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Estimation of the Water Table Position in Unconfined Aquifers with MODFLOW 6

Journal Article · · Ground Water
DOI:https://doi.org/10.1111/gwat.13270· OSTI ID:2424131
 [1];  [2];  [3]
  1. Department of Environmental Geosciences University of Vienna Austria; Independent Consultant (currently) Santiago Chile
  2. U.S. Geological Survey Mounds View MN USA
  3. Pacific Northwest National Laboratory Tri‐Cities WA USA
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Abstract

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.

Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Organization:
USDOE
DOE Contract Number:
AC05-76RL01830
OSTI ID:
2424131
Journal Information:
Ground Water, Journal Name: Ground Water Journal Issue: 5 Vol. 61; ISSN 0017-467X
Publisher:
Wiley - NGWA
Country of Publication:
United States
Language:
English

References (14)

Scripting MODFLOW Model Development Using Python and FloPy journal March 2016
MODFLOW‐NWT: Robust Handling of Dry Cells Using a Newton Formulation of MODFLOW‐2005 journal August 2012
Choosing appropriate techniques for quantifying groundwater recharge journal January 2002
A simple method to assess unsaturated zone time lag in the travel time from ground surface to receptor journal January 2013
NWTOPT – A hyperparameter optimization approach for selection of environmental model solver settings journal January 2022
Improved Calculations for Dewatered Cells in MODFLOW journal November 2001
Global synthesis of groundwater recharge in semiarid and arid regions journal January 2006
The Role of Hand Calculations in Ground Water Flow Modeling journal March 2006
Robust Representation of Dry Cells in Single‐Layer MODFLOW Models journal October 2008
Recharge and groundwater models: an overview journal January 2002
Are Water Tables a Subdued Replica of the Topography? journal August 2005
Numerical Solution of Richards' Equation: A Review of Advances and Challenges journal October 2017
Approaches to the Simulation of Unconfined Flow and Perched Groundwater Flow in MODFLOW journal June 2011
MODFLOW-NWT, a Newton formulation for MODFLOW-2005 report January 2011

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Related Subjects

Geology
Water Resources