The Temporal And Spatial Evolution Of Rainfall Erosivity In The Nujiang River Basin

The Nu River is one of the great rivers in the southwest of China,and the terrain conditions in the basin are complex.Studying the characteristics of rainfall erosivity and erosive rainfall in the Nujiang River Basin has certain guiding significance for the quantitative prediction of soil erosion and soil and water conservation in the basin.Based on the daily rainfall data of 12 meteorological stations in the Nujiang River Basin from 1961 to 2010,this paper analyzes the temporal and spatial distribution of rainfall and rainfall erosivity according to the daily rainfall erosivity model.A simple algorithm for rainfall erosivity was established by regression analysis,and the concentration and concentration period of erosive rainfall were studied.The main findings are as follows:1.The average annual rainfall in the Nujiang River Basin is low in the northwest and high in the southeast.The average annual rainfall is 698.5mm.The spatial distribution of rainfall in the spring and winter is gradually decreasing from the central to the southeast and northwest,and the summer and autumn are gradually increasing toward the southeast and northwest.Rainfall in the Nujiang River Basin is mainly concentrated in the three months of June,July and August,accounting for more than half of the annual rainfall.The month with less rainfall is from December to February.2.The average annual rainfall erosivity in the Nujiang River Basin is low in the southeast and high in the northwest.The rainfall erosivity in spring and autumn is gradually reduced from Gongshan Station to the northwest and southeast.The rainfall erosivity in summer and autumn is generally high in the southeast and low in the northwest.The trend of rainfall erosivity in the Nujiang River Basin has not changed much in the past 50 years,showing a slight downward trend.The rainfall erosivity changed suddenly in 2004.The results of wavelet analysis show that the annual rainfall erosivity of the basin has a main cycle of 40 years and a sub-main cycle of 17 years.The spatial distribution of PCD and PCP in the Nujiang River Basin is generally the same,both of which are characterized by high in the southeast and northwest regions,low in the central region,uneven distribution of erosive rainfall,relatively concentrated erosive rainfall in the southeast,followed by the northwest region and the central region..The average annual erosive rainfall in the Nujiang River Basin is 322.91 mm,and the erosive rainfall is increasing year by year.The average annual growth rate is 1.2701 mm/year.The regression function is analyzed by determining the coefficient of the power function model.A brief algorithm for monthly rainfall erosivity based on monthly erosive rainfall and a brief algorithm for annual rainfall erosivity based on annual erosive rainfall are obtained.The research results can provide a certain technical reference for the work of ecological restoration,soil and water conservation in the Nujiang River Basin.