不同坡度黄土微地形条件下SCS-CN模型参数研究

SCS-CN Parameter Determination Using Rainfall-Runoff Data on Microtopographic Surfaces of Different Gradient Loess Slopes

基于自然降雨数据研究径流曲线数(SCS-CN)模型参数难以排除坡度的干扰,从而影响模型计算径流量的精度。为了准确探究黄土微地形条件下不同坡度(5°,15°,25°)对模型的初损率(λ)和径流曲线系数(CN)的影响及其变化规律,从而为后续SCS-CN模型参数研究提供科学依据和优化径流预测模型。通过开展人工降雨试验(90 mm/h雨强、人工掏挖耕作),探究黄土微地形不同坡度下SCS-CN模型的λ值和CN值。结果表明5°坡度下,λ=0.2,CN=75.58时模拟效果最佳;15°坡度下,λ=0.15,CN=77.28时模拟效果最佳;25°坡度下,λ=0.1,CN=72.91时模型的模拟效果最佳。λ=0.2这一标准参数值不能满足不同坡度条件下的径流模拟,且随着坡度增加呈现显著的递减趋势。

The most popular hydrological models are based on the Soil Conservation Service Curve Number(SCS-CN) model for its simplicity. If using data obtained in natural rainfall events, the effect of slope gradient will be significant as the model is parameterized that way, which may interfere with calculating runoff in the events. This work tries to explore the influence of slope gradients(5°,15° and 25°) on initial abstraction rate λ and curve number(CN) and their evolution in the events on the loess slope surface under microtopographic conditions, which can prepare ground for future SCS-CN parameterization research and for runoff prediction modeling in the related fields. A laboratory rainfall experiment(rainfall intensity at 90 mm/h and slope surfaces tilled by manual hoeing and digging) was carried out to determine appropriate values of λ and CN for a SCS-CN model. The results showed that the model provided the most appropriate values of λ and CN and prediction for runoff volume which fit measured rainfall-runoff data when the model determined that λ=0.2,CN=75.58 at 5°;λ=0.15,CN=77.28 at 15° and λ=0.1,CN=72.91 at 25°. It was also found that the standard parameter λ=0.2 alone could not verify runoff prediction modeling at different slope gradients and a more appropriate value tended to decrease when the slope gradient increased.