Hydrological responses to wetland changes in the Yangtze River Basin

Guo, Ziying (2026) Hydrological responses to wetland changes in the Yangtze River Basin. PhD thesis, University of Glasgow.

Abstract

As the most productive ecosystems in the world, wetlands play a vital role in carbon cycling, climate change mitigation, socio-economic development, and natural disaster protection. The Yangtze River Basin (YRB) contains 40% of the national wetlands and the most frequent floods in China. In recent decades, the abundant wetland resources in the YRB have experienced substantial changes due to the climate change and human activities, significantly affecting the flood risk. Due to the lack of a long-term time series wetland dataset with comprehensive categories for the YRB, the effects of wetland variations on flood risk, as well as improved assessments of past and future flood risk incorporating wetland dynamics, remain underexplored. Moreover, wetland-related flood risk mitigation efforts in the YRB are less widely adopted. It is crucial to address these gaps for enhancing the sustainable wetland management and flood risk mitigation in the YRB.

This thesis aims to achieve three primary objectives: 1) to establish a long-term time series wetland classification dataset with the comprehensive categories in the YRB and analyze driving forces of their variations; 2) to investigate the long-term wetland effects on the flood risk in the YRB based on an improved GIS-based multi-index flood risk assessment model incorporating wetlands input; and 3) to predict the future flood risk with wetland effects in the middle-lower YRB under climate change and socio-economic scenarios.

The Long-term Wetland Classification Dataset for YRB (LTWCD_YRB) with nine wetland categories from 1984 to 2021 was created by using the Random Forest machine learning classifier on the Google Earth Engine platform with 30m resolution Landsat images. The LTWCD_YRB revealed that: 1) the total wetland area of the YRB in 2021 was larger than that in 1984, with a constant increase in human-made wetlands and fluctuating natural wetlands; 2) aquaculture ponds expanded the most by 4,987 km2, while inland marshes in the source region exhibited the most fluctuations; and 3) seasonal changes in wetlands were prominent in the Poyang Lake Basin, Dongting and Honghu Lake Basin, and YRB source region; and 4) human activities were found to be more dominant than natural driving forces in affecting wetlands. The LTWCD_YRB offers a consistent agreement of wetland area variations with the other satellite-based wetland datasets in the YRB.

To investigate the long-term effects of wetland variations on flood risks in the YRB, this thesis developed an improved GIS-based multi-index flood risk assessment model incorporating the wetland input obtained from the LTWCD_YRB. The findings indicated that: 1) wetlands in the Taihu Lake Basin, Wanjiang Plain, Poyang Lake Basin, and Dongting and Honghu Lake Basin could mitigate flood risks, while wetlands in the Sichuan Basin have aggravated but limited impacts on flood risks; and 2) Precipitation in the Taihu Lake Basin and Poyang Lake Basin, runoff and vegetation cover in the Wanjiang Plain, GDP in the Taihu Lake Basin, population density in the Taihu lake Basin, Dongting and Honghu Lake Basin, and the Sichuan Basin are dominant flood risk indicators under wetland effects. The wetland-related suggestions to mitigate flood risks including maximizing stormwater storage capacity of wetlands and increasing vegetation coverage in urbanized and precipitated regions.

The flood risk prediction of the middle-lower YRB applied the improved flood risk model to assess the flood risk from 2021 to 2100 under the Shared Socioeconomic Pathways (SSP) 2 - Representative Concentration Pathways (RCP) 4.5 and SSP5-RCP8.5 scenarios. The results indicated that: 1) the high and very high flood risk areas will totally cover 38% and 40% of the total study area under the SSP2-4.5 and SSP5-8.5 scenarios by 2100, respectively; 2) the overall flood risk of the MLYRB was predicted to become severer by 2100 under both scenarios; and 3) there would be a prominent northward expansion of the high and very high flood risk areas in Jiangxi, Hunan and the southern part of the Taihu Lake Basin in Jiangsu.

In summary, this thesis provides the data support for the long-term wetland variations in the YRB, develops an improved flood risk model to investigate the long-term wetland effects on the flood risk and predicts the future flood risk incorporating wetland dynamics in the YRB. The efforts of thesis contribute to the sustainable wetland conservation and flood risk mitigation in the YRB, aligning with the United Nations Sustainable Development Goals.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
• Colleges/Schools: College of Social Sciences > School of Social & Environmental Sustainability
• Funder's Name: The Royal Society (ROYSOC), Economic and Social Research Council (ESRC), Economic and Social Research Council (ESRC)
• Supervisor's Name: Shi, Dr. John and Zhao, Professor Qunshan
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-85720
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 28 Jan 2026 11:04
• Last Modified: 28 Jan 2026 11:04
• Thesis DOI: 10.5525/gla.thesis.85720
• URI: https://theses.gla.ac.uk/id/eprint/85720

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