The Variation of Runoff Volume and Sediment Load and Its Driving Factors in Huangfuchuan River Watershed

Huangfuchuan River watershed is located in the rich and coarse sand area in the middle reaches of the Yellow River.The variation of runoff volume and sediment load in this area has an indicating significance to the change of water-sand regime in the lower reaches of the Yellow River.In this study,the typical periods of the variation of runoff volume and sediment load have been ascertained by double cumulative curve and the variation trend of runoff volume and sediment load has been analyzed in the Huangfuchuan River watershed.In addition,the driving factors of the variation of runoff volume and sediment load have been analyzed considering the soil and water conservation measures since the 1950s.The results show that the evolution process of runoff volume and sediment load could be divided into four typical periods,i.e.,1954 to 1978,1979 to 1987,1988 to 2002 and 2003 to 2010.During the period from 1954 to 1978,the watershed was slightly affected by human activities and its control degree was low;therefore this period is called natural variation period.The effects of runoff volume and sediment load reduction resulted from soil and water conservation measures have been increasing in the period of 1979 to 2010.The effect of runoff volume reduction reaches to 41.8% and the effect of sediment load reduction reaches to 49.7% by double mass curve method.The values are respectively 44.7% and 48.3% by runoff/sediment coefficient method.