Coastal low-lying sand islands confront an imminent threat owing to global warming, primarily stemming from the confluence of rising sea levels and amplified precipitation variability. These islands harbour delicate freshwater reservoirs in unconfined aquifers, reliant significantly upon precipitation for replenishment. This investigation focuses on a sand island situated along Australia’s eastern coast, resembling islands prevalent across the Indian and Pacific Oceans. The study involves comprehensive instrumentation to monitor Actual Evapotranspiration (AET) concurrently with rainfall patterns and water table fluctuations. Eddy Covariance (EC) systems were employed across three distinct vegetation zones: a wetland, a swamp, and a commercially managed pine forest plantation. The aim was to gauge evapotranspiration dynamics, comparing computed reference evapotranspiration (ET0) at each site with EC-measured values to establish novel reference vegetation coefficients (Kv) tailored to these specific environments. Actual evapotranspiration was found the largest at the wetland, the swamp, and the pine plantation in decreasing order. Pine plantation evapotranspiration was found the most sensitive to water table depth, while the native swamp and wetland maintained high evapotranspiration rates through dry periods. A simple idealized water balance is proposed for the island for the dry and wet seasons. Large rainfall events during the wet season were found critical in providing recharge of the aquifer, highlighting the importance of such events in maintaining the freshwater resource and vegetation health on such islands.

中文翻译：

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沿海低洼亚热带沙岛三种不同植被类型蒸散量的直接观测


由于全球变暖，沿海低洼沙岛面临迫在眉睫的威胁，这主要是由于海平面上升和降水变化加剧的共同作用造成的。这些岛屿的无承压含水层中蕴藏着脆弱的淡水水库，其补给很大程度上依赖于降水。这项调查的重点是位于澳大利亚东海岸的一个沙岛，类似于印度洋和太平洋上常见的岛屿。该研究涉及综合仪器来监测实际蒸散量 (AET)，同时监测降雨模式和地下水位波动。涡流协方差 (EC) 系统应用于三个不同的植被区域：湿地、沼泽和商业管理的松树林种植园。目的是测量蒸散动态，将每个地点的计算参考蒸散 (ET0) 与 EC 测量值进行比较，以建立适合这些特定环境的新参考植被系数 (Kv)。实际蒸散量最大的是湿地、沼泽、松林，依次递减。研究发现，松树种植园的蒸散量对地下水位深度最敏感，而原生沼泽和湿地在干旱时期保持较高的蒸散率。为该岛提出了旱季和雨季的简单理想水平衡。研究发现，雨季期间的大降雨事件对于含水层的补给至关重要，凸显了此类事件对于维持此类岛屿淡水资源和植被健康的重要性。