Effects of water discharge and sediment load on evolution of modern Yellow River Delta, China, over the period from 1976 to 2009

The Yellow River, which is the second largest river in China, is regarded as the world's largest contributor of fluvial sediment load to the ocean. In recent decades, the dramatic reduction in water discharge and sediment load due to climate change and human activities in the drainage basin has greatly constrained the evolution process of Yellow River delta. We highlight how runoff and sediment load discharged into sea affected extension of shoreline length and area of modern Yellow River delta during 1976-2009 based on remote sensing interpretation and long-term monitoring data in hydrological station. Average runoff of 207.47x10(8) m(3) yr(-1) and average sediment load of 4.63x10(8) m(3) yr(-1) were discharged into the sea from 1976 to 2008. The annual runoff reduced by similar to 59.7% in 1990-2002 and annual sediment load reduction up to similar to 72.1% in 2003-2008. Both shoreline length and area of Yellow River Delta extended overall in the studied period, but with decreasing rates in accordance with changes of runoff and sediment load. High increasing rate of shoreline length of similar to 3.63 km yr(-1) and quick area extension of similar to 16.26 km(2) yr(-1) were observed in 1976-1985. Since 1996 however, the average increase rate of shoreline length and area decreased to similar to 0.80 km yr(-1) and similar to 3.94 km(2) yr(-1), respectively. In addition, the fluctuated changes of shoreline and area were great and the net negative increase of land area was occurred during this period. There exist significant exponential relationships between the accumulated sediment load and extensions of shoreline length and the area during the evolution of the modern Yellow River Delta. Our results indicate that the evolution of shoreline and change of area of the Yellow River Delta are directly affected by the dramatic reduction of runoff and sediment load, which are much close related human being activities in Yellow River drainage basin in recent decades.