| As the main tillage soil in the Three Gorges Reservoir area, purple soil has soft texture, loose structure and poor anti-erosion characteristics. With the occurrence of severe soil erosion, the nutrients are lost from the surface soil, resulting in the decline of land productivity. Based on the theory of hydrology, hydroecology and hydropedology, taking the purple soil from Southwest University, the research was carried out in the 119 Laboratory with artificial simulation of rainfall(Vegetation cover and bare slope and rainfall interception experiment) and double ring infiltration experiments to study how the different rainfall intensity(0.38, 0.55, 0.75, 0.93, 1.1mm/min),slope(5 degrees, 10 degrees, 15 degrees, 20 degrees),and vegetation coverage to affect hydrological process, at the same time, clarifies the relationship between slope water balance. The main results of this paper are as follows:(1) In most cases, the runoff-rainfall processes present logarithmic changes either with interflow or without interflow, only a few being polynomial relationship, the relationship are quite strong. Generally, the correlation coefficient R2 decreases with the increasing of rainfall intensity, indicating that the greater the rainfall intensity, the more complicated of the runoff process and with more fluctuation. The formula of surface runoff process under the condition of with-interflow has smaller coefficient than that of without-interflow. The stable surface runoff of with-interflow groups and without-interflow groups present linear growth with the increase of rainfall intensity. With the same slope and rainfall intensity, the steady surface runoff of with-interflow group is smaller than the steady surface runoff of without-interflow. Furthermore, the fitted linear relationship between stable surface runoff and rainfall intensity of without-interflow group is larger than that of with-interflow group, and the slope of correlation coefficient of interflow group is smaller than without-interflow group. Regardless of interflow, the infiltration intensity gradually decreased, reaching stable, presenting roughly logarithmic change. There is no obvious relationship between stable infiltration intensity and rainfall intensity in the case of without-interflow. The stable infiltration intensity increases with the increase of rainfall intensity in the case of with-interflow.(2) Under the influence of slope and rainfall intensity, the process presents a logarithmic or polynomial change. For the without-interflow group, thevariability of runoff process decreases with the increase of slope in relatively small rainfall intensity. Surface runoff yield presents a cubic change in the case of relatively small rainfall intensity and runoff process is relatively complex, thevariability of runoff process gradually decreases with the increase of slope. For the with-interflow group, the variability of runoff process on slope increases gradually with the increase of slope, the process is complex. The influence of the slope on the runoff process is not obvious under the condition of relatively large rainfall intensity. The relationship between surface runoff yield and the cosine value of the slope presents a double-curve relation. There is an exponential relationship between stable infiltration rate and the cosine value of slope. The comparison expression is: y = 1.1392 cos(θ)1.9251,r2 = 0.9364.The soil stable infiltration rate decreases with the increase of slope gradient.(3) For the without-interflow group, its stable surface runoff will not change with the increase of vegetation coverage when the other conditions kept the same. However, for the with-interflow group, there is a quadratic relationship between stable surface runoff and vegetation coverage. The stability of surface runoff decreased with the increase of vegetation coverage. The impermeable layer interflow varies with the changes of vegetation coverage, and the intensity of the stable impermeable layer interflow increases with the increase of the degree of vegetation coverage.And the greater the degree of vegetation coverage is, the greater the amount of surface runoff increases. The maximum interception(mm) shows double-curves change with the change of vegetation coverage. The comparison expression is:Maximum interception decreased with the increase of vegetation coverage, and the maximum interception was minimum when vegetation coverage reaches a critical value of c=22.88%, and then the maximum interception increased with the increase of vegetation coverage. Regardless of interflow, the impact of vegetation coverage on the water balance is small when the flow reaches a steady equilibrium state. In the same situation, fitted water balance model of interflow group is better than the no interflow group. |
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