雨强和坡度对红壤坡耕地地表径流及壤中流的影响

地表径流和壤中流是坡面重要水文过程,雨强和坡度是影响坡面地表径流和壤中流产流主要因素。为研究降雨强度和地表坡度对坡耕地地表径流和壤中流的影响,该文采用人工模拟降雨试验法,在长3.0 m、宽1.5 m、深0.5 m土槽,设计4个不同坡度(5°、10°、15°、20°)和3个不同雨强(30、60、90 mm/h)对红壤坡耕地地表径流及壤中流产流过程进行模拟试验。结果表明:1)壤中流开始产流时间滞后于地表径流,降雨强度从30到90 mm/h,地表径流、壤中流产流开始时间均随雨强增大而减小,壤中流比地表产流开始滞后时间随着雨强增大先增大后趋于稳定;2)地表径流强度随雨强增大而增大,壤中流初始径流强度随雨强增大而增大,不同雨强下壤中流径流峰值相近;3)地表径流和壤中流产流过程曲线有明显差异,地表径流产流过程线先增大后趋于稳定,壤中流产流过程线呈抛物线型即先增大后减小;4)从5°到20°,地表产流开始时间随坡度增大而减小,壤中流产流开始时间随坡度增大先减小后增大;5)从5°到20°,地表径流强度先增大后减小,10°为转折坡度,壤中流产流峰值随坡度增大而减小,并且随着坡度增大达到壤中流峰值时间不断减小。

Effects of rainfall intensity and slope on surface and subsurface runoff in red soil slope farmland

Abstract: The surface and subsurface runoff in the red soil slope farmland result in soil moisture and nutrient loss. In addition, the surface and subsurface runoff are important components contributing runoff at the watershed scale. An extensive literature shows that rain intensity and slope are two main factors playing an important role in the surface and subsurface runoff. In this paper, the surface and subsurface runoff in the red soil slope land under different rainfall intensities and slopes were studied by stimulated rainfall experiments in the flume (3.0 m length×1.0 m width×0.5 m depth) with variable slopes. The experiments were conducted in the Jiangxi Soil and Water Conservation Ecological Science and Technology Park. Stratified soil samples from different profiles including 0-20 cm (the plow horizon) and 20-40 cm (the plow pan) were collected and then filled respectively into the flumes by controlling the bulk density. For the rain intensity of 90 mm/h, we set four slopes including 5°, 10°, 15° and 20° in the simulated rainfall experiment. Three rain intensity levels (30, 60 and 90 mm/h) were set for the plots with slope of 10°. The results indicated that: 1) the subsurface runoff lagged behind the surface runoff, and the initiation time of the surface and subsurface runoff decreased with the increase of rainfall intensity from 30 mm/h to 90 mm/h. The lag time of the subsurface runoff initiation increased with the increasing rain intensity, and then tended to be stable; 2) the initial and steady surface runoff increased with the increase of the rain intensity; and the initiation subsurface runoff intensity increased with the increase of rainfall intensity. An increase trend was observed in the runoff produced by per unit rainfall; 3) the initial intensity of the surface runoff increased with the increase of rainfall intensity from 30 to 90 mm/h. However, no significant differences were found for the peak values of the subsurface runoff under different rainfall intensities. The attenuation curves of the surface runoff under different rainfall intensities were similar; 4) the obvious differences were observed between the runoff process curves of the surface runoff and subsurface runoff. The surface runoff increased firstly and then tended to be stable, but the soil subsurface runoff increased firstly and then decreased; 5) the initiation time of the surface runoff decreased with the increase of slope from 5° to 20°, but the initiation time of the subsurface runoff decreased firstly and then increased with the increase of the slope. The lag time of the subsurface runoff to the surface runoff also decreased firstly and then increased with the increasing slopes; 6) the surface runoff intensity first increased and then decreased with the increasing slope from 5° to 20° with a critical slope of 10°. The peak values of the subsurface runoff in soils increased firstly and then decreased with the increasing slopes. Moreover, the time to reach the peak value of the subsurface runoff decreased gradually with the increase of the slopes.