Skip to content

OpenCDSS / StateMod

StateMod is the State of Colorado's water allocation model. Use the following links to download StateMod software.

Additional StateMod information and resources are available below:

General/User Information

The following sections provide background and information that is useful to StateMod users. StateMod users generally fall into two categories: "modelers" and "users of model results". The former develops model input and runs StateMod on the model dataset whereas the latter may just review models results that someone else has run.

The CDSS approach has in the past support modelers and there is an opportunity to improve access to model results. This is challenging because model results files can be very large and finding a way to access and view the results, such as on the web, presents technical challenges. A new project has been funded to publish complete model input and results on the web to facilitate access without needing to run the model.


StateMod is the State of Colorado's water allocation model, which simulates allocation of natural streamflow (supply) to demands and operations. It operates under Colorado's Prior Appropriation Doctrine. The model can be run using a monthly or daily timestep, depending on supplied input data.

Input to the model consists of a river network definition, stations/nodes (stream gage, diversion, reservoir, etc.), and data associated with stations (water rights, time series, etc.). Input is typically created using "Data Management Interface" (DMI) software including TSTool and StateDMI, which automate processing of "command files" to create model input files.

Output from StateMod consists of binary files with time series data, text file reports, and log and check files, depending on run options. Binary files are often processed using TSTool.

The StateMod GUI (Graphical User Interface) was developed in the Colorado River Decision Support System (CRDSS) project but has not been well maintained. Modelers often prefer to use the TSTool and StateDMI software to create input files because the approach is automated and can be repeated, whereas the GUI, if it is allowed to edit files, introduces changes that are not represented in the DMI command files. These issues could be resolved with more investment.

StateMod datasets are not currently maintained in GitHub and can be downloaded from the CDSS website.

User Documentation

  • The StateMod User's Manual is available on the CDSS StateMod page.
  • Model datasets have documentation - see the CDSS website for model datasets and documentation.
  • There is a need for user-friendly documentation, for example navigable documentation such as this documentation. Prototype StateMod online documentation has been created and will be enhanced.


The software is licensed using GPL v3+ license.

Report an Issue

To report an issue or request an enhancement, use the StateMod GitHub repository issues. Software developers will evaluate the issue.

Developer Information

StateMod is written in Fortran (Fortran 77 with some newer code) and consists of approximately 250 source modules and 140,000 lines of code. Previous accepted versions (15.00.01 and older) have been compiled using an older commercial Lahey 95 compiler, whereas OpenCDSS is transitioning to the open source gfortran compiler.

A small project is underway to evaluate options for alternative programming languages for the next generation of StateMod. This is a research study and near-term changes to StateMod language are not planned.

Software Developers

The State of Colorado has designated the following as product contacts for development.

Person GitHub User Role/Comment
Ray Bennett Rayrbennett Legacy developer, developing for ArkDSS
Kelley Thompson (DWR) kelleythompson State of Colorado lead developer for StateMod
Brian Macpherson (CWCB) macphersonbr State of Colorado CWCB lead
Steve Malers (OWF) smalers OpenCDSS lead, facilitating implementation of open source project

Developer Documentation

Development Environment

Compilation is via a makefile, although the OpenCDSS project has evaluated using Eclipse Photran. A text editor can be used to edit the code. See the Developer Documentation for information about the development environment. Important information includes:

  • Lahey and gfortran compile from the same source code. This is possible because Lahey produces .obj object files and gfortran produces .o object files, and the compile scripts create different executable names.
  • A new naming convention is being phased in for executable program names in order to differentiate between Lahey/gfortran, 32/64 bit, and Windows/Linux.

Version Control

StateMod code and other electronic assets are housed in the following repositories.

Content Repository Comment
Software code cdss-app-statemod-fortran
Automated tests cdss-app-statemod-fortran-test
Developer documentation (MkDocs) cdss-app-statemod-fortran-doc-dev
User documentation (MkDocs) cdss-app-statemod-fortran-doc-user

StateMod software should be updated using a "feature branch" approach as per the OpenCDSS Workflow and StateMod developer documentation.

Adding an Issue

The GitHub issues tool is how developers track issues and communicate on progress. For an overview of using GitHub issues, see "Mastering Issues". The following general procedure should be to used add an issue (bug, enhancement request, question, etc.).

  1. Add a New issue on the StateMod code repository issues page.
    1. The issue title should short and clear, for example "Operating rule x output is incorrect" (which will be indicated as a bug below) or "Need command to ABC" (which will be indicated as an enhancement below).
    2. An issue template (via .github folder in repository) is provided with instructions on how to submit the issue. The template provides default fill-in-the-blank sections that are useful for developers. The template text should be edited as appropriate to explain the issue, and is then submitted. Attachments can be used to provide test data or other useful information. Use a zip file if necessary.
    3. The issue labels should be specified as completely possible. Labels can be adjusted later as necessary. See the OpenCDSS Version Control / GitHub Repository Issues guidelines. If the issue author does not have write permissions on the repository, they will not be able to select issue labels.
      1. Select the issue type as bug, enhancement, or question.
      2. Select the issue priority as low, medium, high, or critical.
      3. Select the issue size as XS, S, M, L, or XS. Note that these are relative sizes and not intended to be detailed hourly estimates.
  2. A StateMod product manager lead can also then add the issue to the StateMod project board as part of overall coordination.


StateMod testing has traditionally not been automated and has relied on running model datasets to confirm output. Testing is complex due to the following issues:

  1. Software needs to be tested for Lahey compared to gfortran (at least until gfortran version is vetted).
  2. Software needs to be tested for 32-bit Lahey (current), 32-bit gfortran (current) and 64-bit gfortran (desirable).
  3. Software needs to be tested for Windows and Linux versions (desirable).
  4. Software needs to be tested on small datasets such as the legacy examples mentioned in documentation (but need to be updated to current CDSS standards).
  5. Software needs to be tested on full datasets such as CDSS basin datasets, for each response file and program option.
    1. For example, check the *.xwb water balance report to make sure the overall water balance is OK.
    2. Improvements are needed to understand how decisions are made at each timestep, to confirm logic.
  6. Software needs to be tested on daily and monthly datasets.
    1. This is challenging because daily models have not typically been the focus.

The level of effort for the above is daunting and needs to be addressed by implementing standard test protocols that rely on automation. This is in progress and is ongoing as the OpenCDSS project protocols are adopted by various persons that are involved with StateMod.

The StateMod testing approach is being updated to be more rigorous and automated:

  • cdss-app-statemod-fortran-test repository is used for tests, and is under development
  • Rely on TSTool and other software to automate tests
  • The above repository includes scripts to run small tests (examples)
  • The above repository includes scripts to run large tests (full datasets)