Preprint 2026-05
Rodrigo Abarca Del Rio, Fernando Campos, Cristóbal Caro-Ramírez, Jean François Cretaux, Daniel Moreira, Alfredo Ribeiro Neto, Jonas Felipe Santos De Souza, Mauricio Sepúlveda:
First insights into the performance of the SWOT Level 2 River Single-Pass Vector Data Product in rivers with complex morphology: application to the Bíobío River basin, Chile
Abstract:
Hydrological monitoring in Chile is hindered by sparse and unevenly distributed gauging networks, particularly in mountain basins with limited accessibility. The Surface Water and Ocean Topography (SWOT) mission offers a unique opportunity to complement in situ observations through high-resolution radar altimetry. The Biobío River basin presents a demanding environment for SWOT due to its narrow channels, steep gradients, and strong geomorphological heterogeneity. This study evaluates the performance of the SWOT L2_HR_RiverSP (version C) product in the Biobío basin by comparing satellite-derived water-surface elevations with in situ measurements from nine DGA streamflow stations. Standard hydrological metrics (R, NSE, NRMSE, MAE) were applied along with quality filters (wse_u < 0.15; node_q = 0–1). Results show strong spatial variability linked to channel width and morphology: wide reaches (>200 m) exhibit high correlations (R ≈ 0.80) and moderate errors (NRMSE < 0.7), whereas narrow or sinuous segments yielded negative NSE values and substantial dispersion. Geometric inconsistencies in the SWORD database were also identified, along with indications of reduced observational consistency following the transition to version D, although this version was not formally analyzed. Overall, SWOT shows considerable potential for enhancing hydrological observation in Chile, but its operational application in narrow or morphologically complex rivers requires local validation, geometric correction, and integration with lower-level products (e.g., PIXC) to better interpret observations under challenging fluvial conditions.
