Monitoring wetland vegetation pattern response to water-level change resulting from the Three Gorges Project in the two largest freshwater lakes of China

A rule-based model based on time series MODIS (moderate resolution imaging spectroradiometer) imagery was developed to simulate the wetland vegetation pattern responding to water-level change in Dongting Lake and Poyang Lake before and after the impoundment of the Three Gorges Reservoir. The accuracy of the model was evaluated by the error matrix and indicated satisfactory results. Similar development trends of wetland vegetations were found in the two lakes during 2000–2012. It was particularly noticeable that most marshlands experienced an inflection point during the period from 2002 to 2003. Moreover, most wetland vegetations were tending toward the lake center. Finally, reasons for changes in wetland vegetations and the possible succession of the wetlands were analyzed in this paper, as well as defects and improvements of the model were discussed. This study took the use of time-series water images derived from the MODIS data rather than spectral characteristics of remote sensing images in limited phases, which established an efficient method for extracting the wetland vegetation pattern and its dynamic change for years. It is a significant study for understanding the impacts resulting from the Three Gorges Project on relationships between the Yangtze River and the two lakes. This study can provide the relevant scientific basis for wetland management, water-level regulation and wetland restoration.