Potential of SWOT Mission in Monitoring Taiwan Surface Water Dynamics
Chia-Hao Wang1*, Kuo-Hsin Tseng1,2

1Department of Civil Engineering, National Central University, Taiwan
2Center for Space and Remote Sensing Research, National Central University, Taiwan
* kevinwang081[at]gmail.com

Abstract

The Surface Water and Ocean Topography (SWOT) mission, equipped with a Ka-band interferometric altimeter, has provided high-precision, wide-swath measurements of terrestrial water bodies and oceans since its launch on December 16, 2022. However, the accuracy of SWOT water surface elevation (WSE) data over small waterbodies still requires further evaluation. This study utilizes SWOT Level 2 LakeSP and Pixel Cloud (PIXC) products to conduct a time-series comparison with in-situ data collected from 14 reservoirs and 15 ponds across Taiwan. Through this comparison, LakeSP is found to capture temporal variations in water levels, with average root-mean-square errors (RMSEs) of 1.55 m for reservoirs and 1.21 m for ponds, and standard deviations (STDs) of 0.97 m and 1.02 m, respectively. With the application of a predefined water mask and a tailored processing workflow to extract valid PIXC data points, the accuracy was significantly improved, reducing RMSEs to 0.53 m and 0.15 m, and STDs to 0.30 m and 0.10 m for reservoirs and ponds. Additionally, detectability was enhanced, with the PIXC product successfully identifying water bodies as small as 11,992 square meters (approximately 110* 110 m) -substantially smaller than the original mission requirement of 250* 250 m. These findings highlight SWOT strong capability in tracking seasonal water level dynamics and evidence its value for managing water resources in small and ungauged water bodies.

Keywords: SWOT, Inland water bodies, Elevation change

Topic: Topic B: Applications of Remote Sensing