Aquaveo & Water Resources Engineering News

In 2018, USGS released MODFLOW 6. This version of MODFLOW uses object-oriented programming to provide support for multiple models within the same simulation. Like many of you, we at Aquaveo were excited to see this new development and started on working on ways for GMS to interface with this new version of MODFLOW.

Did you know that with GMS 10.4 you can export your MODFLOW project for use with MODFLOW 6? This allows you to convert your older or current GMS projects for use with MODFLOW 6. This is just one of the new features in GMS 10.4.

Support has also been added to run MODFLOW 6 from GMS and read the head and flow outputs which may be contoured.

The general workflow process for saving, running, and importing the MODFLOW 6 files is as follows:

1. After building your MODFLOW model, open the MODFLOW Global/Basic Package dialog.

2. In the dialog, turn on the Save MODFLOW 6 copy option under the MODFLOW Version section.
3. Save your project.
4. Open MODFLOW | Advanced | Run MODFLOW Dialog... to run the MODFLOW 6 files.
5. Use the Custom MODFLOW option to point to the mf6.exe executable in program files (e.g., C:\Program Files\GMS 10.4 64-bit\models\mf6\mf6.exe).
6. Browse to and select the NAM file out of the *_MODFLOW_mf6 folder that will have saved in the same directory as your GMS project. This is not the default, so you will need to browse for it at least the first time.
7. Run MODFLOW.
8. Use MODFLOW | Read Solution to select the MFN file out of the *_MODFLOW_mf6 folder.

The exported files can also be used directly in MODFLOW 6.

In the future, we plan to add more MODFLOW 6 functionality to GMS including a full interface. For now, get ready by converting your projects to MODFLOW 6 using GMS 10.4.

With WMS there is no need to sit and calculate your channel properties by hand, you can use the Channel Calculator to help you obtain the hydraulic data you need. The Channel Calculator, a function of the Hydraulic Toolbox, has the ability to give values for flow, depth, area of flow, wetted perimeter, hydraulic radius, average velocity and so much more. Even better, the Channel Calculator only requires some basic cross-section data including the slope and either the flow or depth of the channel.

This blog post will cover how to compute depths for your channels, which can be used to create floodplain delineation maps, and also how to generate rating curves for your channels, which can be used for things such as predictions. To get started, make sure you have cross-section arcs and river centerlines in your model.

To Compute Depths:

The Channel Calculator is a good tool for approximating channel flows or flow depths. Given a flow rate, the Calculator can compute a flow depth, and vice versa.

1. In the Hydrologic Modeling Module, select Calculators | Channels to open the Channel Calculations dialog.
2. Toggle on the Use Cross-Section Database option to enable the ability to import existing cross-section data.
3. Click the Select Cross Section button to bring up the Assign Cross-Section dialog.
4. Select your cross-section file along with the cross-section you would like to work with.

The cross section displays in the small graphics window of the Channel Calculations dialog. Adjust the Z scale using the drop-down menu to better visualize the cross section. With the cross section selected, set the necessary parameters to perform calculations for depths.

1. Click the Launch Channel Calculator button to open the Channel Analysis dialog.
2. Enter a value for Longitudinal slope. This is an estimate for the ground slope in the vicinity of your cross-section.
3. Enter a value for the Flow or the Depth depending on which values you have and which ones you are trying to find.
4. Select the Calculate button. This will populate the right-side of the dialog with hydraulic values calculated for the cross-section.
5. Select the Create Stage Point button in the Channel Calculations dialog to create a stage point based off the values computed in the channel calculator. This is useful if you are planning to use the depths to delineate a floodplain later on.

To Generate a Rating Curve:

The Channel Calculator can also be used to create different rating curves, to be used to calculate things such as storage potential.

1. Click on the Launch Channel Calculator button to open the Channel Analysis dialog.
2. Select the Compute Curves button to open the Curve Selection dialog.

The default is to create a rating curve for the entered flow vs. depth for the selected cross section, but it’s possible to also create curves for all of the other options listed.

1. When exiting the Curve Selection dialog, the selected rating curves are generated and the plot shouldappear.
2. If you double-click in the rating curve plot window a dialog will appear that presents many different options for how you can use the rating curve, including an option to export the curve in a chosen format.

As you can see, with just a few steps, you can obtain the hydraulic data you need for your channels in WMS. Try it out today!

Does your MODFLOW model contain a confined aquifer? A confined aquifer layer is defined as "an aquifer below the land surface that is saturated with water. Layers of impermeable material are both above and below the aquifer, causing it to be under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer."

In MODFLOW, a layer is considered confined when the head in the cell is above the top of the cell. Additionally, any cell located above the water table will be unconfined because the head in those cells will be below the top of the cell.

The layers in your GMS MODFLOW model can be assigned as confined or convertible in any of the flow packages, such as in the LPF package. Other flow packages can be used as well, including the BCF, HUF, and UPW packages. When setting up the MODFLOW model, select the desired flow package in the MODFLOW Packages dialog. The selected flow package must be compatible with the specified MODFLOW version.

In any of the flow package dialogs, under the Layer Type subheading, a layer can be defined as "Confined" or "Convertible". "Convertible" means GMS will automatically assign the layer as confined or unconfined depending on the elevation of the water table in the simulation. Only one layer type can be assigned to each layer. By default, all layers are set to convertible unless specified otherwise.

When a layer is explicitly set to be confined, MODFLOW will use the thickness of the cell, rather than the saturated thickness, to compute a transmissivity value. It will not check for the unconfined condition in the layer.

After defining the layers as confined or convertible, you will have a confined aquifer for your simulation. Try using confined aquifer layers in your GMS models today!

Are you ever tempted to refine your mesh after creation using the mesh editing tools? Manually changing hundreds or thousands of mesh elements using the mesh tools can be very time consuming.

Although possible to use the mesh tools, it is better to recreate a new mesh when wanting to refine or relax the elements. This will maintain the accuracy of your mesh, and reduces possible issues that may arise later on in the project due to inconsistencies that editing manually creates.

To recreate a refined or relaxed mesh:

1. Create a mesh generator coverage.
1. If the existing mesh was created from a mesh generator coverage, you can use that coverage or a duplicate of that coverage.
2. If a mesh generator coverage does not exist, you can create a mesh generator coverage by converting the mesh boundary or nodestrings to a new mesh generator coverage.
2. Go to your mesh generator coverage and redistribute the vertices so that there are either more or less arc segments depending on what you are trying to accomplish with your model. To relax the mesh, fewer arc segments are desired, and to refine the mesh more arc segments are desired.
3. Assign the desired meshing type (paving, patch, etc.) to the polygons in the mesh generator coverage and set the bathymetry source to use. Be certain to preview how the mesh will generate with the new spacing for each polygon.
4. Now generate a new 2D mesh using the edited mesh generator coverage.
5. Add the new mesh to your model simulation and run the model using the relaxed or refined mesh.

Sometimes you might not want to relax ro refine the entire mesh. To only relax ro refine part of the mesh do the following.

1. Create a new mesh generator coverage.
2. Create a polygon in the area of the mesh you wish to relax or refine.
3. Redistribute the vertices along the arcs in the polygon to so there is a great or fewer number of segments along each arc.
4. Set the meshing type for the polygon and assign it a bathymetry source. Be certain to preview the mesh for the polygon to be certain you are getting the mesh you want.
5. Generate a new 2D mesh for the area being refined or relaxed.
6. Select both 2D meshes and merge them together.
7. Add the new merged mesh to your model simulation and run the model.

Using these steps when editing a mesh can make a huge difference in your model and save you time. Try out relaxing and refining meshes in SMS today!