Newsletter and Technical Publications
<Sourcebook of Alternative Technologies for
in Small Island Developing States>
PART B - ALTERNATIVE TECHNOLOGIES
3. TECHNOLOGIES APPLICABLE TO SMALL HIGH, VOLCANIC ISLANDS
3.1 Freshwater Augmentation Technologies
3.1.4 Spring Capping
Springs are a naturally-occurring source of freshwater on many small
islands, and are often exploited using a gravity-fed delivery system.
Springs developed for a gravity-fed water supply should be at an elevation
above the supply area, and, while an excellent source of water, should be
"capped" to prevent contamination. Spring capping typically
takes the form of a containment structure, constructed from concrete or
masonry, which direct spring flows to an outlet pipe. Spring capping is
found in many forms, ranging from relatively simple, uncovered systems to
more sophisticated, covered systems designed to exclude leaves, soil and
other contaminants such as animal and bird excreta. An example of an
enclosed spring capping is shown in Figure 31.
Figure 31. Typical development of a gravity spring. The
spring feeds into the rear of the concrete or masonry
intake box, which can either be buried as shown or left exposed depending
on site conditions. A
delivery pipe fitted with a screen is placed
through the front or lower wall of the at a level below the minimum
level. To relieve pressure due to high flows an overflow pipe is also
placed through the chamber at an
higher level (UNESCO, 1991).
Where the spring discharge is below sea level, special difficulties are
experienced when attempting to develop the spring for freshwater
abstraction. The development of submarine springs is difficult because it
requires the use of underwater construction techniques. Also, should the
spring be successfully capped or dammed, the freshwater often finds
alternate exit via other fissures to the sea. In addition, even relatively
small drawdowns from pumping can induce mixing with seawater.
Extent of Use
Springs are used extensively in SIDS for freshwater supply purposes.
Operation and Maintenance
The type of spring capping shown in Figure 31 would generally require
minimal intervention for operation and maintenance. Periodically, however,
the chamber should be inspected and cleaned.
Level of Involvement
Local people can be trained to develop, cap, and manage springs.
There are many types of spring caps, ranging from a simple weir
structure (open) to more complex constructed (closed) systems. There is
also a range of sizes depending on the flow and areal extent of a given
spring. Costs are highly variable, but, in general, range from $500 to $5
000 for most applications. These costs do not include pipeline costs which
are also highly variable, and depend on location, length, terrain, etc.
Effectiveness of the Technology
Spring capping is an effective method of supplying water. However, care
must be taken not to decrease flows through spring development.
Spring capping is suitable for use of high islands where perennial
springs occur naturally.
Springs can provide good quality water at low (operation and
Spring development may be detrimental to the rate of discharge of the
spring, unless carefully implemented.
Some cultures are reluctant to use spring water.
Further Development of the Technology
The basic technology is well known. Depending on site-specific
conditions, capping design concepts could be improved to provide for
better use of local materials, greater protection of water quality, and
more efficient delivery of water to users.
AWRC [Australian Water Resources Council] 1989. Guidelines
for the Design and Operation of Surface Water Information Networks.
Water Management Series No. 18, Australian Water Resources Council,
Davies, J. and R. Lambert 1995. Engineering in Emergencies.
Intermediate Technology Publications, London.
Gormley, W., D. Goff, and C. Johnson 1984. A Workshop Design for
Spring Capping; a Training Guide. Water and Sanitation for Health
Project Technical Report No. 28, United Nations Development Programme, New
Hall, A.J. 1983. Surface Water Information Network Design for Tropical
Islands. In: Proceedings of the Meeting on Water Resources Development
in the South Pacific, United Nations Water Resources Series No. 57,
Hofkes, E.H. (Ed.) 1983. Small Community Water Supplies, Technology
of Small Community Water Supply Systems in Developing Countries,
International Reference Centre for Community Water Supply and Sanitation
Technical Paper Series No. 18, John Wiley and Sons, New York.
ILO [International Labour Organization] 1989. Spring Protection Works -
An ILO Special Works Programme in Western Samoa. In: Interregional
Seminar on Water Resources Management Techniques for Small Island
Countries. United Nations Department of Technical Cooperation and
Development, United Nations Development Programme, Suva.
Jordan, T.D. 1984. A Handbook of Gravity-flow Water Systems.
Intermediate Technology Publications, London.
Spangler, C.D. 1980. Low-cost Water Distribution - A Field Manual.
Appropriate Technology for Water Supply and Sanitation. The World
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.
WHO [World Health Organization] 1976. Typical Designs for
Engineering Components in Rural Water Supplies. World Health
Organisation South-East Asia Series No. 2, WHO, New Delhi.