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Environment and development in coastal regions and in small islands |
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Environment and development in coastal regions and in small islands |
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| Update Number 3 | November 1996 (UNESCO-APIA) |
Text of articles
Buanerake;
a new word for evaporation
Groundwater
a crucial source
Does
pumping affect the coconut trees?
Level
changes small
SPOTting
catchment from Space
Next
steps on Groundwater studies
Many
Sources Pollute Water
Buanerake; a new word for evaporation
The UNESCO-South Pacific
Applied Geoscience Commission SOPAC study of atoll
groundwater recharge has helped coin a new word for evaporation
in the Pacific Island nation of Kiribati. The word is buanerake
which means vapour upwards.
Team members Ian White (Centre for Resource and Environmental Studies, Australian National University, Canberra), Tony Falkland (ACTEW Corporation, Canberra), Leonie Crennan (Consultant, Social Science), and colleagues from the Kiribati Public Works Division (PWD) met with local village elders in August to discuss the project and seek approval to carry out the work on village land. The team discovered that there was no word for evaporation in the I-Kiribati language. After a hasty discussion, the PWD participants came up with the word buanerake, which conveys the idea of steam rising from a kettle.
Groundwater a crucial source
The UNESCO-SOPAC study is part of UNESCO's International
Hydrological Programme, and a contribution to UNESCO's new
project on Coastal Regions and Small Islands. The August team
also included participants from Cook Islands, Federated States of
Micronesia and Tuvalu. The study aims to quantify the recharge of
fresh groundwater lenses which float above seawater in islands,
atolls, and some coastal areas. The sustainability of water
extraction from these shallow freshwater lenses is crucial to
many Pacific nations where groundwater is the major water
reservoir. Overpumping can lead to salt moving into the
groundwater from underlying seawater. In addition, these shallow
groundwater systems, in highly permeable coral sands, are easily
contaminated by surface wastes, and are therefore extremely
fragile.
This study aims to supply relevant information on the amount of
fresh groundwater used by coconut trees and the effect of pumping
on the groundwater lens. The study also aims to record oral
traditions, particularly on climatic fluctuations and groundwater
pumping and their impacts on crops and drinking water.
A weather station has been established on the island of Bonriki
in Tarawa atoll, Republic of Kiribati to monitor relevant
climatic variables. Watertable monitors and tree sap flow
monitors have also been installed. As well, the salt in the
groundwater is being monitored using specially designed salinity
wells.
Does pumping affect the coconut trees?
Groundwater beneath a water reserve on this island provides
drinking water for the majority of people on Tarawa. Local
villagers, who owned the land and live adjacent to the water
reserve were also interviewed. The interviews revealed a
politically, economically and socially complex situation.
The Bonriki people have lost land due to the water reserve and
the building and expansion of the international airport. The
villagers have recently been paid compensation by the government
for the loss of land. However they believe the coconut trees and
taro, which grow in pits excavated to the watertable, are not as
productive in the water reserve since pumping began.
Level changes small
Preliminary results from the first field measurements
indicate that the lowering of the watertable due to pumping in
the specially designed horizontal pumping galleries was less than
20 mm. Since the watertable fluctuates diurnally by about 120mm,
due to tidal influence, this drawdown is negligible. Perceived
changes in vegetation do not therefore seem due to the pumping.
It was shown that direct evaporation from the lens can be no greater than 4
m/day. Potential evaporation rates are close to 4.6 mm/day. Coconut trees appear
to use between 100 to 150 litres of water per day in the dry season, about three
times the water allocated per head to people in Kiribati.
Adapted from an article by Ian White, Leonie Crennan and the
study team. See page 2 for future plans.
SPOTting catchments from Space
As a possible contribution to the proposed UNESCO (IHP &
CSI) Catchments and Communities study, the ORSTOM laboratory in
Noumea, New Caledonia has prepared a proposal for a remote
sensing study on catchments on Guadalcanal island, Solomon
Islands, which they will submit for French funding. This depends
on historical remote sensing data held by ORSTOM to compare with
newly acquired data. ORSTOM hold such data for many Pacific
islands, and for others it is available for purchase from SPOT
image, so an alternative site could be chosen.
First indications are that the use of biological/ecological
monitoring for the study is promising but considerable
preparatory work would be needed. The Solomon Islands contacts
led by Mr Donn Tolia are continuing work to identify suitable
catchments for ground truth and community involvement. An IHP
working group meeting next year in Fiji, already funded, will be
an opportunity to push forward the study plans.
Next steps on Groundwater studies
Atoll Groundwater Recharge. Following the successful
initial field work and training in August (see front page
article) the main consultant Prof Ian White will return to
Kiribati for a monitoring visit in November 1996. He will also
pass through Suva and meet with Trevor Sankey and SOPAC. The
three consultants have recommended a return visit during the wet
season say February 1997, to make physical measurements in rainy
conditions, to follow-up social aspects and counterpart training,
and to plan application of the results. It appears that CSI and
HYD funds allocated for work on the studies in 1996-1997 will be
sufficient for this. Ideally, the overseas trainees should attend
as well, but funding would have to be found.
Groundwater pollution in villages. Dr Leonie Crennan will
return to Tonga in November 1996 to follow-up the community
contacts and counterpart training. Mr Trevor Sankey will make a
24 hour stopover in Nuku'alofa, Tonga on his way to the CSI
Experts Meeting. He will meet with Dr Crennan and the Tongan team
members to plan application of the results.
Looking further ahead. A workshop to follow-up both
groundwater studies is expected to be held in July 1997 in Suva
at the time of the Pacific Science Association VIII
Inter-Congress. Trevor Sankey will make preliminary plans for
this during his mission to Suva in November 1996. A number of
participants at the SOPAC Annual Session, Rarotonga, Cook
Islands, 2-9 October 1996, expressed strong interest in receiving
the results of both groundwater studies.
Many Sources Pollute Water
Mr Lindsay Furness made a return visit to Tonga at the end of September
1996 to monitor measurements and analyze stored samples for tracer dye. He was
able to carry out work as planned and has now submitted his report. The results
found reinforced his conclusion that contamination is widespread from multiple
sources and that groundwater movement is not the major source or vector in well
contamination.
Goodbye to Mr Derrick Depledge who is leaving SOPAC's Water and Sanitation
Programme in early December 1996. Our thanks to Derrick for his interest in
the IHP studies, and his thought-provoking comments
