黄土丘陵区不同盖度生物结皮对坡面产流及SCS-CN模型CN值的影响

以黄土丘陵区典型退耕地不同盖度的生物结皮坡面为研究对象,通过野外人工模拟降雨试验,研究不同盖度生物结皮对坡面产流的影响,解析了生物结皮盖度与SCS-CN径流模型参数CN值的关系。结果表明:(1)在90 mm/h雨强条件下,初始产流时间随生物结皮盖度增加而降低,低盖度(0~20%)生物结皮坡面初始产流时间分别为中盖度(40%~60%)和高盖度(80%~100%)的1.64,2.46倍;(2)降雨前15 min,高盖度生物结皮较中、低盖度生物结皮促进产流,15 min后,高盖度生物结皮较中、低盖度生物结皮抑制产流,降雨45 min后各处理小区径流系数趋于稳定;(3)径流深随生物结皮盖度增加呈对数函数降低(y=-13.87ln x+73.515,R^2=0.7614);(4)生物结皮盖度(CBSC,%)与CN值呈极显著负相关关系,CN=-0.2672×CBSC+79.0166,R^2=0.6800,通过调整CN值可使SCS-CN模型适于生物结皮坡面的径流估算。研究结果揭示了生物结皮对SCS-CN径流模型参数CN值的影响,对建立考虑生物结皮的水文模型奠定了基础。

Effects of Biological Soil Crusts' Coverage on Slope Runoff and the CN Value of SCS-CN Model in Hilly Loess Plateau Region

Runoff yield from revegetated grasslands with different coverage of biocrust was measured by simulating rainfall in the study. Meanwhile, the relationship between biocrust coverage and CN value of SCS-CN model was analyzed. The results showed that: (1) Under a 90 mm/h rainfall intensity, the initial runoff yield time decreased against the increase of biocrust coverage, and the initial runoff time with low biocrust coverage (0~20%) was 1.64 and 2.46 times of that with medium biocrust coverage (40%~60%) and high biocrust coverage (80%~100%), respectively. (2) In the first 15 minutes of rainfall, biocrusts with high coverage promoted runoff yield compared with medium and low biocrust coverage. After 15 minutes, high biocrust coverage inhibited runoff yield compared with medium and low biocrust coverage. After 45 minutes of rainfall, runoff coefficient of each treatment tended to be stable. (3) There was a significant negative correlation between biocrust coverage and runoff depth, and runoff depth decreased in the form of logarithmic function with the increase of biocrust coverage (y=-13.87ln x+73.515,R²=0.761 4). (4) By adjusting CN value, SCS-CN model could be suitable for runoff estimation from biocrustal slope, and there was a significant negative correlation between biocrust coverage and CN value, the relational expression is that CN=-0.2672×C_BSC+79.0166,R²=0.680 0. In which, C_BSC was the percentage coverage of biocrust. In this study, the influence of biocrust on the parameters of runoff model was revealed, which was of great significance to the establishment of hydrological model considering biological crust.