Model Files

The Goulbi Maradi model has been developed for the MODFLOW numerical model. MODFLOW is a groundwater modeling code developed by the United States Geologic Survey (USGS) and it is the most widely used and trusted groundwater model in the world.

MODFLOW uses a Cartesian finite different grid where the model domain has been subdivided into grid cells organized in rows, columns, and layers. Before running MODFLOW, the user must create a computational grid for the aquifer and define aquifers properties (hydraulic conductivity, storage coefficients, etc), sources and sinks (recharge, wells, rivers, etc), and all of the other model options and features into a collection of text-based input files. When running MODFLOW, these files are passed as input to MODFLOW and MODFLOW reads the contents of the files and saves the solution (head, flows, etc.) to a set of output files.

The Goulbi Maradi model was created using the Groundwater Modeling System (GMS) software. GMS is one of several pre- and post-processors, or graphical user interfaces ("GUI's") that have been developed for MODFLOW. Since the input files for MODFLOW are incredibily detailed and complicated, it is customary to use software like GMS to automate the process of preparing the files and reading and visualizing the solution. While this model has been built with GMS, it could be edited with any other GUI using the MODFLOW intput files linked below.

To run the model, one would typically:

1. Download the model files
2. Load the model in GMS
3. Modify the model inputs
4. Save the model files
5. Run MODFLOW
6. Read the solution into GMS to visualize the results

Steps 1-2 are described below. Steps 3-6 are described in the Predictive Simulations page.

Downloading the Model Files

We have prepared three versions of the MODFLOW simulations:

Title	Link	Description
Calibrated Steady State Model	Download	Steady state simulation corresponding to average conditions from 2002 to 2009. This was developed and calibrated before the transient model was developed.
Calibrated Transient Model	Download	Transient simulation with dynamic inputs (well pumping rates, recharge) corresponding to the period from 2002 to 2009.
Predictive Model	Download	This is a modified version of the calibrated transient model where the simulation period has been extended from 2002 to 2021 so that the model can be used to explore the consequences of various pumping strategies and recharge assumptions. The Predictive Simulations page describes how to modify and run this model.

File Organization

Each set of model files linked above is in a ZIP archive. After downloading the files, you should unzip the archive into a folder. Each MODFOW simulation is saved in two parts:

1) A GMS project file (*.gpr) where * is the name of the simulation.

2) A folder containing the MODFLOW input and output files called *_MODFLOW.

Here is an example:

The folder of MODFLOW files contains a large number of files:

Loading the Files in GMS

To load the files in GMS:

1. Launch GMS and select the File|Open command.
2. Path to the folder where you have saved and unzipped the files.
3. Select and open the GMS project file *.gpr.

This will read the entire simulation into GMS.

Once you have loaded the simulations, you can toggle features on and off using the Project Explorer window on the left. To make the downloads smaller, we did not include model solutions in the download archives. To see a solution, you will need to:

1. Save the simulation using the File|Save command.
2. Run MODFLOW by selecting the MODFLOW|Run MOFLOW command.
3. Close the Model Wrapper window when the simulation is finished.

For more information on how to build/calibrate/use MODFLOW models, please visit the following resources:

Prof. Norm Jones Groundwater Modeling Course Website	http://ce547.groups.et.byu.net/syllabus/
Prof. Norm Jones Youtube Channel on GW Modeling	https://www.youtube.com/@groundwatermodeling

To learn how to modify the model to run predictions, see the Predictive Simulations page.