水土保持研究

为探讨自然降雨在黄土区干化土壤中的入渗性能,研究干化黄土的降雨入渗机制,在陕北米脂试验站,建立野外10 m大型土柱模拟枣林地深层干化土壤,利用CS650-CR1000土壤水分自动监测系统对2014—2019年的土壤水分状况进行了连续定位监测。结果表明:(1)日降雨量为33.6,35.6 mm的大雨(降雨强度分别为3.73,2.97 mm/h,降雨历时9.0,12.0 h)状况下,最大入渗深度为140,100 cm,累积入渗量达20.05,16.10 mm; 日降雨量为19.0,16.8 mm的中雨(降雨强度分别为2.24,1.53 mm/h,降雨历时8.5,11.0 h)状况下,最大入渗深度为90,60 cm,累积入渗量达8.12,9.77 mm; 日降雨量为9.6,8.8 mm的小雨(降雨强度分别为1.48,0.76 mm/h,降雨历时6.5,11.5 h)状况下,最大入渗深度为30,20 cm,累积入渗量仅为1.05,0.23 mm。(2)降雨入渗的湿润锋运移深度(Zi)随时间(T)呈幂函数Zi=aTb增加。(3)雨水的入渗历时包括降雨历时、自降雨停止至入渗结束两个时段。6次降雨(33.6,35.6,19.0,16.8,9.6,8.8 mm)在降雨停止后时段内的入渗深度分别为100,60,70,40,30,20 cm,入渗量依次为9.86,10.78,2.09,8.42,1.05,0.23 mm。在总入渗历时内,6次降雨入渗补给系数分别为0.60,0.45,0.43,0.58,0.11,0.03。黄土区降雨入渗深度受降雨量、降雨强度、入渗历时影响较大,提高单次降雨的雨量有助于提升雨水入渗补给系数,促进干化土壤得到有效水分修复。

In order to explore the capacity of natural rainfall infiltration, and to study the mechanism of rainfall infiltration in the drying soil in the loess area, a field soil column up to 10 m was established to simulate the jujube forests drying soil in Mizhi experimental station which is located in the north of Shaanxi Province. By using the CS650-CR1000 automatic system, changes of soil moisture within different depths were observed continuously under natural conditions during the period 2014—2019. The results were as follows.(1)Under the conditions of heavy rain with daily rainfall of 33.6 mm and 35.6 mm(the rainfall intensities were 3.73 mm/h and 2.97 mm/h, as well, the duration was 9.0 h and 12.0 h, respectively), the maximum infiltration depths were 140 cm and 100 cm, and the cumulative infiltration amounts were up to 20.05 and 16.10 mm, respectively. Under the conditions of moderate rain with daily rainfall of 19.0 mm and 16.8 mm(the rainfall intensities were 2.24 mm/h and 1.53 mm/h, as well, the duration was 8.5 h and 11.0 h, respectively), the maximum infiltration depths were 90 cm and 60 cm, and the cumulative infiltration amounts were up to 8.12 mm and 9.77 mm, respectively. And under the conditions of light rain with daily rainfall of 9.6 mm and 8.8 mm(the rainfall intensities were 1.48 and 0.76 mm/h, as well, the duration was 6.5 h and 11.5 h, respectively), the maximum infiltration depths were 30 cm and 20 cm, and the cumulative infiltration amounts were up to 1.05 mm and 0.23 mm, respectively.(2)The depths of wetting front(Zi)increases with time(T), which follows the power function Zi=aTb.(3)The duration of infiltration includes two stages, namely from the beginning of the rain to the end, and from the cessation of rainfall to the end of infiltration. The infiltration depths of the 6 typical rainfall events(33.6 mm, 35.6 mm, 19.0 mm, 16.8 mm, 9.6 mm, 8.8 mm)were 100 cm, 60 cm, 70 cm, 40 cm, 30 cm, 20 cm in the period from the cessation of rainfall to the end of infiltration, and the infiltration amounts were 9.86 mm, 10.78 mm, 2.09 mm, 8.42 mm, 1.05 mm, and 0.23 mm, respectively. During the duration of infiltration, the coefficients of the 6 rainfall infiltration were 0.60, 0.45, 0.43, 0.58, 0.11 and 0.03. The infiltration depths were greatly affected by precipitation, intensity, and duration of the rainfall in the loess hilly region. Increasing the precipitation of the rainfall was helpful to improve the recharge coefficient and could promote the effective water restoration of dry soil in this region. This study was of great importance to understand the natural restoration ability of the drying soil in the Loess Plateau under the conditions of bare land, and could provide a strong theoretical support for the sustainable utilization of the drying soil.