Estimation of water level time series for lakes and rivers using SWOT KaRIn measurements 

For more than three decades classical satellite altimetry has been successfully used to monitor water levels of inland waters such as rivers, lakes and reservoirs. In December 2022, a new generation of altimeter mission called Surface Water and Ocean Topography (SWOT) was successfully launched. SWOT is equipped with a classical radar nadir altimeter comparable to Jason-3, but also with a new Ka-band Radar Interferometer (KaRIn). KaRIn uses the principle of SAR interferometry, which has the capability to monitor almost every inland water body worldwide because of its swath.  In this contribution, we present a new approach to derive water level time series for lakes and rivers using the high-resolution SWOT pixel cloud dataset. This dataset allows us to monitor water levels of very small lakes (> 100m²). We use SWOT data measured on the fast sampling orbit (03/2023 – 07/2023, 1-day repeat cycle) and the science orbit (since 07/2023, 21-day repeat cycle). For quality assessment, the resulting water level time series will be validated with in-situ data. All water level time series will be freely available on the web portal of the "Database of Hydrological Time Series of Inland Waters" (DAHITI, https://dahiti.dgfi.tum.de).