Aquaveo & Water Resources Engineering News

New Unstructured Grid Generation Tools in SMS 13.3

The Surface-water Modeling System (SMS) allows use of unstructured grid (UGrid) geometries with multiple numeric models. With that, we have been adding functionality to make generating UGrids easier and more convenient. The toolbox in SMS offers many tools to help speed up UGrid creation and simplify the process. SMS 13.3 beta offers the same tools as before, as well as some new ones. As of now there are fifteen tools under the Unstructured Grids folder in the toolbox. The tool types cover conversion from different types of data to a UGrid, import and export tools, and more. This blog post will explore just two of the many different options in the toolbox.

UGrid creation tools in SMS 13.3

The first UGrid creation tool we will explore in this blog post is the UGrid from Coverage tool. The UGrid from Coverage tool takes the feature objects on a selected coverage and generates a UGrid from the properties of those feature objects. The tool can work with multiple coverage types. Like using the mesh generator coverage to create 2D meshes, the spacing of vertices on the arcs will determine the refinement of the generated UGrid. To generate a UGrid, the coverage must have at least one polygon in it. The parameters required when executing the tool are a coverage, and a name for the new UGrid. We recommend choosing a name that is short, but references the input data for easy reference.

The second UGrid tool we will explore is the UGrid from Surface tool. The UGrid from Surface tool takes an existing mesh, scatter set, or Cartesian grid and creates a new UGrid with copies of all of the datasets. This can be useful because it changes the data into a form that can be modified and manipulated while still preserving the original data. The input parameters include an input mesh, scatter set, or Cartesian grid, and an output grid name. Again, we recommend choosing a name that is short and references the input data.

All of the UGrid tools are accessible by clicking on the toolbox macro at the top of the window, then expanding the Unstructured Grids folder.

Download the SMS 13.3 beta and explore how the UGrid from Coverage and UGrid from surface tools, as well as the numerous other UGrid tools, can help your project today!

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Understanding the MODFLOW Translator

When importing a MODFLOW file into Groundwater Modeling System (GMS), you may need to translate the file to ensure compatibility with GMS's features and tools. This blog post includes details about the versions of MODFLOW supported by GMS, how GMS uses the translator dialog to transform the MODFLOW file into a version that GMS is able to read and alter, and methods you can use to determine the file version.

Example of the MODFLOW Translator

GMS supports MODFLOW versions 88, 96, 2000, 2005, MODFLOW-NWT, MODFLOW LGR, and MODFLOW USG. However, MODFLOW 88 and 96 are only supported as imports and require conversion to MODFLOW 2000. When importing a MODFLOW file into GMS, if the file was not created in GMS 6.5 or later, translation is necessary for full compatibility with GMS's features and tools, so the MODFLOW Translator dialog will appear. GMS will create a copy of the file before performing the translation which will ensure that the original file is preserved, however you should still always double check that all the data was converted successfully and hasn’t been changed and that none of the data has been lost. During the translation process, you can select the appropriate MODFLOW version from the list provided by the translator for accurate interpretation and conversion.

You can also alter the MODFLOW version inside GMS between supported versions by going to Global Options under the MODFLOW menu. It should be noted, however, that while most versions can be changed back and forth, it can’t be changed back from MODFLOW USG Transport.

There are specific indicators for each version of MODFLOW that can help you to determine what kind of MODFLOW file you are working with if you are unsure which file type it is, which you can view by opening the file as a text file. In a MODFLOW 88 file, the third line of the basic package file contains an IUNIT array with 12 or 24 slots, 24 being the more common option. A MODFLOW 96 file, on the other hand, lacks the IUNIT array and instead features the keyword "FREE" on the third line, indicating that data is in free format, or the third line is entirely blank. Files with a *.dis extension are likely to be MODFLOW 2000, 2005, or NWT models, all of which are supported by GMS.

Certain features and versions of MODFLOW are not supported in GMS. If you have more questions about what MODFLOW features are not supported by GMS, you can follow this link to Aquaveo’s wiki for more information. Head over to GMS and see how this can work for your own MODFLOW models today!

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Combining Runoff in Watershed Basins with WMS

The Watershed Modelling System (WMS) includes use of the Rational Method, which enables the calculation of peak flows for small watersheds in urban and rural areas. This feature can combine runoff from multiple basins to find the values.

The Rational Method requires a couple specific components to calculate the runoff coefficient for an area. The required inputs are soil data, along with either a table relating soil IDs to runoff coefficients, or a runoff coefficient coverage. Composite runoff coefficients use an area-weighted average of all runoff coefficients that overlay each basin for computation. The inputs chosen will depend on what method you choose to calculate runoff in the Rational Method module. The two primary methods to calculate runoff are first, to assign coefficients to polygons within a coverage, and second, to import a table with all of the coefficients already assigned to a land or soil use ID.

Example of Land Use in WMS Example of Soil Group in WMS

There are two ways to assign runoff coefficients to a polygon. The first way is to enter the coefficients polygon by polygon, and the second is to assign the coefficients through the Soil type mapping dialog.

To assign runoff coefficients polygon by polygon, do the following:

  1. Start with a Runoff Coefficient coverage.
  2. Select one of the polygons that intersects the drainage basin.
  3. Enter the runoff coefficient that matches the soil or land type for that polygon in the Runoff Coefficient dialog window that appears.
  4. After entering the data for each polygon that intersects the basin, activate the Hydrologic Modeling Module and go to Calculators | Compute GIS Attributes.
  5. In the Compute GIS Attributes dialog, make sure the following options are active:
    • “WMS Coverages” is selected as the data type.
    • Under Computation, Runoff coefficients is selected on the dropdown menu.
    • The “Use” dropdown is set to runoff coefficient coverage.
    • The “coverage name” dropdown is set to your new coverage.

To assign runoff coefficients to polygons by soil mapping, do the following:

  1. Start with a “Soil Type” coverage.
  2. Select one of the polygons that intersects the drainage basin.
  3. On the bottom left of the Soil type mapping dialog that appears, turn off the "SCS Soil Type" checkbox and turn on the "Runoff Coefficient" checkbox.
  4. You will now have a list of soil IDs and names with a field for runoff coefficients. Enter a coefficient value for each of these fields according to the material type.
  5. Open the Compute GIS Attributes dialog as described above.
  6. Set everything the same as are in the last set of steps, except change the "Use" dropdown to Coverage.

There are multiple ways to create runoff coefficient tables to import into a project. One of the ways is to create a table from scratch. If you choose this route, you can view the structure requirements on the Aquaveo wiki to make sure it includes everything you need. To import a table with the runoff coefficients, do the following:

  1. With the “Soil Type” coverage active, double-click on a polygon that intersects the drainage basin.
  2. Select “Import file” under Import soil attribute file.

You can also import a table in the Compute GIS Attributes dialog.

Head over to WMS and try out the different ways to assign runoff coefficients to your watershed project today!

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Announcing SMS 13.3 Beta

Our developers have been hard at work making improvements and expanding the functionality of SMS. Aquaveo is happy to announce the release of the beta version of SMS 13.3!

To show you some of the things you'll see in this version of SMS, we've compiled a short list of some of the new features included in this release.

Improvements to SRH-2D

In SMS 13.3 beta, we have added support for the use of unstructured grids (UGrids) in SRH-2D modeling and simulations in addition to meshes. SRH-2D also now supports the use of DIP files in its modeling, and we updated the scour calculator. We also updated the model execution to eliminate false positives and SRH-2D will only call HY-8 one time when running multiple simulations which removes the possibility of collisions.

Changes in the Toolbox

If you visit the Toolbox in SMS 13.3 beta, you'll find that it has been reorganized and some of the naming conventions have been changed, as well as an added folder for 2D Mesh tools. If you can't find a tool that you've used in previous versions, don't worry. All the same tools are available to you, it may just be under a slightly different name or in a different folder.

New Tools

There are also several new tool options in the Toolbox. This includes, but is not limited to:

  • Polygons from UGrid Boundary: converts the outer boundary of a UGrid to polygons in a new coverage. This tool only functions on UGrids with 2D Cells.
  • Fill Holes in UGrid: fills all voids in a given mesh with new mesh elements. The output is a mesh that can be converted back into a UGrid if needed. This tool also works on meshes.
  • Refine UGrid: create a 2D UGrid that has been refined based on an existing 2D UGrid and one or more elevation rasters.
  • Curvilinear Grid tools: import and export a curvilinear grid in the form of a CH3D or EFDC file.
Example of the Smooth UGrid Tool in SMS

As always, the help button in the tool dialog will direct you to a page on our wiki that will give you a more thorough description of the tool and its function.

The Community Edition of SMS 13.3

One of the major changes in SMS 13.3 beta is that we have made four models available in the free community edition of SMS. New models that are now included in the community editions are:

  • ADCIRC (ADvanced CIRCulation): a hydrodynamic model used for modeling oceans, inlets, rivers, and floodplains.
  • AdH (Adaptive Hydraulics): a model used for groundwater and overland flow.
  • CMS-Flow: used for more local modeling, mainly for inlets, the nearshore, and bays.
  • STWAVE (STeady State Spectral WAVE): models wave refraction, shoaling, breaking, diffraction, wind-driven wave growth, and wave-wave interaction with energy redistribution and dissipation.

These are only a few of the new features offered in SMS 13.3 beta. You can find the list of all new features on this page of our wiki. Try out SMS 13.3 by downloading it today!

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Selecting the Right MODFLOW Solver Package

Have you wondered which MODFLOW solver to use for your MODFLOW project in the Groundwater Modeling System (GMS)? When creating a groundwater model in GMS using MODFLOW, the selection of the solver package is an important decision that will affect the accuracy, speed, and efficiency of your model. This post will cover different complexities to consider while using GMS for your project.

Example of MODFLOW Solvers available in GMS

MODFLOW offers different solver packages, and the appropriate selection depends on the specific characteristics of your model. Here are some tips and ideas on how to select a solver package for your MODFLOW project in GMS:

  • Consider the size and complexity of your model. Some solver packages are more suitable for large and complex models, while others are better for smaller and simpler models.
  • Look at the type of boundary conditions you are using. Some solver packages are more appropriate for models with sharp contrasts in hydraulic conductivity, while others are better for models with more gradual changes.
  • Consider the amount of memory available on your computer. Some solver packages require more memory than others, and this can affect the size of the model you can simulate.
  • Look at the speed of the solver. Some solver packages are faster than others, but this may come at the expense of accuracy.
  • Consider the level of expertise you have with the solver package. Some solver packages are more user-friendly than others, and require less knowledge to set up and run.

Here are some general pros and cons of the available solver packages in MODFLOW:

  • PCG - this is the most commonly used solver package in MODFLOW. It is versatile and can handle a wide range of models. It is efficient for small to medium-sized models. However, it can be slow and memory-intensive for larger models.
  • GMG - this solver package is suitable for models with irregular grids and can handle models with steep gradients in hydraulic conductivity. It is efficient and requires less memory than PCG. However, it can be slower than PCG for models with smoother gradients.
  • LMG - this solver package is designed for large-scale models with highly heterogeneous geology. It is efficient and can handle models with multiple stress periods. However, it requires more memory than PCG and can be slower for smaller models.
  • NWT - this solver package is suitable for models with nonlinearities and can handle models with large gradients in hydraulic conductivity. It is efficient and requires less memory than PCG. However, it may be less accurate than PCG for models with sharp contrasts in hydraulic conductivity.

In summary, selecting the appropriate solver package for your groundwater model in MODFLOW requires careful consideration of the size, complexity, and boundary conditions of your model, as well as the amount of memory available on your computer, the speed of the solver, and your level of expertise with the solver package. Using GMS makes it easier to see which MODFLOW solver is best suited for your project. GMS also prevents selecting MODFLOW solvers that are incompatible with the selected version of MODFLOW.

Try out using the different MODFLOW solvers in GMS today!

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Troubleshooting an SRH-2D Model

Do you have an SRH-2D model that is failing to converge or has other errors? It is important to understand that errors in SRH-2D model runs are not uncommon and not necessarily an indication of a major problem. This post will give you some guidance so you can quickly identify and fix errors. This will allow you to produce accurate and useful results.

Common errors often appear around items that were missed during the model development. To avoid errors, it is important to review all data that’s been important into SMS. Also, care should be taken in designing and generating the mesh or grid being used in the simulation. While SRH-2D is rather forgiving, sometimes small issues in the mesh or grid can cause errors. Finally, double-check all boundary conditions that they are in the correct location and that all model parameters have been set.

It's important to note that while the SMS model checker can identify some errors, it does not validate the data and cannot catch all errors. Therefore, it is important to be familiar with the SRH-2D error codes and how to troubleshoot them.

Example of error found in an SRH-2D project

When encountering an error, it is important to remain calm and follow the steps outlined in the blog post, recording the error number and referring to the SRH-2D error page for guidance. Often, solutions involve minor adjustments to data inputs or boundary conditions.

If you were unable to record the error from the model wrapper, don't worry. You can still see this information by reviewing two of the files generated by SRH-2D during every model run. These files will be named [projectname].OUT.dat and [projectname].DIA.dat files.

To use these files:

  1. Locate the files in the model run directory with your project file.
  2. Open the *.OUT.dat or *.DIA.dat files using a text editor such as Notepad.
  3. Look through the text file to locate the error code.
  4. Go to the SRH-2D error page to find the solution.
  5. Make the needed change(s) to your project and run SRH-2D again.

By mastering the process of troubleshooting SRH-2D errors, you can produce accurate and useful results that can inform important decisions related to water resources and hydraulic engineering. The Community Edition of SMS is a great resource for exploring the capabilities of SRH-2D in SMS. Use SRH-2D with SMS today!

A previous version of this article was publish in 2018

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Fixing Negative Water Depth

If you've worked with an SRH-2D model in the Surface-water Modeling System (SMS), you may have noticed that there will be times that some nodes appear to have a negative water depth. This can be problematic because it often doesn't reflect the true nature of the body of water. SRH-2D simulations default their calculations to be cell-centered, while meshes calculate data from the nodes. Inactive cells are set to have a null value of -999, but if you're working with meshes, the nodes that touch the inactive cells will interpolate with the value of -999, thus causing a negative water depth to generate on that node. If this is something you want to avoid, here are some ways to eliminate a negative water depth.

Example of negative depths in an SRH-2D project

The first way to eliminate these negative water depth values from your SRH model when working with a mesh is to run your simulation as normal, and then use the Data Calculator in the Data Set Toolbox to truncate the data to a more desirable number, often this number will be zero. Follow these steps to truncate the data:

  1. Open the Data Set Toolbox under the Data menu.
  2. Under the Math section, select the Data Calculator.
  3. Find the dataset you are wanting to truncate, which will be labeled with "d#".
  4. Enter the following formula into the Calculator: "trunc(x,a,b)" where x is the dataset to be truncated, and where all the data will be greater than or equal to a, and less than or equal to b.
  5. Change the Output dataset name to one that suits your project.
  6. Click Compute, then close the Data Set Toolbox.

Make the new truncated dataset active in the Project Explorer, and note that the new minimum water depth is zero.

Example of truncated values in an SRH-2D project

Another way to get rid of negative water depths is to use an unstructured grid (UGrid). Ugrids use the same cell centered calculations that SRH-2D does, so you won't run into the same issues with how the data is interpolated. If you have already created your simulation on a mesh, you can follow these steps to convert to a UGrid:

  1. In the Project Explorer, right-click the desired mesh and select Convert | Mesh → Ugrid.
  2. If desired, change the Output grid name to something that suits your project.
  3. Remove the mesh from the simulation by right-clicking on the mesh name under the SRH-2D Simulations folder and selecting Remove.
  4. Drag the newly converted UGrid under Sim in the SRH-2D Simulations folder.
  5. Run the simulation again.

SRH has now recalculated the data with the UGrid with only cell-centered interpolation, which should remove any unintended negative water depth calculations.

Go to SMS and try out these ways to eliminate negative water depth today!

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Creating a Pathline for Every Time Step With MODPATH

Have you ever wanted to be able to visualize the movement of particles along every time step in a MODFLOW simulation using MODPATH? MODPATH is a program in the Ground-water Modeling System (GMS) for tracing particles that is utilized in conjunction with the flow data in a MODFLOW simulation. MODFLOW defaults to showing particle movement one time step at a time, but it is possible to show all time steps at once by making use of the Pathlines → Arcs feature.

Example of pathlines generated by MODPATH

To create the particle pathlines as arcs, you need a complete MODFLOW and MODPATH simulation. Once you have that, creating arcs to represent every time step is as simple as going to the MODPATH menu and selecting Pathlines → Arcs. This will create new coverages under your Map Data, the number of which will depend on how many Particle Sets exist in the simulation. It may be useful to go to your display settings and make sure that vertices are turned on under Map Data to see the time steps along the pathline arc more clearly. Each segment of the arc represents a single time step, with the subsequent segment starting where the previous ended.

By right-clicking on one of the particle sets, you can select View Pathline Report, which will show the same data from the arcs on a table. By doing this, you can view the exact values for each point and vertex along the pathline arc. You can also export this data as a text file, which can be opened in Excel in order to view the data outside of GMS. Additionally, you can view the data in several different types of plots by using the Plot Wizard under the Display menu.

You can also export the data from each particle set as a shapefile, making it simple to import the pathline arc data into a different project or program. To do this, all you need to do is right-click on the particle set, export the data, and save it as a Pathline Point Shapefile (*shp).

Head over to GMS and try out the different ways to visualize particle data with MODPATH and MODFLOW today!

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Filling Missing Raster Data

Do you have a raster that has holes in it? The Fill Nodata can fix small holes in raster data. Available in GMS, SMS, and WMS. In this article, we will explore the ways that the Fill Nodata tool can be used in WMS.

The Fill Nodata tool fills in small areas or gaps in a raster where no elevation data exists. It is located in the Rasters/Fill Nodata section of the Toolbox. The tool will interpolate an elevation to raster cells that are classified as "NODATA". Then the tool will create a new raster in the project that has the fillable no data areas filled.

Example of the File Nodata tool

These holes in the raster can occur for a number of reasons, one of the most common being that the data is incomplete. WMS is flexible enough that it can use a raster with small amounts of missing data for most simulations. However, it is recommended that you have data that is as complete as possible to ensure the generated model is as accurate. Therefore using the Fill Nodata tool can help ensure the accuracy of your model.

The Fill Nodata tool has a few input parameters to keep in mind. The input raster is the most important parameter. This needs to be a raster that has been imported into the project. The maximum distance to interpolate determines how far out WMS will look to fill data. It will use pixel units to do this. The number of 3x3 average filter smoothing iterations to run determines how many smoothing interactions will be run after the interpolation has been calculated. Additional interactions can help in improving the fill data.

Keep in mind that the tool was not intended to create data for large regions of missing data cells, especially regions on the border of the raster. If you have a large area of missing data, it would be best to use other processes to fill in the missing data, such as downloading the missing data and merging it with your raster.

The Fill Nodata tool is one of thetools provided in WMS to let you modify and edit raster data. Try out the Fill Nodata tool in WMS today!

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Converting a 2D Mesh to a CAD Surface

Using CAD files can be a useful way to transfer project data between different modeling software that may not support all of the same file types. The Surface-water Modeling System (SMS) supports the conversion of terrain in the form of scatter surfaces and mesh surfaces to and from CAD data for easy transfer between systems that utilize CAD data.

To save a terrain from SMS as a CAD surface file:

  1. Deselect everything in the Project Explorer that doesn't contain the terrain data you want to work with. Depending on the amount of data currently in the Project Explorer, the simplest way to achieve this may be to right-click on an empty section of the Project Explorer and select "Uncheck All".
  2. Reselect the terrain data in the Project Explorer.
  3. Right-click in any empty space in the Project Explorer and select "Save as CAD". A save window will pop up and you'll be able to name the CAD surface file and choose where it will save outside of SMS.

The CAD surface data will then also appear in the Project Explorer. Once you assign a name to the file, you should be able to import it into your CAD software and make modifications. This file set will contain all the necessary surface data, including elevation, node, and element information.

Using CAD Faces to 2D Scatter Triangles

When importing CAD surface data into SMS, you'll need to convert it into a form that SMS can recognize so you can make changes and use the information stored in the file. To convert the data back into a form you can use within SMS, you just need to right-click on the CAD data under the CAD Data file folder in the project explorer. Then, select the "Convert → CAD Faces → 2D Scatter Triangles" command.

Head over to SMS and see how using CAD data can benefit your project today!

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