人工降雨和放水冲刷试验下红壤坡面径流与泥沙特征分析

南方红壤丘陵区是我国水土流失最严重的区域之一,严重的水土流失会导致土壤退化,也会影响农业生产的可持续发展,因此,研究红壤坡面侵蚀规律对南方红壤丘陵区水土流失防治意义重大。以红壤坡面为研究对象,应用人工降雨和放水冲刷试验,选择5°,10°,15°,20°四个坡度,设计0.8,1.2,2.1,2.6 mm/min四种降雨强度(相对应的放水流量分别为1.4,3.0,5.7,7.0 L/min),对红壤坡面的径流和泥沙特征进行了研究。结果表明:2种试验条件下,红壤坡面初始产流时间均随着坡度和降雨强度(放水流量)的增大而减小,尤以5°坡和0.80 mm/min降雨强度(1.40 L/min放水流量)下变化幅度最为明显,且在坡度较小时(5°和10°),人工降雨试验产流快;2种试验条件下红壤坡面径流量稳定时间为15~20 min,人工降雨试验红壤坡面泥沙量稳定时间为10~15 min,放水冲刷试验红壤坡面泥沙量稳定时间为15~20 min;径流和产沙总量随降雨强度(放水流量)和坡度增加而增大,在降雨强度(放水流量)和坡度较小时变化幅度较大;降雨试验的径流总量超过放水试验,产沙总量在降雨强度(放水流量)和坡度较小时,放水试验多,但随着降雨强度(放水流量)和坡度的增加,降雨试验多;5°坡在不同的降雨强度和放水流量下,径流和泥沙总量变化幅度最大,故应重视5°坡的水土流失预防。研究结果有助于全面了解红壤侵蚀规律,并为南方红壤丘陵区开展土壤侵蚀治理提供数据支撑。

Characteristics of Runoff and Sediment Yield on Red Soil Slope under Artificial Rainfall and Scouring

Hilly red soil region in south China is a region with the most severe water and soil loss in China. Severe soil erosion will lead to soil degradation and will also affect the sustainable development of agricultural production. Studying the erosion law of red soil slope is of great significance for the prevention and control of water loss and soil erosion in hilly red soil region in south China. The features of runoff and sediment yield on red soil slope were studied in this research through artificial rainfall and scouring test. Slope gradient was designed as 5°, 10°, 15°, and 20°, and rainfall intensity at four levels, namely, 0.8 mm/min, 1.2 mm/min, 2.1 mm/min, and 2.6 mm/min, and the corresponding scouring discharge 1.4 L/min, 3.0 L/min, 5.7 L/min, and 7.0 L/min, respectively. Research results are concluded as follows: 1) Under both artificial rainfall and scouring conditions, the initial runoff yield duration of red soil slope declined with the increase of slope gradient and scouring discharge, and such decline was the most remarkable on slope of 5° gradient in the presence of 0.8 mm/min rainfall intensity (1.4 L/min scouring flow rate). On slope of small gradient (5° and 10°), initial runoff yield in artificial rainfall test came earlier than in scouring test. 2) Under both test conditions, runoff stabilized within 15-20 min; sediment load stabilized in 10-15 min under artificial rainfall and 15-20 min under scouring. 3) The total volume of runoff and sediment yield on red soil slope increased with the rise of rainfall intensity and scouring discharge, and such increase was particularly apparent on slopes of small gradient in the presence of small rainfall intensity and scouring discharge. The total volume of runoff in artificial rainfall test was larger than that in scouring test; on the contrary, the total sediment yield in artificial rainfall test was smaller than that in scouring test under small rainfall intensity and scouring discharge, but became larger with the rise of rainfall intensity. 4) In addition, attentions should be paid to the prevention of soil and water loss on slopes of 5° gradient as the total runoff and sediment yield on 5° slope gradient changed more dramatically than on other gradients despite rainfall intensity and scouring discharge. The research results are conducive to understanding red soil erosion and offer data support for the treatment of red soil erosion in south China.