In this article, based on the example of the Toliara lagoon in Madagascar, we identified the major impacts of the two main drivers of the water renewal in a typical channel lagoon: the tide and the swell breaking on the reef. For this purpose, we applied the numerical model Croco which is based on ROMS-AGRIF and uses a realistic and high-resolution configuration. The validation was performed with in situ ADCP data, then, realistic and sensitivity simulations were run to infer tides and waves role in ocean-lagoon exchanges and to estimate water age and water origin. The modelling approach adopted enabled an understanding of the effects of swell and tide on the water renewal. During low wave conditions, tide and waves counteract each other on cross-reef flow: the cross-reef inflow tends to increase with waves breaking on the reef, whereas cross-reef flow tends to decrease or to be outflowing with tidal action. Hence, the lagoon-ocean exchange is reduced and is at a minimum when wave height reaches 0.85 m and the tide has minimum amplitude. During high wave conditions, both tide and waves increase ocean-lagoon exchanges by increasing the cross-reef inflow, whereas during low wave conditions, the cross-reef flow is mainly outward with increase with tidal amplitude and decrease with wave height until the threshold of 0.85 m.

在本文中，我们以马达加斯加的 Toliara 泻湖为例，确定了典型河道泻湖中水更新的两个主要驱动因素的主要影响：潮汐和珊瑚礁上的膨胀。为此，我们应用了基于 ROMS-AGRIF 并使用逼真和高分辨率配置的数值模型 Croco。验证是使用原位 ADCP 数据进行的，然后运行现实和敏感性模拟以推断潮汐和波浪在海洋-泻湖交换中的作用，并估计水年龄和水源。所采用的建模方法有助于了解涌浪和潮汐对水更新的影响。在低波条件下，潮汐和波浪在跨礁流中相互抵消：跨礁流入趋向于随着波浪在礁石上破裂而增加，而跨礁水流趋于减少或随着潮汐作用流出。因此，当波高达到 0.85 m 且潮汐波幅最小时，泻湖-海洋交换量减少并最小。在高浪条件下，潮汐和波浪都通过增加跨礁流入量来增加海洋-泻湖交换，而在低波条件下，跨礁流主要向外流动，随着潮幅的增加而增加，随着波高的增加而减少，直到达到阈值0.85 米。