Modeling Variably Saturated Subsurface Solute Transport with MODFLOW‐UZF and MT3DMS
Modeling Variably Saturated Subsurface Solute Transport with MODFLOW‐UZF and MT3DMS
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DOI：
10.1111/j.1745-6584.2012.00971.x
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发表时间：
2012-07
期刊：
影响因子：
2.6
通讯作者：
E. Morway;R. Niswonger;C. Langevin;R. Bailey;R. Healy
中科院分区：
文献类型：
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作者：
E. Morway;R. Niswonger;C. Langevin;R. Bailey;R. Healy
利用MODFLOW开发的非饱和带流（UZF1）包，对MT3DMS地下水溶质运移模型进行了修正，模拟非饱和带溶质运移。修改后的MT3DMS代码使用体积平均方法，其中基于拉格朗日的UZF1流体通量和存储变化被映射到固定网格上。该模型被称为UZF - MT3DMS，与已发布的基准分析解决方案以及其他已发布的代码进行了测试，其中最常见的是美国地质调查局的可变饱和二维流动和运输模型。一组测试用例的结果表明，修改后的代码准确地模拟了溶质在非饱和区的平流、分散和反应。二维和三维模拟也进行了研究，以确保非饱和-饱和区相互作用的模拟是正确的。由于UZF1解决方案是分析性的，因此可以进行大规模的流动和输运研究，而不需要Richards方程的数值解决方案所需要的计算和数据负担。结果表明，使用UZF - MT3DMS可以显著节省模拟运行时间，这是在参数估计和不确定性分析期间需要数百或数千个模型运行时的重要发展。三维可变饱和流动和输运模拟表明，UZF - MT3DMS的运行时间不到依赖Richards方程的模型所需时间的十分之一。鉴于其准确性和效率，以及MODFLOW和MT3DMS的广泛使用，在这个熟悉的建模框架中增加的不饱和区域传输能力将使广泛的用户受益。
The MT3DMS groundwater solute transport model was modified to simulate solute transport in the unsaturated zone by incorporating the unsaturated‐zone flow (UZF1) package developed for MODFLOW. The modified MT3DMS code uses a volume‐averaged approach in which Lagrangian‐based UZF1 fluid fluxes and storage changes are mapped onto a fixed grid. Referred to as UZF‐MT3DMS, the linked model was tested against published benchmarks solved analytically as well as against other published codes, most frequently the U.S. Geological Survey's Variably‐Saturated Two‐Dimensional Flow and Transport Model. Results from a suite of test cases demonstrate that the modified code accurately simulates solute advection, dispersion, and reaction in the unsaturated zone. Two‐ and three‐dimensional simulations also were investigated to ensure unsaturated‐saturated zone interaction was simulated correctly. Because the UZF1 solution is analytical, large‐scale flow and transport investigations can be performed free from the computational and data burdens required by numerical solutions to Richards' equation. Results demonstrate that significant simulation runtime savings can be achieved with UZF‐MT3DMS, an important development when hundreds or thousands of model runs are required during parameter estimation and uncertainty analysis. Three‐dimensional variably saturated flow and transport simulations revealed UZF‐MT3DMS to have runtimes that are less than one tenth of the time required by models that rely on Richards' equation. Given its accuracy and efficiency, and the wide‐spread use of both MODFLOW and MT3DMS, the added capability of unsaturated‐zone transport in this familiar modeling framework stands to benefit a broad user‐ship.