流域水文模拟的自动参数化:SWAT2005在香溪河的应用

Autocalibration in Hydrologic Modeling at Watershed Scale:Using SWAT2005 in River Xiangxi

流域的空间异质性和水文过程的复杂性增加了基于物理过程的分布式水文模型的参数化、校准和验证过程的难度。SWAT是具有很强的水文物理机制的分布式流域水文模型。SWAT的2005版本(SWAT2005)包含了一个参数敏感性分析和自动参数化的模块,用以模型的参数优化。本研究以位于长江三峡大坝坝首的香溪河流域为例,评估了SWAT2005参数敏感性分析和自动参数化对径流模拟的效果。模型的率定期和验证期分别为1970-1974年和1976-1986年。根据率定期香溪河流域兴山水文站的月径流观测值,对SWAT2005预先设定的27个参数进行敏感性排序,选择了CN2,CANMX,CH_K2,ESCO,SURLAG,BIOMIX和ALPHA_BF7个较为敏感的参数对模型进行了自动参数化以获得最优参数值。根据最优参数值模拟了率定期和验证期兴山水文站的月径流量,并与实际观测值进行了对比评估。率定期和验证期兴山水文站月径流量的观测和模拟的平均值和标准差都较为接近,在率定期和验证期确定性系数R2为0.80,Nash-Suttclife效率系数Ens分别为0.70和0.77。评估结果表明,SWAT2005的参数敏感性分析和自动参数化功能在香溪河流域径流模拟的自动参数化过程中效果很好,其他流域利用SWAT开展水文模拟时可以考虑利用SWAT2005的自动参数化功能。

Due to the spatial heterogeneity in watershed and the complexity of hydrologic processes,calibration can become difficult.Compared with manual calibration,autocalibration could increase the efficiency of calibration process and improve the objectivity and creditability of the calibrated results.SWAT(Soil-Water-Assessment-Tool) is a physically based model at watershed scale.An autocalibration-sensitivity analysis procedure was embedded in SWAT version 2005(SWAT2005) to optimize model parameters.The objective of this study was to evaluate the effectiveness of the autocalibration-sensitivity analysis procedure in a meso-scale watershed River xiangxi,the largest tributary of Yangtze River in Hubei part of Three Gorges Reservoir.The calibration period and validation period were 1970-1974 and 1976-1986,respectively.The sensitivity rank of pre-define parameters by SWAT2005 were obtained based on observed monthly flow for 5-year calibration period at Xiangshan gauging station.The parameters of CN2,CANMX,CH_K2,ESCO,SURLAG,BIOMIX and ALPHA_BF were selected for autocalibration.Monthly discharge was simulated based on the optimal parameter sets for both calibration and validation periods,and compared with observed values for effectiveness evaluation.The results showed that slight difference exist between the mean and standard deviation for monthly discharge during calibration and validation period.The Nash-Sutcliffe efficiency(Ens) was 0.70 and 0.77,and the coefficient of determination(R2) was both all 0.80 during calibration and validation period.Overall,the autocalibration-sensitivity analysis procedure in SWAT2005 was useful as evidenced by statistical measure in discharge simulation in River Xiangxi,and could be used for other watershed for hydrologic modeling.