As the second largest lake in Africa, the extent of Lake Chad has over 50% seasonal variations with large parts of water under aquatic vegetation. Although a great area shrinkage since the 1960s divided the lake into two parts, namely, the northern and southern basins, it still feeds millions of people from four countries around it. Given sparse in situ measurements, remote sensing with seamless spatial coverage has served for acquiring the long-term area series of Lake Chad. This study retrieves the open (unvegetated) surface water area series of Lake Chad and the total inundation area, including open water and water under macrophytes, combining multiple remote sensing data from around 1980 to 2020 with satellite-based water level and in situ observations at the Bol gauge as validation and auxiliary. Results show that the total inundation area continuously recovered at a rate of 145 km²/year from 1982 to 2020 with large annual fluctuations. Approximately two- to three-month time lags between the open surface water and the total inundation area reveal the hydrological asynchrony of Lake Chad, which can be attributed by the large area of rooted macrophytes. The overspill of the southern surface water flowing over the Great Barrier into the northern lake also has a one-month lag with the open surface water of the southern lake. The Google Earth Engine-based online application can be easily shared for use and data downloaded by the general public, and the open code can be adjusted for any other lakes worldwide.

作为非洲第二大湖，乍得湖的范围有超过 50% 的季节性变化，大部分水域都在水生植被之下。尽管自 1960 年代以来面积大幅缩小，将该湖分为北部和南部盆地两部分，但它仍然养活了周围四个国家的数百万人。鉴于现场测量稀少，无缝空间覆盖的遥感有助于获取乍得湖的长期区域系列。本研究结合 1980 年至 2020 年左右的多项遥感数据，结合卫星水位和在Bol 规作为验证和辅助。² /年，从 1982 年到 2020 年，年度波动较大。开放地表水和总淹没区之间大约有两到三个月的时间滞后，揭示了乍得湖的水文不同步，这可以归因于大面积的有根大型植物。南部地表水越过大坝流入北部湖的溢流，也与南部湖的开阔地表水相滞后一个月。基于谷歌地球引擎的在线应用程序可以很容易地共享供公众使用和下载数据，并且开放代码可以针对全球任何其他湖泊进行调整。