Abstract
The operation of the Three Gorges Dam (TGD) has significantly impact on downstream wetland ecosystems. This study applied 3S technology, landscape ecology, and computational models to investigate impact of the TGD on downstream spatial dynamics of floodplains in future. Results revealed the relationship between siltation patterns and wetland types transformation after the operation of the TGD, which are critically important to understand ecological characters dynamics in new environmental setting, and provide science-based conservation and restoration recommendation. After the operation of the TGD, changes between water surface and floodplains areas were spatial heterogeneity. With the increase of distance to the TGD, floodplain erosion force declining gradually. The most important finding is the asymmetric erosion between main river course and its associated floodplain lakes, e.g., Dongting lake.This has significant implications for dam operation in autumn and habitat management. After the operation of the TGD, floodplain in the estuary is driven by both the Yangtze river and ocean currents. The strong hydrological force and reduced sediments of Yangtze river drive erosion of the southern river course in the estuary, whereas, the weakened hydrological force in the northern river course attracts sedimentation.
Highlights
Global wetland changes are affected by climate change and human activities (Vörösmarty et al, 2000; Ramsar Convention on Wetlands, 2018), in river diversion or damming (Postel et al, 1996; United Nations Department of Economic and Social Affairs, 2015; Jean-François et al, 2016), which have been identified as global aquatic stressors (Etienne et al, 2020), or regional level, such as the Curuai floodplain in the lower Amazon River (Park et al, 2020), West Bengal (India) (Das et al, 2020)
On basis of hydrological station data and impact of river flow downstream, study area was divided into four sections, i.e., Yichang StationChenglingji Station (Y-C), Chenglingji Station-Hukou Station (C-H), Hukou Station-Nantong Station (H-N), and Nantong Station-Estuary (N-E)
Based on spatial overlay analysis of water surface and floodplains in H-N section, the added floodplain area extended around original floodplain patches, and they were mainly distributed in downstream region of H-N section, close to estuary (Figure 5)
Summary
The operation of the TGD changed hydrological regime downstream (Zhang et al, 2016; Tian et al, 2019), through storing water in autumn, and releasing of clear water that disturb balance between riverbed erosion and siltation (Li, 2009; Jiang et al, 2014; Han and Huang, 2018), leading to asymmetric erosion on riverbed and lake (Lu et al, 2018) Such disturbance has significant impact on waterbird habitat (Cao et al, 2008; Guan et al, 2014; Liu et al, 2015), as well as fish populations (Xie et al, 2016)
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