WEPP模型在北京山区的适用性评价
Assessment of WEPP model applicability in Beijing mountainous area
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摘要: 土壤侵蚀是目前全球面临的环境问题之一。如何防治及准确预测水土流失已成为研究土壤侵蚀面临的巨大挑战。基于降雨事件及水文过程,WEPP模型的产生为土壤流失预测及评估提供了重要支撑。基于2001—2006年北京延庆径流小区的次降雨及25场次野外径流小区监测数据,对WEPP模型的参数进行了率定与验证,评价了该模型在北京土石山区的适用性,对北京土石山区土壤侵蚀及其预报具有重要意义。在北京山区褐土表土(0~10 cm)条件下,通过计算实测值和模拟值的最小累积误差法率定模型土壤参数,同时采用Nash-Sutcliffe效率系数(E)和决定系数(R2)对模型有效性进行验证。结果表明,当模型有效水力传导系数、临界剪切力和细沟土壤可蚀性分别为1.400 mm/h、1.000 Pa和0.010 s/m时,模型模拟效果最佳,且径流量的模拟效果(E=0.730)优于侵蚀量的模拟效果(E=0.670)。相关系数和通径系数显示,关于降雨参数对径流量和侵蚀量的影响,最大30 min雨强(I30)与其呈极显著相关,对其直接影响最大;其次是降雨量;而降雨历时与径流量和侵蚀量没有关系,对其直接影响最小。Abstract: Soil erosion is one of the global environmental problems at present. Accurate prediction and prevention of soil erosion has become a huge challenge. The development of WEPP model provides an important support for the prediction and assessment of soil erosion. To evaluate the applicability of WEPP model in Beijing mountainous area, we measured rainfall-runoff-sediment data during 2001-2006 at Yanqing field runoff plots of Beijing and applied them in model calibration and validation. We evaluated the applicability of WEPP model in the mountainous area of Beijing, which has important implications for soil erosion prediction in mountainous areas. Under cinnamon topsoil (0-10 cm) condition, the minimum cumulative error and Nash-Sutcliffe efficiency coefficient (E) were used to perform model calibration and validation. Results showed that the calibrated values of effective hydraulic conductivity, soil critical shear, and rill erodibility were 1.400 mm/h, 1.000 Pa and 0.010 s/m, respectively. For the validation, the WEPP model presented a higher simulated accuracy for runoff than for erosion yield according to E of 0.730 and 0.670. Correlation coefficients and path analysis of rainfall parameters indicated that 30-minute maximum rainfall intensity (I30) has the greatest impact on runoff and erosion yield, and subsequently on the precipitation. Duration of rainfall has no correlation with runoff and erosion yield, with little direct impact on them.