Image of Sau reservoir during 2023 drought © @LaSequeradel22
A new methodology leveraging Fully-Focused SAR (FF-SAR) altimetry data from Sentinel-6 enables highly accurate estimation of Lake Water Levels, one of the essential climate variables. This approach has been tested over a collection of reservoirs in the Ebre River basin in Spain, reporting overall measurements of roughly 5 cm in both precision and accuracy.
The methodology was applied to five study cases in reservoirs in the Ebre River basin. FF-SAR-derived estimates closely matched in-situ measurements at monitoring points regardless of seasonal water level fluctuations, as it can be seen in the data from the Mequinensa reservoir. This consistency demonstrates the capability of FF-SAR data to provide reliable and accurate water level estimations under varying hydrological conditions.
Results in the Mequinensa - South reservoir spot show strong agreement with in-situ data © Contains modified Copernicus Sentinel-2 data (2022).
Enhancing lake water level monitoring worldwide
Improved resolution of Fully-Focused SAR (FF-SAR) altimetry processing allows to have water level measurements in the direction of the satellite track at one-meter intervals, a significant improvement compared to the 300-meter spacing of traditional Delay-Doppler altimetry. This increased measurement density not only enhances the quantity of data but also improves its clarity, leading to more reliable water level estimates in particular over small reservoirs
Image of Sau reservoir during 2023 drought © @LaSequeradel22
“The technique proposed for the Ebre basin analysis is world-wide scalable, as it has been developed in an operationally-oriented way”, explains Ferran Gibert, researcher involved in the study. “It can be a solid alternative to current available altimetry data to monitor water level In areas without in-situ data, thus supporting more effective water management” adds the researcher.
Reference:
Domingo, X.; Gibert, F.; Molina, R.; Escorihuela, M.J. Improved Inland Water Level Estimates with Sentinel-6 Fully Focused SAR Processing: A Case Study in the Ebre River Basin. Remote Sens. 2025, 17, 531. https://doi.org/10.3390/rs17030531