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.

Biologging is suspect to cause corneal opacity in two populations of wild living Northern Bald Ibises (Geronticus eremita)

Background:In this paper,we present evidence that biologging is strongly correlated with eye irritation,with sometimes severely impairing effects.A migratory population of the Northern Bald Ibis(Geronticus eremita,NBI)is reintroduced in Europe,in course of a LIFE+project.Since 2014,all individuals have been equipped with GPS-devices.Remote monitoring allows the implementation of focussed measures against major mortality causes.Methods:Initially all birds carried battery-powered devices,fixed on the lower back of the birds.Since 2016 an increasing amount of birds has been equipped with solar-powered devices,fixed on the upper back,the more sunexposed position.In 2016,we observed opacity in the cornea of one eye(unilateral corneal opacity;UCO)during a regular health monitoring for the first time.Results:By 2018,a total of 25 birds were affected by UCO,with varying intensity up to blindness.Clinical examination of the birds revealed no clear cause for the symptoms.However,only birds carrying a device on the upper back were affected(2017 up to 70%of this group).In contrast,none of the birds carrying devices on the lower back ever showed UCO symptoms.This unexpected relationship between tagging and UCO was discovered in 2017.After we took countermeasures by removing the device or repositioning it on the lower back,we observed an immediate reduction of the incidence rate without any new cases reported since January 2019.NBI roost with their head on the back,one eye closely placed to the device if it was positioned on the upper back.Thus,we conclude that the most parsimonious explanation for the symptomatology is either a repetitive slight temperature rise in the corneal tissue due to electromagnetic radiation by the GSM module of the device or a repetitive slight mechanical irritation of the corneal surface.Concrete evidence is missing so far.Meanwhile,cases of UCO were found in another NBI population.Conclusion:Our observations indicate that further research in the fast-growing field of biologging is urgently needed.The findings question the positioning of devices on the upper back in birds roosting with the head on the back.