GMS

Tips for Flow Budget in GMS

By aquaveo on November 13, 2019

In any groundwater model, knowing how much of the groundwater is available for use determines the fate of any project planned for the area. It is often a crucial part of a model to determine an accurate water budget or flow budget. MODFLOW can calculate its own flow budget and can also make use of the ZONEBUDGET program to calculate the water budget for subregions of a model. Knowing how to use both the MODFLOW flow budget and the ZONEBUDGET program greatly enhances the value of models built in GMS.

PZONEBUDGET example

With that in mind, here are some tips for making use of a flow budget and ZONEBUDGET in GMS:

  • If ZONEBUDGET is used to calculate a budget for the entire modeled area, the values for each budget term should match the MODFLOW budget except in situations where there are multiple stresses of the same kind in the same cell (e.g. a pumping well and a recharging well in the same cell).
  • You can confirm your approach by calculating the cumulative volumes for the entire model and seeing if they match the MODFLOW outputs.
  • Computer precision could be a cause of small discrepancies between the budgets produced by ZONEBUDGET and MODFLOW. ZONEBUDGET accumulates budget totals using double precision, and MODFLOW uses single precision. Because of the use of double precision, ZONEBUDGET's output should generally be more accurate than MODFLOW's; however, differences in output are not likely to be significant except for some very large models.
  • You can find the correct cumulative volume of water entering a given zone using the flow rate. This is done by multiplying the rate by the length of the corresponding time step.
  • Rates reported are for the same duration of the matching time step. Time steps stair step, so there the value is the same for the entire time step.

For an overview of ZONEBUDGET in GMS, see our tutorial and try it out in GMS today!

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Tips for Using Multiple Conceptual Models

By aquaveo on October 23, 2019

Have you ever built a model in GMS that uses multiple conceptual models? Doing this offers a few advantages. However, there are potential pitfalls as well when doing this. We will discuss some of the advantages in using multiple conceptual models and what to watch out for.

A conceptual model may contain one or more map coverages. Each coverage should contain feature objects defining key structures of the groundwater model, such as wells, rivers, or recharge. Everything in the conceptual model can then be mapped over to a grid or MODFLOW model.

Example of multiple conceptual models in the Project Explorer

Beyond using folders under a single conceptual model, one of the main advantages with using multiple conceptual models is for organization. When wanting to make variations on a model, it is helpful to have one base conceptual model and then multiple variant conceptual models. The entire base conceptual model may be duplicated to provide a starting point for other variations, or individual coverages may be duplicated and dragged to other conceptual models. Duplicating the base conceptual model can be particularly helpful if you already have transport species defined for MODFLOW-related models.

For example, you can use one conceptual model for a base steady-state model, then create another conceptual model for a transient predictive model. With this you can map the base conceptual model to MODFLOW and run that model. After you have the base results, you can duplicate the solution datasets to preserve them, adjust Global Options—such as Stress Periods—if needed, and then map the predictive model to the grid to run your second MODFLOW model.

When using multiple conceptual models, there are few items to look out for. These include:

  • When changing the conceptual model, changes are not automatically made to the MODFLOW model or other models being used. The conceptual model must be mapped over to the groundwater model in order for the defined features to be included in the model run.
  • When mapping over the conceptual model, it will overwrite any existing data in the same packages contained in the conceptual model. If you want to update the model with the new conceptual model, this is the correct workflow. However, if the original conceptual model used packages that are no longer used in the new conceptual model, then there could be an error in the model run. Always review your model after mapping to confirm the features mapped as you intended.
  • When using MODFLOW-USG, and you have multiple UGrids, make certain the conceptual model is mapping to the correct UGrid or model. It will map to the active UGrid.

Working with multiple conceptual models can expand your options for your model. Try out the conceptual model and other features of GMS today!

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GMS

Aquaveo User Conference 2019

By aquaveo on October 9, 2019

The 2019 Aquaveo User Conference is going on now. It started yesterday, October 8th, and will wrap up today, October 9th. We are enjoying meeting with users from around the world. In attendance are users from the United States, Germany, Portugal, South Africa, and other places around the globe.

At the conference, we announced some of the new features and upcoming changes to our products that we are excited about:

  • Making XMS functionality available for use outside of the traditional interface.
  • More web-based applications for portability and ease of access.
  • Simplifying and unifying tools so it is easier to find and use the functionalities available.
  • Project management tools to track the history of a model.
  • 3D bridge modeling in SMS.
2019 Aquaveo User Conference

Talking to those in attendance, we learned they enjoyed:

  • Learning more about software features and functionality.
  • Learning how to improve their model development process.
  • Discovering benefits of Aquaveo’s software over other software.
  • Talking to developers and learning tips for model development.
  • Being able to show off their models and receive feedback on them.
Eva Loch presenting at the 2019 Aquaveo User Conference

We’d like the thank the following for participating during our user conference:

If you couldn’t make it to the Aquaveo User Conference this year, watch our website and Facebook page for future conferences.

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CityWater

Classifying Material Zones

By aquaveo on October 2, 2019

Do you ever struggle to assign materials to a grid from solids? In GMS, the Solids to MODFLOW command is a useful tool for this, but it’s not successful in all cases. This command can sometimes make alterations to the stratigraphy. The command also does not work with models that make use of a mesh.

The good news is, there is another way! The Classify Material Zones command allows you to assign material zones from solids to a grid using just a few steps. The general workflow for doing this is as follows:

  1. First, you'll want to create a grid or mesh that is the same shape and has as many layers as your solids.
  2. Next, right-click on your grid and choose the Classify Material Zones command.
  3. In the Classify Material Zones dialog, ensure that your solids are selected and choose your desired classify algorithm.
  4. Finally, click OK and your grid materials will be matched to the solids.

When setting the classify algorithm, there are two options: "Centroid" and "Predominant material". The "Centroid" option assigns each cell the material located at its centroid. Using the "Predominant material" option assigns each cell the material that is present in the highest volume.

Below is a comparison between the two classify algorithms on a sample grid, "Centroid" on the left and "Predominant material" on the right. Select the algorithm that best represents your modeling area.

Example of the Classify Zones algorithms

The end result of using the Classify Materials Zones tool is that a new material set, based on the materials in your solids, will be added to your grid or mesh.

Try using the Classify Material Zones tool in GMS today!

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