Information about the Ref-ET: Reference Evapotranspiration Calculator
Ref-ET is a Windows based software package that calculates reference evapotranspiration (ET). ET is defined as the amount of water that evaporates from vegetation (transpiration) and from the underlying soil. Reference evapotranspiration is defined as the ET that occurs from a standardized “reference” crop such as clipped grass or alfalfa. Common usage in the United States and elsewhere has been to use the two reference crops of clipped grass (cool season varieties) and full-cover alfalfa (lucerne).
The Ref-ET program provides standardized calculations of reference evapotranspiration for fifteen of the more common methods and equations that are currently in use in the United States and Europe. The calculations are based on the weather data measurements that are made available by the user.
The two primary purposes of Ref-ET are to:
- Provide standardized calculations of reference ET and other intermediate micro meteorological parameters that can be compared to calculations by other programs for error checking purposes.
- Read weather data from a wide range of data file types, data unit types and time steps.
The Ref-ET program includes commonly used algorithms and assumptions required in estimating reference ET. However, application of the Ref-ET program to various combinations or types of data may occasionally violate assumptions or may require extrapolation beyond endpoints of algorithms, resulting in incorrect ET and parameter estimates. Therefore the user of this software assumes all responsibility and reliability for accuracy and correctness of estimates.
All source code and executable code of this program is copyrighted by Richard G. Allen and the University of Idaho.
Fill out the form on this page to download the Ref-ET software.
Users are welcome to use the software freely without registering. The University of Idaho will provide limited telephone and written support to registered users of REF-ET. No telephone nor written support is available to non-registered users or to users who have obtained copies from sources other than the University of Idaho. Registration fees for Ref-ET are $49 plus shipping and handling. The registered user of REF-ET receives:
- The REF-ET and QAQC programs on electronic media.
- A printed copy of the Users Manuals.
- Support via a special support electronic mail system
- Registration by check or purchase order.
- Registration with credit card, please call 208-423-6611
Disclaimer: Neither the American Society of Civil Engineers, the United Nations Food and Agriculture Organization, the University of Idaho, nor the author of Ref-ET (R.G. Allen) accept any liability for errors or incorrect results from the Ref-ET program nor any problems associated with installation of the software onto the user’s computer system.
Contact Richard Allen for more information on this software.