Comparison of Some Reference Evapotranspiration Equations for California
Publication: Journal of Irrigation and Drainage Engineering
Volume 131, Issue 1
Abstract
Four reference evapotranspiration (ETo) equations are compared using weather data from 37 agricultural weather stations across the state of California. The equations compared include the California Irrigation Management Information System (CIMIS) Penman equation, the Penman–Monteith equation standardized by the Food and Agriculture Organization (FAO), the Penman–Monteith equation standardized by the American Society of Civil Engineers, and the Hargreaves equation. Hourly and daily comparisons of ETo and net radiation are made using graphics and simple linear regressions. ETo values estimated by the CIMIS Penman equation correlated very well with the corresponding values estimated by the standardized Penman–Monteith equations on both hourly and daily time steps. However, there are greater differences between the values estimated by the two procedures. Although there are exceptions, the Hargreaves equation compared well to the FAO Penman–Monteith method. Spatial variability of the resulting correlations between the different equations is also assessed. Despite the wide variability of microclimates in the state, there are no visible spatial trends in correlations between the different ETo and/or estimates.
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Information & Authors
Information
Published In
Journal of Irrigation and Drainage Engineering
Volume 131 • Issue 1 • February 2005
Pages: 73 - 84
Copyright
© 2005 ASCE.
History
Received: Jan 31, 2003
Accepted: Jan 8, 2004
Published online: Feb 1, 2005
Published in print: Feb 2005
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