Erosion and deposition within Poyang Lake: evidence from a decade of satellite data

Poyang Lake, an important wetland in the Ramsar Convention List, is the largest freshwater lake in China and an essential component of the Yangtze River system. The lake is increasingly experiencing serious water crises including seasonal desiccation, decreased wetland area, and water shortages, all of which are closely related to progressive changes in the lake's topography over recent years. Atime-series of bottom topography would contribute to our understanding of the lake's evolution during the past several decades. However, quality bathymetric data for Poyang Lake are scarce owing to the highly dynamic and turbid nature of its water. To resolve this limitation, we used a total of 146 medium-resolution satellite images to build annual and quasi-annual bottom topography maps of Poyang Lake during the period from 2000 to 2010 based on the well-established waterline method. Our results show that: (1)the average elevation of the lakebed relative to sea level has decreased by 14.4 cm/yr. from 2000 to 2010; and (2)the observed annual changes in the lakebed elevation were well correlated (r = 0.84) with measured changes in the lake's annual net sediment flux. The observed trends may be attributed to the impacts of human activities, especially the operation of the Three Gorge Dams, frequent sand mining, and the implementation of a large water conservancy project. This decade-long quantitative understanding of the lake's evolution and bottom topography elevations might assist both researchers and local policymakers in ecological management, wetland protection, and lake navigation safety. (C) 2016 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.