[Objective] Researching the characteristics of runoff changing in the upper reaches of Bailong River in recent 50 years

and further analyzing the lagging effect of runoff to precipitation and the impacts of precipitation and human activities on runoff changes.[Methods] Based on monthly runoff observation data in Wudu hydrological station and monthly rainfall data in weather stations in the upper reaches of Bailong River basin in 1961-2010

the monthly

seasonal and annual variations of runoff in upper reaches of Bailong River basin and its tendency were analyzed using methods of concentration frequency

concentration period

Mann-Kendall test

rescaled range analysis

and so on.[Results] The annual runoff distribution in the studied area was extremely uneven. The multi-year average of runoff concentration frequency was about 34.92%; the inter-annual change of annual runoff demonstrated a decreasing trend significantly

at a rate of -3.942×108 m3/10 a(p<0.001). The Hurst index was 0.98

which indicated that the decreasing trends of runoff in the studied area will continue in the future. The seasonal and monthly change of runoff also decreased significantly(p<0.05). The annual runoff dropped off abruptly in 1990 which indicated that annual runoff showed a significantly decreasing trend. There was an about 22.6 days hysteresis in the response of runoff to precipitation

and the hysteresis had slightly rising trend. The annual runoff coefficient showed that the runoff from rainfall decreased significantly(p<0.001) with the time due to plant interception

infiltration and evaporation in recent 50 years. The runoff coefficient after 1990 decreased by 0.14 as compared with the previous period.[Conclusion] Before 1990

precipitation was the dominant factors

whilst

the variations of runoff in the studied area were mainly attributed to human activities after 1990.