Validation of Water Surface Elevation Estimated by SWOT Pixel Cloud Product in Taiwan

In recent years, advances in radar altimetry, particularly Synthetic Aperture Radar (SAR) techniques, have enabled the observation of fine-scale features over coastal oceans and inland water bodies. Since its launch in late 2022, the Surface Water and Ocean Topography (SWOT) mission has provided unprecedented spatial detail and measurement accuracy for resolving water surface gradients. This capability offers a unique opportunity for the timely and repeated monitoring of ungauged rivers and inland water bodies. In this study, SWOT Level-2 Lake and Pixel Cloud (PIXC) products are employed to monitor lakes, ponds, and reservoirs across Taiwan. Field validation conducted at 14 small ponds and 12 major reservoirs demonstrates that SWOT is capable of capturing water surface elevations and their temporal variations with sub-meter accuracy over mission cycles 3–37. Furthermore, reprocessing the PIXC data through clustering within predefined water masks improves the accuracy to better than 10 cm. These results indicate that SWOT provides a valuable alternative perspective on hydrological parameters and has significant potential to support future water resources monitoring and management.