Purple Soil Sloping Cultivated Land With Different Micro Topography Research On The Characteristics Of Runoff Energy

The soil erosion problem of purple soil slope farmland is prominent,and the surface undulation is an important factor affecting the slope water erosion.The essence of hydraulic erosion is a complex energy conversion process.The study of the energy characteristics of different microtopography can help to clarify the erosion mechanism of the surface relief of the microtopography.Therefore,this paper takes the purple soil slope farmland as the research object,and through the artificial rainfall simulation experiment in the field,under the rainfall intensities of 60,90 and 120 mm/h,7 kinds of surface micro-topographic relief forms(Control check CK,Alternate mounds AM,Continuous mounds CM,Alternate depressions AD,Continuous depressions CD,Alternate mounds and depressions AMD,Continuous mounds and depressions CMD),and analyzed different surface microtopography Influence on runoff energy and energy consumption,evaluate the soil and water conservation benefits of different micro-topography from the perspective of runoff energy,in order to further clarify the role of micro-scale soil and water conservation measures in reducing soil erosion,and provide information for soil erosion control of sloping farmland in purple soil areas.theoretical guidance.The main results are as follows:(1)The surface micro-topography has two effects on the runoff energy,in which the depression mainly reduces the runoff energy,while the bulge may increase or reduce the runoff energy at the same time.The order of the runoff energy under different surface relief forms is AM>CK>AD>AMD>CM>CD>CMD;the runoff energy reduction rate of each measure under 60 mm/h rainfall intensity is CMD>CD>CM>AD>AMD> The rule of AM is CD>CMD>AMD>CM>AD>AM under 90 mm/h and 120 mm/h rain intensities,and with the increase of rain intensity,the runoff energy reduction rate of each measure decreases.trend.It shows that the impact of rainfall intensity on runoff is greater than that of micro-topography,and there is no significant difference in the runoff between various surface micro-topography measures under heavy rainfall intensity.The distribution characteristics of the runoff energy of the surface micro-topographic measures are consistent with the distribution characteristics of the water depth,indicating that the runoff potential energy occupies the dominant position of the runoff energy.At the same time,the runoff energy was positively correlated with the soil erosion rate,and the coefficients of determination under the three rain intensities were between 0.70 and 0.87,and the correlation between the runoff energy and the erosion intensity was higher under the light rain intensities.(2)By analyzing the hydrodynamic parameters and erosion energy consumption of different surface micro-topography measures,it was found that in addition to the runoff shear force,with the increase of rainfall intensity,the runoff velocity,Reynolds number,Froude number,water flow power and erosion The energy consumption increases with it,but the growth rate slows down and gradually approaches the hydraulic characteristics of the flat slope.Under the three rain intensities,the distribution law of the runoff velocity of each measure was consistent with the Froude number(AM>AD>AMD>CMD>CD>CM),and the size rules of other parameters were different.For the spaced convex/concave microtopography,the runoff velocity,Reynolds number,Froude number and water flow power all show the law of AM>AD>AMD,but the related parameters of the continuously distributed convex/concave microtopography There is no obvious pattern in size.In addition,by fitting the relationship between different energy parameters of each measure and soil erosion rate,it is found that the fitting effect of erosion energy consumption and soil erosion rate is the best.>CMD>CD>CM.(3)Comparative analysis of the flow and sediment reduction rates of different surface micro-topographic measures.Surface depressions have obvious inhibitory effects on flow and sediment production,but uplifts have two effects of promotion and inhibition at the same time.The variation law of sediment reduction rate and flow reduction rate is different.With the increase of rain intensity,the flow reduction benefit of each measure becomes significantly worse.Except for AMD,the flow reduction rate of the other measures decreases by about 30% when the light rain intensity changes to the heavy rain intensity..The sediment reduction rate is polarized according to the different measures.With the increase of rainfall intensity,the sediment reduction effect of CD and CM measures is more obvious.obvious.The flow reduction rate,sediment reduction rate and runoff sediment carrying capacity of each measure under 90 and 120 mm/h rain intensities showed the same magnitude and regularity,but they were quite different from those under60 mm/h rain intensity.The empirical mathematical model of runoff energy and flow reduction rate,sediment reduction rate and runoff sediment carrying capacity was established.,the empirical equation of runoff energy and sediment reduction rate is between 0.7-1,and the empirical equation of runoff energy and runoff sediment carrying capacity is a quadratic function,and the determination coefficient is between 0.74-0.83.In conclusion,AM has the largest runoff energy and runoff sediment carrying capacity,and the runoff hydraulic characteristic parameters are the closest to the control group CK.It is also the only micro-topographic surface relief form that promotes runoff and sediment production and increases erosion.The other groups have different degrees of flow and sediment reduction benefits,among which CD has the best comprehensive benefits.