Variation trends analysis and its ecological impact of sediment discharge in the mainstream of the Yellow River

The evolution process of the river sediment is closely linked with changes of river eco-environment system. Studying the variation trend of river sediment elements is great significant to understand the responding relationship between river sediment and ecological system. Through different characteristics statistical analysis of river sediment elements, it is known development law and mutation characteristics of different river sediment indicators in long-term evolution process on Tangnaihai, Lanzhou, Toudaoguai, Tongguan and Huayuankou cross section on the Yellow River. The result is of great value to construct healthy water circulation and river ecological security. The research shows that sediment transport capacity of the mainstream of the Yellow River is in downward trend, but not significant. Flood season is the most critical periods for sediment transporting, most sediment moved in flood season. But reservoirs operation has some influence on sediment transporting in flood season, the influence is mainly sediment discharge reducing, the largest decrease reaches 60%. The conclusion is Visible in the mainstream Yellow River reservoir operation produced certain influence to sediment transport, especially to sediment discharge in the flood season on the middlestream.