Project History

Between January 2000 and February 2005, The Idaho Department of Water Resources and the University of Idaho's Department of Biological and Agricultural Engineering worked on a NASA Synergy grant to develop an efficient and accurate method of mapping evapotranspiration.

IDWR and UI worked, first, with the Surface Energy Balance Algorithm for Land (SEBAL). SEBAL was significantly modified into METRIC (Mapping EvapoTranspiration with High Resolution and Internalized Calibration). Both SEBAL and METRIC are energy balance models that use satellite image-data to compute a complete radiation and energy balance, sensible heat, and ET for each pixel of the satellite image. For this application, IDWR and UI used Landsat data.

The goal of the project was to develop METRIC into an operational tool for IDWR to use in administering Idaho water.

This project was one of eleven 'Infomart' projects across the United States awarded as part of a NASA program called the Earth Data Observing System Data and Information System (EOSDIS). The Raytheon Company administered these Infomarts as part of their Synergy Program (EOS Synergy Fact Sheet). In addition to the support from Synergy, this work was supported by funding from The Idaho Department of Water Resources, the University of Idaho's Departments of Biological and Agricultural Engineering and Civil Engineering, and by the U.S. Bureau of Reclamation.

The Idaho Synergy project was structured in phases. Each phase was designed to stand on its own, with self-contained goals, tasks, and products, while building on the accomplishments of previous tasks (project reports).

Phase I (1/2000 - 12/2000) of the project was completed at the end of 2000. IDWR and UI began working with Wim Bastiaanssen, who developed SEBAL, to modify SEBAL and apply it in Idaho. Phase I was limited in scope, designed to apply SEBAL in Idaho's Bear River Basin, to evaluate the results, and to develop any necessary modifications. The results of Phase I were encouraging, and Phase II was funded.

Phase II (1/2001 - 12/2001) was a much more ambitious project, processing multiple years of Landsat data through SEBAL on the Eastern Snake River Plain. The work included making modifications to the SEBAL model suggested by Phase I, the comparison of SEBAL ET with ET measured by the precision weighing lysimeters at the Kimberly Research Station near Twin Falls, and the comparison of SEBAL-computed ET with estimated ground-water pumpage for water rights on the Eastern Snake Plain. Two graduate students completed Ph.D. studies working on Phase II.

Phase III (1/2002 - 12/2002) was designed to further refine the SEBAL model for use in the western United States, and to demonstrate that it could be used operationally as a tool for administering water-rights. It was with the Phase III modifications that METRIC fully diverged from SEBAL. IDWR stopped using the term "SEBAL" in order to protect Wim Bastiaanssen's intellectual property rights to SEBAL.

Phase IV (1/2003 - 12/2003) was designed to begin the transition to an operational system.

Phase V (1/2004 - 2/2005) was designed to finish the transition of METRIC into an operational system.

Since 2005 Rick Allen has continued to refine METRIC and apply it in other western states (METRIC in other states). IDWR has expanded its operational use of METRIC as described in the section above.