# Aquaveo & Water Resources Engineering News

## 2D Mesh Editing Versus Regeneration: Which is More Apt?

If you need to make a change to a mesh, should you use the toold in the 2D Mesh module to edit, or instead regenerate the mesh? A 2D mesh consists of elements that define the computational domain of the numerical model. A numerical simulation requires a geometric definition of its domain– the mesh, available for use in SMS 13.3. Occasionally when constructing a mesh, a moment occurs where the mesh is insufficient for any reason.

In most cases the recommendation is to regenerate the mesh; as opposed to editing the mesh manually. The following list involves common circumstances where one may manually edit a mesh:

• There is no mesh generator coverage present.
• Deleting Outer Elements: Since the triangulation process creates elements (i.e. thin triangles) outside the mesh boundaries, deleting outer elements provides some refinement.
• Merging Triangles/Element: Numeric solvers are more stable and accurate when quadrilateral elements are rectangular and triangular elements are equilateral.
• Editing Individual Elements: After compound edits, a mesh could benefit from individual manipulation to increase stability. Swapping edges: Think of the two triangles as a quadrilateral, and the common edge between them is a diagonal of the quadrilateral. By swapping this common edge, it changes to be along the opposite diagonal of the quadrilateral. If this edge is clicked again, it returns back to its original state.
• Turning a specific element into a void element.

You may make edits in the Mesh Generator coverage. Manual edits should be intentional and reserved for small sections of a mesh. Generally, manual edits of a mesh ought to be minimal.

In nearly all cases the recommendation is to regenerate the mesh; as opposed to editing the mesh manually. This is because any process that edits a mesh, causes the node and element ordering to become disorganized. Additionally, editing a mesh invalidates any solution files that have been previously saved. Manually editing a 2D mesh risks creating issues with the assigned elevation data or other datasets being used. As such, if there is a solution dataset attached to the mesh, the model simulation should be re-run.

A useful tip is reviewing your mesh before generating, using the preview tools that are available in a given dialog. Make adjustments to the arcs, vertices, and polygons on the mesh. Do not be afraid to add more arcs, vertices, or polygons if further refinement is needed.

If you want to generate a new mesh with the desired edits, you will need to create a mesh generator coverage. The following are examples of tools that can create a new mesh:

• Map → 2D Mesh tool.
• 2D Mesh from 2D Grid in the toolbox.
• Additionally, most of the Unstructured Grid tools may be utilized to generate a new mesh.

Make use of the mesh editing and generating capabilities of SMS 13.3 today!

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## Export UGrids Seamlessly With the Export UGrid Tool

Do you have an unstructured grid (UGrid) in the Groundwater Modeling System that you want to share with other projects or applications? Having a portable UGrid allows you to share data between projects or with colleagues. The Groundwater Modeling System (GMS) has several ways to export data, including UGrids, from a model. The Export UGrid tool in the Toolbox allows you to export your UGrid to a file location your computer.

When you open the Export UGrid tool, found under the Unstructured Grids section in the Toolbox, you have only three steps to take:

1. Select the UGrid you wish to export.
2. Select the file type.
3. Save it with a name and location.

There are three primary file types in the Export UGrid tool to choose from: XMC, STL, and OBJ. Two of these, XMC and STL, have two additional variations on the formats for saving: ASCII and binary.

Aquaveo has provided the XMC format, our format, for exporting structured and unstructured grids of all varieties: 2D grids, 3D grids, quadtree/octree, nested, and voronoi.

GMS also provides the STL file format. This stereolithography file can be used with 3D CAD printing and should be able to be read by CAD software. It may also be converted to other file formats. This can only be used with triangular grids.

The last format type is OBJ. A geometry definition file format originally created for animation software, it has since been used for modeling and simulations in various applications. An OBJ file can be converted to STL and other formats. The OBJ format is limited to triangular grids only.

The ASCII formats of both the XMC and the STL file types, as well as the OBJ file type can be viewed and edited in a text editor.

The variety of file formats gives you flexibility in choosing how best to use the data. Head on over to GMS and see what the Export UGrid tool can do for you.

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## Discover the Refine UGrid Tools in SMS

The Surface-water Modeling System (SMS) continues to expand its capabilities. Currently, SMS is expanding to make more use of unstructured grids. An unstructured grid (UGrid) is a flexible geometric object that can include cells such as 2D and 3D cells with any number of faces and nodes. This flexibility allows for more realistic modeling of geological features.

In SMS, UGrids can be imported directly or created by converting an existing geometry such as a 2D mesh, 2D scatter set, Quadtree or map feature objects. When creating an UGrid from an existing geometry, it is usually best to make certain the geometry already refined to the level you need for your project. However, sometimes the Ugrid needs to be refined after it has been generated or imported. To do this, SMS provides two tools for refining UGrids: Refine UGrid and Refine UGrid by Error.

Both tools are located in the SMS Toolbox under the Unstructured Grids folder.

The Refine Ugrid uses an existing UGrid then splits (refines) the elements into smaller elements. The Refine UGrid tool provides you with the option to select datasets with “locked” nodes—any node with a non-zero scalar value. Any cell edges that contain one or more locked nodes will not be split. Utilizing such a tool will equip you to complete a surface-water modeling project with focused accuracy and efficiency. .

Similar to the Refine UGrid tool, the Refine UGrid by Error tool produces a 2D UGrid that has been refined as a result of an existing 2D UGrid, however this tool integrates elevation rasters into the process. Entering a value that guides the acceptable error threshold, the maximum number of iterations to perform, and the necessary elevation rasters are all required components of the input parameters for this tool.

Being able to refine UGrids adds increased accuracy for your surface-water projects in SMS. Check out the refine UGrid tools in SMS today!

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## Eliminate Null Values in SMS

Does your Surface-water Modeling System (SMS) model contain null values? Null values can be useful at times. Some models are even built around them. But what about when you don’t want them in your model? The tools in the Toolbox have ways to change, correct, or exclude data, including null values, without needing to manually edit the files and re-importing them, to clean up the data. These tools have multiple uses for viewing data in different ways, modifying current datasets, and creating new ones from the modifications made.

The Toolbox holds a very useful option in the Filter Dataset. It can be used to modify data in existing datasets by using various filters to include, exclude, or change the data being processed. When you have null values inside your project that you wish to exclude, you can use this tool to eliminate null values and assigning them to 0.

In order to use the Filter option, follow these steps:

1. Go to Toolbox | Dataset | Filter Dataset.
2. Click on Run Tool…
3. Under Input dataset, select the dataset from the dropdown.
4. For the If condition, select null from the dropdown.
5. For Assign on true, select Specify from the dropdown.
6. Enter 0.0 for the Specified Value.
7. Under Output dataset, enter a new name for the results of the test.
8. Click OK to run the tool.

Once you have created a filtered dataset, the new dataset can then be viewed in the simulation or used with other tools in the toolbox to modify, view, or create other new datasets for better visualization.

This filter function can also be found under Data | Data Set Toolbox… under the Tools section in the left-hand column. It has a slightly different look but the exact same utility.

Head over to SMS and try out the Filter tool to see how it can improve your model results and data visualizations.

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## Streamlining GMS by Using Keyboard Shortcuts

No matter how long you have been using the Ground-water Modeling System (GMS), you can enhance your experience with keyboard shortcuts. GMS comes equipped with various keyboard shortcuts–quick keys, hotkeys, accelerator keys, keybindings–in order to make the process more efficient for you. Whether you are just beginning or seasoned, such shortcuts are useful for any water modeling project.

The newest addition to the collection is related to the GMS unstructured grid (UGrid) feature, and facilitates progress with one click: Select all cells in UGrid layer using the “l” (L) key.

Here are a few more shortcut options that expedite the groundwater modeling process:

• CTRL+D (Display Options): Quickly populate your display options module for view and modification.
• CTRL+F (Frame Image): Use this option to scale and frame your model in the Main Graphics Window.
• View: Utilize these options and view your project from any perspective quickly.
• Shift+P (Plan View)
• Shift+F (Front View)
• Shift+S (Side View)
• Shift+O (Oblique View)

With all of the intricacies of the GMS software, simplifying even the smallest commands may increase productivity in infrastructure planning:

• CTRL+N (New Project): Clear the contents of your previous project easily with this command.
• CTRL+O (Open File): Import a new file with this command.
• Delete Key: Delete objects easily with this command.
• CTRL+A (Select All): Select all objects easily with this command.
• CTRL+U (Unselect All): Unselect all objects easily with this command.

Mastering keyboard shortcuts is a key aspect of becoming a proficient user of GMS. By taking advantage of these time-saving tools, users can navigate the environmental engineering software more efficiently, focus on their modeling tasks, and ultimately achieve better results in their water modeling projects. Use the "GMS Keyboard Shortcuts" article on the Aquaveo wiki to view these commands and more.

Additional shortcuts continue to be added to GMS. Access the latest version of GMS to make use of the newest shortcuts today!

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## Discover MODRAT Percent Impervious

When working with the Watershed Modeling System (WMS) and the MODRAT model, one potential aspect of your watershed analysis would be determining the percent impervious values for each sub-basin. Accurate percent impervious calculations may significantly influence your hydrologic modeling outcomes. Here is a guide to help you navigate this process effectively.

##### Importing Land Use Data

To compute the percent impervious for each sub-basin in MODRAT, you need to start with accurate land use data. Land use data in WMS is typically stored in the GIS and Map modules. The most efficient way to read this data into WMS is through a shapefile. Here’s how you can do it:

1. Create a Land Use Coverage: In WMS, start by creating a new land use map coverage. This coverage will hold all the land use data you import.
2. Import the Polygon File: Import your land use polygon shapefile into WMS. This file should contain various land use types and their respective boundaries.
3. Assign the Percent Impervious Field: Ensure that the percent impervious field, often labeled as IMPERV_ by the Los Angeles County Department of Public Works (LACDPW), is correctly mapped to the LA County Soil land use field in WMS. This step is crucial as it links the impervious data to your land use coverage.
4. Compute and Assign Percent Impervious: With the land use data now present in WMS, use the "Map Attributes" command in the MODRAT menu to compute and assign the percent impervious values. This function will analyze the land use data and calculate the percent impervious for each sub-basin.
##### Using Coverage Overlay Options

Another method to determine the percent impervious values is by using the Coverage Overlay options in WMS. This approach is similar to calculating curve numbers and involves overlaying land use coverage with drainage coverage.

1. Overlay Land Use and Drainage Coverage: Start by overlaying your land use coverage with an existing drainage coverage. This will combine the datasets, allowing for an analysis of land use types within each drainage area.
2. Calculate Percentages: The overlay will provide you with the percentages of different land use types within each sub-basin.

Whether you choose to import land use data directly or use the coverage overlay options, both methods can aid in determining the percent impervious. Use either method in your MODRAT projects in WMS today!

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## Quick Polygon Generation from Raster Data

Do you have raster data that you like to use to quickly generate polygons for your Surface-water Modeling System (SMS) project? SMS 13.3 introduces the Polygons from Raster Bounds, Polygons from Index Raster, and Polygons from Raster Nodata tools Each of these tools make use of raster data to generate polygons in the Map module. This can help you quickly define model domains or areas of interest in your model.

All of these tools can be found under the Coverages section in the Toolbox. Two of these tools can help resolve issues where the raster data is missing data. These "no data" areas can occur when the raster is trimmed, or when some of the data is incomplete in the database of origin.This can create holes in the data that will interfere with a model.

Using the Polygon from Raster Bounds tool creates a polygon that includes only the active region within the raster. It is especially useful when a downloaded raster has been trimmed to the model area. It eliminates the "no data" areas on the edges that were created by the trimming. This cleans up the data for the model. It can also be used when running models, such as for flooding, when one area needs a different coverage than the original.

With Polygons from Raster Nodata tool, areas that are "no data" inside active regions can be separated from the active regions so the "no data" areas don’t interfere with the model. For example, modeling a river, but not the flood plain, means you may want to exclude the land including islands in the river. Using this tool, polygons can be placed around all active areas and defined for the surface water model while the NODATA areas can then be ignored.

The Polygons from Index Raster tool can come in very handy when elevations and materials match fairly well. It will only work if an index raster is being used. Using this tool, polygons can be created around elevation changes in such a way that it becomes much easier to assign materials to polygons.

Creating the polygons can be a time consuming task. These tools can automate part of the process and eliminate some of the problematic areas within your surface modeling area for you. You can use more than one of these tools, as your model requires.

Head over to SMS and try out these tools in the Toolbox today.

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## New Recharge Options for MODFLOW-USG Transport

Do you have to refine the recharge options in your MODFLOW-USG Transport model in the Groundwater Modeling System (GMS)? With GMS 10.8, we’ve added two options to the MODFLOW-USG Transport Recharge Package. Concentrations (CONC) option and Use Seep Elevation (SEEPELEV) option have now been added as options to the main dialog. This makes it easier to add the data required when concentrations and/or seepage elevations are required for certain species. These additions can improve the accuracy and applicability of groundwater models, particularly in complex and variable hydrological settings.

Adding the Concentrations (CONC) feature to the Recharge (RCH) package in MODFLOW-USG Transport allows you to account for the spatial and temporal variations in the concentration of contaminants or solutes in recharge water.

The Use Seep Elevation (SEEPELEV) feature enables you to consider the elevation of seepage faces in your simulations. This is particularly important in areas with complex topography and variable groundwater-surface water interactions.

In order to use these options:

1. Go to MODFLOW | Global Options.
2. In MODFLOW Global/Basic Package, select Packages.
3. Make sure “RCH1” has been selected as one of the packages.
4. Then, access the RCH package options using the RCH - Recharge Package command in MODFLOW | Optional Packages menu. You can also reach the options by double-clicking on the RCH package in the Project Explorer.
5. In the MODFLOW Recharge Package dialog, look for “Concentrations (CONC)” and “Use Seep Elevation (SEEPELEV)”. They will appear below the “Recharge option (NRCHOP)” drop down.
6. Select one or both of them, depending on your model’s needs.
7. For the seep elevation, you can manually enter or import the appropriate data.

Note: These options are only a part of USG Transport and are not available in other versions of MODFLOW..

With these two options now available in MODFLOW-USG Transport, better refinement in your groundwater models is now possible. Head on over to GMS 10.8 to try out the Concentrations (CONC) and Use Seep Elevation (SEEPELEV) options in your MODFLOW-USG Transport projects today!

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## Accessing 3DEP Data for SMS

The Surface-water Modeling System (SMS)[2] continues to expand the types of data it can use for your water modeling projects. For models in the United States, there is a very comprehensive set of elevation data that you can use in your modeling–3DEP data.

3DEP data is an amalgamation of high-resolution 3D elevation and 3D hydrography data from multiple sources. It is also "bare earth," meaning the images are ground-level only. No buildings, trees, shrubs, or ground cover of any sort have been included. Seeing the most precise shape of the ground can be very important to surface modeling. The high quality lidar data in the 3DEP project covers the vast majority of the United States and several of its territories. Coverage is becoming more comprehensive over time. We have added 3DEP as one of our options when you import map elevation information from the web.

When creating a surface-water model, you are looking for the USGS 3DEP Bare Earth DEM (North America) option from the web.

To access 3DEP data in SMS, do the following:

1. Click File | Import from Web… to open the Virtual Earth Map Location.
2. Make your location selection here (United States and some territories only)
3. You may have to set your Display Projection settings
4. When you reach the Data Service Options dialog box, scroll right until you see an option for USGS 3DEP Bare Earth DEM (North America).
5. You then save your image to the appropriate location on your computer, after you set or accept the default raster cell size.

Once you have saved your image, it will show up in the Project Explorer window under GIS Data. When saving, it will add the " _elevs.tif" extension to the name you chose. The elevation data can then be applied to your model in the usual way.

Head on over to SMS and see how 3DEP data can help your surface-water modeling.

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## Making Use of Recent Files in SMS

Jumping between multiple projects can be commonplace in most organizations. For this reason, the Surface-water Modeling System (SMS) includes a way to see your most recent projects. This feature makes it easier to jump between projects.

When starting SMS, you can see your recent projects by going to the File menu. Towards the bottom of the File menu, you will see the five most recent projects. Selecting any of these projects will load them into SMS.

Only the five most recent projects are listed in the File menu, but SMS provides a way to access more of your recent projects. Clicking the More… command under the recent files in the File menu will bring up the Recent Files dialog. The Recent Files dialog contains a list of recent projects. This list will go back to when the major version of the software was installed.

The Recent Files dialog allows you to search for past projects using the Search field at the top of the dialog. This can be immensely helpful when trying to find a project that has been neglected for a while.

Also helpful is a feature that lets you open the location of the project files. You can right-click on any project and select the Open Containing Folder command to bring up the folder containing the project files in the File Explorer window. This can help you locate files you haven’t been working with in a while and may have forgotten the location.

There are some caveats to this feature. If the project files have been moved, the project will still appear in the list of recent files but SMS will not be capable of importing the file because it is being directed to the wrong location. This is also true if a folder in the directory is renamed.

The Recent Files dialog provides a great tool to help you manage your projects in SMS. Head over to SMS and see what projects you have been working on recently!

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