Reference evapotranspiration based on temperature in Minas Gerais state, Brazil

Marcus André Braido Pinheiro,Evandro Chaves De Oliveira,Aline Lílian Marques Oliveira,João Carlos Ferreira Borges Júnior,Luiz Gonsaga De Carvalho

doi:10.1590/1413-7054201943004219

Abstract

ABSTRACT In the last decades, the areas of irrigated crops in the state of Minas Gerais have grown considerably, contributing to increase agricultural production in the country. Among the techniques of irrigation management, the determination of the water consumption by the plants is based on the reference evapotranspiration (ET0), the objective of this work was to evaluate and calibrate the Hargreaves-Samani (HS) method and a Proposed Method (MP) against the standard Penman-Monteith-FAO method (PM-FAO) for the state of Minas Gerais. For that, data from 52 conventional meteorological stations of the National Institute of Meteorology (INMET) were used. ET0 was estimated by the methods cited including the Hargreaves-Samani calibrated method (HScal) based on the mean absolute error (MAE). The analysis of the methods was carried out using the following statistical indicators: root mean square error (RMSE), systematic root mean square error (RMSEs), unsystematic root mean square error (RMSEun), the proportions of systematic and unsystematic mean square error, Willmott’s concordance index (d), confidence index (C) and Pearson correlation coefficient (r). It was verified that after the calibration, the HScal method obtained a superior performance to the original HS method in all the studied stations. It was also observed a superior MP performance with respect to the HScal method, in all stations studied.

Highlights

Brazil has about 6.95 million hectares of irrigated area according to data from 2017 of the National Water Agency - ANA
Data from the National Water Agency-ANA (ANA, 2017) reported the existence in 2015, in Minas Gerais, of 1082.373 hectares irrigated which are distributed by different forms of irrigation
The coefficients of the Hargreaves-Samani calibrated method (HScal) and Método Proposto (MP) equations are listed in Tables 2 and 3

Summary

Introduction

Brazil has about 6.95 million hectares (ha) of irrigated area according to data from 2017 of the National Water Agency - ANA. The State of Minas Gerais contributes significantly to the production of grains in Brazil, mainly through irrigated agriculture. Data from the National Water Agency-ANA (ANA, 2017) reported the existence in 2015, in Minas Gerais, of 1082.373 hectares irrigated which are distributed by different forms of irrigation. Evapotranspiration is the basis of water management and is commonly the largest and most important component in the water balance in agricultural systems. His knowledge is essential for the design of irrigation projects, establishment of irrigation management and planning in agricultural systems. The importance of evapotranspiration is verified in several studies, in the field of Agricultural Sciences, and in Meteorology, Geography, Hydrology and Ecology

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