Aquaveo & Water Resources Engineering News

The HDF5 file format is a cross platform binary format for storing scientific data. HDF5 allows you to reduce the size of the file data by compressing repeated values. This allows your data to be read and written much faster than if you stored the data as ASCII (plain text) files. GMS can read and write to HDF5 files, and stores its own HDF5 files with the other MODFLOW data files.

There are no hard file size limits. The number of objects within an HDF5 file is not limited, and the format supports complex relationships through grouping and linking. In addition to support for common metadata types, you can create user-defined metadata to accommodate whatever needs you have in your project. The only limits with these are the capabilities of your computer.

HDF5 was designed to be extensible and to allow for future changes to the platform. GMS takes advantage of this by checking HDF5 data for key values in order to substitute them into your arrays or lists. This allows you to better use transient parameters and very large pilot point sets. GMS handles the pilot point interpolation through an external routine that helps speed up the processing.

There are external HDF5 file viewers and editors, such as HDFView. However, it is very easy for you to modify the data in such a way that it makes the HDF5 unreadable by GMS. Because of this, we recommend only viewing the files using these tools. You should only manually edit the file if given explicit directions by a developer. If modifications need to be made to the HDF5 file, we recommend you make the changes to your project in GMS which will re-export the HDF5 file.

Learn more about the HDF5 file format from the HDF Group, a consortium of scientists worldwide that works on the HDF5 format. You can also read the article on the XMSWiki about using the HDF5 format with MODFLOW. This article goes into more details about multiple specific uses for the file format.

Make use of HDF5 files with MODFLOW in GMS today!

With the release of SMS 13.1 beta, a new option has been added to the Vector tab. The existing Vector tab in the Display Options dialog allows viewing vector data as arrows as data points in your project. SMS can change the density of how the vector arrows are displayed and to display the vector arrows along a constant elevation. This new option allows you to display the model vectors relative to a selected dataset.

To use this option:

1. Open the Display Options, turn on vectors, and go to the Vector tab.
2. On the Vector tab and change the Origin to be "Relative to dataset".
3. Select the Dataset button under the Origin to bring a tree item selector dialog.
4. Select the Dataset you want to use.

After closing out the Display Options dialog, you will be able to see the vectors relative to the selected dataset. For example, if you use a water surface elevation dataset, you would be able to see the vectors relative to the water surface elevation.

This option is available for all modules that allow displaying vectors. This includes the 2D mesh module, Cartesian grid module, quadtree module, and scatter set module.

There is also an option to specify an offset for the selected dataset. For example, you could set the offset to 1 or 2 to get the vectors slightly above the surface. The result would show the vectors mapped 1 or 2 feet above the ground elevation.

This addition to the vector display option can be used with any dataset in the same module. Therefore, any dataset in the mesh module can be used with a mesh, any dataset in the scatter module can be used with a scatter set, etc.

Try out using the new "Relative to dataset" vector display option in the SMS 13.1 beta today!

Both TOPAZ and TauDEM make computing flow directions and accumulations for basin delineation easier. One of these two programs is typically used during the process of delineating a watershed. During this process, it is not unusual to run into some issues. Below are some common issues and how to resolve them.

Missing DEM

DEM data is required to run TOPAZ or TauDEM. A DEM can be imported from a file or downloaded from a web service. If you get an error stating that no DEM exists after you have imported the DEM data, this is typically because the DEM was not imported correctly.

Often, the DEM has been imported as a raster file and is in the GIS data module. In order for TOPAZ or TauDEM to use this as a DEM it will need to be converted from a raster to a DEM using the Convert to | DEM right-click command in the GIS module.

Not Enough Data

In order for TOPAZ or TauDEM to work properly, a DEM is needed that has enough data to work with. When working on modeling very small areas, TOPAZ or TauDEM may fail to execute correctly because there is not enough data available to complete the process.

In order to fix this issue, it is recommended that you slightly expand the size of the area you are modeling. In particular, the resolution of the DEM being used may need to be increased. Use your best judgement as to how much additional data to add.

Too Much Data

The opposite of having too little data would be to have too much data which causes TOPAZ or TauDEM to slow down or stop running altogether. This typically happens when attempting to model a very large watershed. In this case, the issue typically isn’t related to problems with TOPAZ or TauDEM but is more likely related to the available processing power of the computer being used.

With many projects that have too much data, often much of that data is unnecessary. Often a lower resolution DEM can be used. When modeling a large watershed area, you should use your engineering judgement to find areas of greatest interest and then focus on those areas. If that is not possible, then you will need to find a way to increase your computer's processing power.

TOPAZ and TauDEM tools for delineating a basin. Try them out in WMS today!

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!