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Towards global mapping of dynamic surface water extents using Sentinel-1 SAR data

Remote Sensing of Environment
By: , , , , , , , and 
https://doi.org/10.1016/j.rse.2026.115326

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Abstract

We introduce a fully automated and scalable method for mapping surface water extents from single-acquisition Sentinel-1 synthetic aperture radar (SAR) imagery. This approach integrates adaptive thresholding of radiometric terrain-corrected SAR backscatter data, fuzzy-logic classification, region growing, dark land estimation, and a bimodality test to minimize false positives in low-backscattering areas and false negatives in high-backscattering areas. By combining these steps, the algorithm achieves classification accuracies exceeding 85% in detecting surface water extents across diverse environmental conditions.

Accuracy was first assessed at meter scale using 52 PlanetScope scenes acquired worldwide in September–October 2019; the algorithm achieved 93% overall accuracy, 86% user's accuracy, and 94% producer's accuracy. Global robustness was then evaluated by processing every Sentinel-1 acquisition from 1 to 12 November 2023 and cross-comparing the resulting maps with 6561 temporally matched observational products for end-users from remote sensing analysis (OPERA) dynamic surface water extent from Harmonized Landsat and Sentinel-2 (DSWx-HLS) products. This large-scale test yielded 90% user's and 94% producer's accuracies, confirming reliable performance at continental extent.

Additional case studies demonstrate the algorithm's ability to handle surface water extent in sand-dominated deserts, to track seasonal amplitude in Folsom Lake (California), drought-induced loss in Cerro Prieto Reservoir (Mexico), and rapid filling of the Grand Ethiopian Renaissance Dam. These results show that the method scales across local to global domains and maintains high accuracy, providing a practical tool for near-real-time monitoring of floods, droughts, and water-resource management. Because the approach is sensor-agnostic, it can be ported to forthcoming L- and S-band missions such as NASA-ISRO synthetic aperture radar (NISAR), broadening its applicability to future hydrologic observations.

Suggested Citation

Jung, J., Fattahi, H., Jeong, S., Bonnema, M.G., Jones, J.W., Bekaert, D., Chan, S.K., and Handweger, A.L., 2026, Towards global mapping of dynamic surface water extents using Sentinel-1 SAR data: Remote Sensing of Environment, v. 337, 115326, 21 p., https://doi.org/10.1016/j.rse.2026.115326.

Publication type Article
Publication Subtype Journal Article
Title Towards global mapping of dynamic surface water extents using Sentinel-1 SAR data
Series title Remote Sensing of Environment
DOI 10.1016/j.rse.2026.115326
Volume 337
Year Published 2026
Language English
Publisher Elsevier
Contributing office(s) WMA - Observing Systems Division
Description 115326, 21 p.
Additional publication details