Abstract:Fen River watershed was located in the middle reaches of the Yellow River. The variation of runoff volume and sediment load in this area especially the upper watershed had an indicating significance to the change of water-sand regime of the Yellow River. The Lancun station was the most important hydrological monitoring station on the upper Fen River. Based on runoff, suspended sediment load data observed at Lancun station in rainy season from 1954 to 2013, the characteristics and driving factors of suspended sediment load variation were analyzed by using linear trend analysis. The results showed that the declined trend of sediment and runoff were obvious in recent 60 years. But the changes of them not synchronous which the former’s trend was stronger than the latter’s. The precipitation showed no trending variation. However, the precipitation and runoff (P<0.01), precipitation and sediment load (P<0.01) showed a significant linear correlation. Floods had a decreased tendency, and this trend was the most evident in the beginning of the 21st century. Using the analysis of double-mass curve, the effect of driving factors on the variation in suspended sediment load had been studied. The double-mass curve showed three breaks (1959, 1981 and 2002) which divided the evolution process of suspended sediment load into four typical periods. The suspended sediment load was mainly affected by rainfall and runoff. Then it decreased significantly after 1959 which might be explained by Fen River reservoir construction. During the period from 1981 to 2002, the runoff and suspended sediment load decreased again. It could be related to the rainless, large-scale mining, urban construction, soil and water conservation measures. The runoff and sediment yield decreased significantly since 2002. In addition to the above reasons, reduction in precipitation especially storm and the second Fen River reservoir trapping sediment were the major cause for sediment reduction in the upper Fen River.