iTOUGH2反演模型在地下水模拟中的应用

Application of iTOUGH2 to groundwater modeling

模型参数快速校准是地下水数值模型应用中非常重要和困难的工作,反演模型提高了该工作的效率。在阐述i TOUGH2反演模型流程和TOUGH2/EOS9模块原理的基础上,介绍了i TOUGH2关于敏感性分析、参数估计和不确定性分析的原理。以FEFLOW软件中含三个观测井信息的Breyell抽水试验为例,利用i TOUGH2进行了敏感性分析、参数估计和不确定性分析,发现渗透率和孔隙度为敏感参数,而且通过加权最小二乘法的目标函数和优化算法获得了参数的估计值,最后使用一次二阶矩法和蒙特卡罗法分别进行了不确定性分析。将i TOUGH2反演的参数估计值与FEFLOW反演结果对比,发现两者接近,说明i TOUGH2的反演结果是可靠的。i TOUGH2对应的功能全,包括参数反演,敏感性分析,不确定性分析,可作为地下水模型反演模型的选择之一。

Rapid and effective parameter calibration is important and difficult in groundwater modeling. Inverse groundwater modeling makes parameter estimation efficient. This study presents the workflow of iTOUGH2 and the principle of TOUGH2/EOS9 module, and introduces three key functions of the iTOUGH2 software in detail, i. e. , sensitivity analysis, parameter estimation and uncertainty propagation analysis. The Breyell pump test in the FEFLOW software is taken as an example. This paper demonstrates the capabilities of iTOUGH2, and it is found that permeability and porosity are more sensitive to the model outputs than pore compressibility. The estimation of the parameters is obtained and the uncertainty propagation analysis is also performed. Parameters estimated with iTOUGH2 are close to those estimated with FEFLOW. In this case, the first-order-second-moment error propagation analysis is more applicable than the Monte Carlo method. The iTOUGH2 software has powerful functions including parameter estimation, sensitivity analysis and uncertainty propagation analysis. It is an option for inverse groundwater modeling for improving the efficiency of model use.