Analysis of water and sediment changes and characteristics of the aquatic nutrient environment in the middle Yangtze River under sediment regulation
SHI Haoyang
YANG Wenjun
GUO Hui
CAO Huiqun
HU Man
ZHU Xinxin
BAO Chengcheng
Abstract：The joint regulation and operation of the Three Gorges Project and the cascade reservoirs upstream have altered the processes of water and sediment transport in the middle and lower reaches of the Yangtze River.The combined hydrodynamic effects of clear-water discharge and the inflows from major tributaries and lakes in the middle reaches have reshaped the nutrient environment pattern of the river.Based on systematic monitoring during the complete hydrological cycle from 2023 to 2024,this study reveals the spatiotemporal evolution of sediment characteristics,nutrients,and dissolved organic matter(DOM)in the river section from Yichang,Hubei to Jiujiang,Jiangxi.The results show that reservoir regulation significantly changed sediment composition characteristics.During flood discharge,the proportion of silt particles sharply increased to 95.2%,and the median sediment particle size exhibited spatial variation ranging from 3.2 to 59.5 μm.Tributary inflows made significant contributions to local clay enrichment.The coupling of water and sediment had selective effects on nutrient migration and transformation:very fine sediment markedly enhanced the adsorption capacity for phosphorus;dissolved silicate showed a significant positive correlation with sediment content;while nitrogen distribution was mainly controlled by human activities and showed a weak correlation with sediment characteristics.DOM components displayed clear seasonal succession characteristics,with microbial-derived humic acids dominating during the non-flood season,and additional terrestrial fulvic acids and other characteristic humic substances-emerging during the flood season,increasing the number of DOM components from 2 in the non-flood season to 4 in the flood season.The study elucidates the synergistic variation characteristics of the"water-sediment-nutrient-organic matter"system under the regulation of the Three Gorges Project system,providing a scientific basis for ecological protection in the middle and lower reaches of the Yangtze River.
Keywords：middle Yangtze Riverwater and sediment changessediment characteristicsnutrientsdissolved organic matterhydrological cycleThree Gorges Project
Publication Date：2025-11-12
Online Publishing Date：2025-11-28(First online date of this platform, not the publication date of the document)
Pages：7( 25-31 )