Hassan Bazzi (UMR TETIS, University of Montpellier, AgroParisTech, INRAE, CIRAD, CNRS, France); Nicolas Baghdadi (UMR TETIS, University of Montpellier, AgroParisTech, INRAE, CIRAD, CNRS, France); Cécile Cazals (CS GROUP, France); Sami Najem (UMR TETIS, University of Montpellier, AgroParisTech, INRAE, CIRAD, CNRS, France); Damien Desroches (CNES, France); Frédéric Frappart (ISP INRAE, France); Mehrez Zribi (CESBIO, UMR 5126 Université Toulouse UT3/CNRS/IRD/CNES, USC INRAE, France); François Charron (G-EAU Unit, University of Montpellier, AgroParisTech, CIRAD, INRAE, Institut Agro, IRD, Domaine du Merle, France)

While primarily designed for ocean and inland water monitoring through Interferometric SAR (InSAR) technology, the SWOT Ka-band SAR sensor also presents potential for agricultural applications. This study offers a novel perspective of SWOT mission by exploring the sensitivity of SWOT’s Ka-band backscatter to soil moisture variations, focusing on detecting irrigation events. Using the daily calibration/validation time series data from the SWOT Level 1B High-Rate Single-look Complex product over an experimental irrigated grassland site, we examined backscatter variations in response to irrigation events and rainfall. The analysis included first evaluating the stability of SWOT Ka-band backscatter signal, the temporal responses to both irrigation and rainfall, and the influence of vegetation density on Ka-band SAR signal penetration. Main findings showed that the Ka-band SAR data was sensitive to soil moisture variation due to irrigation, inducing an increased backscattering signal by an average of 4.3 dB after irrigation events. Despite the Ka-band’s short wavelength, typically limiting canopy penetration, SWOT’s near-vertical incidence angle appears to enhance its ability to penetrate dense vegetation cover reaching the soil surface and detecting soil moisture dynamics. These findings open new perspectives for leveraging daily SWOT acquisitions to map irrigated areas and support agricultural water management.