Comparison of the Variation between ASCE Penman-Monteith Reference Evapotranspiration and Potential Evaporation in Oregon

Author

Chad M. Cary, Portland State University

Sponsor

Portland State University. Department of Geography

First Advisor

Daniel Johnson

Term of Graduation

Spring 2006

Date of Publication

2006

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Geography

Department

Geography

Language

English

Subjects

Evaporative power, Evapotranspiration, Weather -- Data processing, American Society of Civil Engineers

Physical Description

1 Online resource (73 pages)

Abstract

Evapotranspiration (ET) is an important input in terrestrial water balance equations used in modeling streamflow. Good ET estimates are critical to producing reasonable seasonal and annual streamflow predictions. Due to the lack of sufficient instruments to directly measure ET, researchers have developed numerous empirical equations that use climatic variables to estimate this element. Based on studies over the last 50 years, the American Society of Civil Engineers (ASCE) has standardized the calculation of evapotranspiration with the Penman-Monteith equation. Using the ASCE Penman-Monteith equation, this study compares reference ET (ET₀) estimates to potential evaporation (PE) generated from a study completed in 1982 (Farnsworth et al.) and then tests the ET₀ operational performance using a water balance equation. After comparing the two data sets, the 1982 PE estimates showed little variation throughout Oregon relative to the reference ET estimates. In contrast to the 1982 study, data derived from the ASCE Penman-Monteith equations show that there is no relationship between decreasing ET₀ and increasing elevation in Oregon. Despite ET₀better representing the spatial variation of this element in Oregon, its operational performance when applied in a water balance model failed to accurately simulate natural evapotranspiration.

Rights

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Persistent Identifier

https://archives.pdx.edu/ds/psu/41760

Recommended Citation

Cary, Chad M., "Comparison of the Variation between ASCE Penman-Monteith Reference Evapotranspiration and Potential Evaporation in Oregon" (2006). Dissertations and Theses. Paper 6602.