unsatfit

unsatfit is a Python library for optimizing parameters of functions of soil hydraulic properties (water retention function and hydraulic conductivity function) where equations are explained in the following paper.

Seki, K., Toride, N., & Th. van Genuchten, M. (2022) Closed-form hydraulic conductivity equations for multimodal unsaturated soil hydraulic properties. Vadose Zone J. 21; e20168.

The proposed equations are useful for practical applications as shown in the following paper.

Seki, K., Toride, N., & Th. van Genuchten, M. (2023) Evaluation of a general model for multimodal unsaturated soil hydraulic properties. J. Hydrol. Hydromech. 71(1): 22-34.

User manual

A user manual (日本語) is available.

See install and sample code for a quick start.

If you encounter any issues, feel free to ask questions.

Example output

This is an example output of this program; water retention curve (top) and hydraulic conductivity curve (bottom) of Gilat loam fitted with KBC (KO₁BC₂-CH) model.

KBC

For more examples, see Fig. 6 and Appendix in Seki et al. (2023).

Integration with HYDRUS and PEST

unsatfit can be used together with HYDRUS for forward simulations and with PEST for inverse parameter estimation.

History (Detailed version)

2007-02-27: SWRC Fit started to run on the web.
2021-08-13: SWRC Fit was recommended at 土壌の物理性.
2021-11-24: A paper written with unsatfit was published at VZJ.
2022-01-04: Relased unsatfit 4.0, including a new version of SWRC Fit.
2023-01-06: Released the UNSODA viewer, a web app that displays data from UNSODA 2.0. For each dataset, water retention data is linked directly to SWRC Fit for model fitting.
2023-02-04: A paper introducing unsatfit was published in JHH.
2024-06-10: Added Zenodo integration for permanent archiving.
2024-10-20: Received the JSSP award (土壌物理学会賞) from the Japanese Society of Soil Physics for the paper of dual-VG fitting. A summary report was subsequently published in Japanese.
2024-11-13: Presented a poster on hysteresis and hystfit at ASA, CSSA, SSSA meeting; took a photo with Rien van Genuchten.
2025-05-08: Presented on multimodal soil hydraulic models and unsatfit at Rien van Genuchten conference in Rio de Janeiro.
2025-09-29: Released unsatfit 6.0; added trimodal models and an option for isothermal hydraulic conductivity to the set_model() method.
2026-01-22: Added sample code for trimodal models and isothermal hydraulic conductivity, and added trimodal model support to SWRC Fit.
2026-02-17: A paper presenting trimodal hydraulic models for unsaturated flow was published online in JHH (Early View). The DOI will be available in December.
2026-02-18: A commentary paper related to the trimodal hydraulic models was published in VZJ.
2026-03-30: Released unsatfit 6.2 (update), adding support for integration with HYDRUS and PEST.

Update of this document