The Characteristics Of Runoff And Its Influencing Factors In Beichuan River Basin

In this paper,mathematical statistics method was used to quantitatively analyze the correlation between climate,landform,vegetation change and drainage runoff,and to explore the main influencing factors of runoff,and to provide theoretical basis for rational utilization of water resources in high and cold mountainous area.Combined with the meteorological and hydrological data and the M-K trend test,the change trend and cycle of long time series of air temperature data,precipitation data and the runoflf data were analyzed through morlet wavelet transform method.The land use changes in the Beichuan River Basin in the past 32 years were analyzed through the geography information systein and remote sensing,using the 1:10 million land use type map and DEM data.The spatial structure and time evolution characteristics of the vegetation coverage in the Beichuan river basin for 1982-201 3 years were analyzed using GIMMS NDVI data and MODIS NDVI data through ARCGIS software.The main conclusions are as follows(1)The annual average temperature of the Beichuan river basin were 4.33?,showing an obvious upward trend,without obvious mutation,while the change period is 28a,and the future would be in the period of high temperature.The average annual precipitation was 524mm,and the trend of precipitation was rising,and its rising slope was 1.247 mm/a.Precipitation occurred abrupt in 1988,1989 and 2012.The first main cycle period was 28a,and the second main cycle period was 8a.At present and in the next few years,the precipitation in the Beichuan River Basin would be in a partial period(2)Grassland,arable land and woodland were major land types in the study area,which accounted for 89%of the total area.The transfer of land use types was not the same.The conversion of cultivated land was the most obvious,the woodland was the second,meanwhile the construction land and the water body were not turned out,respectively.(3)The average NDVI value of the Beichuan River Basin was 0.3649 during 1982-2013 years,showing an upward trend.The vegetation coverage was abrupt in 1985 and 2005.Significant differences were existed of NDVI values of different vegetation types(4)The annual average runoff of Cattle,Xiamen,Hering,gorge,East Bridge,Chaoyang were 299.8mm,266.4mm.263.5mm,156.3mm,217.4mm,87.1mm,respectively,showing a downward trend,while the mutation occurred around 1990 and 20l0.The main change cycle was 28a and the runolf would be in decreasing trend in the future(5)The precipitation had the greatest correlation to runoff,followed by vegetation,and the degree of temperature was the weakest.In areas where vegetation coverage was large,vegetation and precipitation both have great contribution to runoff.In areas where vegetation coverage was small,precipitation was the main factor affecting runoff.The average slope had a positive correlation with runoff,The effect of temperature on runoff was a positive correlation between 1-3 and 9-12 months.The runoff was iiot only influenced positively of the precipitation of the month,but also influenced by the precipitation of last month in the summer.The main effects of vegetation on runoff were the negative correlation between the non-growing season,but there was a positive correlation in the growing season.