SWAT模型应用与不确定性综述

Reviews on Application and Uncertainty of SWAT Model

SWAT(Soil and Water Assessment Tool)模型是对大尺度复杂流域进行长时期水文模拟的重要工具,在水文循环、土壤侵蚀、污染物负荷、气候变化与土地利用变化的影响等方面得到广泛应用。SWAT模型在国内外流域模拟中取得良好的模拟效果,但不确定性问题普遍存在。从模型使用者的视角,针对输入数据的准备、子流域划分和输入数据尺度转换、模型参数校准3个SWAT模型应用的重要步骤,讨论了其主要不确定性来源。模型输入数据精度不足以准确反映其空间差异,模拟单元划分粗略导致输入数据向模拟单元尺度转换时参数集总程度过高,模型参数校准过程中观测数据和评价指标的不合理选择以及异参同效现象。对此,总结提出了降低不确定性、提高模拟精度的主要措施:提高输入数据的分辨率和模拟单元划分精度至理想阈值,对模型的关键参数和部分计算方法进行本地化,采用多重评价指标、自动校准与人工校准相结合以及多要素、多站点的参数校准方法。把握模型应用主要步骤中可能的不确定性来源,并结合具体研究区特征和研究目标采取相应的措施降低不确定性,是提高SWAT模型模拟结果可信度的必要途径。

Soil and Water Assessment Tool（SWAT）model is a useful tool for long term hydrological simulation in large scale and complicated watersheds.SWAT model has been widely used in research of hydrological cycle,soil erosion,pollution loads,and impact of climate and land use change.This model has achieved good simulation results,but the uncertainty is widespread.From the perspective of the model user,this paper discussed the main sources of uncertainty through the three important steps in using SWAT model,including input data preparation,sub-watershed delineation and data scale transformation,and model calibration.Input data with insufficient precision is one of the main uncertainty sources,owing to its inability to represent the spatial variability.Insufficient precision of sub-watershed delineation would cause over-lump of parameters during scale transformation,thus cause simulation errors.In calibration process,uncertainty is mainly induced by usage of inappropriate observation and evaluation index,and equifinality.A group of measures is suggested to reduce modeling uncertainties.Increasing resolution of input data and precision of watershed delineation to a certain threshold would reduce input uncertainty.Localization of key parameters and simulation functions based on local literature and expert knowledge can effectively reduce equifinality.And using multiple evaluation indices,automatic calibration combined with manual calibration,and calibration for multi factors and multi stations can limit calibration uncertainty.Grasping the possible uncertainty sources of the main steps during the model applying,taking corresponding measures to reduce uncertainty according to the study area＇s specific characteristics and research goals,is the necessary way to improve the credibility of thesimulation results of SWAT model.