以北江流域45年(1956—2000年)内降雨量及主要控制性水文站石角站水文资料为基础,研究了流域内降雨径流的变化特征,发现降雨系列基本没有变化,而径流系列呈缓慢上升趋势。对径流系数系列进行分析显示,1973年前后径流系数发生了较大的改变,将1956—1972年做为基准期,利用降雨-径流关系,定量分析了人类活动对径流演变的作用,发现人类活动的间接影响是造成径流增加的原因。最后分析了流域内近20年来的水土流失和植被变化情况,进一步说明了流域内下垫面状况发生了改变。

With the development of society and more intensive human activities,especially after the large-scale economic construction in recent decades,some new characteristics appeared beyond the intrinsic laws in water resource.Recognizing the new laws of runoff evolvement under the changing environment seemed very necessary.This paper analyzed the characteristics of precipitation and runoff of Beijiang River basin in the past 45 years(1956-2000)based on the measured data of precipitation and the hydrological data at Shijiao station which is the main controlling station on the river.The research found that the runoff series shows a rising tendency while the precipitation is even,indicating that the rising trend of runoff is caused by human activities.Analysis of the runoff coefficient series.Result showed the coefficient had changed around 1973.So we assumed that the runoff is under the natural conditions before 1973.We obtained a regression equation based on the data of precipitation and runoff in 1956-1972.Using this equation the impact of human activities on runoff can be quantified.The calculated results showed that human induced runoff increase are 3.81×108,2.54×108 and 4.13×108m3 at the three periods of 1973-1980,1981-1990 and 1991-2000 respectively.Finally,we analyzed the water and soil erosion and vegetation change of the basin in recent two decades,and the results further proved that it is the human induced change of the underlying surface that results in the runoff increase.