The Variation Of Streamflow And Sediment Load In The Wei River Basin And The Influencing Factors

The streamflow and sediment loads have been dramatically decreased by climate change and anthropogenic activities in the Wei River basin China.The downstream has been deposited and floods occurr at high rate.Streamflow and sediment transport changes and their potential causes is analyzed,it`s significative to configure management measures scientifically and control soil and water erosion.This study based on 32 hydrological stations nearly 60 years' observation data and meteorological station data,geographic information and soil and water conservation measure data,employed hydrological and statistics method to analysis streamflow and sediment transport changes and their potential causes.The results are as follows:(1)Annual Runoff and sediment load are different significant in the Wei River basin.The average annual runoff is 78.89×108m~3.The average annual sediment is 4.31× 108 t.Runoff and sediment load exhibited significant decreasing trend from 1937-2013.The catastrophe change year of runoff is in 1993.The catastrophe change year of sediment is in 1996.(2)For most hydrologic areas in the Wei River,catastrophe change years of runoff and sediment are in the late 1980 s and early 1990 s.For some hydrologic areas in the Jinghe River,catastrophe change years of runoff and sediment are in the 1990 s.For some hydrologic areas in the Beiluo River,catastrophe change years of runoff and sediment are in the 2000 s.(3)The main runoff yield units are from upper reaches of main stream in Wei River to weijiabao station;south of the laoyukou,qinduzhen,maduwang station;from upper reaches of main stream in Jing River to yangjiaping station.The main sediment yield units are above qingyang station in Jing River,above liujiahe station in Beiluo River.The deposition units are from weijiabao station to huaxian station,from huangling,jiaokouhe station to zhuangtou station.(4)The factors influenced runoff and sediment in the Wei River Basin are climate change,land use,engineering measures and public policy.Precipitation exhibited weakly decreasing trend in the Wei River Basin in 1958-2013.Rainfall erosivity exhibited weakly increasing trend.Grassland,farmland,forest and built-up land were transformed reciprocally.There was as decreasing tendency in proportion of farmland,unused land and wetland,while proportion of grassland and forest was increasing.Influenced by soil and water conservation,the average annual runoff reduction is 37.049×108m~3and the average annual sediment reduction is 1.17×108t.Precipitation contribution rate of runoff and sediment reduction were 15.14% and 7.46%.Human activities contribution rate of runoff and sediment reduction were 84.86% and 92.54%.