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Estimation of the water table position in unconfined aquifers with MODFLOW 6

October 20, 2022

The numerical estimation of the position of the water table in unconfined aquifers is important for many practical applications. Its determination through observations or analytical methods is restricted to a few cases. Therefore, it is often estimated through numerical simulations, which may be affected by numerical artifacts and/or poor stability. We use MODFLOW to estimate the position of the water table for a seemingly simple example problem and demonstrate difficulties that can be faced when performing this kind of numerical simulation. We explain the causes for the numerical challenges that originate from the properties of the mathematical equations that must be solved. Based on the results of more than 600 steady-state simulations, we show how the stability of the numerical solution can be affected by the values of physical parameters that define the problem (e.g., recharge rate, anisotropy ratio, and other parameters that control the numerical algorithm such as settings of the linear and nonlinear solution methods). Finally, we comment on some best practices to apply numerical simulations to estimate the water table position.

Publication Year 2023
Title Estimation of the water table position in unconfined aquifers with MODFLOW 6
DOI 10.1111/gwat.13270
Authors Paulo A. Herrera, Christian D. Langevin, Glenn Hammond
Publication Type Article
Publication Subtype Journal Article
Series Title Groundwater
Index ID 70238589
Record Source USGS Publications Warehouse
USGS Organization WMA - Integrated Modeling and Prediction Division