Tanguy Alexandre Naets (DTU Space, Denmark); Lars Stenseng (DTU Space, Geodesy, Denmark); Ole Andersen (DTU Space, Denmark); Per Knudsen (DTU Space, Denmark)

Obtaining valid and accurate river level estimates from altimetry is challenging due to the annual and inter-annual change of the river systems. Significant improvement has been achieved with CryoSat-2, especially in SARIn mode where it is possible to locate the position of the reflecting target making it possible to correct for range errors. However, the newly launched altimetry mission Sentinel-3 is measuring in SAR mode, hence, correcting for range errors is less straight forward. To take up this challenge will combine high-resolution water masks based on imagery from Landsat and Sentinel-1/2 with altimetry data from CryoSat-2 in a joint data processing. We will investigate how the known position of the water can contribute with information to achieve valid and accurate water levels in river environments. As an example, results from the Brahmaputra River will be shown.