i-Tree Hydro+

(If you have questions about this tool, please contact both Dr. Ted Endreny <te@esf.edu> and i-Tree support <info@itreetools.org>. Note that free technical support is not available for Research Suite tools including Hydro+. Email i-Tree support about consultation.)


  • i-Tree Hydro+ is a unified C++ codebase for various mechanistic environmental models that share common algorithms, organized in a Visual Studio solution called "UnifiedHydro" containing:
    • i-Tree Hydro (semi- and fully-spatially distributed versions): a hydrology model simulating the effects of land cover changes on water quantity and quality, unique in explicitly modeling vegetation processes (Wang et al., 2008). This is the model used by the i-Tree Hydro graphical user interface (GUI) included in the i-Tree Suite, with Hydro+ and Hydro being synchronized at Hydro version 6.3 and UnifiedHydro revision 377.
    • i-Tree Cool Air (fully-spatially distributed): an air temperature model simulating the effects of land cover changes using i-Tree Hydro's water budget and an energy budget that explicitly accounts for vegetation processes (Yang et al., 2013).
  • Test Cases serve as sample input-output.
  • Technical Manual with notes from Hydro+ developers.
  • No free technical support available; to inquire about consultation for these models, contact i-Tree support.


The Hydro+ environmental model suite – called UnifiedHydro in reference to its C++ codebase – includes the models i-Tree Hydro, i-Tree Cool Air, and in the future potentially other models developed by the iTree-ESF collaborative. The Hydro+ code is continually being developed. Below you can find a stable version of UnifiedHydro.exe, used in the i-Tree Hydro v6 GUI, and a latest in-development version of it, including green infrastructure and other model and code improvements.

The Hydro+ Technical Manual includes some history to provide context and institutional knowledge. Serving as an ad hoc FAQ for the researchers developing and using Hydro+, the Technical Manual is expected to evolve and expand over time to include basic information about code architecture and common development practices (e.g. how to add new functions and inputs); explanation and solutions to common problems that come up when working with these complex models; and different options or configurations possible for running this code.

This page offers the UnifiedHydro C++ source code and a compiled executable file for running the code. The model executable is run from the command line along with an extensible markup language (XML) UnifiedHydroConfig.xml file, which includes model settings and parameters. See the Technical Manual for information on how to interact with the source code or use the compiled executable file. UnifiedHydro C++ can be edited and recompiled with Visual Studio 2019 Community Edition (or VS2017 for the stable Hydro v6.3 code), which is freeware.

Being part of the i-Tree Research Suite of advanced tools, i-Tree's usual level of technical support and documentation is not available for Hydro+. This tool is intended for users with a moderate level of expertise in environmental and computer science. Technical support is not available for free, but expert consultation can be arranged. If interested in consultation, reach out to the i-Tree Team at info@itreetools.org.


Video Learning

Hydro+ Package

Scientific papers describing Hydro+ model methods