## 6 Conclusions  
This paper presents a processing chain, which is based on the Fully Focused SAR (FFSAR) algorithm, to monitor the water level (WL) of potentially contaminated small to medium targets, focusing on a case study within the Ebre Basin in Spain. Utilizing two years of regular Sentinel-6 MF data, the study evaluates FFSAR performance over a range of small- to medium-sized reservoirs within the basin, with typical transects spanning tens of meters to 3000 m. FFSAR achieved an average median absolute deviation of approximately 4 cm, significantly outperforming UnFocused SAR (UFSAR) methods, which exhibited deviations of 29 cm with the Offset Center of Gravity (OCOG) retracker and 36 cm with the ocean retracker. Notably, FFSAR demonstrated its capability to accurately monitor small targets (sub-300 m) within the basin, maintaining an accuracy of 4 cm. In addition, we showed that 73.8% of FFSAR range measurements (before filtering) had an error below 20 cm, in contrast to only 9.6% for UFSAR. The enhanced accuracy and precision of FFSAR over current UFSAR methods can be attributed to its higher along-track resolution, which facilitates a better identification and removal of contaminated waveforms. Indeed, with the presented processing, FFSAR achieves an along-track resolution of 5 m compared to 300 m for UFSAR. As such, future efforts in applying FFSAR processors over inland waters may shift from the recently predominant focus on developing complex single-waveform retrackers to instead developing waveform filtering techniques, as a notable improvement has been demostrated with a reasonably simple Gaussian retracker. Nevertheless, exploring the benefits that can be obtained by using more sophisticated retrackers with FFSAR data has been left out of the scope of this study. Furthermore, the study highlights the effectiveness of extending water masks within the Ebre Basin to include waveforms on the ground with water up to 250 m across-track,resulting in a notable increase in acceptable measurements. Specifically, an average increase of 36.6% for UFSAR and 47.7% for FFSAR was observed. Notably, included across-track measurements exhibited comparable accuracy to measurements with nadir over water, offering promising avenues for monitoring narrow targets using radar altimetry. All authors contributed to investigation and analysis. [PERSON], [PERSON] and [PERSON] coordinated the edition of the manuscript. All authors have read and agreed to the published version of the manuscript. This work was partially supported by the European Space Agency in the scope of the HYDROCOASTAL project. During the duration of the study, [PERSON] held an Investigo grant funded by the European Union, Next Generation EU (2021-C23.I01.P03.S0020-0000007). The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author(s). The authors wish to thank EUMESTAT, which provided open access to the Sentinel-6 data, the SAIH Ebre team, who provided the in situ water level information, and Centro Nacional de Informacion Geografica, which provided the Digital Elevation Model data. The authors declare no conflicts of interest.