不同降雨等级下耕作措施对坡地产流产沙的影响

摘要

[Background] As an agricultural measure,tillage practices play an important role in soil and water conservation.To provide the basis for effective prevention and control of soil erosion in different rainfall levels,soil erosion characteristics of sandy soil was explored under cross-ridge and straight-ridge cultivation in the hilly area of western Sichuan.[Methods] Based on the measured data of 1984-1987 in 4 runoff plots (20 m × 5 m of each) in Chaoyang reservoir,Pujiang County,western Sichuan,runoff,rainfall duration,and sediment yields between cross-ridge plots and straight-ridge plots,and between slope 10° plot and slope 20° plot were analyzed using SPSS 20.0 and compared.Rainfall was measured using siphon rain gauge.The generated rainfall runoff,the depth of runoff and runoff coefficient were calculated when each rainfall process finished and the water level in each plot was recorded.[Results] Heavy rain and rainstorm were erosive rainfall patterns which mainly occurred in July and August in western Sichuan.It was difficult for light rain and moderate rain to cause soil erosion.Runoff coefficient of every runoff plot gradually increased along with rainfall levels.The runoff coefficient of straight-ridge cultivation plot was 1.33 to 3.81 times that of the cross-ridge of cultivation plot,which reached the biggest value during the period of rainstorm.Under the same cultivation measures,the runoff coefficient of 10°and 20°slope was equal.The soil concentration increased with the rainfall level first and then decreased,and the soil concentration was the largest during the period of heavy rain,and the effect of the slope was more obvious.With the increase of rainfall level,the dispersion degree of runoff in every plot was decreasing.It showed that the effect of large rainstorm and extraordinary rainstorm on soil's initial water content was not obvious.The sediment yield was irregular,for example,the sediment yield of extraordinary rainstorm was less than that of large rainstorm.By establishing the regression equation between runoff and sediment yield and rainfall duration,we may see that the simulation effect of runoff depth was better than that of sediment yield.[Conclusions] Overall,runoff volume did not increase with the increase of rainfall level in the farmland of hilly region of western Sichuan.Under extraordinary rainstorm,sediment yield of the cross-ridge area was higher than that of the straight-ridge area.Meanwhile,the sediment yield of extraordinary rainstorm was less than that of the large rainstorm.It indicated that the mechanism of sediment yield was relatively complex under different rainfall levels.%探明川西丘陵区沙壤土在横坡和顺坡垄作下水土流失特征,可为该区不同降雨等级下的土壤侵蚀有效防控提供依据.本文基于蒲江县朝阳水库的4个坡耕地径流小区连续4年的观测数据,对10°和20°坡度下横坡垄作和顺坡垄作在不同降雨等级下的产流产沙进行统计分析,结果表明:大雨和暴雨是该区发生频次较高的侵蚀性降雨类型,且集中发生于7-8月;小雨和中雨基本不引起土壤侵蚀.各小区径流系数均随降雨等级增加呈增加趋势,顺垄小区的径流系数在暴雨时达到最大,是对应横垄小区的1.33 ～3.81倍.在同一耕作措施下,10°和20°坡度小区的径流系数相当.含沙量随降雨等级呈先增加后减少的变化趋势,在大暴雨时含沙量达最大,坡度的作用较明显.随着降雨等级的增加,各小区的径流深的离散程度逐渐变小,说明大暴雨和特大暴雨下土壤前期含水量作用不明显,但产沙量呈不规则变化,特大暴雨的产沙量反而小于大暴雨.通过建立产流产沙量和降雨量、降雨历时之间的回归方程可知,径流深的模拟效果较好,但产沙量的模拟效果欠佳.总体来看,坡耕地产流产沙量并没有随降雨等级的增加而增加,特大暴雨下横垄小区的含沙量高于顺垄小区,但产沙量却小于大暴雨时期,说明不同降雨等级下坡耕地产沙作用机制较为复杂.