Modelling the response of fresh groundwater to climate and vegetation changes in coral islands

Comte, J.-C.; Join, Jean-Lambert; Banton, Olivier; Nicolini, Eric

Modelling the response of fresh groundwater to climate and vegetation changes in coral islands | Modéliser la réponse des eaux souterraines douces aux changements climatiques et de végétation dans les îles coralliennes Modelación de la respuesta del agua subterránea dulce a los cambios climáticos y de vegetación en islas coralinas 模拟地下淡水对珊瑚岛气候和植被变化的响应 Modelação da resposta da água subterrânea doce às alterações no clima e na vegetação em ilhas de coral

2014

Comte, J.-C. (Jean-Christophe) | Join, Jean-Lambert | Banton, Olivier | Nicolini, Eric

In coral islands, groundwater is a crucial freshwater resource for terrestrial life, including human water supply. Response of the freshwater lens to expected climate changes and subsequent vegetation alterations is quantified for Grande Glorieuse, a low-lying coral island in the Western Indian Ocean. Distributed models of recharge, evapotranspiration and saltwater phytotoxicity are integrated into a variable-density groundwater model to simulate the evolution of groundwater salinity. Model results are assessed against field observations including groundwater and geophysical measurements. Simulations show the major control currently exerted by the vegetation with regards to the lens morphology and the high sensitivity of the lens to climate alterations, impacting both quantity and salinity. Long-term changes in mean sea level and climatic conditions (rainfall and evapotranspiration) are predicted to be responsible for an average increase in salinity approaching 140 % (+8 kg m⁻³) when combined. In low-lying areas with high vegetation density, these changes top +300 % (+10 kg m⁻³). However, due to salinity increase and its phytotoxicity, it is shown that a corollary drop in vegetation activity can buffer the alteration of fresh groundwater. This illustrates the importance of accounting for vegetation dynamics to study groundwater in coral islands.

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