Environment and development
in coastal regions and in small islands
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UNESCO Pacific Science Programme Update

Update Number 3   November 1996

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

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