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abstract 308

Water resources of small coral islands facing climate change and disasters

Author(s): Olivier Banton(3), Jean-Christophe Comte(3), Lionel Bigot (2), Antony Finizola(2), Jean-Paul Ambrosi(4), Pascale Chabanet(1)(2), Hiroya Yamano(5), Yves Travi(3)
1.Université de la Réunion, France 2.Institut de Recherche pour le Développement, New Caledonia 3.Université d'Avignon, France 4.UMR 161 CEREGE CNRS,Aix en Provence, France 5. National Institute for Environmental Studies, Japan

Keyword(s): groundwater, coral islands, climate change, modelling

Article:
Poster:

Session: Poster session 3

AbstractLow lying coral islands are complex and vulnerable

ecosystems that can be strongly affected by natural or human changes. The Tuvalu’s experience has shown that the

global warming impact is a big issue for these islands that are very close to the sea level. However cause-effect

relations remain difficult to highlight. In many places, the anthropic influences make the analysis more complex.

The purpose of the project “INTERFACE” granted by the French research agency (ANR) is to predict the

vulnerability of coral reef island ecosystems to climate change. To achieve this goal, the spatial and temporal

variability of potential indicators (such as hydrogeological, sedimentary, biological and microbiological parameters)

are studied with regard to climatic and oceanic variations. Two small islands without human influence were

instrumented with observation wells for groundwater monitoring and with automatic measuring stations for climate

and oceanic level monitoring. These islands are located in the same oceanic province (Indo-Pacific) but face different

climatic regimes. One is located in the Glorieuses archipelago in the Mozambic Canal and the other in the New

Caledonia lagoon.
This communication focuses on the groundwater as the most important condition to maintain

the terrestrial ecosystem. The freshwater lens is lying at the earth-sea and atmosphere interface. It may reflect any

evolution of one of these boundary conditions. Hence monitoring of the groundwater lens may be a valuable indicator

of the ecosystem state and evolution.
For this, observation wells were drilled to monitor the water head, the

temperature and the quality of groundwater. In parallel, geophysical investigations were carried out for the

characterization of the geological structure and the freshwater/seawater distribution.
By the way of numerical

modelling, we study the response of freshwater lens to water recharge or to sea level variations related to periodic

fluctuations (tides, seasons) and sudden or extreme events (storm, cyclone or drought). Variable-density flow

modelling is used to compare the impact of different expected scenarios of climatic and oceanic

evolutions.
Results of this project will conduct in guidelines for future assessment of small island groundwater

which constitutes an important societal challenge for low lying areas facing climate change. Associated with other

environmental indicators, groundwater monitoring can be a valuable tool for the assessment of islands ecosystems

vulnerability.

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Water resources of small coral islands facing climate change and disasters