GMS

Viewing an Aquifer's Water Level

By aquaveo on December 4, 2019

After completing a MODFLOW groundwater model in GMS, have you needed to see the aquifer water level? Viewing the water level can aid in visualizing the saturated thickness of an aquifer. The water level can be viewed by doing the following:

Ensure that the Ortho Mode option is toggled on.
Go to Display | Display Options, choose 3D Grid Data, and go to the MODFLOW tab.
Toggle on the Water Table option, and click OK.
Choose either the Front View or the Side View option, or select a cross section to view the water table level.

Additional information about the MODFLOW display options, including the Water Table option, can be found on our wiki.

After viewing the water table, it is possible to save the spatial 2D data for the saturated thickness (water table thickness from the aquifer base).

There isn't a shortcut way to save the 2D water table thickness. However, the desired dataset can be created by converting the head and bottom elevation datasets to 2D datasets, and using the dataset calculator to create a dataset of the difference between the two datasets. The workflow is outlined below.

Right-click on your 3D grid and select Convert To | 2D grid.
Select your Head 3D dataset.
Go to the Grid menu, and select 3D data → 2D data.
Choose the desired option in the Create dataset using dialog box selecting the option that best fits your desired dataset.
Repeat steps 2–3 for the Bottom MODFLOW dataset.
Select the 2D grid and go to Edit | Dataset Calculator.
Create the expression: head dataset minus bottom dataset.
Note: If you would like to create a dataset of all time steps, check the box next to Use all time steps before computing.
Give the new dataset a name in the Result option, and click Compute.
Your new dataset will appear under the 2D grid.

Now that you know how to view and save a water table, try it out in GMS today!

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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.

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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GMS

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.