黄土丘陵沟壑区(Ⅲ)土壤抗冲性研究——以天水站为例

Soil Anti-scourability Research in the Third Region of Hill and Gully on Loess Plateau——Taking Tianshui Soil and Water Conservation Station as an Example

以天水水保站1945—1957年径流小区观测资料为依据。分析了径流小区1144场降雨径流动力因子的特征以及与径流冲刷量的相关状况。结果表明,次降雨径流深与其对应所产生的侵蚀量关系非常密切;在目前无法用解析式计算径流冲刷动力的条件下,用次降雨径流深做为描述土壤径流冲刷的动力因子是合理的;进一步分析表明,年降雨径流深与次降雨径流深分布极不均匀,其方差λ甚至大于其数学期望E,不可以用上述均值简化代表次降雨径流深,并进而做为描述土壤径流冲刷的动力因子;年降雨径流深的分布以10～20mm较为集中,概率为67.648％,次降雨径流以2.5～4.0mm之间分布较为集中,概率为55.883％。其次提出了土壤抗冲性指标及计算方法。以单位面积单位径流冲刷动力即单位径流深冲刷侵蚀量做为描述土壤抗冲性的指标。最后笔者讨论了单位径流深径流冲刷侵蚀量均值的作用以及土地利用状况及地表坡度对其影响。结果表明,农地的土壤抗冲性指标是人工牧草地的3.872倍,是林地的9.142倍。对于农地,其抗冲性指标与地表坡度在4°05′～23°43′之间呈幂函数递增关系。

In accordance with the total 13 years runoff plots information from 1954 to 1975 of Tianshui soil and water conservation station, based on the analysis of 1144 times runoff-sediment information of 35 runoff plots, firstly, we analysed the characteristic of runoff force factor and the relationship between sediment yield and runoff. The results shows, the relationship between individual rainfall runoff depth and it's sediment yield is very close. Now, we can use the individual rainfall runoff depth as the runoff scouring force by the condition of no other way to computer runoff scouring force. The further analysis shows, the distribution of yearly and individual rainfall runoff depth is not very uniform, and it's variance is bigger than it's average value. We don't use it's average value instead of individual rainfall runoff depth, even as a factor to represent the erosion force. The distribution of yearly rainfall runoff depth is in 10～20mm, it's probability is 67. 648％, the distribution of individual rainfall runoff depth is in 2.5～4.0mm, it's probability is 55. 883％. Secondly, we advanced the soil anti-scour index is the sediment yield in unit area runoff plots by unit runoff scouring force or unit individual runoff depth. Finally, we discussed the action for the average value of soil anti-scour index and the effect of slop gradient and land use on it, The results shows, the average value of soil anti-scour index for agriculture land is 3. 872 times than artificial forage grass land, and is 9. 147 times than forest land. The relationship between the average value of soil anti-scour index and slop gradient from 40°5′ to 23°43′in agriculture land is power function.