A preliminary estimate of human and natural contributions to the decline in sediment flux from the Yangtze River to the East China Sea

This paper attempts to give a comprehensive explanation of the sediment discharge decrease from the Yangtze River to the East China Sea, taking into consideration its large scale and the basin wide complexity of changing human activities and precipitation. We examined various influencing factors include climate change, water and soil conservation measures, sand dredging, floodplain deposition and channel erosion, and dam construction. Correlation/regression analysis was used to examine the relations between data such as precipitation and water discharge, erosion or deposition in the river channel and sediment supply from the river basin. The sediment and water discharge of two major stations (Yichang and Datong) on the main river and 13 stations of the major tributaries were provided. The average precipitation in each tributary and its relationship with the water and sediment discharge were examined, and contributions of water and soil conservation measures, sand dredging, floodplain deposition and channel erosion, and dam construction to the sediment decrease were discussed. A quantitative estimation of the contribution of each impact factors to the sediment decline was attempted. Dam construction was the dominant factor (similar to 88%) contributing to the decline in sediment influx, followed by the water and soil conservative measures (15 +/- 5%). Climate change is responsible for a slight increase in sediment influx, approximately 3%. Floodplain deposition and channel erosion had an adverse effect, and the contribution of sand dredging was very limited. (C) 2007 Elsevier Ltd and INQUA. All rights reserved.