Aquaveo & Water Resources Engineering News

The Data Calculator is a useful feature that is available in the Groundwater Modeling System (GMS). The Data Calculator performs many functions and can enhance your project and simplify the visualization of data. This blog post will provide an overview of how to use the Data Calculator in GMS to pinpoint locations where the water level in a selected aquifer falls below the top elevation in a MODFLOW simulation.

As you might expect, a MODFLOW simulation containing aquifers needs to be completed before you are able to use the Data Calculator to find the time step where the water level falls lower than the top elevation in the simulation. The datasets required for this calculation are the top elevation dataset and the head dataset.

Before opening the Data Calculator, you will first need to duplicate the top elevation dataset. This is because the Data Calculator isn’t able to recognize the datasets directly under the MODFLOW simulation in the Project Explorer. Right-clicking on the top elevation dataset and selecting duplicate will create a copy of the dataset under the grid folder in the Project Explorer, and this duplicate can now be read into the calculator. If desired, you can right-click on the duplicate dataset and rename it to something that makes more sense to you.

The next step is to go to the Edit menu at the top of the screen and select Dataset Calculator to open the Data Calculator dialog. There is also a Data Calculator macro on the top row, which will bring up the same dialog. Follow these general steps to calculate the data once the Data Calculator is open:

1. On the left side of the dialog, find and select the Head dataset.
2. On the right side of the dialog, either select a specific time step from the list, or check the box that says “Use all time steps”.
3. Click the “Add to Expression” button to add the Head data at the selected time steps to the calculation.
4. Click the subtraction button (-), or use your keyboard to type the subtraction symbol.
5. Select the copy you made of the top elevation dataset and click “Add to Expression”.
6. In the Result field, enter a name for the new dataset.
7. Press Compute, then click done to close the dialog.

After generating the new dataset, you can right-click on it in the Project Explorer and select “View Values”, which will let you view the data values for the selected time step. Any values denoted by a negative number indicate a water level lower than the highest point of the aquifer.

Head over to GMS and see the many ways the Data Calculator feature can be useful to you and your project!

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.

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!

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.

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!

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.

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!