入渗和径流是水循环的重要环节。降雨条件下，坡面入渗径流过程是非常复杂的物理过程，对坡面水文和土壤侵蚀过程有着重要的影响。对坡面入渗径流规律和影响因素的研究是进行土壤侵蚀预报、制定水土保持方案的基础。本研究首先利用变雨强的室内人工模拟降雨实验揭示坡长与坡面入渗径流的关系，并对入渗及径流过程进行模拟。实验选择了7个坡长处理（1，2.5，4，5.5，7，8.5和10 m），每个坡长处理包括干、湿运行两场降雨，湿运行在干运行结束24 h后进行，每场降雨持续120 min，雨强范围在0.45~2.37 mm/min，平均雨强1.01 mm/min。其次，在黑土及黄绵土区选择典型的野外坡面，进行野外实地人工模拟变雨强降雨试验，揭示黑土和黄绵土的入渗径流规律以及其与土壤性质的关系，分析了剖面含水量的变化以及两类土壤的入渗径流过程差异。野外实验的每个小区进行干、湿运行两场降雨，为减少蒸发和天然降雨影响，湿运行在干运行结束约12 h后进行，每场降雨历时60 min，雨强范围介于0.72~1.85 mm/min，总雨量约为63 mm。本文得到以下主要结论：（1）在变雨强降雨过程中，7个坡长的径流率和入渗率随时间的变化过程基本一致，均受雨强变化的影响。雨强与径流率呈线性正相关关系。（2）坡长对干、湿运行产流时间均没有明显影响。退水历时与坡长呈幂函数关系，随坡长增加，退水历时增加，湿运行增加幅度大于干运行。（3）坡长对时段径流深和累积径流系数的影响受土壤表层含水量、降雨历时和雨强变化的综合影响。在产流初始到雨强峰值时段，虽然雨强不断增大，但由于土壤含水量较低，随坡长增加时段径流深明显减小，且随降雨历时的延长，下降幅度增大；峰值后雨强逐渐下降时段，土壤含水量较高，但平均雨强仍然相对较大，坡长对时段径流深没有显著的影响；在雨强较小且相对稳定阶段，时段径流深随坡长增加又呈现下降的趋势，但下降幅度小于降雨最开始时段。干运行坡长对时段径流深的影响较湿运行明显。（4）坡长对累积径流系数的影响，干运行时累积径流系数随着坡长的增加呈显著的线性减小趋势，减小幅度表现为先增加后减小再增加；而湿运行，只在雨强峰值前时间内，随坡长增加累积径流系数有显著的下降趋势，之后则变化趋势不明显。（5）Horton模型和Kostiakov模型可模拟产流后不同坡长入渗过程，但无法反映雨强变化对入渗率的影响。运动波公式结合Horton模型或Kostiakov模型模拟流量过程效果较好，能很好地表达径流量随雨强变化的过程，两种入渗模型方法模拟值相差较小，但Horton模型条件下模拟的径流总量要稍好于Kostiakov入渗模型。（6）黑土剖面在侵蚀严重的地点土体构型一般为A11-AC-C，而侵蚀稍弱的地点一般为A11-A12-ABh（BhC，AC）-C。腐殖质层厚度在20~40 cm；黄绵土的剖面土体结构一般为A-C或A-AC-C形式，土体结构相对较简单，耕作层厚度一般在10~20 cm左右。总体来说，黑土剖面土壤性质垂直差异要大于黄绵土。相比于黄绵土，黑土耕层容重小，全氮、有机质、水稳性大团粒含量都较高，粘粒含量明显较高，而黄绵土粉粒以及砂粒含量要高于黑土。各剖面之间横向比较，耕层土壤大多数土壤性质为中等变异性。不仅黑土和黄绵土之间土壤性质有很大差异，而且同一土壤类型各实验点之间土壤主要理化性质也有一定的差异，黄绵土小区的差异要大于黑土小区之间差异。（7）黑土剖面初始含水量随深度基本不变，表层含水量略低；黄绵土大多数剖面含水量有随土层深度的增加而增加的趋势。黑土剖面含水量总体上明显高于黄绵土。干湿运行降雨后，黑土和黄绵土水分增加都主要在表层20 cm内，0-10 cm增量更明显。平均来看，黄绵土表层水分增加量要略大于黑土。黄绵土表层水分增量与土壤多种性质有显著的关系，而黑土则不显著。（8）干湿运行实验，黑土和黄绵土小区平均产流时间没有显著的差别。而黄绵土平均退水历时要略短于黑土。无论是干运行还是湿运行，黑土和黄绵土的平均径流系数也均没有显著差异，但黄绵土四个实验点之间径流系数的差别在干湿运行都较大，而黑土四个实验点的径流系数差异相对较小，特别是湿运行实验几乎没有差别。黑土小区的产流时间、退水历时及径流系数与绝大多数土壤性质没有显著的关系，而黄绵土的这些指标则与多种土壤性质有显著的相关性。（9）黑土各小区，干、湿运行稳定入渗率分布范围均较集中，分别介于0.12~0.28 mm/min和0.1~0.2 mm/min左右，平均值分别为0.20 mm/min和0.15 mm/min，湿运行稳定入渗率平均值略小于干运行，但差别不大；黑土稳定入渗率主要受到粘粒含量的影响。黄绵土小区，干运行稳定入渗率分布范围较大，介于0.09~0.55 mm/min，较黑土分散，平均0.27 mm/min；湿运行稳定入渗率则在0.07~0.12 mm/min之间，平均0.10 mm/min，较干运行时分布集中；且黄绵土湿运行稳定入渗率平均值明显小于干运行；黄绵土稳定入渗率则主要与有机质含量以及0.002~0.1 mm中一些颗粒组成含量有显著关系。（10）变雨强降雨条件下，黑土和黄绵土小区的径流率及入渗率随降雨历时的变化过程也均受雨强变化影响。Horton模型和Kostiakov模型可模拟本实验条件下黑土和黄绵土小区的坡面降雨入渗过程，且对黑土小区入渗过程模拟效果较黄绵土好；同时，Horton模型对两类土壤的模拟结果则都要好于Kostiakov模型。可用有关土壤性质的多元线性方程估算模型中的部分参数。

Infiltration and runoff are two important processes of the hydrological cycle on the earth. They involve very complicated physical processes and have significant effects on soil erosion and hydrological process on hillslopes. Understanding the mechanism of and the affecting factors of infiltration and runoff for different conditions on hillslope are the basis of soil erosion prediction and of soil and water conservation.This study firstly analysed the relationship between slope length and runoff under artificial rainfall with varied rainfall intensity in laboratory, and modeled the processes of infiltration and runoff using proper eaquations. Plots of seven different slope lengths (1, 2.5, 4, 5.5, 7, 8.5, 10 m) were selected in the research. There were two rainfalls for each slope, named dry run and wet run, separated by about 24 h. For each run, the rainfall lasted for 120 min, and the rainfall intensity varied between 0.45 and 2.37 mm/min with an average of 1.01 mm/min. Secondly, artificial rainfall experiments were conducted in the field on black soil in Northeast China and on loessial soil on the Loess Plateau. Changes of water content in soil profiles and the infiltration and runoff for the two soils were compared and contrasted. The relationship between infiltration and runoff and soil properties were investigated. In the field study, there were also dry and wet run for each experimental plot, and in order to induce the effect of evaperation and natural rainfall, the wet run was conducted 12 h after the dry run. For every run, a total rainfall depth of 63 mm was applied at intensities ranging from 0.72 to1.85 mm/min in 60 min. The main conclusions obtained are as follows:(1) During the simulated rainfall, the processes of infiltration rate and runoff rate on all of the seven plots of different slope lengths were overall the same and they were all affected by the varied rainfall intensity. Runoff rate and rainfall intensity were positively related linearly.(2) Slope length had no significant effect on the time to runoff generation for both dry and wet run, whereas the recession time increased with the increasing slope lengths, confroming a power function, and it increased more rapidly in wet run than in dry run.(3) The influence of slope length on interval runoff depth and runoff coefficient was affected by the topsoil water contents, rainfall duration and rainfall intensity. During the period from runoff initiation to the peak rainfall intensity, the rainfall intensity kept growing, the interval runoff depth decreased obviously with the increasing slope lengths due to the low soil water content, and the decreasing rate increased as the rainfall proceeded. Immediately after the maximum rainfall intensity,, the rainfall intensity began to decrease but was still high, and the soil water contents was relatively high, the slope length did not significantly influence the interval runoff depth. In the stage of low and steady rainfall intensity, interval runoff depth declined again as slope length increasing, but the rate was smaller than the initial stage. The influence of slop length in dry run was more significant than that in wet run.(4) The effect of slope length on cumulative runoff coefficient was consistent with the effect on interval runoff depth. In dry run, runoff coefficients reduced remarkably with increasing slope length,and the rates of reduction firstly increased and then decreased, at last increased again. In wet run, there was decreasing trend only before the peak of rainfall intensity, and no significant change in the other stages.(5) The Horton and Kostiakov models could model the infiltration processes after runoff generation on every slope length, but they could not reflecte the effect of varied rainfall intensity on infiltration rates. Combining the kinematic wave model with the above two infiltration models respectively could estimate runoff process satisfactorily. but the Horton model was a little better than Kostiakov model concerning total runoff.(6) In general, the profiles of black soil were A11-AC-C in seriously eroded soils, and A11-A12-ABh (BhC, AC)-C in less eroded soils. The thickness of the humus layer was 20~40 cm for black soils. The profiles of loessial soil were relatively simpler,being A-C or A-AC-C. The thickness of the plow layer was about 10~20 cm for loessial soils. Overall, the soil properties within every profile of black soil had stronger variation than loessial soil. Compared with the loessial soils, the black soils have lower soil bulk density, more total nitrogen, more organic matter, larger water stable aggregates and more clay, while less silt and sand. For the plow layers, The variability of most of the soil properties in both black soil and loessial soil areas were moderate, and differences existed not only between the two kinds of soils, but also between different sites within each kind of soils. The variability within loessial soil was greater than that within black soil sites.(7) The initial water content of black soil was similar through profile and topsoil water content was slightly smaller; while in loessial soil profiles, water content had some trend of increase as going deeper, and, overall, was obviously smaller than that of black soil. After rainfall of dry run, the increase soil water contents was confined within the upper 20 cm of soil profiles, especially the upper 10 cm, for both black and loessial soils. On average, compared with black soil, the increase of water content of loessial soil was much larger and had a significant relationship with soil properties.(8) In both dry and wet run, the average time to runoff generation of the two soils was similar, while the average recession time of loessial soil was shorter than that of black soil. Although the average runoff coefficient of the two soils had no remarkable difference for both dry and wet run, the differences between the four sites of loessial soil was remarkable, and slight between black soil sites, particularly in wet run. For black soil, the time to runoff generation, recesstion time and runoff coefficient had no significant relationship with most of soil properties, but it was significant for loessial soil.(9) The infiltraion rates in plots of black soil varied within a range of 0.12~0.28 mm/min and 0.1~0.2 mm/min for dry and wet run, respectively. The average steady infiltration rate of all black soil plots were 0.20 mm/min and 0.15 mm/min in dry and wet run, respectively, with the former slightly larger than the latter. Correlation analysis indicated that the steady infiltration rate for black soil was influenced mainly by clay content. Compared with black soil, the steady infiltration rates of loessial soil varied more widely, being between 0.09~0.55 mm/min and 0.07~0.12 mm/min for dry and wet run, respectively The average steady infiltration rates of all loessial soil plots were 0.27 mm/min and 0.10 mm/min for dry run and wet run, respectively, with the latter much smaller than the former. It could also be seen that the steady infiltration rates on different loessial soil plots tended to be identical in wet run compared with dry run. The steady infiltraion rate was mainly related to organic matter content and particles content of 0.002~0.1 mm diameter.(10) Under the condition of varied rainfall intensity, the processes of runoff rate and infiltration rate of black and loessial were affected by rainfall intensity. Horton and Kostiakov equations could be used to modelling the infiltration processes, and it was better for black soil.In addition, Horton model is better for the two soils than Kostiakov model. Part of the parameters in the models could be estimated by using regression equations of soil properties.