黄土丘陵区第三副区人工牧草SCS-CN值率定研究

Study on the Rate of SCS-CN Value of Artificial Forage Grass in the Third Sub-district of the Loess Hilly Area

径流曲线数法(SCS-CN模型)是估算地表径流的常用方法,可以快速评估不同地表覆盖对降水径流关系的影响。为探讨径流曲线数法在黄土高原地区人工牧草措施下的适用性,提高植被恢复对黄土高原水资源影响的理解,为黄土高原人工牧草地表径流估算提供理论参考,选取黄河水利委员会天水水土保持科学试验站罗玉沟试验场7个径流小区中73场降雨径流事件资料,采用步长法对黄土高原人工牧草标准SCS-CN模型的径流曲线数(CN)和初损率(λ)进行优化率定。结果表明:(1)人工牧草最优λ值为0.15,而对照农田为0.18;(2)不同种类牧草CN值差异不显著,约为79,对照农田CN值为81,表明美国土壤保持局推荐的CN值对黄土高原人工牧草径流计算具有适用性,但λ值需根据实际情况进行优化率定;(3)根据前期土壤湿度情况修正S值,模拟效果较为理想,修正后的SCS-CN模型适用于黄土高原半干旱人工牧草地区。

The SCS-CN model is one of the most widely method for estimating surface runoff, which can quickly assess the effects of different ground covers on precipitation-runoff relationships. To explore the applicability of the Soil Conservation Service Curve Number Model under artificial grazing measures in the Loess Plateau region, to improve the understanding of the impact of vegetation restoration on water resources in the Loess Plateau, and to provide a theoretical reference for the estimation of surface runoff from artificial grazing in the Loess Plateau, this paper selects data from 73 rainfall runoff events in seven runoff plots at the Luoyugou test site of the Tianshui Soil and Water Conservation Experiment Station of the Yellow River Water Conservancy Commission, and uses the step-size method to estimate the runoff from artificial grazing in the Loess Plateau. The runoff curve number(CN) and the initial abstraction ratios(λ) of the standard SCS-CN model were optimized by the step method. The results showed that:(1) The optimal initial abstraction ratios value for artificial grazing was 0.15, while that for control farmland was 0.18;(2) The difference of curve number values for different species of pasture was not significant, about 79, and that for control farmland was 81, indicating that the curve number values recommended by the U.S. Soil Conservation Service were applicable to the calculation of artificial pasture runoff on the Loess Plateau, but the the initial abstraction ratios values needed to be optimized and rate determined according to the actual situation;(3) The S values were modified according to the previous soil moisture S value was corrected according to the previous soil moisture condition, and the simulation effect was more satisfactory, and the modified SCS-CN model was applied to the semi-arid artificial grazing area of Loess Plateau.