AGSO Journal of Australian Geology & Geophysics, 14 (2/3), 123- 133
© Commonwealth of Australia 1993
Aquifer vulnerability on small volcanic islands in the southwest Pacific
region - an example from Norfolk Island
Robert S. Abell!
Island ecosystems in the southwest Pacific region are noted for
their fragility and susceptibility to degradation, particularly in
regard to groundwater systems. In general, island aquifers are
relatively free of major pollution problems, but human develop•
ment suggests that potential long-term dangers exist. The character
of groundwater resource development on small islands in this
region is reviewed with regard to geologic framework, water
availability, recharge, and aquifer risk. Norfolk Island serves as a
case study of aquifer vulnerability on a small volcanic island. The
research and training needs for the long-term protection of island
water resources are briefly outlined.
Introduction
oceanic (Peterson, 1984). The former are associated with
island arc volcanism and lie on the continental side of deep
ocean trenches (zone of plate subduction). The water-bear•
ing properties of the volcanic rocks are generally poor since
low-porosity and/or low-permeability submarine basaltic
pyroclastics and deeply weathered lavas predominate.
Typical examples of island groups within this province are
the Solomon Islands, Vanuatu, Fiji, and Norfolk Island
(Fig . 1). Islands with oceanic affinities are associated with
intraplate volcanism and lie on the ocean side of the
subduction zone . The volcanic rocks in this province are
typically youthful basaltic lava flows which may be
extremely permeable and provide important aquifers, e.g.
Hawaiian Islands, French Polynesia, and Samoa (Fig. 1).
Water is the most critical of all resources on oceanic
islands. In the Pacific Ocean alone there are over 30 000
small islands most of which are in tropical regions; the
number of populated islands is in the order of 1000. For the
purpose of this paper, the introductory material draws
heavily on information given in Falkland (1991, 1992) and
refers mainly to islands in the southwest Pacific Ocean
region (Fig. 1). The area selected for the upper limit of a
small island is 2000 km 2 , but many are smaller having
areas of less than a few hundred square kilometres.
On small islands, groundwater resources are generally
available in limited quantities. This is evident on low-lying
limestone islands and coral atolls where groundwater
occurs as freshwater lenses. Many small islands have or are
beginning to experience major problems with the availabil•
ity, over-extraction, and pollution of their limited water
resources, largely induced by increasing population. Water
demand has risen significantly as living standards have
improved. Competition has developed for the availability
of water between urban and rural communities, tourism and
small agro-industries (e.g. sugar, oils, and copra). Adverse
impacts are over-pumping of groundwater leading to
increases in salinity of water. Faecal contamination of
groundwater by infiltration from closely located sanitation
facilities is a common problem on many crowded islands.
The use of biocides and fertilisers is an emerging problem.
The susceptibility of tropical islands to natural disasters
(e.g. cyclones, earthquakes, and volcanic eruptions) and
water supply degradation is generally higher than on
continental land masses. Their isolation from sources of
materials and equipment, high costs of freight, and often a
lack of trained professional and technical staff make water
resource development a challenging problem for island
communities.
Hydrogeological framework
In general, small islands in the southwest Pacific Ocean can
be topographically subdivided into high and low islands.
The high islands are principally composed of an emergent
or submerged volcanic core of basalt often surrounded or
capped by thick coral limestone (raised atolls). These
islands are older and much larger than low islands, the
latter consisting mainly of coralline atolls standing only a
few metres above sealevel. Further, high volcanic islands
fall into two geological provinces, namely continental and
Australian Geological Survey Organisation, GPO Box 378,
'Canberra, A.C.T. 2601.
For hydrogeological purposes, islands with an emergent
volcanic core may have a rugged interior, e.g. Rarotonga
(Cook Islands) and Western Samoa, from which rainfall
shed as surface runoff may provide viable water supplies
(Dale & Waterhouse, 1985). That part of rainfall that
percolates to the water table can be perched or confined to
fracture systems and sedimentary interbeds which behave
independently from each other because of vertical and/or
horizontal low permeability barriers, such as dykes or
buried soils (e.g. Hawaiian Islands.) Groundwater will
move to lower levels, where it may accumulate as basal
water to form for most practical purposes a freshwater lens.
The highly variable geology of volcanic rocks makes it
difficult to identify and manage the subsurface components
that control groundwater. Raised atolls with a submerged
volcanic core, surrounded and capped by generally thick
coral limestone, are assumed to have formed in response to
tectonic uplift and subsidence of the volcanic edifice, e.g.
Tongapatu, Niue, and Nauru. On these islands, no streams
are present and the karst topography allows rainwater to
penetrate rapidly to a freshwater lens. Overpumping with
consequent lowering of the lens surface to or below
sealevel will induce seawater intrusion. Coral atolls
normally occur as a ring of closely spaced coral islets
encircling a shallow lagoon varying in diameter from
1-100 km. The submerged deeply buried rock core is
presumed to be volcanic, e.g. Kiribati, Tuvalu, Tokelau,
northern Cook Islands, and several examples in French
Polynesia. A limited groundwater source may, with care,
be exploited from a thin freshwater lens underlying the
atoll.
Water availability
The availability of groundwater from storage is influenced
by the size of the island, recharge patterns, and a wide
spectrum of geological conditions. The turnover time of
groundwater systems on small islands tends to be short (a
124
130'
ROBERT S. ABELL
150'
170' E
170' W
150'
130'
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19/091190
Figure 1. Island groups of the southwest Pacific Ocean.
few years at most). Thus, perched aquifers and freshwater
lenses may deplete in dry seasons to a stage where there are
minimal or no freshwater resources. In some cases, the
rocks may be too permeable to enable a freshwater lens to
form. Few high islands have topographical and hydrologi•
cal conditions suited to the construction of significant
water storages. Catchments are often large in number, but
small in size; natural runoff of more than a few tenths of
litres/second cannot be guaranteed. Other sources of
freshwater are rainwater collected from roofs and other
surfaces, desalination of seawater, importation, treated
wastewater, and substitution (e.g. coconut juice).
Recharge
Recharge processes on small islands are largely influenced
by rainfall, evapotranspiration, vegetation, and soil. The
tropical areas of the Pacific Ocean are affected by warm,
moist northeast and southeast trade winds, which generally
result in heavy rainfall. Controlling mechanisms affecting
regional variability of rainfall include tropical cyclones, El
Nino Southern Oscillation (ENSO) events, and long-term
climatic change including 'the greenhouse effect'. Local
rainfall variations due to the orographic effect are evident
on high islands. Evapotranspiration can be more than the
rainfall on an annual basis and often exceeds the rainfall
for individual or consecutive months during dry seasons or
droughts. Despite its importance, evapotranspiration is the
least-quantified component of the water balance on small
islands. Vegetation affects recharge by intercepting a part
of rainfall and by causing transpiration. Depending on the
depth to water and the type of vegetation, direct transpira•
tion losses may be promoted as in coconut trees on coral
atolls (losses of 70-130 litres/day). In other respects, a
vegetation cover is desirable for food and reduction in
surface runoff and erosion. The ability of soils to hold
water is important for recharge generation. High water
retention (clayey) soils favours evapotranspiration, thus
reducing effective rainfall while low water retention
(sandy) soils allows rainfall to penetrate below roots to the
water table.
Aquifer risk
Despite their limited area, small islands often have high
population densities which place great stress on natural
water resources . People not only create high demands for
water, but also increase the risk of pollution since they
often live above the groundwater used for potable and other
purposes . The tourist industry, a major activity on small
islands, demands large volumes of water with high
physical, chemical, and bacteriological standards. Fre•
quently, tourist accommodation has such a high water
consumption that it can severely stress the water resource
capacity of an island.
Groundwater pollution may be caused by natural or
artificial processes. The commonest example of the natural
process is mixing of fresh groundwater and seawater at the
base of a freshwater lens to form a transitional zone of
brackish water. The geometry of a lens is dependent on
rainfall recharge, rock permeability, tidal fluctuations, and
AQUIFER VULNERABILITY, NORFOLK ISLAND
the size and shape of the island. However, the artificial
process of overpumping in excess of recharge capacity may
aggravate such a system to cause seawater upconing and a
thickening of the brackish water zone. The consequences
of groundwater pollution last far longer than those of
surface water.
125
water table aquifers. Groundwater pollution from pesti•
cides has been detected in small amounts in pineapple
plantations on the Hawaiian Islands (Peterson, 1991).
Biological contaminants (bacteria and viruses) move in
groundwater, but more slowly than water due to adsorption
onto solid surfaces. It is probable that island communities
have tolerances to water quality levels that may not be
acceptable on mainland Australia. A limited amount of
published information exists on the bacteriological quality
of groundwater on islands (Morrison & Brodie, 1985;
Detay & others, 1989).
Some contaminants are conservative, i.e. they are not
eliminated with time in a given environment. Examples are
the chloride ion (salinity), while sulphate and nitrate are
preserved under aerobic conditions . Other contaminants,
such as biocides, are degradable - that is they are
transformed into other substances by biochemical reac•
tions. The sandy soils of atoll islands offer weak resistance
to the free percolation of contaminants, but clay soils of
volcanic islands are effective barriers until their buffering
properties (exchange and adsorption) are exceeded.
Norfolk Island
Norfolk Island is a territory of the Commonwealth of
Australia, and with an area of 35 km 2 is the largest and only
inhabited island of a remote group of three islands in the
southwest Pacific Ocean , at latitude 29 S and longitude
168 E (Fig. 2) . The island is a small landmass situated on
the Norfolk Rise - a pronounced north-trending continen•
tal ridge between New Zealand and New Caledonia.
Norfolk Island is an erosional remnant of a number of local
volcanic centres that erupted several times in the Pliocene
between 3.05 and 2.3 Ma ago (Jones & McDougall, 1973).
The climate is subtropical with a mean annual rainfall of
1324 mm. May to August are the wettest months (monthly
averages of about 140-150 mm), and November to January
tend to be the driest (averaging 70-90 mm) ; cyclonic
storms may occur in summer. Periods of low rainfall are
0
Typical pollution sources are home sanitation systems
(septic tanks and latrines) . High bacterial counts may be
noticeable in areas with scarce soil and relatively high rock
permeability (e.g. coral limestone, recent volcanic rock) .
Domestic garbage disposal is a major problem, as good
sites are hard to find because of unsuitable ground
conditions and conflicting land use. Runoff from impervi•
ous roads, airport runways and leaking fuel tanks may
release hydrocarbons into the groundwater. Contamination
from human, animal waste, and agricultural fertilisers is
forewarned by increased nitrate concentrations in shallow
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Figure 2. Location of Norfolk Island.
126
ROBERT S. ABELL
associated with ENSO events (Fig. 3). Mean monthly
temperature fluctuates from a minimum of 12° C in winter
to a maximum of 25° C in summer. As the weather is under
an oceanic influence, there are no extremes of heat or cold,
although humidity is generally high during summer
months. There is little variation between day and night
temperatures (5_6° C). At the August 1991 Census, the
population on the island was 1912 (1478 permanent and
434 temporary residents). The majority live in and around
the central business area of Burnt Pine-Middlegate.
Geology and geomorphology
The cliffs surrounding Norfolk Island provide a nearly
continuous section of the geology (Fig. 4) . Outcrop is
obscured by a weathered mantle (up to 80 m thick) and in
places by thick vegetation. The unweathered part of the
volcanic sequence suggests a series of complex and
spasmodic eruptive events in which basaltic lava and
pyroclastic units were deposited on a series of weathered
or eroded topographic surfaces. Hyaloclastite rocks ex•
posed on the northern side of the island represent a
lithofacies formed through quenching and fragmentation as
subaerial basaltic lava flowed into seawater. Along the
shore of the Kingston lowland (and also forming Nepean
Island) are exposures of cross-bedded and massive cal•
carenite originally deposited by on-shore winds during
periods of low sealevel in the Late Quaternary. Strips of
alluvium occur in active creek catchments.
The geomorphology is dominated by elevated terrain in the
northwest, rising to a semi-circular ridge on which
Mt.Bates (318 m) is the highest point. The remainder of the
island consists of a deeply incised southern plateau, about
100 m high and sloping southeast to a coastal plain at
Kingston (Abell & Falkland, 1991). The drainage pattern
is typical of volcanic terrain consisting of a network of dry
valleys leading into perennial and intermittent streams.
Radial drainage occurs around the main volcanic vent. On
the southern plateau, jointing has modified the dendritic
pattern (tributaries joining the main stream at right angles)
developed in the headwaters of each catchment.
Groundwater occurrence
Groundwater functions as a dynamic system within the
islands hydrological cycle (Fig. 5). The main agent of
recharge is rainfall. An elevated water table in the
weathered mantle represents the upper groundwater bound•
ary (Abell, 1976). Groundwater moves laterally in the
direction of the water table gradient, discharging either in
valley floors where the ground surface intersects the water
table or as high-level coastal seepages. At the base of the
weathered mantle, hydraulic continuity is maintained as
vertical leakage through a network of fractures and
interconnected openings in fresh volcanic rock. Some
groundwater moving through this system may discharge as
coastal seepages close to sealevel, or it may recharge tuff
beds and fragmented layers between lava flows to form
local semi-confined aquifers; the remainder continues to
deeper levels where it is discharged as submarine springs
at and beyond the margin of the island or ultimately mixed
with seawater in volcanic rocks below sealevel.
Water resource development
The heterogeneous permeability of volcanic bedrock
promotes the natual mixing and formation of a brackish
zone of groundwater at the base of the island. To some
extent this is offset by (a) the high and well distributed
annual rainfall, which guarantees rainwater storage, and (b)
the clay-rich nature of the weathered mantle which supports
limited catchment runoff and a high level unconfined
aquifer. Exploitation of groundwater is limited to the
southern and northwestern plateaux, where it is tapped by
more than 450 wells and bores. Deeper semi-confined
groundwater in fractured basalt and interbedded tuff is
recovered from boreholes that may reach up to 35 m BSL
(Fig. 6). A groundwater recharge estimate of 30% of
average annual rainfall (Abell & Falkland, 1991) is based
on the relationship G = P - (E + R), where G = recharge,
P = rainfall, E = evapotranspiration, and R = runoff.
Groundwater is of the NaCl-type, with the salt derived
initially from oceanic spray (Fig. 7). The water is generally
of good quality and suitable for domestic use (based on a
potability of <1000 mg/L). However, rainwater and most
groundwaters are acidic, with low pH values (5-7).
Hydrogeological factors and water balance data suggest
that sufficient resources probably exist for future needs.
Aquifer vulnerability
Groundwater contamination by natural processes is evi•
denced by high salinities associated with the stable
chloride ion. The classical Ghyben-Herzberg model of a
fresh water lens is not considered totally applicable to
Norfolk Island (Abell & Falkland, 1991). The extent of
deep groundwater underlying the island is still unknown,
but considering the difficult geological conditions (such as
presence of fractured volcanic rocks, the effect of tidal
fluctuations, and the size of the island), it is expected that
the natural thickness of the brackish water transition zone
may be substantial. Local pockets of topographically
elevated saline groundwater (source unknown) may indi•
cate restricted flow systems within the weathered mantle
(Abell & Taylor, 1981).
Artificial pollution, particularly owing to waste disposal,
presents special problems (Fig. 8). High levels of bacterio•
logical and chemical pollution from the disposal of sanitary
and livestock waste have been detected in shallow
unconfined groundwater in the Burnt Pine-Middlegate
area. Around the island perimeter there is evidence that
localised pumping can induce seawater intrusion to bores
tapping bedrock aquifers at or below sealevel (Abell &
Falkland, 1991). Until recently, the treatment and disposal
of sewage from private homes and communal estab•
lishments was through a septic tank system with the
effluent draining to absorption trenches in the ground.
Larger establishments, such as hotels and the hospital, were
served by package treatment plants generally of the
'activated sludge' or 'Imhoff' types . Effluent from such
plants was discharged into absorption trenches, disposed
onto the ground surface with overland drainage to creeks,
or in one case discharged down a borehole. Effluent
discharged into or on the ground percolates through the soil
into the weathered mantle, where it acts in most cases as a
form of recharge to the water table. During droughts,
summer months, or at times when demand is high (tourist
season), the constant re-use of shallow groundwater with a
component of sanitary waste tends to increase salinity
levels (closed system circulation). In the past, bacteriologi•
cal tests on groundwater have indicated high levels of
faecal contamination (Goldfinch & Cross, 1980; DHC,
1987). A program of testing on 150 groundwater samples
in 1981-83 showed that 68 exceeded the E.Coli guideline
value (11100 ml), while many others exceeded the total
coliforms guideline value (10/100 ml). The distribution of
nitrate in the groundwaters is uneven; most contain some
VULNERABILITY, NORFOLK ISLAND
AQUIFER VULNERABILITY,
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128
ROBERT S. ABELL
nitrate, but values of> 1 0 mg/L and up to a limit of 45 mg/L
are mainly associated with wells (uncased) which tap only
the upper part of the saturated zone in the weathered mantle
where groundwater moves seasonally under oxygen-rich
conditions. The higher nitrate levels are attributed to
domestic and livestock waste. Livestock wanders freely
over the island and distributes considerable amounts of
waste. High livestock densities also occur around watering
points and at the dairy farm.
167°58'
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Figure 4. Geology of Norfolk Island.
19/09/161
AQUIFER VULNERABILITY, NORFOLK ISLAND
"
Approximately 8 kms
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Perched watertable
Main watertable
19/09/191
Figure S. The hydrological cycle for Norfolk Island.
Aquifer stress may be promoted by short and long-term
climatic change, in particular droughts associated with
ENSO events. The annual rainfall record (Fig . 3) can assist
in predicting low rainfall years and hence periods of falling
water levels reflecting diminishing recharge to groundwa•
ter storage (Abell & Falkland, 1991). For instance, since
1950 there have been 11 ENSO events, the average period
between events is 3-4 years . In low rainfall years, the water
table aquifer may deplete to a stage where wells dry out and
additional demand is placed on deeper groundwater,
sometimes inducing brackish water upconing. In contrast,
the elevated nature of Norfolk Island (cliffs averaging
100 m ASL) suggest that possible sealevel rise due to the
'greenhouse effect ' (estimated at up to 0.5 m) is not
expected to have a deleterious effect, although it may
aggravate existing salinity problems in bores and wells in
the low lying coastal plains at Kingston .
There is an increased demand for water (mainly groundwa•
ter) caused by an expansion of the tourist industry (Fig. 9),
which has also meant a rapid development of accommoda•
tion and shops . On average, tourists represent about 1/ 6 of
the islands population at anyone time, though the figure
can be as high as V3 during peak holiday periods. The
tourist industry is a major seasonal user of groundwater.
One of the peak periods of tourism (November to January)
occurs during the dry season. Many tourists come from
communities with plentiful water supplies, and having
sufficient disposable income are accustomed to a high
standard of living, and consequently high rates of water
consumption, which in turn places extra pressure on waste
disposal facilities.
In island environments, waste disposal should if possible
be directed to areas where it cannot pollute groundwater.
On Norfolk Island, a Water A ssurance Scheme for the
disposal of sewage effluent from the Burnt Pine-Middle•
gate area has been partially completed and was opened in
December 1990 (Fig. 10). The scheme in essence removes
sewage from individual establishments into the main
sewerage line, which is then taken to an outfall site in an
intertidal cave at the foot of Headstone cliffs. The effluent,
when it reaches the treatment plant, is passed through a
screen and then over large rotating drums (rotating
biological contact) for oxygenation. However, the recom•
mended legislation - making it compulsory for all
premises either to be connected or have effluent holding
tanks installed - has not yet been formulated .
The main issue with respect to water supply on Norfolk
Island is the quality of water, and the ability to monitor and
control quality on an on-going basis. At present, little is
known about quality degradation in the deep groundwater
system. It is expected that it is safeguarded to some extent
against the contaminated shallow aquifer in the weathered
mantle by intervening rock layers, although according to
DHC (1983) rates of underground flow may be very rapid
(up to 40 m/hr) . Nevertheless, in the long-term, manage•
ment of a safe water supply will depend on protecting and
concentrating deep groundwater development in volcanic
bedrock aquifers above sealevel to safeguard against
seawater intrusion. There is probably some scope for
development below sealevel provided abstraction rates are
kept low. This, however, requires further deep drilling to
monitor the thickness of freshwater and transition zones.
130
ROBERT S. ABELL
EO
Perennial
stream
c
Approximately 3 km
')
Seasonal
100m
Sealevel
~-
-
-
HWT _"'_
High water table
~ Fracture system
LWT -51_
Low water table
; - - - Clay - sealed fracture
~ Temporary groundwater
~ storage
A and B
(Vertical scale exaggerated)
Brackish water
Kv
Vertical Permeability
KH
Horizontal Permeability
19/09/192
Bore or well taps the water table in the weathered mantle. Water supplies obtained are subject to periodic drought conditions,
bacteriological and chemical pollution.
C
Bore taps saturated tuff bed recharged by a wet fracture system and confined by impermeable basalt;
gives subartesian water supply.
D
Bore intersects dry fracture system and bedrock cavity; lost circulation during drilling.
E
Bore penetrates impermeable and poorly fractured basalt; no water supply.
F
Deep bore supply from bedrock aquifers; gives subartesian water supply but overpumping will induce saline upconing.
G
Subartesian bore supply from a saturated bedrock cavity recharged from wet fractures.
H
Small water supply from vesicular / rubbly zone between basaltic lavas.
I
Safe subartesian bore water from bedrock aquifers above sea level in the coastal zone.
J
Unsafe subartesian water supply in the coastal zone tapping brackish water in bedrock aquifers at and below sea level.
Figure 6. Simplified scheme for groundwater development in the weathered mantle and volcanic bedrock beneath the southern
plateau.
Conclusions
Small islands in the southwest Pacific have limited fresh
water resources. They are highly vulnerable to over-exploi•
tation (resulting in seawater intrusion), pollution from
human activities, and to the predicted global climatic
change leading to a rise in sealevel. Water resources are
threatened by increasing water demand due to demographic
pressure, agricultural development, and modernisation of
consumption patterns. Deterioration in quantity and quality
of groundwater resources is a limiting factor in economic
development and must be considered in the formulation of
development programs.
Research
Effective management and protection of small island
groundwater resources relies on the acquisition and
integration of reliable hydrological data. Through model•
ling, these data can be synthesised to generate groundwater
flow models and vulnerability maps as predictive tools to
support ecologically sustainable development. However,
there are significant gaps in knowledge that may be
addressed by: (a) establishment of observation bore
networks for monitoring aquifer salinity; (b) evaluation of
techniques for the estimation of evapotranspiration, par•
ticularly of the interception capacity of typical vegetation;
(c) research into the movement of urban and agricultural
pollutants through aquifers with special attention to
transport in terrain devoid of soil cover or with little
adsorption capacity; and (d) simple but accurate methods
for estimating groundwater resources particularly of the
recharge process using limited hydrometric, soil, and
vegetation data.
Training
Long-term water resource development and management
on small islands have not always achieved their goal, as
technologies, design, and materials have not been suitable
for the environment or cultural habits of the people, or
because operation and maintenance costs are excessive.
The situation is further aggravated by lack of qualified
personnel, financial resources, and geographical isolation.
The ability of islands and island groups to manage better
their water affairs will depend on: (a) legislative control,
technical solutions, and community education to overcome
threatening pollution hazards; (b) increased technology
transfer in the form of equipment and expertise best suited
to the needs of practical island management of water
supplies, e.g. drilling technology, water quality analysis,
and methodologies for optimising the safe yield from
freshwater lenses; and (c) professional and' technical
training programs by way of formal training at recognised
AQUIFER VULNERABILITY, NORFOLK ISLAND
131
GROUNDWATER
(%epm)
J
~
~
~
'" ~
"
~
~.,
.,..
\
)(
~"" .:;>
~
"
,
d'.
"
.:;>
"'-~
r
"b
~
~
~
~
~
~
r.
<b
(-;, _\
~
~
.-~~
.
-,. ...
. \.s:.
\J
" , ' _.
~~ 'b
•
I
(e
80
70
60
50
40
30
20
10
10
20
30
40
~Ca
50
- ..
-__
'-
~/~---
90
.
.. •
I
(.
~
,.
••
•
'
-...............
60
90
80
70
~
.. -. e\,
---)
CI~
Surface
Rainwater
~ Seawater
Groundwater
epm Equivalent per million
x
®
OTHER
WATERS
(%epm)
<b
~
J
"b ~
~
~.,
)(
r--
~x
/
...... ......
~
.; .:;>
\
~
~
~
~.,..
~"".:;>
~
~
~
~~
/ ®
~
(®
\:.o__
90
80
70
60
50
40
30
.
"b
~
x
x
, \X
<b
(0'
\
"
® :-,
r ®
' ...... ' --
/ __ J
~
"'•
~~
®®®~
!!/ - _ /
20
,x
~
i!l.'
'-;&.,~
~ ~
-~--~/
10
10
20
30
~Ca
40
50
60
70
80
90
CI~
19/09/ 173
Figure 7. Trilinear plots of ground and other waters on Norfolk Island.
institutions, on-island seminars and workshops conducted
by personnel from external agencies, aid agreements, and
continued support for locally based monitoring and
protection of groundwater resources.
Acknowledgments
The author is indebted to A .C. Falkland (ACT Electric•
ity and Water) and G. Jacobson (Australian Geological
Survey Organisation) for reviewing the manuscript and
providing information on small islands in the southwest
Pacific region; and G.C. Duvall for supplying details on
the Water Assurance Scheme on Norfolk Island, and
1. Eddowes (Cartographic Services Unit, AGSO) for the
line drawings.
References
Abell, R.S., 1976 - A groundwater investigation on
Norfolk Island. Bureau of Mineral Resources, Austra•
lia, Record 1976/62 .
Abell, R.S. & Taylor, F.J., 1981 - Hydrogeological and
geophysical investigations on Norfolk Island 1981.
Bureau of Mineral Resources, Australia, Record
1981178.
Abell, R.S. & Falkland, A.C. , 1991 - The hydrogeology
of Norfolk Island , South Pacific Ocean. Bureau of
Mineral Resources Australia, Bulletin 234.
Dale, W.R . & Waterhouse, B.C., 1985 - Pacific islands
hydrogeology and water quality. In Environment and
Resources in the Pacific. United Nations Environment
132
ROBERT S. ABELL
Small scale
irrigation
\".
Sealed roads /
Airport runway
--
"
Livestock
"_-Lair-·
1
~I
'"
~!
'"
~
o
----"--1
~I
I'"~
.2 __ -V
t~o
~I
I~
z~
i'il
'. ~ .'"
"...
A
Stream runoff
\~
__ - - L . - -
I
House sanitation
(tanks / latrines)
Refuse disposed in disused
well or landfill site
I"
'$~
. ~-$
'"
<if
/
/'"--~,
lv'
PPtiO~'
;...,/ •
,J, __________ ,J,
.'
Hydrocarbons
WEATHERED MANTLE
(Decomposed basaltic rock)
'-. \
Fe
FRACTURED VOLCANIC
BEDROCK
~·>I
'
v
" ,JI
(":'';u\
" : '
.
\ ... ' '. . '.' .' I
1
'i' Leachate
"'I·~~~~I PLUME OF SALINE
'i' NITRATE AND 'i'
MICROBIOLOGICAL
POLLUTION
GROUNDWATER
1<-'
Deep
Bore
-"~
--- -->
Watertable
Pollutant Input
Groundwater movement
U
------;;.. Runoff
Bore/Well
19/09/193
Figure 8. Sources of shallow groundwater pollution on Norfolk Island.
Program, Regional Seas Reports and Studies, 69,
57-67.
Detay, M., Allessandrello, E., Come, P. & Groom, 1.,1989
- Groundwater contamination and pollution in Micro•
nesia. Journal of Hydrology, 112, 149-170.
DHC (Department of Housing and Construction), 1983 Norfolk Island investigation of groundwater movement,
May-August 1983. Report preparedfor the Department
of Territories and Local Government, Canberra.
DHC (Department of Housing and Construction), 1987 Norfolk Island - Reassessment of water supply and
sewerage proposals. Draft report to the Norfolk Island
Government and Department of Territories, Canberra.
Falkland, A.C. (editor), 1991 - Hydrology and water
resources of small islands: a practical guide. United
30000
25000
.,
20000
;;
....E
..S
......
15000
~
10000
5000
1960
1965
1970
1975
VIal
1980
1985
1990
19/09/185
Figure 9. Annual tourist population on Norfolk Island
(1960-1992).
Nations Educational Scientific and Cultural Organisa•
tion. Studies and Reports in Hydrology, 49, 435pp.
Falkland, A.C., 1992 - Water resources of small islands.
Workshop on climatic impacts of the coastal zone.
James Cook University, Townsville, 1992.
Goldfinch, R.F. & Cross, R.W., 1980 - Proposed water
supply and sewerage project for Norfolk Island. Visit
report. The Australian Department of Housing and
Construction, ACT region.
Jones, J.G. & McDougall, I., 1973 - Geological history of
Norfolk and Philip Islands, Southwest Pacific Ocean.
Journal of the Geological Society of Australia, 20 (3),
239-254.
Morrison, R.J. & Brodie, J.E., 1985 - Pollution problems
in the South Pacific: Fertilisers, biocides, water supplies
and urban wastes. In Environment and Resources in the
Pacific. United Nations Environment Programs. Re•
gional Seas Reports and Studies, 69, 69-74.
Peterson, F.L., 1984 - Hydrogeology of high oceanic
islands In Water Resources of Small Islands Technical proceedings (Part 2). Commonwealth Science
Council Technical Publication Series, 154,431-435.
Peterson, F.L., 1991 - Hawaiian Islands (Case study
No.6). In: Falkland, A.c. (editor), Hydrology and
Water Resources of Small Islands: a Practical guide.
United Nations Educational, Scientific and Cultural
Organisation. Studies and reports in Hydrology, 49,
362-367 .
AQUIFER VULNERABILITY, NORFOLK ISLAND
POINT
167' 55'
133
167' 58'
VINCENT
Sewerage system
6
D
Roads
Treatment plant
29' 00'
Pump station
Streams
2km
CASCADE
BA Y
('-'
\
(
'- --('
/'
)
STEELS
(
POINT
29' 02'
"
\
____ I
~/' .-1
OUTFALL
I
BALL
BAY
POINT
COLLINS
SYDNEY
POINT
BA Y
ROSS
HEAD
POINT
29' 04'
HUNTER
19/09/ 194
Figure 10. Plan of the water assurance scheme on Norfolk Island.