基于SWAT模型的三峡库区大宁河流域产流产沙模拟及土壤侵蚀研究

Runoff and Sediment Yield Modeling and Soil Erosion Analysis in Daning River Watershed in Three Gorges Reservoir Region Based on SWAT Model

为研究三峡库区大宁河流域土壤侵蚀的状况和特点,应用SWAT模型对大宁河流域进行了产流产沙模拟,并基于SWATCUP工具中的SUFI-2方法对模型进行了参数敏感性分析、校正、验证和不确定性分析(2008—2010年为校正期,2011—2013年为验证期),进而分析了流域内土壤侵蚀状况和不同土地利用、土壤类型和坡度对土壤侵蚀的影响,并提出了土壤流失超标区域防治措施。结果表明:(1)校正后的SWAT模型在大宁河流域产流模拟中,校正期和验证期的p-factor值分别为0.89和0.75,r-factor值分别为0.75和0.69,R^2分别为0.92和0.91,NS分别为0.87和0.91;在产沙模拟中,校正期和验证期的p-factor值分别为0.90和0.95,r-factor值分别为1.04和1.05,R^2分别为0.77和0.75,NS分别为0.74和0.72。构建的SWAT模型适合大宁河流域产流产沙模拟和土壤侵蚀状况研究,且不确定性满足要求。(2)整个大宁河流域2008—2013年的平均侵蚀模数为468.88t/(km^2·a),总体土壤侵蚀强度属于微度,但在局部子流域(1,2,3,4,22)的土壤侵蚀强度属于轻度,超过了流域土壤流失容许量500t/(km^2·a),其面积占整个流域的37.44%。(3)导致轻度土壤侵蚀区域土壤流失超标的因子包括土地利用类型中的耕地和草地、土壤类型中的深色淋溶土和饱和黏磐土以及坡度>25°的耕地和草地,其中饱和黏磐土所占面积过多可能是导致轻度侵蚀区域土壤流失超标的最主要原因。建议在轻度土壤侵蚀区域,对饱和黏磐土、坡度>25°的耕地和草地进行一定比例的退耕还林和退草还林。

To analyze the soil erosion status and characteristics of Daning River basin in Three Gorges Reservoir Region, this study firstly applied SWAT to create a model to simulate runoff and sediment yield, in which the calibration period is from 2008 to 2010 and validation period is from 2011 to 2013. The parameter sensitivity, calibration, validation and uncertainty analysis of the model were further conducted through the use of SWATCUP and SUFI-2. Afterwards, the calibrated model was used to analyze the status of soil erosion and explore the influence of different land use, soil type and slope gradient on soil erosion. Finally, a suggestion to prevent and control soil loss was put forward. The results indicated that： （1） In the runoff simulation in Daning River watershed by using the calibrated SWAT model, during the calibration and validation period, the p-factor values were 0.89 and 0.75, the r-factor values were 0.75 and 0.69, R2 values were 0.92 and 0.91, and NS values were 0. 87 and 0. 91, respectively. While in the sediment simulation, the D-factor values were 0.90 and 0.95, the r-factor values were 1.04 and 1.05, R2 values were 0.77 and 0.75, and NS values were 0.74 and 0.72, respectively. The constructed SWAT model could be successfully used for simulation in Daning River watershed and uncertainty of the model could meet the requirements. Furthermore, the model could be used to analyze soil erosion status of Daning River watershed. （2） The average erosion modulus of the whole basin was 468.88 t/（km^2·a）, which indicated the micro-erosion of soil. The overall status of Daning River watershed was good. However, the average erosion modulus of local regions of the watershed （1, 2, 3, 4, 22） exceeded the soil loss tolerance, 500 t/（km^2·a）, and the soil erosion intensity of these regions was mild. The total area of these local regions accounted for 37. 44% of the whole river basin. （3） The factors resulting in the local regions exceeding soil loss tolerance based on average erosion modulus included AGRL, PAST, eutric planosols, Chromic Luvisols, and slope gradient 〉25°. Among them, the proportion of the area covered by eutric planosols in mild soil erosion region was too large, which may be the main reason resulting in the average erosion modulus of mild soil erosion region exceeding the soil loss tolerance. To prevent and control soil loss in mild soil erosion region, it is suggested that a certain percentage of AGRL （agricultural land） and PAST （pasture land） covered by eutric planosols with larger than 〉25° of slope gradient should be gradually returned to FRST（forest land）.