摘要:由美国农业部土壤保持局开发的SCS-CN模型在其他国家地区使用过程中的适用性仍存在争议，直接采用其给定的初损率λ来计算CN值易出现问题，尤其对于中国黄土高原这样具有复杂自然环境的干旱半干旱生态系统来说，有必要针对CN模型参数做进一步校正。基于地处黄土丘陵区的定西共计47个径流小区连续五年生长期的观测数据，采用平均值法计算典型植被和整地类型下的CN值，并结合前人在不同坡度下对初损率λ的率定结果进行校正，同时运用经验公式法计算土壤饱和导水率、确定土壤水文组。结果表明：①陇中地区土壤质地以壤土、粉砂壤土为主，饱和导水率介于18-180mm/h之间，最小渗透率介于3.81-7.26mm/h之间；②土壤前期含水量、植被种类、植被盖度、土地利用、坡度以及整地工程措施等均对CN值存在影响，依照坡度校正后的CN值与之前计算的存在较大差异；③典型植被覆盖类型下的CN₁值为：灌木林地（沙棘） < 撂荒地（冰草） < 人工草地（苜蓿） < 坡耕地（小麦） < 乔木林地（油松），相同坡度的同类型植被措施下，CN值随植被覆盖度增加而减小；④水平沟、水平阶和反坡台等整地措施在不同土壤湿度条件下均降低了CN值，有效提高了土壤饱和导水率。



Abstract:The applicability of SCS-CN model developed by Soil Conservation Service of United States Department of Agriculture (USDA) is still disputed. The calculation of curve number (CN) values in other countries or regions using assigned fixed initial abstraction ratio is inaccurate. It is necessary for the further calibration of parameters, especially when the model runs in the areas with complex natural environment, such as the Chinese Loess Plateau. In this study, based on the observed data of 47 runoff plots for five years during the growing season, the CN values of typical terracing and vegetation measures were determined by the arithmetic mean method, and the empirical equation method was used to identify the saturated hydraulic conductivity and hydrologic soil groups. The results indicate that ① the soil in middle region of Gansu Province is made up of loam and slity loam, whose saturated hydraulic conductivity is between 18 and 180 mm/h, and the minimum infiltration rate is between 3.81 and 7.26 mm/h. ② The CN was strongly affected by antecedent soil moisture, plant species, vegetation cover, land use, slope and terracing measures. There is an obvious difference between the calculation with correction in terms of slope and without. ③ The CN₁ values in different typical vegetation patterns sort by size:shrubland (Hippophae rhamnoides) < abandoned land (Agropyron cristatum) < artificial grassland (Medicago Sativa) < farmland (Triticum aestivum) < arboreal land (Pinus tabulaeformis), and the CN values decrease with increasing vegetation coverage among the same kind of plots with same slope gradient. ④ The terracing measures including zig terraces, leveled benches and leveled ditches all increased the saturated hydraulic conductivity and decreased the CN values in different antecedent moisture conditions remarkably.





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