GMS

Using the UPW Package for MODLFOW-NWT

By aquaveo on June 22, 2022

Do you have a groundwater model that might benefit from using the UPW package in GMS? The Upstream-Weighting (UPW) package is one of the four available options for flow packages for MODFLOW. It is used for calculating intercell conductances in a different manner than is done in the Block-Centered Flow (BCF), Layer Property Flow (LPF), or Hydrogeologic-Unit Flow (HUF) packages.Rather than the discrete approach of drying and rewetting that is used by the BCF, LPF, and HUF Packages, the UPW package treats nonlinearities of cell drying and rewetting by use of a continuous function of groundwater head.

In order to use the UPW, you first need to have a MODFLOW-NWT simulation as part of your groundwater model in GMS. Once you have selected the MODFLOW-NWT version, you can use the Packages dialog to activate the UPW package.

The UPW flow package is based on the LPF package but differs in that the rewetting and vertical conductance correction options are not available. Otherwise, the UPW package allows you to work with both confined and convertible layers. It also has options for vertical hydraulic conductivity and interblock transmissivity. Array values can be set for the horizontal hydraulic conductivity, and vertical and horizontal anisotropy using the MODFLOW array editor in GMS.

Additional options are also included here. It is possible to remove vertical leakance correction or set a head value for dry cells. These options are in their own dialog accessible through the main UPW package dialog.

It should be noted that the UPW flow package is only available for use in the MODFLOW-NWT model and is not available with other versions of MODFLOW. The UPW is designed to work with the NWT linearization approach which generates an asymmetric matrix.

If you have a MODFLOW-NWT groundwater model that needs a different approach to calculating conductance, try out the UPW package in GMS today!

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Defining UGrids Layer Attributes in GMS

By aquaveo on June 1, 2022

In your groundwater model, do you need to define MODFLOW-USG attributes for a UGrid that vary by layer? For example, you might have multiple polygons that define your recharge zones for your model where the attributes on each polygon are only meant to be applied to specific layers on the UGrid. GMS provides tools for specifying how those attribute definitions get applied to UGrids.

First, you can always apply attributes directly to a UGrid using the grid approach. Doing this has the advantage of having direct control over the attributes assigned to each cell and element on each layer. However, doing this on a large UGrid or for more complex models, this can become tedious and time consuming. Using the conceptual model can aid in managing assigning attributes to layers in more complex models.

For the conceptual model approach, the Coverage Setup allows you to specify the layer range for sources, sinks, boundary conditions, and areal properties. The Layer range option must be turned on in order to specify the layer range for attributes applied to feature objects in the coverage. If Layer range option is not applied then the default layer range will be used when applying attributes on the coverage to the UGrid.

Example of Specified Layer Ranges in the Attribute Table

It should be noted that once you have chosen to assign attributes to specific layers, you will need to pay attention to which attributes are being assigned. It is recommended that you review the assigned MODFLOW attributes. Keep in mind that you cannot mix specified layer ranges with the default layer range. GMS does not give priority to the default layer range over the specified layer ranges and vice versa. For example, if you assign refinement attributes to a polygon to use a specific layer range, but leave other polygons on the same coverage to use the default layer range for refinement, this will likely cause issues in the model run or results.

GMS allows you to be as general or specific as you need when assigning MODFLOW attributes to UGrid layers. Try out defining the layer attributes for UGrids in GMS today!

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GMS

Using the MODFLOW 6 Run Queue

By aquaveo on May 11, 2022

Have you noticed that in GMS MODFLOW 6 uses a different model wrapper than other MODFLOW versions? This model wrapper is the SImulation Run Queue and it has a few new options. Since MOFLOW 6 in GMS allows having multiple simulations run, the Simulation Run Queue helps you manage the different simulation runs.

The new Simulation Run Queue dialog functions a little differently from the Model Wrapper dialog. Some of the changes include:

You must click Load Solution to load the desired simulation solution into the project. This does not happen automatically when you click close as it does with the MODFLOW model wrapper.
If you try to run a simulation already in the queue, you will be prompted to remove the simulation from the run queue before it can be run again.
If changing an active simulation’s settings, renaming the active simulation, or taking any action that affects a simulation currently in the queue, you will be asked to remove the simulation from the queue prior to making the changes.
The maximum number of concurrent processes allowed can be as many as you want. However, it should be noted that the more complicated the simulations the longer it may take for the processes to complete. Therefore, allowing a large number of processes to run concurrently may slow down processing time if you are running multiple complex simulations.
Turning on the Monitoring data will allow you to see the command line run for each process. This can be used to troubleshoot issues that may have occurred during the simulation run. If the simulation encounters an error look to the Command line to see what has caused the error. If there are no errors then your simulation should show 100% in green instead of red (denoting an error).
Another important note is that you can still work while the simulation is running. You can move the Simulation Run Queue to the side and continue to work on your project while it runs. Right-clicking on the simulation folder in the Project Explorer provides a command for opening the Simulation Run Queue if you accidentally close it.

Example an error in the MODFLOW 6 simualtion in the Simulation Run Queue

Now that you know a little more about the Simulation Run Queue dialog in GMS 10.6 try it out today!

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GMS

Tips for Working with Virtual Machines

By aquaveo on May 4, 2022

Have you installed GMS, SMS, or WMS (collectively referred to as XMS) on a virtual machine in your office? Using a virtual machine is often done in order to run multiple operating systems, consolidate computing resources, provide integrated disaster recovery, or a number of other reasons. XMS software can be installed on a virtual machine in order to fit your needs. Here are some tips for working with XMS when using a virtual machine.

First, make certain that your XMS license is compatible with a virtual machine. Both local and flex license codes can be used with a virtual machine. However, local codes will not allow the software to be used by other machines. Older single-user locks cannot be used with a virtual machine.

When using a flex license, the virtual machine will need to have access to the local network in order for other machines to access the XMS license and use the software. Both the XMS application and the Aquaveo License manager need to be installed on the virtual machine.

When sharing files between a virtual machine and a host machine, pay attention to where XMS is running. XMS requires that all files be placed where XMS is installed. Therefore, you cannot save your project on the host machine and run them from the virtual machine if XMS is installed on the virtual machine. You will need to move the files to the virtual machine where XMS and XMS license is installed.

It should also be noted that some simulation runs and application processes in XMS will run slower on a virtual machine than running the same process directly on a physical machine. This is due to the nature of using a virtual machine. If there is a process that is taking an unusually long time, it is recommended that you try running the application on a physical machine.

If you are experiencing issues running XMS on a virtual machine, contact our technical support team and they will be happy to assist you.

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