Research On The Characteristics Of Rainfall,Runoff And Sediment Production Under The Action Of Typical Soil Types And Slopes In Dianchi Lake Basin

The study on the characteristics of rainfall,runoff and sediment production of three main soil types in the Dianchi Lake Basin and their comparison can provide theoretical support for the design of soil erosion defense and the establishment of soil erosion models according to local conditions.This paper took the three main soil types(red soil,purple soil,and yellow-brown soil,accounting for 69.19%of the soil types in the Dianchi Lake Basin)as the research objects.Based on indoor artificial simulated rainfall experiments,the hydrological effects and differences of slope surface under different rainfall intensities(10,30,40 mm/h)and slopes(5,10,15,25~o)were studied.During the simulated rainfall experiment,sediment water samples were collected regularly to quantitatively analyze the rainfall-run-sediment producing processes and characteristics of the three soil types and their differences under the same conditions.The main results are as follows:(1)The differences in rainfall,runoff and sediment production characteristics of three soil types under different rainfall intensities were compared.When the slope was constant,under the condition of light rain,the average velocity of surface runoff order was purple soil>red soil>yellow-brown soil,under moderate rain conditions,the purple soil was the largest,followed by the red soil,and the yellow-brown soil was approximately equal to the red soil,and under heavy rain conditions,the order was red soil>purple soil>yellow-brown soil,and the increase in rainfall intensity will reduce the difference in the average velocity of surface runoff among the three soil types.With a certain slope,the average runoff intensity under the three rain intensities was purple soil>yellow brown soil>red soil;under light rain conditions,the average sand yield intensity order was purple soil>yellow-brown soil>red soil,under moderate rain conditions,it was yellow-brown soil>red soil>purple soil,and under heavy rain conditions,it was yellow-brown soil>purple soil>red soil.(2)The differences in rainfall,runoff and sediment production characteristics of three soil types under different slope conditions were compared.When the rainfall intensity was constant and the slope were 5~oand 15~o,the average velocity of surface runoff order was purple soil>yellow-brown soil>red soil,under the condition of 10~o,the order was purple soil>red soil>yellow-brown soil,and under the condition of 25~o,the order was red soil>purple soil>yellow-brown soil.The average runoff intensity orders under 5~o,10~oand three rain intensities were purple soil>yellow-brown soil>red soil,under the condition of 15~o,it was yellow-brown soil>purple soil>red soil,and under the condition of 25~o,it was purple soil>red soil>yellow-brown soil.The increase of rainfall intensity and slope will reduce the difference of average runoff intensity among the three soil types.Under the conditions of 5~o,10~oand three rain intensities,the production flow orders were purple soil>red soil>yellow-brown soil,under the condition of 15~oslope,it was purple soil>yellow-brown soil>red soil,and under the condition of 25~oslope,it was red soil>purple soil>yellow-brown soil.Under certain conditions of rainfall intensity,the average sediment yield intensity order was purple soil>yellow-brown soil>red soil except for 15~o,which was yellow-brown soil>red soil>purple soil.(3)The hydrodynamic mechanism of slope erosion in three soil types was studied.The average sediment production intensity of red soil and purple soil slopes increases with the increase of the average flow velocity as a power function(P<0.01),while the average sand production intensity of the yellow-brown soil slope increases with the increase of the average flow velocity as a logarithmic function(P<0.01).The average sand yield intensity of red soil and yellow-brown soil slopes increases as a polynomial function with the increase of Froude number(P<0.01),while the average sand yield intensity of purple soil slope also increases as a power function with the increase of Froude number(P<0.01).The average sediment yield intensity of red soil and yellow-brown soil slopes decreases with the increase of the resistance coefficient as a polynomial function(P<0.05),while the average sand yield intensity of the purple soil slope decreases with the increase of the resistance coefficient as a logarithmic function(P<0.05).The important predictors of the average sediment production intensity and hydraulic change trend of the three soil types are the average flow velocity on the slope.The main influencing factor of rainfall-runoff-sediment production is rainfall amount,followed by rainfall intensity,and the greater the rainfall amount and rainfall intensity,the greater the runoff and sediment production intensity.