Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub
    Author(s): Jianbiao Lu; Ge SunSteven G. McNultyDevendra Amatya
    Date: 2005
    Source: Journal of American Water Resources Association. 41(3): 621-633.
    Publication Series: Miscellaneous Publication
    PDF: Download Publication  (1.40 MB)


    Potential evapotranspiration (PET) is an important index of hydrologic budgets at different spatial scales and is a critical variable for understanding regional biological processes. It is often an important variable in estimating actual evapotranspiration (AET) in rainfall-runoff and ecosystem modeling. However, PET is defined in different ways in the literature and quantitative estimation of PET with existing mathematical formulas produces inconsistent results. The objectives of this study are to contrast six commonly used PET methods and quantify the long term annual PET across a physiographic gradient of 36 forested watersheds in the southeastern United States. Three temperature based (Thornthwaite, Hamon, and Hargreaves-Samani) and three radiation based (Turc, Makkink, and Priestley-Taylor) PET methods are compared. Long term water balances (precipitation, streamflow, and AET) for 36 forest dominated watersheds from 0.25 to 8213 km2 in size were estimated using associated hydrometeorological and land use databases. The study found that PET values calculated from the six methods were highly correlated (Pearson Correlation Coefficient 0.85 to 1.00). Multivariate statistical tests, however, showed that PET values from different methods were significantly different from each other. Greater differences were found among the temperature based PET methods than radiation based PET methods. In general, the Priestley-Taylor, urc, and Hamon methods performed better than the other PET methods. Based on the criteria of availability of input data and correlations with AET values, the Priestley-Taylor, Turc, and Hamon methods are recommended for regional applications in the southeastern United States.

    Publication Notes

    • You may send email to to request a hard copy of this publication.
    • (Please specify exactly which publication you are requesting and your mailing address.)
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Lu, Jianbiao; Sun, Ge; McNulty, Steven G.; Amatya, Devendra. 2005. A comparison of six potential evapotranspiration methods for regional use in the Southeastern United States. Journal of American Water Resources Association. 41(3): 621-633.


    potential evaptoranspiration, actual evapotranspiration, forest hydrology, regional hydrological modeling, southeastern United States

    Related Search

    XML: View XML
Show More
Show Fewer
Jump to Top of Page