MODFLOW (USGS Modular Groundwater Flow Model)
Criterion | Explanation | ||||||
General Description | MODFLOW simulates groundwater flow using a finite difference equation solution to the groundwater flow equation. | ||||||
Model Domain | The physical domain of the model includes the unsaturated and saturated zones. | ||||||
Developer | US Geological Survey | ||||||
Hardware computing requirements | The code has been used on UNIX-based computers and personal computers running various forms of the Microsoft Windows operating system. | ||||||
Code language | Fortran. The most recent version, MODFLOW 6 was programmed in Fortran using a modern programming style. Many of the simulation components were programmed using an object-oriented design described in Adams and others (2009) provides a comprehensive description of the details for implementing object-oriented programming concepts using Fortran. The object-oriented design is different from the procedural program design that was used for previous MODFLOW versions. | ||||||
Original application | The original MODFLOW model was developed in 1984 to simulate groundwater flow using a finite difference equation solution to the groundwater flow equation. It used a modular framework in which sententence not complete | ||||||
Public/proprietary and cost | Public, no cost | ||||||
Physically or empirically based | Physically based | ||||||
Mathematical methods used | MODFLOW solves the groundwater flow equation using a finite-difference numerical solution. | ||||||
Input data requirements | Hydraulic conductivity, storativity, boundary fluxes (recharge, lateral fluxes), boundary conditions (constant head, head-dependent boundary, etc.) | ||||||
Outputs | Outputs include spatial distribution of heads, water budgets, and boundary flows. | ||||||
Pre-processing and post-processing tools | Multiple pre-and post-processing programs can be used with MODFLOW. These include Visual MODFLOW (Waterloo Hydrogeologic), Groundwater Vistas (Rockware), USGS Model Muse and Model Viewer. | ||||||
Representation of uncertainty | Uncertainty is represented through the results of sensitivity analysis which can be used to provide ranges of model outputs. | ||||||
Prevalence | Of all the groundwater flow models widely available, MODFLOW, is regarded by many as the most widely used by government agencies and consultant firms (Loudyi et al. 2014). | ||||||
Ease of use for public entities | There is a high level of use ease. The code is readily available for free. Training and support are readily available. Multiple graphic interfaces are available. | ||||||
Ease of obtaining information and availability of technical support | There is substantial online information available through the USGS. The USGS continues to support MODFLOW with upgraded models and addition features. User groups exist. | ||||||
Source code availability | The source code is available for modification if needed at https://water.usgs.gov/ogw/modflow/MODFLOW.html#related | ||||||
Status of model development | Whether the model is developed and available for immediate use; this may include models that continue to be updated. What is the future direction of model updates?This field was not completed | ||||||
Uses in Delta | MODFLOW has been used in the Delta to simulate groundwater hydrologic conditions for the entire Delta (CVHM-D) to simulate groundwater resources impacts analysis for the BDCP EIR/EIS, and individual islands (e.g. Deverel et al. 2017). | ||||||
Challenges for integration | For integration with surface water modeling, temporal and spatial scales and calculations associated with MODFLOW modeling are different that those used for surface water models.
The water must have a constant density, dynamic viscosity (and consequently temperature) throughout the modelling domain (SEAWAT is a modified version of MODFLOW which is designed for density-dependent groundwater flow and transport). The principal components of anisotropy of the hydraulic conductivity tensor does not allow non-orthogonal anisotropies, as could be expected from flow in fractures. Challenges for use in the Delta include correctly simulating island geometry using finite differences; simulating ET and drains can be also challenging. MODFLOW unstructured grids may be better suited. |
REFERENCES
Adams, J.C., Brainerd, W.S., Hendrickson, R.A., Maine, R.E., Martin, J.T., and Smith, B.T., 2009, The Fortran 2003 handbook—The complete syntax, features and procedures, Springer Science + Business Media, 713 p., accessed June 27, 2017, at https://doi.org/10.1007/978-1-84628-746-6.
Deverel, S. J, Leighton, D. A, Lucero, C., & Ingrum, T. (2017). Simulation of Subsidence Mitigation Effects on Island Drain Flow, Seepage, and Organic Carbon Loads on Subsided Islands Sacramento–San Joaquin Delta. San Francisco Estuary and Watershed Science, 15(4). Retrieved from https://escholarship.org/uc/item/4q340190
Loudyi, Dalila; Falconer, Roger; and Lin, Binliang, "MODFLOW: An Insight Into Thirty Years Development Of A Standard Numerical Code For Groundwater Simulations" (2014). CUNY Academic Works.
http://academicworks.cuny.edu/cc_conf_hic/168
See https://en.wikipedia.org/wiki/MODFLOW for summary and history.