不同坡度和前期土壤含水率下裸地和草地的降雨产流试验分析

坡度和前期土壤含水率是降雨产流过程的重要影响因素。为探讨其对降雨产流过程的影响,采用人工降雨模拟试验,对太行山前平原区不同坡度和前期土壤含水率下草地和裸地降雨产流过程进行了研究。结果表明:(1)草地和裸地的径流量均随坡度和前期土壤含水率的增加而增大,且裸地在稳定阶段的产流量以及累积产流量均高于草地;同时,前期土壤含水率较高时,累积产流量与降雨历时呈现出分段函数的关系;(2)径流系数、产流滞时以及入渗率随坡度和前期土壤含水率的增加分别呈现出增大、减小和减小的趋势,且两影响因素对草地径流系数、产流滞时及入渗率的影响程度均强于裸地;(3)裸地和草地的入渗率均随坡度和前期土壤含水率的增加,其变化速率逐渐增大,且较其他入渗模型,Horton入渗模型可以很好地估算土壤入渗率以及入渗量。通过试验研究,以期为进一步探索太行山前平原区降雨产流规律提供参考。

Analysis of bare soil and grassland rainfall-runoff experiment in different slope gradient and antecedent soil moisture content

Background] Slope gradient and antecedent soil moisture content are important factors in the rainfall-runoff process. Previous researches that related to rainfall-runoff process were mainly focusing on the Loess Plateau, but ignoring the North China Plain, which is the major grain producing areas of China. Therefore, it is essential to study the rainfall process in the North China Plain under environmental change. Methods] Based on the field soils, artificial rainfall simulation experiments were conducted in this study. The rainfall-runoff process has been studied by setting various combinations of different slope gradients (5°, 10° and 15°) and antecedent soil moisture contents (0.20, 0.25 and 0.30) on the grassland and bare soil. The rainfall duration is 120 min, and the runoff volumes were measured every 3 minutes during the rainfall process, and the time interval became short (1 min) after the rain had stopped. Results]. During the experiment process, at the initial stage of runoff, the rate of runoff in bare soil was faster and the time of stable infiltration was shorter than that of grassland, and the runoff per minute in bare soil was higher than that in grassland. The cumulative runoff and rainfall duration can be fitted by an exponential function before the steady infiltration, and then they can be fitted by a linear function. When the antecedent soil moisture content was 0.25cm3/cm3 and 0.30cm3/cm3, among different slope gradients, the mean differences of runoff coefficient for the bare soil was 0.02 and 0.06, respectively, and grassland was 0.09 and 0.14, respectively. A comparison between underlying surfaces shows that the influences of slope gradient and antecedent soil moisture content on time lag and infiltration are more conspicuous in grassland. Conclusions] (1) The runoff of grassland and bare soil increased with the increase of slope and soil water content, and accumulated runoff of bare soil were higher than that of grassland. Piecewise function can be used to describe the relationship between cumulative runoff and rainfall. (2) For both underlying surfaces, the runoff coefficient and infiltration rates increased with the increase of slope gradient and antecedent soil water content, while time lag is negatively correlated with slope gradient and antecedent soil moisture content. And under the same conditions, the influence of slope and antecedent soil moisture content on the grassland is stronger than the bare soil. (4) For the soil (sandy loam) that used in this experiment, regression analysis for infiltration shows that the Horton infiltration model is able to properly estimate the infiltration rate and capacity. This paper can provide a reference for rainfall-runoff regulation in the Taihang Piedmont.