Variation of flow and sediment of the Yellow River and their influential factors

Variation of flow and sediment along the main stream of the Yellow River is analyzed using the long-term data published in China Gazette of River Sedimentation and long-term precipitation data.Based on analysis of the precipitation depth of 17 gauge stations,it is concluded that precipitation depth has little influence on the runoff of the Yellow River.The annual runoff decreases along the river from upper to lower reaches,and the decrease is mainly caused by increasing water diversion from the Yellow River and water and soil conservation practices.The sediment content in middle and lower reaches has a clear downward trend.The decrease of sediment loads is caused by human activities such as water and soil conservation,construction and operation of reservoirs on the Yellow River,and water transfer and intake,as well as climate change.Sharp changes in sediment amount can be observed downstream of a reservoir when it is put into operation or when its regulation mode changes.The average annual runoff and sediment loads at Lijin gauge station,the most downstream station on the Yellow River,decreased from 47.4×109 m3 and 1.4×109 t of average values of 1950 s to 13.2×109 m3 and 0.15×109 t of average values of latest 6 years since 2000,respectively.The changes will have significant effects on the evolution of the Yellow River mouth.