Aquaveo & Water Resources Engineering News

Defining Constant Concentration for Multiple Species in MT3DMS

Are you struggling to define separate constant concentrations for different chemicals in your MT3DMS model areas? MT3DMS is an invaluable tool for groundwater modeling, but like any software, it has its limitations. The Groundwater Modeling System (GMS) incorporates MT3DMS into its interface, which includes both the benefits and limitations of MT3DMS. The inability of MT3DMS to define separate constant concentrations for different chemicals in the same area can be a hindrance for modelers aiming for precision and accuracy in their simulations. So what should you do if your MT3DMS model requires defining constant concentration for two or more chemicals in separate areas?

There's a workaround provided by the MT3DMS developers for defining multispecies simulations. By using negative values in the table for species that need to be left undefined, you can effectively overcome this constraint and tailor your model to your specific needs. In GMS, this value is entered on the Source/Sink Mixing Package dialog for MT3DMS.

Example of the Constant Concentration Settings for MT3DMS

Note that it may seem as though a value of zero would have the same result when defining concentration. However, this is not the case. Entering a value of zero will be recognized as the same as entering a positive value. Therefore, it is important to enter a negative value for species that need to be left undefined when working with a multispecies simulation.

When running MT3DMS, cells that have negative values entered for a species will not have constant concentration for that species applied to that cell. Concentration, constant or varying, will be applied to all cells where the value is positive. As always, it is important to review the entered species values before running the model to ensure accuracy.

Now with more understanding of how to work with constant concentration values for multiple species in MT3DMS, see if you can use it in your GMS project today!

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Streamlining Watershed Analysis with AGWA

If you work with GSSHA, then you'll definitely want to check out the Automated GSSHA Watershed Analysis, or AGWA, app. AGWA is an online web application for managing proposed changes to watershed models. The app is powered by GSSHA--a hydrologic model developed by the U.S. Army Corps of Engineers.

Example of the AGWA Workflow

AGWA is web-based and therefore can be used from anywhere as long as you have an internet connection and a web browser. It includes simple step-by-step workflows to help you break down a more complex watershed analysis. These workflows can be applied to any number of GSSHA projects. The current workflows include:

  • Detention Basin Analysis
  • Culvert Resize Analysis
  • Find Discharge Tool
  • Land Use Change Analysis

AGWA uses the Tethys platform for managing accounts and access to projects. The GSSHA Models page in AGWA shows a list of all the GSSHA projects that are available for your account. The list includes the project name, project creator, description, and date of creation for each project. You can also view details about the model or the model map from the GSSHA Models page.

Clicking the launch button next to a GSSHA project on the GSSHA Models page will take you to the Model Summary page, which includes two tabs: the Summary tab and the Workflows tab. The Summary tab shows a summary of the GSSHA model including the name and description, map preview, creation date, and a list of scenarios. The Workflows tab shows all workflows that have been created or started, and is where you can create a new workflow.

All completed AGWA workflows have options to view the output data as plots. You can also download the flow and time series data as a CSV file so that you can use the results of your finished workflow outside of AGWA.

Check out AGWA, the app that lets you use GSSHA from anywhere! Follow this link to see a more complete list of the components of AGWA.

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Tool to Fill a Hole in an Unstructure Grid

Have you ever found yourself working on a mesh in the Surface-water Modeling System (SMS) that has holes in places you don’t want them? Then you may want to check out the new Fill Holes in UGrid tool in the SMS toolbox. This tool can be a quick and easy way to fill in any undesirable voids in your 2D mesh or unstructured grid (UGrid).

Example of a UGrid before using the Fill UGrid tool

The Fill Holes in UGrid tool can be found in the SMS toolbox under the Unstructured Grids folder. From there, all you need to do is select the mesh or UGrid that has holes or voids you want filled from a dropdown list, give the new mesh a name, and run the tool. From there, SMS will create a duplicate of the input mesh, only now the mesh will have elements where the holes used to be.

Example of a UGrid after using the Fill UGrid tool

But what if you want to keep some of the voids in your mesh? That’s where the Extract Subgrid tool comes in handy. The Extract Subgrid tool can isolate a portion of a mesh, which is useful if the mesh is particularly large, or if you want to confine any changes to one specific area.

To create a subgrid, first you need to create an Area Property coverage with a polygon outlining the area you want to isolate. Then open the toolbox and find the Extract Subgrid tool, which is located in the Unstructured Grids folder. Select the mesh from the “Grid” dropdown, the coverage from the “Subgrid boundary coverage” dropdown, and enter a name for the new mesh. Now you can use the Fill Holes in UGrid tool to fill the voids in just the isolated portion of the mesh.

If you use the subgrid method to fill the voids in your mesh, there is one more tool you’ll want to know about: the Merge 2D UGrids tool. You can use this tool to merge the subgrid back with the original mesh. This tool is also in the toolbox under the Unstructured Grids folder. To use this tool, select the subgrid from the “Primary grid” dropdown, the original mesh from the “Secondary grid” dropdown, and choose a name for the new mesh.

The Fill Holes in UGrid, Extract Subgrid, and Merge 2D UGrids tools can help simplify and smooth the mesh editing process, no matter the project. Open SMS 13.3 and check out what these three tools can do for you today!

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