The variation process of water and sediment and its effect on the yellow river delta over the six decades

In order to find out the variation process of water and sediment and its effect on the Yellow River Delta, this paper, by means of statistics, analyzed the water and sediment discharge from 1950 to 2007 at Lijin and the reduction of water and sediment in Yellow River Basin caused by human activities. Results show that the water and sediment discharge into sea decreased from 1950 to 2007 with serious fluctuation. The human activities were the main cause for the reduction of water and sediments into sea. From 1950 to 2005, the multiyear average reduction of water and sediment by means of water and soil conservation were 2.02×10⁹ m³ and 3.41×10³ t, respectively, while the multiyear average usage of water and sediment for industry and agriculture were 2.52×10¹⁰ m³ and 2.42 ×10³ t, respectively. From 1960 to 2007, the multiyear average sediment silted in the Sanmenxia Reservoir was 1.45 ×10⁸ t and that silted in the Xiaolangdi Reservoir was 2.398×10⁸ t. Compared to the data of Huayuankou, in the lowere reaches, the water and sediment discharge into sea decreased with siltation and increased with erosion. The coastline near the estuary extended and the delta increased when the ratio of total water and sediment into sea was about 0.0257 t/m³ in different periods.