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Anaqsim is an analytic element software for simulating groundwater flow.  It uses subdomains as described in Fitts (2010), which gives it strong capabilities with respect to heterogeneity and anisotropy.  It also employs high-order line elements, spatially-variable area sinks, and finite-difference time steps to allow multi-level aquifer systems and wide-ranging transient flow simulations.  Anaqsim is a product of Yellow Sub Hydro and was developed by Dr Charlie Fitts.  It is coded in C#. 

Anaqsim Versions

There are two versions of Anaqsim: 'Quick Designer' and 'Deep Designer'.  The installed software is the same for both, but the capabilities of the software vary depending on what license has been activated.   

By default the download provides you with an un-licensed, demo version of 'Quick Designer'.  This Demo version is not for commercial use, and incorporates a watermark.  It can be used to run all of the tutorial models on the website.

Activating a 'Quick Designer' license gives you permission to use the model outputs for commercial use and removes the watermark.  It allows modeling of a wide array of situations, both steady and transient.  When solving, its limits are as follows:

  • Allows multi-level (3D) simulations with up to three aquifer levels.
  • It allows steady state and limited transient simulations with up to two different time periods and up to five time steps in each period.
  • The number of equations in the model's system of equations is limited to 2000.  This allows fairly complex models, but users needing greater complexity should consider the 'Deep Designer' license.

Activating a 'Deep Designer' license allows you to solve larger, more complex models with these capabilities:

  • Allows multi-level (3D) simulations with up to 15 aquifer levels.
  • It allows steady state and fully transient simulations with any number of time periods and up to 20 time steps in each period.
  • The number of equations in the model's system of equations is not limited, but somewhere around 40,000 to 50,000 equations is a practical upper limit based on computer memory and the time required to solve.

These constraints only apply to the model solve step.  It is therefore possible with a 'Quick Designer' license to examine, make plots, and use analysis features on existing model results that are larger than the 'Quick Designer' constraints by opening the model file and then loading a saved solution.  This way, it is possible to allow others to review any Anaqsim model with the free, unlicensed Anaqsim.   

Licensed Anaqsim  is licensed using one-year activations.  See for license and pricing details. 

System Requirements

  • 64-bit Windows operating system.
  • At least 500 MB of available disk space.
  • At least 1 GB memory.  More memory is needed for larger problems and most users have 8+ Gb.
  • Microsoft .NET v 4.8 or higher.

Installing Anaqsim

Anaqsim can be downloaded from the website.  The downloaded file is a Windows Installer package (.msi) file. To start the installer, run or double-click on the  downloaded file.  The installer guides you through a typical installation process. The installer also checks to see if the right version of the Microsoft .net runtime libraries are installed on your computer (these are used  by .net programs like Anaqsim).  If they are not there, they will be downloaded (free) from a Microsoft web site and installed before Anaqsim is installed.

Once installed, the program will be included in the Programs part of your Start Menu.  Anaqsim is typically installed in the following directory on your hard drive: 
Program Files/Yellow Sub Hydro/Anaqsim.

Anaqsim control files (with extension .anaq) are not automatically associated with the Anaqsim.exe executable.  In order to assign an association which enables Anaqsim to open automatically when double clicking on a .anaq file, the following process needs to be undertaken:

  1. Right-click on an existing .anaq file (for example one of the tutorial files, found under the 'Documentation' folder)
  2. Select 'Open with', and then 'Choose another App'
  3. Scroll down to 'Choose an App on your PC'
  4. Navigate to where you installed Anaqsim (typically Program Files/Yellow Sub Hydro/Anaqsim) and select the anaqsim.exe file
  5. Select 'Always' to ensure that the file extension association is saved, and applied to all .anaq files.

When you first start Anaqsim it is unlicensed;  it will run but will have constraints when solving the system of equations, and a watermark when plotting outputs.  Activating a 'Quick Designer' license will remove the watermark, and activating a 'Deep Designer' license will additionally lift the model solve constraints.  If you have purchased activations, see License Menu/Activating a License for instructions on how to activate your license.

Anaqsim License

You may purchase time-limited licenses for Anaqsim, which increase its capabilities.  Licenses are node-locked to a specific computer.   To learn about license activation or other license operations, see the License Menu topics.  

Release Version and History

The current Anaqsim release number and a history of Anaqsim releases, including lists of changes from one release to another, are posted on the Anaqsim website.   The release numbering scheme gives the year followed by the release number in that year.  New releases are posted to the website and may be downloaded, installed, and run by anyone with a valid license.  See the next topic about how to update to a newer release.

You can see the release number of your installed Anaqsim by selecting About Anaqsim on the main menu.

Updating to a Newer Release

As long as you are within the term of your Anaqsim license, you may upgrade Anaqsim to the current release.  To update, first check that there is a newer release available from  If there is and you want to update:

  1. Download the newer release installation file from the to your computer,
  2. Uninstall the older release from your computer using the Windows Control Panel -> Add/Remove Programs dialog,
  3. Install the newer release as described in the Installing Anaqsim section.

Updating will not affect your license, as the Anaqsim license file is not removed by the uninstall operation.

Help and Documentation

Help is available in many forms: this User Guide, tutorials, and example models available at the website.

The Anaqsim User Guide can be accessed by selecting Help from the main menu in Anaqsim. 

Three tutorials that walk the user through construction of Anaqsim models of increasing complexity are available on  A quick way to get familiar with Anaqsim is to work through these tutorials in sequence, building your own Anaqsim models like the ones shown in the tutorials.  The tutorials lead you through creating these models step-by-step.  The tutorials are pdf files with outlines at the first page that contain clickable links, so you can easily jump forward and backward to review, if needed.  The completed tutorial models are included in the Documentation directory of the Anaqsim software installation:

  • tutor1.anaq is the input file for a simple one-level steady model with irregular boundary conditions, a recharge basin, a river, and a well, and anisotropic K.
  • tutor2.anaq is the input file for a steady model with heterogeneity and a 3D area with multiple levels.
  • tutor3.anaq is the input file for a transient dewatering simulation model within a 3D area.

All three tutorials may be done with either the unlicensed or licensed Anaqsim.

Contact and Support

Support is available for licensed Anaqsim users to make sure that Anaqsim is functioning properly on their computer.  Please first check the Anaqsim User Guide (Help) and the tutorials on the website to see if your question may be answered there.

The contact information for support is [email protected]