Impact of the Three Gorges Dam on hydrological connectivity and vegetation growth of Poyang Lake floodplain, China

Poyang Lake, the largest freshwater lake naturally connected Yangtze River, are facing significant ecohydrological change since the implementation of Three Gorges Dam (TGD). Both hydrological connectivity (HC) and wetland vegetation play important roles in sustaining the biodiversity of freshwaters. It is necessary to enhance the understanding of the influences of large hydropower on the HC and vegetation, which may provide the scientific evidence of evaluation of large dams' effects. This study uses hydrodynamic modeling and remote sensing to quantify the change of the hydrological connectivity and vegetation growth of Poyang Lake floodplains subjected to TGD. The results show the obvious change of lake water level during post-TGD than pre-TGD, which results in the abrupt reduction of hydrological connectivity. Most of the NDVI of lake floodplains increased greatly during post-TGD especially on floodplain wetlands. What's more, floodplain sub-lakes show different response to TGD compared to floodplain wetlands, where the former has small change of connectivity and NDVI, and the latter has obvious change. This study highlights the unique role of floodplain sub-lakes in large river–lake system influenced by large hydropower. The moderate connectivity of floodplain sub-lakes is quite important to maintain the biodiversity of floodplains under changing environment.