used on larger islands: Guam, Malaysia, Indonesia, China, Cook Islands, and Hawaii	Suitable for use on large islands where topography, geology and economic factors permit	Provides medium to large volume storage Limited operating and maintenance costs and requirements	Can have environmental and public health consequences Water quality may be variable throughout the year Constructions costs are high Risk of failure exists
SPRING CAPPING	Extensively used in SIDS	Suitable for use on high islands where natural springs occur Suitable for use in all climates	Provides good quality water Low operating and maintenance costs	Could negatively impact spring discharge
IMPORTATION	Rarely used; Fiji and Bahamas Frequently used in emergencies	Suitable for use in emergencies or where economic demands can sustain this option (e.g., resort islands)	Provides freshwater	Incurs an high cost of transportation May be affected by sea conditions and availability of suitable vessels/barges Requires loading/offloading facilities and distribution systems
SUBMARINE PIPELINES	Rare; Seychelles, Western Samoa, Hong Kong, China, Malaysia	Suitable for use on small islands located close to continents or large islands with surplus water	Gravity-fed systems have low operating costs Effects distribution of water from water-rich areas to water-poor areas	High construction costs Subject to damage from storms, tidal flows, or shipping
DISTILLATION	Netherlands Antilles, Guernsey, Canary Islands, US Virgin Islands, Singapore, Antigua, and Cayman Islands	Suitable for use in all climates Most suitable for use in dual purpose facilities (e.g., water supply and power generation)	Provides good water quality More tolerant of poor quality feedwater than most desalination processes	High capital cost High production (operation and maintenance) cost Large capacity plants are unwieldy to transport and install
ELECTRODIALYSIS	Gran Canary, Bermuda, and some Chinese and Japanese islands	Best suited for use with feedwater having a total dissolved solids content of less than 4 000 mg/1	Provides an high rate of recovery of product water Energy efficient Requires little chemical pretreatment of feedwaters	Clogging may occur if the feedwater has an high bacterial content Not economic for seawater desalination
REVERSE OSMOSIS	Malta, Gran Canary, Bermuda, and Cape Verde	Suitable for use in desalinating brackish and sea waters in all climates	Simple design Removes ionic and non-ionic particulates Can be combined with energy recovery processes	Membranes are sensitive to feedwater quality Skilled operators are required Process requires spare parts availability and chemical pretreatment	See Case Study, Part C
SOLAR DESALINATION	Limited	Not suitable for use on most islands due to cost	Low energy costs	High capital costs Requires large land area for solar energy generation	Further development to make this technology more cost effective is required
WASTEWATER REUSE	Cape Verde, US Virgin Islands, Fiji, Canary Islands, Bermuda, and Barbados	Suitable for use on islands that have wastewater collection and treatment systems, where there is a need for large volumes of low quality water	Conserves potable water resources Provides large volumes of water suitable for use in irrigation, etc.	Potential public health risk Consumer resistance Variable quality of product water if system is not operated efficiently	See Case Study, Part C
DUAL DISTRIBUTION SYSTEMS	US Virgin Islands, St. Lucia, Bahamas, Kiribati, and Marshall Islands	Suitable for use where non-potable water resources are available	Conserves potable water resources Suitable for distributing seawater/wastewater for fire fighting, irrigation, etc.	High capital cost due to the need for two parallel distribution systems High operation and maintenance costs Risk of cross-contamination and/or groundwater contamination Potential public health risk among children and elderly

Figure 1. Possible applications of water supply technologies for small high islands.

Figure 2. Possible applications of water supply technologies for small low-lying islands.

It should be noted that there are no fundamentally new technologies available to resolve the difficulties imposed on SIDS by their limited water resources. For very small, coral islands, either rainwater or groundwater is available. Most SIDS cannot afford desalination as an option, and importation of water by barge or submarine pipeline, similarly, is not often feasible. Small volcanic islands often have surface water as a third option, together with rainwater and groundwater. However, desalination and importation, likewise, are rarely used and only where there is no other feasible alternative and consumers can afford to pay for it. For these reasons, emphasis is placed on conserving and protecting the quality of the existing water resources. Pollution of groundwater and surface water resources is increasing due to untreated human waste discharges from individual households, hotels and industries, and urgent steps need to be taken to halt or minimise pollution of these water resources. Similarly, the water that is supplied to consumers is often wasted, and/or lost through delivery system leaks and illegal connections, and improved management of water resources and supply systems is needed. Often water is supplied without charge, even though costs are incurred in providing and maintaining the supply service. The technologies described in Part B address many of these issues.