不同放牧条件下坡面初始产流时间和径流流速变化特征

Characteristics of Initial Yield Time and Velocity of Runoff Under Different Grazing Conditions

[目的]研究不同降雨强度下植被覆盖度和坡度对我国北方典型草地坡面产流的影响,以期进一步丰富我国有关北方典型干旱半干旱草原的水土保持研究理论,为合理配置草原资源提供理论及实际参考依据。[方法]研究基于野外人工模拟降雨试验的方法,分析了不同雨强下初始产流时间与植被盖度和坡度的相关规律,以及不同放牧条件下坡面径流流速的变化规律,建立了初始产流时间与植被盖度和坡度以及坡面流速与植被盖度和坡度的多元回归模型。[结果]雨强为1.5 mm/min时,3个坡度4°,9°,14°坡面的初始产流时间相比裸地,放牧条件下分别增加了1.23,1.39,1.30倍,围封条件下分别增加了2.02,2.03,1.38倍。整个模拟降雨的坡面径流流速变化范围0.05~0.3 m/s,围封状态下,坡面流速仅是放牧条件下的63%~68%。[结论]植被盖度和坡度对初始产流时间的影响较为显著,在其他条件相同的情况下,初始产流时间随着雨强或坡度的增大均减短,随着植被盖度的增加而明显延长。在其他条件相同的情况下,雨强或坡度越大,坡面流速越大;植被盖度越大,坡面流速越小,产流总量与之规律相同。

[Objective]This paper studies the influence of vegetation coverage and slope on slope runoff of typical grassland in northern China under different rainfall intensities in order to further enrich the research theory of soil and water conservation of typical arid and semi-arid grassland in northern China,and to provide theoretical and practical reference for the rational allocation of grassland resources.[Methods]A series of studies on slope runoff yield under different grazing conditions were carried out based on field artificial simulated rainfall experiments.According to the field survey results,different grazing scenarios were simulated by means of manual grass cutting.The pattern of correlation between initial runoff time and vegetation coverage and slope under different rainfall intensities and the pattern of variation of runoff velocity under different grazing conditions were analyzed,and the multiple regression linear equations of initial runoff time,vegetation coverage and slope,as well as the multiple regression linear equations of slope velocity and vegetation coverage and slope were established.[Results]When the rainfall intensity is 1.5 mm/min,the initial runoff generation time of the three slopes 4°,9°and 14°increased by 1.23 times,1.39 times and 1.30 times,respectively,compared with that of bare land,under grazing conditions,under the condition of enclosure,it increased by 2.02 times,2.03 times and 1.38 times,respectively.The variation range of runoff flow velocity of the whole simulated rainfall was between 0.05 and 0.3 m/s,in the enclosed state,the slope velocity was only 63%~68% of that under grazing conditions.[Conclusion]vegetation coverage and slope have the significant impact on the initial runoff time.Under the same other conditions,the initial runoff time decreases with the increase of rainfall intensity or slope,and significantly prolonges with the increase of vegetation coverage.With other conditions being the same,the heavier the rainfall or the steeper the slope is,the higher the slope velocity will be,while the higher the vegetation coverage is,the lower the slope velocity will be,the pattern of total runoff production is the same.