黄土高原生物结皮对SCS-CN模型初损率的影响

水文模型是水文过程研究的有效工具,初损率(λ)是径流模型SCS-CN模型的参数,对模拟流域水文过程具有重要意义。为了确定生物结皮对λ的影响,提高该模型在黄土高原生物结皮广泛分布的退耕地的预测精度,本研究以陕西省定边县鹰窝山涧流域不同盖度的生物结皮坡面为对象,采用模拟降雨试验,分析土壤潜在最大入渗量(S)与实际入渗量(F)的关系,以及生物结皮盖度对λ的影响,并修订了λ;在此基础上,采用陕西省安塞县纸坊沟流域生物结皮径流小区的模拟降雨试验数据校验了参数修订后的模型。结果表明: 生物结皮坡面S与F的关系式为: S/F=2.5×60/T(其中T为降雨历时);模型参数λ与生物结皮盖度(C_BSC)呈极显著负相关关系,二者关系式为: λ=0.0791×e^{(-0.015×C_BSC}),R²=0.60;较λ取标准值,依生物结皮盖度修订λ后,SCS-CN模型Nash效率系数提高338.7%,合格率提升16.1%。研究结果为黄土高原生物结皮坡面λ的确定提供了科学依据,对准确评估黄土高原退耕还林(草)工程的水文效应具有重要意义。

Effects of biological soil crusts on the initial abstraction ratio of SCS-CN model in the Loess Plateau

Hydrological model is an effective tool for hydrological research. The initial abstraction ratio (λ) is a key parameter of SCS-CN model, a commonly used runoff model of great significance to simulate the hydrological process at the watershed scale. In order to examine the effects of biological soil crusts (biocrusts) on λ and improve the accuracy of the model used in the restored grasslands where biocrusts widely presented in the Loess Plateau region, we firstly determined the relationship between the amount of the potential maximum infiltration (S) and the amount of the actual infiltration (F), and then investigated the effects of biocrust coverage on λ by using the simulated rainfall experiment in the Yingwoshanjian watershed in Dingbian County, Shaanxi Province. The revised model was verified by the runoff results of the simulated rainfall experiments in the Zhifanggou watershed in Ansai County, Shaanxi Province. The results showed that the relationship between S and F on biocrust slope was described as S/F=2.5×60/T (where T was the rainfall duration). There was a negative correlation between λ and biocrust coverage (C_BSC) described as λ=0.0791×e^{(-0.015×C_BSC}), R²=0.60. Compared with that using the standard value of λ, the efficiency coefficient of the model was increased by 338.7% and the qualified rate was increased by 16.1% after revising λ according to the biocrust coverage. The results provided a scientific basis for the calibration of λ on biocrust slopes in the Loess Plateau region, and were of great significance to accurately assess the hydrological effects of the implementation of the “Grain for Green” Program on the Loess Plateau.