GMS

Working with Units in GMS

By aquaveo on November 25, 2020

For any groundwater modeling project, having the correct units is essential in creating a valid project. When working with GMS, make certain that the project units are correct. To help you with having the correct units, here are some tips for working with units in GMS.

Check Input Units

Before importing data into GMS, check units of the data. Ideally, all of your data will be using the same units. So, for example, if you are working in meters then make certain all the data you will be importing is in meters.

It is recommended that you convert the data into the correct units before importing it into GMS. GMS will not change the units of your data during the import process. That said, it is recommended to check the units of imported data to make certain the data imported correctly. This is done by checking the data’s projection.

Please note that GMS also does not perform unit conversions when writing values to input files for models, such as MODFLOW or MT3DMS packages, but writes the values to input files as they are shown in their respective package dialogs.

Converting Units

Instead of converting the units of your data before importing it into GMS, you can convert some data inside GMS. GMS does not do automatic conversion of units for data. So if all of your data is in meters and you bring in one set of data that is in feet, GMS will not automatically convert the data from feet to meters.

Instead, after importing the data, you have two options for converting the data into the correct units.

The first of these options is to reproject the data. This is done by right-clicking on the data in the Project Explorer and selecting the Reproject command. This option can quickly change the units of the data in GMS.

The other option is to create a new dataset with the correct units. This is done using the Data Calculator. In the Data Calculator, you would select the dataset with the wrong units then enter the equation to convert the dataset units into the calculator. Once the new dataset is calculated, make certain that dataset is being used in the project and not the older dataset.

Using the Data Calculator to convert units

Check Output Units

After completing your model and running it, it is recommended that you check the units of the output data. In most cases, the units in the output data will be correct. If the units are not correct, this often indicates an issue with the input values of the model. GMS does not change the units of data during the model run.

Having correct units will make your groundwater modeling in GMS run smoother. Check out GMS today!

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GMS

Batch Running MODFLOW Files

By aquaveo on November 4, 2020

Do you have several MODFLOW simulations that you have created using GMS and would like to set all of the simulations to run overnight or over a weekend? Running a batch of MODFLOW simulations can be accomplished using a batch file. A batch file allows using the Command Prompt to run several commands in a sequence of actions. Therefore, a batch file can be used to run multiple MODFLOW simulations.

To do this, you will need to create a batch file that references the MODFLOW executable and the name file for each MODFLOW simulation you intend to run. To create a batch file, you can create the file from scratch, or you can use GMS to generate a batch file for a single simulation which can then be edited to add additional simulations.

When using GMS to create a single simulation batch file, do the following:

In the Global/Basic Package dialog for the simulation, turn on the Use Custom Run Dialog option.
Run the MODFLOW simulation.

Among the simulation files, you will have a *.bat file. To use this file to run multiple MODFLOW simulations, do the following:

Create multiple simulations in GMS and export the MODFLOW files for each simulation.
Using a text editor, open the custom run *.bat file.
Edit the file include the name files for additional MODFLOW simulations.
Use the Command Prompt to run the edited batch file which will then run the MODFLOW simulation sequentially.

Once the simulations have run to completion, you can load the results into GMS by creating a GMS MODFLOW results file (or MFR file) for each simulation. The file name of the MFR file should match the MODFLOW name file.The format for an MFR file can be found by examining an existing GMS MODFLOW solution set.

It is recommended that you use the GMS model check for each simulation and resolve any issues found before including the simulation in the batch run. However, if the simulation does include a problem, it will not stop the following simulations from running. In this way, MODFLOW can be run for multiple GMS projects.

Try creating a batch run for multiple MODFLOW simulations using GMS today!

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GMS

Tips for Importing Wells to the Conceptual Model

By aquaveo on October 14, 2020

In many MODFLOW projects, having the correct placement and settings for wells is important for getting correct results. GMS facilitates the implementation of wells by allowing well data to be imported directly into the conceptual model. This article gives an overview of importing well data directly into the conceptual model along with some tips.

Importing wells directly into the conceptual model first requires that the wells be in a file with the correct format. Typically this is a text file. Please refer to our wiki article for the correct format that GMS will use.

Other file formats, such as shapefiles, are also common, but often cannot be imported directly into the conceptual model. These other formats will import the wells into a different module, such as the GIS module, and will need to be converted over to the conceptual model.

Before importing well data into the conceptual model, make certain you have an existing map coverage with the well option turned on. Without this, the well data cannot be imported directly to the conceptual model.

When importing well data in a text file, you will use the Open command then the Import File Wizard. In the second step of the File Import Wizard, you must select "Well data" for the GMS data type. Also in the second step, make certain all the data columns are correctly assigned. Failing to assign the data columns correctly can result in errors.

It should be noted that you are not limited to the number of data columns you have in the file. Therefore, you can import multiple wells at the same time. You can also import multiple time series or other data applicable to the wells using this method. Please note that while the wells and time series can be defined in the same text file, it is necessary to import the file twice: once to create the wells, and once to assign the time series to the wells. Constant flow rates can be imported at the time of well creation.

Review the well data after it has been imported. That can be done quickly by bringing up the coverage attribute table dialog for the wells. If the data was not imported correctly, minor changes can be made in using the tools in GMS.

Try out importing well data directly into the conceptual model using GMS today!

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GMS

Using the SAMG Solver for MODFLOW

By aquaveo on September 23, 2020

Are you needing to use multiple processors to run your MODFLOW or MODFLOW-USG model? Using multiple processors can speed up the model processing time. In order to use multiple processors for MODFLOW in GMS, the SAMG solver provides the means to do this.

The SAMG solver is developed by the Fraunhofer Institute for Algorithms and Scientific Computing (SCAI). It contains a library of subroutines for the highly efficient solution of large linear systems of equations with sparse matrices. SAMG has an advantage in being almost unconditionally numerically scalable. This means that the computational cost using SAMG depends linearly on the number of unknowns.

Before using the SAMG solver, check to see if you have it added to your license. Do this by going to the Register command in the Help menu. Look through the list of components to make certain the SAMG parallel interface / solver has been enabled.

The SAMG solver works with the LMG solver package in MODFLOW. The LMG solver needs to be selected to access the SAMG solver. The LMG solver links the MODFLOW project to the SAMG solver.

To activate the SAMG solver do the following:

Open the MODLOW Global/Basic Package dialog.
Then open the MODFLOW Packages dialog.
Turn on the LMG – Link-AMG option.
A warning may appear discussing the SAMG solver. This warning can be turned off if desired.
Once the LMG solver has been turned on, the Link-AMG (LMG) Package dialog can be accessed through the MODFLOW menu in order to set the solver parameters.

Using the SAMG solver is not ideal for all MODFLOW projects. It is generally meant for large linear problems and simulations which use several time steps. For the right project, SAMG can help significantly accelerate the model run time.

For MODFLOW-USG, the SAMG solver is used with the SMS Solver. You can select the SAMG solver in the SMS Solver options.

Contact Aquaveo's licensing team to see about using the SAMG solver with your GMS projects.

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GMS