土壤可蚀性K值最优估算方法遴选——以陕北安塞集水区为例

The optimal estimation method for K value of soil erodibility:A case study in Ansai Watershed

基于EPIC公式、诺谟方程、修正诺谟方程、Torri模型和Shirazi模型5种土壤可蚀性(K值)估算方法,以降水、土壤、遥感影像和社会经济数据为基础数据,运用GIS技术,结合CSLE模型,计算安塞集水区2006—2014年土壤侵蚀量,对比相应年份输沙量监测值,遴选集水区尺度K值最优估算方法。结果表明:基于5种模型的集水区2006—2014年平均土壤侵蚀量分别为65.59、106.00、108.47、76.69和47.68 t/hm2。相较于安塞水文站相应年份的平均输沙量监测值17.73 t/hm2,按照平均绝对误差(MAE)、平均相对误差(MRE)和均方根误差(RMSE)越趋近于0,精度因子(Af)越接近于1,模型区域适用性越高的原则可知,Shirazi模型的适用性最高,其MAE、MRE和RMSE值依次为30.93、3.25和43.66,Af值为4.41;EPIC法次之,Af值为5.80;Torri模型的适用性处于中间水平;修正诺谟方程和诺谟方程的适用性最低,与实际情况相差最大,Af值分别为7.99和7.88。因此,相对于其他4种方法而言,Shirazi模型在研究区具有最佳的适用性,在未来集水区尺度土壤可蚀性K值估算乃至土壤侵蚀评价工作中,应优先选用基于几何平均粒径的Shirazi模型。

[Background] Soil erosion has become a global ecological and environmental problem. It is now being recognized as a severe threat to socio-ecological security and stability,and it is relative with the food security,resilience to climate change and geosocial stability. Soil erosion is particularly acute in the Loess Plateau. In order to control soil erosion,the quantitative study of soil erosion must be strengthened. Soil erosion is affected by many factors such as climate,vegetation,and land use and soil properties. Among those factors,soil erodibility has been qualitatively evaluated as a key indicator for estimating soil loss and usually being measured by K value. The research of soil erodibility is significant to understand the principle of soil erosion,to estimate soil erosion modulus quantitatively and to controlsoil and water loss reasonable. The estimation method of soil erodibility is numerous,but the regional applicability of different models remains to be discussed. [Methods]We conducted a study to select the optimal estimation method of soil erodibility（ K value） based on the basic data of precipitation,soil,remote sensing images and socioeconomic data in Ansai Watershed. We used GIS technology and CSLE model to calculate soil erosion modulus in 2006-2014 and compared it with the corresponding monitoring value of sediment. Tthe K value was calculated by EPIC,NOMO,M-NOMO,Torri and Shirazi model.The comparison between the simulated value of soil erosion modulus and the monitoring value of sediments is based on the principle that the mean absolute error（ MAE）,the mean relative error（ MRE） and the root-mean-square error（ RMSE） are closer to 0,the accuracy factor（ Af） is closer to 1,the regional applicability of model is higher. [Results] The mean soil erosion modulus of Ansai watershed in 2006-2014 based on the five models of EPIC,NOMO,MNOMO,Torri,and Shirazi was 65. 59,106. 00,108. 47,76. 69 and 47. 68 t/hm2 respectively. The mean monitoring value of sediment in corresponding year was 17. 73 t/hm2. Based on the above evaluation indexes,we knew that the Shirazi model＇s regional applicability was the highest, the value of MAE, MRE and RMSE was 30. 93,3. 25 and 43. 66 respectively,the Afvalue was 4. 41,The regional applicability of EPIC model took second place,the value of Afwas 5. 80,The regional applicability of Torri model was in the middle level. The regional applicability of NOMO model and M-NOMO model was lowest,it had the biggest difference with the actual situation,the Afvalue was 7. 99 and 7. 88 respectively. [Conculsions] Based on the above analysis,we concluded that the Shirazi model had the best applicability in study area comparing to the other four K value estimation methods. We should be preferred to choose the Shirazi model in the future watershed scale soil erodibility（ K value） estimation and soil erosion evaluation.