Flood mitigation effects of lake-reservoir group on the Poyang Lake watershed based on runoff-weighted model from multi-satellite weekly observation

Abstract

Study regionThe Poyang Lake watershed is located on the south bank of the middle and lower reaches of the Yangtze River in China. It has been hit by frequent floods in past few decades. Study focusLake-reservoir groups (LRG) are important in extreme hydrologic event mitigation in watersheds. This study used runoff-weighted model to quantify the influence of LRG on the flood mitigation in Poyang Lake based on weekly observations of GF-1 and Sentinel-1. New hydrological insights for the regionThe weekly water storage volume of LRG in the Poyang Lake watershed showed a unimodal trend of increasing (April-September) first and then decreasing (October-March) from 2016 to 2020. The runoff-weighted model has a better effect on the calculation of detained flood volume and residence time of retained flood. The average annual total detained flood volume of LRG were 4.39 × 108 m3, 5.06 × 108 m3, 1.64 × 108 m3, 0.54 × 108 m3, and 0.15 × 108 m3 in the Xiushui, Ganjiang, Fuhe, Xinjiang, and Raohe basins, respectively, among which Xiushui and Ganjiang basins contributed the most to flood detention. The residence time of retained flood by LRG in the five basins are long during the dry season (October to March) but short during the wet season (April to September), and they are generally longer than those in the natural state with no reservoir. The delay days of the LRG to flood peaks were about 12, 7, 13, 22, and 26 d for each basin, respectively.