Interpretation of the environmental change of Dongting Lake, middle reach of Yangtze River, China, by 210Pb measurement and satellite image analysis

The present study examined the recent environmental history of the Dongting Lake, located in the middle Yangtze River region, central China. The sediment was recovered by 22 vibrocores in different lake sectors, primarily characterizing subaqueous delta and bay subfacies. High sedimentation rates, revealed by Pb-210 measurement in different subfacies of the lake, ranged from 0.77 to 2.33 cm/year. These rates equate to deltaic sedimentation associated with mobile channels resulting from Yangtze flood events. Satellite images confirm that the Dongting Lake does not contain the biggest Yangtze floods. Moreover, comparative bathymetric surveys verify that the Dongting Lake has lost almost two-thirds of its total area in the past century, due primarily to siltation by Yangtze sediment. In the late 19th century, a major flood-induced channel avulsion resulted in the coupling of the 'Four-Tributary' subbasin to the Dongting Lake, causing a massive increase in the sediment supply into the lake since then. Hydrological data demonstrate that about 83% of the lake's annual sediment influx are derived from the Yangtze. In addition, pressures from a growing population and associated human activities, such as reclamation, embanking, aquaculture, slope modification and deforestation, are compounding the loss of the lake surface area and associated storage capacity. (C) 2001 Elsevier Science B.V. All rights reserved.