Estimating Evapotranspiration by Using Atmometers for Irrigation Scheduling in a Humid Environment
Publication: Journal of Irrigation and Drainage Engineering
Volume 137, Issue 11
Abstract
Evapotranspiration data from three commercial atmometers () were compared over an irrigation season for instrumental precision, and compared against Penman-Monteith () data from an automatic weather station for accuracy. The effects of using contrasting estimation methods on the timing and amounts of water application were then evaluated by using an irrigation-scheduling water-balance computer model. The data were statistically analyzed using linear regression, coefficients of determination (), root-mean-squared error (RMSE), mean bias error (MBE), and the -test. The study found that the data from individual atmometers were closely correlated both with each other and with the data (). On the basis of water-balance modeling, using an atmometer for scheduling irrigation on potatoes would have resulted in a very similar distribution of irrigation events, but 15% more water would have been applied over the season compared to using data. Day-to-day measured values may differ from as the atmometer can only be read to accuracy, but when averaged over the period of a typical irrigation cycle these errors are reduced and the impact on the irrigation schedule is small. The study suggests that atmometers would be appropriate for scheduling deep-rooted irrigated crops in humid regions with long growing seasons in which the irrigation interval is not less than 5–7 days.
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Acknowledgments
Thanks to the British Atmospheric Data Centre (BADC), which is part of the NERC National Centre for Atmospheric Science (NCAS) for meteorological data from Wattisham.
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Information & Authors
Information
Published In
Journal of Irrigation and Drainage Engineering
Volume 137 • Issue 11 • November 2011
Pages: 685 - 691
Copyright
© 2011 American Society of Civil Engineers.
History
Received: May 4, 2010
Accepted: Jan 27, 2011
Published online: Jan 29, 2011
Published in print: Nov 1, 2011
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