Small islands water resources development-a holistic approach
by
Nicos X. TSIOURTIS
Senior Water Engineer
Water Development Department
Nicosia Cyprus
Abstract: Small islands have fragile ecosystems with very limited water and other
resources and great care of the environment is required for support of the inhabitants. The
nature of small islands with very small catchments area for rainfall, the small and limited
surface storage capacity, the limited groundwater storage capacity combined with the fact
that aquifers are surrounded by saltwater, the fact that that high porosity aquifers allow
mixing of fresh water with sea water and the fact that wastewater may be discharged to the
aquifer, make the management of the limited water resources very complicated. With the
available water resources not being enough and getting less due to pollution by the human
action and with demand growing due to population growth, due to improvement of the
standard of living and the introduction of other activities needing water for a
socioeconomic development, the need for the protection of the existing water resources is
becoming a top priority, where additional water resources must be developed. The small
islands water problem may be tackled by the introduction of the holistic approach, which
provides an integrated water resources management. The solution would be the protection
and development of the freshwater resources, the introduction of water demand
management, the treatment and re-use of the domestic effluents and if still the fresh water
resources are not enough to cover the demands for a sustainable development from the
socioeconomic and environmental aspects then desalination of sea or brackish water or
barging or transportation of fresh water would be introduced. All domestic effluents must
be treated and re-used for irrigation and the production of desalinated water to be made by
the installation of wind power generators either for co-production of electricity and water
or by stand-alone systems supported by generators or the local grid. The choice of the
technology of unconventional water production has to be based on a techoeconomic study
and environmental study.
Keywords: Small islands, water scarcity, integrated water resources, Re-use,
desalination, cogeneration of water and electricity, stand-alone desalination systems.
1. Definitions, classification
1.1 Definition of small and very small
islands.
From a hydrological perspective, a small
island can be considered to be one on
which water resources are very scarce.
Water development measures on small
islands are special and usually they are
not those normally considered as standard
on continents or larger islands. The
definition adopted by UNESCO in 1991
defines as small islands those having an
area equal or less than 2000 square
kilometers and the width does not exceed
10 kilometers. The definition also
introduces the concept of a “very small
islands” which includes islands whose
surface area does not exceed 100 square
kilometers or the width is not greater than
3 kilometer and where the water scarcity
is even more acute and surface water
resources are normally absent. On small
runoff and the groundwater is a major
component of the water balance. Low
islands are also affected by their height
above sea level, which determines the
risk of overtopping.
or very small islands groundwater is
normally the only naturally occurring
water resource, where surface water is
very scarce and difficult to catch if any.
From 64 islands in Greece 37 have an
area less than 100 square kilometers, 8 no
between 100 and 200 Km2, 12 no
between 200 and 500 Km2, 3 no between
500 and 1000 Km2, 2 no between 1000
and 2000 Km2 and 2 no above 2000
Km2. In other words 37 can be classified
as very small islands, 25 no as small
islands and the rest two as large islands.
The
geology
and
hydrogeology
influences the availability, the type and
the distribution of the water resources.
Groundwater is abundant in islands with
soils and rocks of moderate to high
permeability, where surface water
resources occur on islands with soils and
rock with low permeability. Very high
permeability causes the mixing of
freshwater and seawater resulting to
brackish groundwater. UNESCO has
classified the small islands according to
their geology into Volcanic islands,
limestone islands, coral atolls, bedrock
islands, unconsolidated or sand islands
and islands of mixed geology. Volcanic
islands are of the andesitic sub-type
(islands on the continental sides of deep
trenches) with groundwater yields
generally low and the basaltic or oceanic,
which rises from the ocean floor in the
middle of the tectonic plates with high
groundwater potentials. Volcanic islands
are of the High type islands. Limestone
islands are generally karstic and
weathered due to fluctuating sea levels
and alternate periods of submergence and
exposure. Permeabilities are relatively
very high and freshwater lenses are
generally no more than 10 cm to 20 cm
thick, with caves and cavities found along
the shoreline and within the interior of
the islands. Limestone Islands are of the
low type islands. Coral Atolls islands
are found in the Pacific and the Indian
oceans and typically they consist of a
chain of low coral islands surrounding a
shallow lagoon, consisting of a layer of
recent sediments on top of an older
limestone. The upper sediments are of
primary importance since freshwater
lenses are found in this layer due to its
moderate permeability. Bedrock islands
are formed by igneous or metamorphic
1.2 Special characteristics of small
islands
The major influences on the small islands
hydrological characteristics are the
climate the physiography, the geology,
the hydrogeology, the soils, the
vegetation cover, the location, the shape
and the human intervention.
The climate influences the availability of
freshwater. The rainfall quantity and its
variation with respect to time and space
and the evapotranspiration play an
important role on the availability of the
freshwater resources. The temporal
variation is usually high in small islands
where the spatial variation is a function
of the islands physiography.
The physiography plays an important
role on the classification of small islands
high or low. High islands are those that
can influence the precipitation patterns
and with some runoff and low islands are
those without any effect on the
precipitation pattern and no significant
surface runoff. High islands have steep
topography with flashy surface water
resources, since they are volcanic islands,
with low permeability bedrocks. These
islands have small perennial streams at
high elevations and the surface water
may form an important component of the
water balance. Low islands have a flat
topography with a minimum of surface
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high potential for pollution of the water
resources. High water demand causes
over-abstraction and depletion of the
aquifers and increased development
(housing) has led to the contamination of
the underlying or nearby aquifers. Small
islands are vulnerable to aquifer
depletion, groundwater contamination by
human and animal activities, and suffer
from water scarcity. Another hazard is
the use of agrochemicals (herbicides and
insecticides) and the fuel storage
facilities. Generally small islands require
special measures for their water
development
and
protection
and
additional water must be imported from
outside sources for safeguarding the
sustainable development and preserving
the present level of standard of living.
rocks such as granite, diorite and schist,
found mainly on the continental shelves
or
adjacent
to
large
islands.
Unconsolidated islands are consisting of
sand, silt or mad and are found in the
deltas of major rivers, where mixed
geology islands are those islands with a
mixture of volcanic and limestone rocks.
Soil types play an important role in the
hydrological cycle. Sandy soils found in
limestone and coral islands with high
permeability do not allow the creation of
surface runoff, where clay soils found in
volcanic
islands
have
a
lower
permeability allow the creation of surface
runoff. Soil water retention capacity is an
important factor in the evapotranspiration
and recharge. The retention capacity is a
function of the texture of the soil and the
thickness of the soil. Recharge is
enhanced by coarse grain soils (sand) and
fine grain soils reduce the recharge.
2. Water Management and
development in small islands
Vegetation in small islands, generally
adapted to the local climatic conditions,
consists of a variety of trees, bushes and
grasses, and normally does not require
irrigation. The type and density of the
vegetation affects the hydrological cycle,
water interception and transpiration
reduce recharge, slow surface runoff and
reduce erosion on High Islands thus
increasing infiltration of water into
ground. Generally the benefits of
vegetation outweigh the negative effects
on the water resources.
2.1 General
Small island’s freshwater resources are
very limited, scarce and fragile. With
growing demand (due to population
growth and other development), on water
quantity and quality there is a need to
maximize the use of the existing
freshwater
resources
before
unconventional options are considered.
Therefore the planning and management
of small islands water resources and
water developments are limited to the
issue of maximizing and augmenting
freshwater resources as follows.
The Location of the islands with respect
to the continent or other large islands
classifies the island to those that can be
supplied with water, by pipelines or sea
transport and those that have to be
supplied only from their own sources or
by desalination.
2.2 Freshwater resources development
Freshwater includes all naturally
available water, surface, groundwater and
wastewater.
i) Freshwater resources assessment.
The first step in water resources
management is the assessment of the
available
water
resources
both
1.3 Special Problems of the islands
Small islands are usually densely
populated with high water demand and
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effective and efficient use of the potable
water and for the treated effluents, one
distribution system for potable water and
a second distribution system for the
treated effluents. Disposal of treated or
even untreated wastewater to the sea or to
the aquifers must be avoided, after all it is
banned by the European Directives, for
environmental,
water
conservation
reasons and for eliminating the risk of
pollution of the groundwater aquifers.
groundwater and surface. The assessment
should be made through a water survey
using sound hydrological and hydrogeological methods.
ii) Water demand assessment. Water
demand assessment and projections
should be made taking into consideration
present population and future population
growth, present and future tourist
development and present and future
activities in irrigation, in industry and
other activities for a sustainable
development and demand for the
conservation of the environment.
vi) Water pricing and public
awareness.
Water must be cost
evaluated taking into consideration the
capital investment costs, the operation
and maintenance costs, the energy costs,
the environmental costs and the resource
depletion costs. Water pricing and
tarification must be such as to discourage
wasteful use and encourage efficient and
effective use. It is recommended that
water pricing should be such for full cost
recovery, which will encourage water
saving. Public water awareness must be
created by education of the consumers,
by water saving campaigns and by
adopting the right pricing system both for
freshwater and treated wastewater use
and for wastewater disposal. If the price
is right the consumers will save water and
will also reduce waste disposal.
iii) Water development and use. Water
development includes all structural and
operational measures for freshwater
development and utilization including
surface water structures (dams, offstream ponds), borehole drilling,
controlled
groundwater
pumping,
efficient
water
conveyance
and
distribution systems, infiltration galleries,
water treatment plants, wastewater
collection and treatment plants, and reuse schemes.
iv) Water demand management. Since
water is scarce and very limited, its use
should be done efficiently and
effectively. Distribution systems should
be very efficient, water losses should be
minimized, and water consumption
should be measured and billed to the
consumers, at its total cost. The
consumers must be encouraged to use
water saving equipment, encouraged to
save water and discouraged to use it
wastefully. The principle “the beneficiary
and the polluter pays” must be applied
and public awareness must be promoted.
vii) Environmental Considerations.
Water
conservation
and
water
development measures should not
overlook the environmental needs and
requirements. Environmental needs must
be satisfied to the fullest possible way by
providing water for wetlands, for natural
vegetation, for the wildlife and for any
other important reason related to the
environment. For example aquifer
pumping should be limited to the safe
yield of the aquifer and continuous
monitoring of the pumping must be
carried out.
v) Treated wastewater re-use. This
method of water conservation must be
used in cases and domestic effluents must
be treated and re-used for irrigation or for
other purposes productively. Dualpurpose systems may be used for
viii) Setting up an Entity. Water
management shall be efficient and
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location where there is water for export to
another, by sea, using barge or sea-going
vessel. The ship or barge should have
adequate volume capacity and the
distance
should
be
such
that
transportation is low cost and effective.
The method requires qualified and skilled
personnel for loading and unloading the
water, on land storage capacity for
storing the water and loading and
unloading facilities. Barging is a
relatively expensive method since it
requires expensive loading and unloading
facilities, and storage facilities on both
ends. Cost varies from $1.5 to $5.0
depending on the distance. The
technology is not dependable since it
depends on sea conditions, but
acceptability is not high in those cases
where the water comes from a different
country and creates dependability to a
foreign country. This technology has
been used in emergency conditions in the
Mediterranean islands of Majorca, and in
the occupied part of Cyprus and in
Morocco. The technology was under
consideration by Cyprus and Israel but
desalination has been chosen instead
because of higher cost, unreliability
depending on sea conditions and the
creation of the dependability to a foreign
country.
effective if an entity is given the
administrative, legal power, technical,
economic and other means to carry out
this task. The entity must have legal and
executive power on the management and
development of water resources for the
whole water cycle including freshwater,
wastewater and desalinated or imported
water.
ix) Level of involvement. Water
resources development should be a
participatory process involving all water
stakeholders, consumers, engineers,
water managers and politicians. The
community should be the owner of the
scheme and should participate at all
stages of project implementation and the
selected technology should be the least
complex technology within the capability
of the community to install and maintain.
x) Integrated water resources. Finally
but not the least water resources
management shall be carried out in an
integrated manner, regarding water
demand, water resources availability and
water
development
technologies,
economic and social development,
energy, human resources availability and
other sources availability and utilization.
Water and energy are interchangeable
commodities and saving of one leads to
the saving of the other and vice versa.
ii) Transportation. Submarine pipelines
are used to convey water to small islands
from nearby continents or other islands
with excess water. The investigation,
design and construction of such pipelines
requires specialized engineering practice
and involves high capital cost and
periodic inspection to ensure its integrity
especially after storms. Submarine
pipelines must be anchored to the seabed
by special anchor blocks and installation
requires a specialized Contractor. Due to
the high costs involved and to the limit of
depth that a pipeline can be installed, the
method is limited to islands not far away
from the water continents with excess
water. The method is suitable for islands
2.3 Non-conventional water resources
Where water resources available are not
adequate or where all available water
resources have been utilized to the
maximum and efficiently and still they
are not enough, non-conventional
technologies may be introduced. Such
non-conventional technologies are water
barging (by ship or barge), water
transportation pipelines and desalination
of seawater or brackish water.
i) Water Barging. This involves the
transportation of freshwater from one
5
from the electrical grid, produced at the
side or use wind or power energy
depending on the specific case. Small
islands situated in windy areas may
utilize the wind energy or the solar
energy, but both require larger surface
areas for their installation. For small units
a solar humidification, or distillation
(both thermal processes) or photovoltaic
cells may be used to capture solar energy
but usually they require well trained and
skilled labor to operate and maintain.
close to the continents, it allows the
transport of water from excess water
areas but reliance on water from offisland or from a foreign country may
cause concern.
iii) Seawater or brackish water
desalination. Desalination is the process
of separation of water form salt to
produce water free of salts. This
technology of water augmentation on
small islands is offered because seawater
or brackish water is abundant.
Desalination can be carried out by
thermal or membrane process. The
thermal process is the distillation and
includes the Multi-Stage Flash (MSF)
method, the Multi Effect Distillation
(MED) method and the Vapor
Compression Distillation (VC) These
methods are usually combined with
thermal power stations for reducing the
energy consumption. About 55% of
desalination
plants
in
operation
worldwide use the thermal method for
water desalination. The membrane
process includes the Reverse Osmosis
and Electro dialysis. Reverse Osmosis
use pressure to desalinate water and
represents around 40% of the total
installed capacity worldwide. The energy
for desalination may be in the form of
fossil oil or renewable forms of energy
such as solar, wind, geothermal, ocean
energy etc. The renewable solar energy
may be in the form of solar using the
humidification, the solar distillation, and
desalination with photovoltaic cells. All
processes require skills and know-how
for carrying out the operations. The
capital investment varies from $1000$2500 per cubic, meter where specific
energy requirements are high varying
from 2.5 to 10 KWh per cubic meter. The
advantage of reverse osmosis is that the
specific energy for desalination is a
function of the salinity of the water, with
brackish water having lower specific
energy requirements. Energy for the
desalination process may be obtained
3. Small islands holistic approach to
water resources management.
3.1 General
Holistic approach means integration of
all water resources (conjunctive use of
surface, groundwater, treated wastewater
and desalinated or imported water) of all
water development technologies, of all
water demand sectors (domestic,
irrigation and industrial sectors), use
water efficiently and effectively at any
stage of the water cycle, combined with
various forms of energy and taking into
consideration economic and social
development and environmental needs.
This approach is most suitable to small
islands or to isolated areas, where the
area is small, the population density is
high and the legal and administration
frameworks are not complicated and the
structures are light.
3.2 Proposed approach for small
islands for freshwater development.
The proposed technology for a holistic
approach should include the following.
• Evaluation of total freshwater, surface
and groundwater
• Evaluation and projection of demands
by sector of the economy and for the
environment for a sustainable
economic and social development.
6
•
•
•
3.3
periods the wind generator provides
enough energy for the desalination plant
and when the energy produced is not
enough energy is taken from the local
grid or produced at the site by diesel
generators. This system requires standby
electric or diesel-produced energy, which
is not always feasible.
Select technology for freshwater
development and effective and
efficient use.
Implement water demand methods for
minimizing water losses and avoiding
wasteful use by utilizing the modern
technology for water distribution,
water use and by implementing full
cost recovery charges.
Provide sewage collection and
wastewater treatment plants and
wastewater distribution systems for
use of treated domestic effluents.
Dual water supply systems, one for
potable water and the other for the reuse may be implemented.
ii) Water and Energy co-generation
system. This system uses wind
generators
for
electrical
energy
production, both for desalination and for
electricity production. During high wind
periods electricity produced is used for
both desalination and electricity supply
and when wind is low velocity the total
power produced is used for desalination
only.
Non Conventional water
Barging of water depends on distance of
transfer and the facilities available at the
source and the point of delivery, which
determine the cost as well as the
acceptance of dependency on the supply
from another country.
iii) Production of steady quantity of
water and use power the grid as a
balancing reservoir. If the national grid
has enough energy capacity to give and
or accept energy the system is tuned to
produce a fixed amount of water and
excess energy produced by wind
generators is diverted to the electric grid
and when energy produced by the wind
generators is not enough for desalination
then the grid supplies the deficit.
Desalination of brackish or seawater is
another method for increasing water
resources. This requires a lot of energy,
high-level technology and skilled
personnel for the erection, operation and
maintenance of the plant. Small islands
found in the open seas are blessed with
relatively strong winds and sunshine,
which can be used as energy for
desalination in addition to local power
produced by using fuel or energy from
the national electric grid. Following are a
few proposals for combination of wind
power with electric power from the grid
or locally produced energy using diesel
engines for a dependable seawater or
brackish water desalination.
iv) Wind generators for water
production. This system is used only for
the production of water and water
produced during high wind periods is
stored in surface reservoirs for use during
high water demand periods. Under these
conditions the water may need further
treatment before us for domestic
purposes.
There may be other combinations with
the objective of cost reduction. The
selection of the best system must be made
after a detailed study of the options
available concerning the availability of
electric power from the local grid, the
wind velocity pattern, the water demand
pattern, the use of water, the costs
i) Stand Alone Wind Generator
Systems. This uses wind energy
produced at the site by wind generators
and electric power from the grid or
locally produced energy by diesel
generators. During high velocity wind
7
involved, the financial and economic
capabilities of the community and the
capability of the community to maintain
and operate such a system.
Υδατικοί Πόροι Ι. Τεχνική Υδρολογία.
Εκδότης Γ. Τσακιρης Αθήνα 1995.
Multicriteria decision analysis in Water
resources Management. Edited by: Janos J.
Bogardi, Hans-Peter Nachtnebel UNESO
1994 Ayers, J.F.
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