Water Resource Monitoring Exploiting Sentinel-2 Satellite and Sentinel-2 Satellite Like Time Series;Application in Yangtze River Water Bodies

As part of the Dragon 4 project,the water extents of Wuchang and Shengjin lakes have been extracted from Sentinel-2 time series,using all exploitable images since the beginning of the acquisitions in 2015.The aim of the study is to assess the capability of the Sentinel-2 constellation and Landsat 8 over the Anhui region,especially the high temporal resolution.A total of 32 dates have been used and 10 Landsat 8 images(Libra)have been added to try to reduce the temporal gaps in the Sentinel-2 acquisitions caused by cloudy conditions.Extractions were done using a SERTIT-ICube automatized routine based on a supervised Maximum Likelihood Classification.These extractions allow to recreate the dynamic of the two lakes and show the drought and wet periods.During the 3 years interval,the surface peaks in July 2016 for both lakes.The lowest level appears at two different dates for each lake;in January 2018 for Wuchang,in February 2017 for Shengjin.Wuchang Lake surface area appears to be more variable than Shengjin Lake,with many local maximum and minimum between the end of 2017 and April 2018.In the case of Wuchang Lake,floating vegetation is a problem for automatic water surface area extraction.The lake is covered by vegetation during long periods of time and the water below can’t be detected by automatic radiometric means.Nevertheless,Sentinel-2 stays a pertinent and powerful tool for hydrological monitoring of lakes confirming the expectation from the remote sensing wetland community before launch.The presence of NIR and SWIR bands induces a strong discrimination between water and other classes,and the systematic acquisitions create dense time series,making analysis more consistent.It makes possible to sensor events occurring over short periods of time.Thanks to this a link can be done between endangered bird species,such as the Siberian Crane and the Lesser White-Fronted Goose and periodically flooded areas.These midterm results illustrated the pertinence and powerful of multi-source optical satellite data for environmental analysis.

Seasonal and regional differences in migration patterns and conservation status of Swan Geese(Anser cygnoides)in the East Asian Flyway

Background:The Swan Goose(Anser cygnoides)breeds across Mongolia and adjacent China and Russia and winters exclusively in China.It is globally threatened,showing long-term major range contractions and declining abundance,linked to habitat loss and degradation.We remain ignorant about the biogeographical subpopulation structure of the species and potential differences in their migration timing,stopovers and schedules,information that could be vital to effective conservation of different elements of the species population,which we address here with results from a telemetry study.Methods:In 2017-2018,we attached GPS/GSM telemetry devices to 238 Swan Geese on moulting sites in three discrete parts of their summering area(Dauria International Protected Area,Central Mongolia and Western Mongolia),generating 104 complete spring and autumn migration episodes to compare migration speed and nature between birds of different summer provenances.Results:Birds from all three breeding areas used almost completely separate migration routes to winter sympatrically in the Yangtze River floodplain.Although many features of the spring and autumn migrations of the three groups were similar,despite the significantly longer migration routes taken by Western Mongolian tagged birds,birds from Dauria Region arrived significantly later in winter due to prolonged staging in coastal areas and took longer to reach their breeding areas in spring.Among birds of all breeding provenances,spring migration was approximately twice as fast as autumn migration.Areas used by staging Swan Geese(mainly wetlands)in autumn and spring almost never fell within national level protected areas,suggesting major site safeguard is necessary to protect these critical areas.Conclusions:This study showed the discreteness of migration routes taken by birds of different summer provenances and differences in their migratory patterns,highlighting key staging areas(Yalu River Estuary in China/North Korea for Dauria Region breeding birds,Daihai Lake for Central Mongolian and Ordos Basin for Western Mongolian birds).Based on this new knowledge of the biogeographical subpopulation structure of the Swan Goose,we need to combine data on subpopulation size,their distribution throughout the annual life cycle and conservation status,to develop more effective conservation strategies and measures to reverse population decline throughout the range.