Engenharia de Sistemas de Irrigação e Drenagem

Sum of Hourly vs. Daily Penman-Monteith Grass-Reference Evapotranspiration under Semiarid and Arid Climate

Abstract

Djaman K, Koudahe K, Lombard K and O'Neill M

Under changing climate and the global warming, accurate estimation of crop evapotranspiration might help improving water management and maintaining or improving water productivity. The objective of this study was to compare the sum of hourly ETo with the daily average ETo using the standardized ASCE Penman-Monteith equation under semiarid dry climate. Pair comparison was performed between the sum of hourly reference evapotranspiration (ETo) and the daily average ETo based on the data from four automated weather stations in the State of New Mexico (USA) for the period of 2009-2017. The results showed good agreement between the sum of hourly ETo and daily average ETo with the regression slopes varying from 1.00 to 1.10 and coefficients of determination from 0.63 to 0.97. The least difference between the hourly and daily results was found at Leyendecker. The RMSE values were 0.98, 0.64, 0.21 and 0.35 mm/day at Fabian Garcia, Farmington, Leyendecker and Tucumcari, respectively. The adoption of the hourly ETo estimation method leads to 16.6, 5.5, -0.2, and 4.1% higher annual ETo at Fabian Garcia, Farmington, Leyendecker and Tucumcari respectively, and can help on accurate evapotranspiration estimation to meet crop water requirement under sustainable agriculture.