How Much Water Can Be Seasonally Buffered by China's Largest Floodplain Lake? A Refined Estimate From SWOT

Abstract

Abstract Poyang Lake, China's largest floodplain lake, plays a crucial role in regional hydrology by seasonally regulating water to mitigate floods and sustain extensive wetland ecosystems. However, complex hydrodynamics and significant spatial hydraulic gradients often invalidate the traditional “flat‐water” assumption, making reliable estimation of the lake's true seasonal buffering capacity a persistent challenge. To address this, we developed a SWOT‐based Floodplain Lake wAter volume and Storage cHange (SWOT‐FLASH) framework. By integrating two‐dimensional water surface elevations from the SWOT mission with reconstructed full‐lake bathymetry, this method explicitly resolves spatial surface gradients to estimate a massive seasonal buffering capacity of 22.71 ± 1.96 km 3 for Poyang Lake, accounting for 95.10% of the maximum lake water storage recorded from July 2023 to July 2025. Beyond revealing the lake's critical regional flood‐mitigation role, this framework introduces a physically realistic tool for quantifying lake water storage dynamics in complex river‐floodplain lake systems worldwide.