Jean-Pierre VERGNES (BRGM, France); Anne JOST (METIS, France); Nicolas GASNIER (CNES, France); Marcello DE MICHELE (BRGM, France)

In the presence of climate change and population growth, hydrogeological models become essential for monitoring and managing freshwater resources and to prevent and mitigate the consequences of flood events. These models integrate a wide range of geomorphological data and need field measurements that are not always sufficient. The SWOT satellite mission therefore appears very attractive as a complement to in situ data on surface waters. The aim of this study is to assess the feasibility of using SWOT data as a complementary tool for building and evaluating regional hydrogeological models, in particular their relation with groundwater level. To this end, we identify hydrogeological models which represent areas with high surface water and groundwater interactions isssues, for which our knowledge can be improved. For now, three French study areas are targeted : the lakes and canals of the Landes region, the Boutonne watershed, and the Tarn-et-Garonne watershed. On the second hand, we develop a method for processing Pixel Cloud HR SWOT products based on the PixC Dust library (outlier isolation, temporal chronicle, linear along the watercourse, assessment of satellite data reliability) with the aim of linking SWOT satellite data to simulated surface water, and indirectly to simulated groundwater levels through river-groundwater exchanges. To do so, Pixel Cloud HR SWOT products undergo various filtering operations (geographical and based on the pixel classification and sigma-0) to eliminate outliers. SWOT temporal and spatial chronicles are evaluated against in situ river flow and water height time series available from the French Hydroportail portal. Among the three chosen study areas, first results from the SWOT data processing show a very good representation of lake extents and surface water elevation variations in the Landes canals, perfectible representation on certain narrow rivers (30m wide) like the Boutonne river likely due to water level not buffered by lakes, and an accurate estimation of the water surface elevations over the Tarn and the Garonne rivers. Next step will be to link those SWOT results to the available hydrogeological models in these areas in order to assess the capability of SWOT to improve the simulated surface water representation and hence the simulated piezometric levels.