Lake Maggiore and the Ticino River are water bodies shared by Italy and Switzerland: they are important resources for drinking water, irrigation and hydroelectricity generation as well as for tourism and biodiversity. The cross-border character and the often conflicting needs of the different users make the shared management of this resource very complex, but of great importance. The `‘Parchi Verbano Ticino´’ project, funded by Regione Lombardia / EU – INTERREG Italia Svizzera 2014/2020, aims to study the effects of water levels of the lake on various environmental components with a particular focus on protected natural areas. The level of the lake is regulated by a dam located at the southern shore of the lake. In this framework, this study aims to analyse the effect of water level on bird migration by: 1) Calculate the inundated bird habitat using a simulation based on measured water level; 2) calculate the inundated habitat from Sentinel-1 remote sensing imagery 3) Use the flooded area derived from S1 as ground truth to validate the previous simulation 1). The study area is centerend around Bolle di Magadino (Switzerland, 8°51’56.90”E, 46°9’42.17”N, a protected wetland located on the north shore of lake Maggiore at the confluence with the Ticino river. The area is a recognized nesting and stopover site for birds, listed as a Ramsar Wetland of International Importance and as Important Bird and Biodiversity Area (IBA). We defined the habitats of interest using a vegetation map provided by Fondazione Bolle di Magadino. The vegetation types collected from a phytosociological field study were aggregated into ten land cover classes that described the habitat types and land use. The final habitat map covers an extent of 6.7 km², including the 1500 ha of wetland called Bolle di Magadino. Daily passage of migrant birds have been recorded at Magadino ringing station and since 2019, traditional net captures were coupled with an Avian Vertical-looking Radar In this study we focus on the following periods, during which bird monitoring systems were both deployed: P1: 2019-05-01– 2019-06-20; P2 2019-10-01–2020-02-20 and P3 2021-02-01– 2021-07-20. The lake level measured at the hydrological station of Locarno (CH) was used to determine the inundated area in GRASS GIS using ther.fill module (GRASS Development Team, 2022) and a DTM that included the lake bathymetry (cell size 0.5 m). The lake level fluctuated between 192.3 and 194.9 m.a.s.l. over the study period, with a minimum in April and May, when the waters are used to irrigate the rice fields downstream, and a maximum in late autumn. We used the Google Earth Engine Platform (GEE) (Gorelick et al., 2017) to extract Sentinel-1 Synthetic Aperture Radar (SAR) images (ESA, 2021) as they are suited for surface water mapping and not affected by cloud coverage (Ovakoglou et al., 2021). We used Edge Otsu Algorithm with terrain correction (Markert et al., 2020) to estimate the inundated areas of the collection of a total of 236 images for the three time periods when bird migration was also monitored. The calculation was implemented GEE with the approach described by Gorelick et al. (2017) calibrating the threshold for our study area, adapting the code provided by Open Geo Blog (2021). The inundated areas were then overlapped with the land use map in order to estimate the extent of the submerged vegetation over the three time period defined. The resolution of all maps was 10 m, except the DTM that has 0.5 m, the CRS used in this work were WGS84 in GEE and the local CRS GCS CH1903 for all the other analysis. The area covered with water, according to S1, varied between 103.9 and 471.7 ha (210+- 83.6), some of the surface is a permanent wetland so it is never completely dry. Each habitat was affected differently by the flooding: when the water was at its highest, croplands were completely inundated, grasslands and reeds were submerged for 80% of their extent whereas urban areas and infrastructures were not affected (less than 1% underwater). The flooded area calculated by filling the terrain model at the level of the ranged from 130.4 to 248.90 ha (208+- 48.6). The correlation between inundated areas obtained using r.fill in GRASS and S1 on the same dates was fair for P1 and P2, but not for P3, when the water of the lake were taken for irrigation, but the habitats were flooded by rainfall. An interpolation of the flooded from S1 is a more efficient way to obtain an estimate of the flooded habitat on a daily basis, that is necessary to study its effect on migratory birds. The results presented here will contribute to the definition sustainable management tools of water management of lake Maggiore taking into account the effect of lake level on biodiversity in general and on bird habitat in particular.