黄土丘陵区小流域土壤水分入渗特征研究

Characteristics of Soil Infiltration in Watersheds in Loess Hilly Region

为给森林对流域减流减沙效益的预测和评价提供科学依据 ,采用“环刀法” ,在流域的横断面上设点 ,对黄土丘陵区森林小流域和荒坡草灌小流域土壤水分入渗特征进行了研究。结果表明 :森林小流域林地土壤入渗速率显著高于荒坡草灌小流域。在 2种小流域类型中 ,阴坡的土壤入渗速率一般高于阳坡 ,其中森林小流域阴、阳坡的差异较小 ,仅在坡上部表现明显 ,稳定入渗速率分别为 7 8mm/min和 7 0mm/min ;荒坡草灌小流域阴坡的土壤入渗速率高于阳坡 ,这与阴坡植被发育较好有关。在坡位上 ,表现出从坡上部到坡下部 ,土壤入渗速率随坡位下移呈逐渐降低的趋势 ,即其空间特征为坡上部 >坡中部 >坡下部。据分析 ,这是上部产生的径流挟沙而下 ,在下部沉积 ,堵塞土壤孔隙 ,并在表层形成一个致密层的结果。根据黄土丘陵区的土壤特性 ,其土壤入渗过程以方正三方程拟合精度最高 ,如将其与A .Kostiakov方程结合使用 。

Using the method of core sampler and taking the suit place on up slope, middle slope and down slope of different slope exposures in perpendicular profile to watershed, the characteristics of soil infiltration in forested watershed and rangeland watershed of loess hilly region are studied. The results indicated that the soil infiltration rate in forest watershed is obviously higher than that in rangeland watershed. In the matter of slope exposure, the soil infiltration rate on the ubac usually is higher than that on adret in both watersheds, in which the difference of the two is small in forest watershed, only to take on obviously in the up slope and final infiltration rates are 7 8?mm/min and 7 0?mm/min. That the soil infiltration rate on the ubac is higher than that on the adret in the rangeland watershed is related to fairly good vegetation growth on the former. In the matter of slope position, it exhibited a tendency of lowering in soil infiltration rate with the drop of position. In other words, the spatial characteristics of soil infiltration rate along the slope is up slope>middle slope>down slope. It is analyzed that the reason may be related with the sediment deposited from the up slope on the down slope, resulting in forming a layer with low infiltration rate on the down slope. For the loess hilly region the process of soil infiltration could be well described by Fang Zhengshan Equation and the mixed use of Fang zhengshan Equation with A. Kostiakov equation, may fully describe the initial and final infiltration rate.