Aquaveo & Water Resources Engineering News

Have you tried dewatering a mine model using MODFLOW-NWT? MODFLOW-NWT is a version of MODFLOW provided by the USGS that uses a method to solve MODFLOW models that are non-linear due to unconfined cells or non-linear boundary conditions, creating an asymmetric results matrix. Because mines that need to be dewatered sit below the water table, cells within the simulation will become dry at times due to the removal of the water from the mine. MODFLOW-NWT is great for such situations as it handles dry cells well.

Mine dewatering models are often used when estimating the required flow capacity for the pumps used in the field. You can create a regional model to establish a baseline, then create one or more models with various pit depths to establish the best approach for the mine in question. While elevations cannot be set to transition during a MODFLOW run, multiple conceptual models can be created within the same project in order to keep all of the data together.

It’s important to remember the difference between wells and drains when creating the dewatering model. Drains only subtract water when the head is above the elevation of the drain. Therefore, drains can be used to represent the seepage face around the edges of the pit, and the drain elevations should be set to equal the ground surface elevations. The amount of water removed by a drain is related to the conductance of the material of the seepage face. Drains are generally used at the bottom and side seepage faces of the mine.

Wells remove a specific amount of flow, and can therefore dewater the cell they are in prior to dewatering the rest of the mine. MODFLOW-NWT, as mentioned previously, handles these dry cells very well, keeping them active in case they become wet again.

Because MODFLOW-NWT uses 3D grids, you should make sure the cells inside the pits are inactive. You do this by creating the boundary polygon, and then removing a "donut hole" of cells within the pit area. Use the Activate Cell(s) in Coverages tool to inactivate the cells. You’ll have to do this for each layer, and each layer should be on its own coverage.

Finally, always use the Model Check to make sure there aren't any obvious errors or missing values in any of the inputs. After MODFLOW-NWT finishes running, you should review the water table by looking at the drawdown output contours. You can also do this by switching to Ortho view and reviewing the head in the appropriate rows or columns.

Try out making a mine dewatering model using MODFLOW-NWT in GMS today!

SMS allows using HY-8 to create culverts in SRH-2D models. HY-8 was created to model culvert profiles. When SRH-2D was being developed, structure boundary conditions were allowed to be linked HY-8 culverts to SRH-2D. Doing this permits SMS to make use of the more robust tools of HY-8 when designing culverts.

When designing a culvert for an SRH-2D model in SMS 13.0:

1. Right-click on the SRH-2D BC coverage and open the HY-8 Options dialog.
2. From the dialog, create the HY-8 file for the project.
3. On the SRH-2D BC coverage, create two arcs for the culvert: one for the inlet side of the culvert and one for the outlet side.
4. Select both arcs and open the SRH-2D Linear BC dialog.
5. In the dialog, select the Culvert HY-8 option and launch HY-8 to connect the HY-8 file.
6. In HY-8 design your culvert.

There are a few items to keep in mind when creating your culvert:

• Pay attention to where the culvert is located and how it snaps to the mesh in SMS. Designing your culvert for a location that doesn’t match up with your culvert is designed in HY-8 can cause discrepancies. Also, it helps to have the inflow entering the culvert at as close to a 90 degree angle as possible.
• Note that the crest length for constant elevation roadway profiles is the length between embankments.
• After the initial model run, the inflow values to the culvert may need to be adjusted and calibrated. If SRH-2D is showing lower or higher flow values, adjust the values in HY-8 as needed.
• Using a monitor line at the inlet or outlet side of the culvert. The results of the monitor lines may be different than what HY-8 reports. Use this difference to calibrate the model.
• 2D mesh elements are disabled between the culvert arcs during the model run.

HY-8 makes a great addition to SRH-2D in SMS. HY-8 is shipped with SMS, so feel free to try it out with your models today!

Have you needed to obtain land use or soil type data for your WMS project? Land use, or land cover, data is used to define the land use or cover of areas in the watershed such as urban, forested, farm, etc. Soil type data is typically used to control the movement of water in a watershed model. Data for land use or soil type can be added to your watershed project in WMS by using files on your computer or by downloading the data from a database.

Import a File

Files containing land use or soil type data are often contained in a shapefile, though other formats are possible. This file can be imported from your computer using the File | Open command. Once imported, the shapefile will appear in the GIS Module. It will likely need to be converted to the map coverage before being used in your watershed model.

Import From Web

Land use or soil type data can be obtained from online web services. To access these services, do the following:

1. Select File | Add Data | Get Data from Map.
2. In the Virtual Earth Map Locator, select the location of your project. If your project already has a set projection, then the location of your project should already be visible.
3. In the Data Service Options dialog, select one of the web services containing land use or soil type data such as the Land Use Shapefile, Statsgo Soil Type Shapefile, or Harmonized World Soil Database.
4. Save the land use or soil type data to your computer. The data will automatically be imported into your project as a shapefile in the GIS Module.

Moving Land Use and Soil Type Data

In most cases, having land use or soil type data on a shapefile will not include the data in your watershed model. Most often the data will need to be moved from the shapefile to the Map module. To do this:

1. Create a map coverage with the Land Use or Soil Type property. Land use data should be placed on a land use coverage and soil type data should be placed on a soil type coverage. Data may be lost if the wrong coverage type is used.
2. After creating the correct map coverage, select the land use or soil type shapefile in the GIS module then select the Mapping | Shape to Feature Object command.
3. When using the GIS to Feature Objects Wizard, select correct map coverage and make certain all of the attributes are correctly assigned.

Once you have imported land use or soil type data and it has been correctly converted to the Map module, it is ready to be used in your watershed model. Try out using land use and soil type data in WMS today!

Have you had a chance to use MODFLOW 6 in the GMS 10.5 Beta? If you have, you may have noticed that MODFLOW 6 operates a little differently than other versions of MODFLOW. This is to allow for some additional tools and options.

When using MODFLOW 6 in GMS 10.5 Beta, here are a couple tricks to try out.

Having Multiple MODFLOW 6 Simulations in the Same Project

You can create multiple simulations in the same project by using the simulation workflow in GMS 10.5 beta. This is particularly useful when attempting to calibrate your project. The way this is done is by doing the following:

1. Right-click on the simulation in the Project Explorer and select the Duplicate command. This will create a duplicate of the simulation that includes all the same parameters and uses the same grid.
2. On the new simulation, change the parameter that needs to be calibrated, such as the head values or the pump values of the wells. It is generally best to only focus on one parameter change when calibrating the model.
3. Run the new simulation and compare the results between the different simulations.
4. Repeat this process with additional simulations to calibrate the model.

Running Multiple Simulations at the Same Time

After you have created multiple MODFLOW 6 simulations, you can run all of the simulations at once. This is done by doing the following:

1. Right-click on the simulation folder and select the Save All and Run command.

The Simulation Run Queue dialog will display all of the simulation model runs. While the simulations are running, the Simulation Run Queue can be moved aside or minimized to allow you to keep using GMS. The results can be loaded into the project for you to review when the simulations have finished.

Additional features for MODFLOW 6 are still being added to GMS and will appear in future versions of the software. For now, check out MODFLOW 6 in GMS 10.5 beta today!