Blog: 2024 | Page 5 | Aquaveo.com

Defining Elevation and Storage Capacity of Detention Basins

By aquaveo on January 16, 2024

Did you know that the Watershed Modeling System (WMS) has a calculator that can define the relationship between the elevation and storage capacity of a detention basin? This is a useful tool for any WMS project with detention basins. The detention basins calculator is a simple tool that can quickly get the storage calculations you need for your model.

WMS uses the Hydraulic Toolbox to perform these calculations for the detention basin calculator. To open the detention basin calculator, first you need to make the Hydrologic Modeling Module active and select an outlet. Detention basins… is one of the options under the Calculator menu. After selecting Detention basins… a dialog named Detention Basin Hydrograph Routing will appear. Clicking the Define… button opens the Storage Capacity Input dialog, which is where you can enter the data that is needed for the calculations.

There are four data input options you can use to calculate storage capacity in the Storage Capacity Input dialog. Only one of the four input options is needed in order to perform the calculations. Which one you use will depend on what data is readily available for your model.

It is important to note that regardless of what measurement the general display projection is set to, the detention basin calculator will measure the elevation in feet and the storage volume in acres per foot.

After you exit the Storage Capacity Input dialog, a plot will be automatically generated in the Detention Basin hydrograph Routing dialog. This plot displays the relationship between the elevation and the amount of storage, as well as discharge if there is any. This plot functions the same way as any other plot window in WMS. You can learn more about plot windows by following this link to our wiki.

Head over to WMS to check out the detention basin calculator and see how you can use it to calculate the storage versus elevation for your detention basins today!

Blog tags:

WMS

Handling Depth vs. Elevation

By aquaveo on January 9, 2024

When creating a surface-water model, your model will make use of bathymetry data as either elevation or depth. Knowing how the Surface-water Modeling System (SMS) represents depth versus elevation is vital when it comes to creating, running, and understanding a model. SMS uses several different numerical models, and some models require that depth be negative and elevations be positive, while other models require the opposite.

It can become confusing when trying to remember what is needed for each model, which is why the decision was made to standardize how SMS treats elevation and depth across all models. SMS treats all depth values as negative and all elevation values as positive. That way you don’t have to remember how data needs to be entered for each model. If depth data is entered with positive values, SMS will read the data as part of the land elevations, which will produce incorrect calculations.

Some of the most used models where you may see that the elevation values have been changed to fit SMS’s conventions after importing are CMS-FLOW, CMS Wave, and CGWAVE. If you’re not sure whether or not the imported elevation data has been changed and would like to check, then this is a great time to make use of the Mesh module’s find function. Under both the Nodes menu and the Elements menu you’ll see a Find… option listed. You can use this to quickly locate a specific node or element inside of SMS to compare the elevation data with the model’s files outside of SMS.

If SMS has changed the values of the elevation data to account for the required negative depth value, there is no need to be concerned about how this will affect the end result for your model. SMS automatically adjusts the data to match the convention of the model when the project information is exported to the model executable.

Take this information and head over to SMS, more confident that your project’s elevation data will be handled correctly.

Blog tags:

SMS

Troubleshooting MODFLOW in GMS

By aquaveo on January 2, 2024

When constructing a MODFLOW model in GMS, there is always the possibility that you will get an error when trying to run your model. While there are a number of things that could be keeping your model from running without an error, here are some tips to help you figure out what may be going wrong.

Before running MODFLOW, make use of the Model Checker. The Model Checker will analyze all the current input data for any obvious errors or potential problems, which could save you from having to hunt down individual input errors. The Model Checker gives you a few options for sorting and displaying errors. The Model Checker is a useful tool for a basic check of the inputs, however the Model Checker coming up clean doesn’t necessarily guarantee that the solution is correct.

The next thing to look at in your MODFLOW model when you’re trying to figure out what the issue may be is the command line output from the MODFLOW model wrapper dialog. When the model does not converge, an error message should appear in the command line output. This message will help you know where to start resolving the issue.

Another place to look when you’ve encountered an error is the MODFLOW output file (*.out) in the solution files in the Project Explorer. You can use this text file to check for any missing or incorrect values.

Now that we've covered some ways to check your MODFLOW model for errors, here is a common issues that may be what is keeping your MODFLOW model from converging properly:

An unbalanced flow budget. This can happen if the inflow is greater than the outflow, which causes extreme flooding, or if the outflow is greater than the inflow, which would cause all cells to go dry.
All grid cells in the model are assigned a specified head boundary condition. This leaves nothing for MODFLOW to compute, causing the model to terminate with an error.
Improper initial conditions or boundary conditions.
You have a highly sensitive model. Highly sensitive areas might keep MODFLOW from converging due to the speed at which flow can be affected.
Elevation and layer values have been incorrectly defined or have inaccuracies.

Additional information can be found in the Frequently Asked Questions section of the MODFLOW user manual under the question "My model hasn’t converged. What can I do?"

Use these tips to help your MODFLOW model run smoothly in GMS.

Note this is an update to a previouisly published blog post.

Blog tags:

GMS