Models for Estimating Reference Evapotranspiration in Different Periods in Rio Verde, Goiás, Brazil

Abstract

The water management in irrigated agriculture begins determining the need of water for the culture. Therefore, it was intended to evaluate the performance of the models of estimation reference of evapotranspiration (ETo) with regard to the method Penman-Monteith (PM), standard method, for Brazilian Cerrado Region (tropical grassland/savannah). The climate elements were obtained from the conventional weather station of Rio Verde from January/1972 to December/2016. It was compared the performance of the daily average ETo, during the dry, rainy and annual periods, by the PM method with regard to another 26 methods. Through the coefficient of determination, it was verified the methods of Turc (T) and Radiation-Temperature (RT) approached more to the PM, at any time of the year, being able to replace the standard method. The ETo average in the annual period was 3.8 mm day-1, for the dry period due to the smallest amount of solar radiation, the period submitted lower levels of ETo. The other models in which were used fewer amounts of climate data, they overestimated or underestimated the PM model by up to 57.9% and 60.7% respectively. With the management of water in agriculture, water availability can be increased in the hydric bodies, characterizing it as a tool for water management with the rational use of water resources.

Evapotranspiración de referencia, evapotranspiración real y el coeficiente de cultivo para el cultivo de cebolla (Allium cepa) c.v. Álvara promedio en invernadero

“…Este método utiliza la siguiente ecuación para estimar la Eto[19]:𝐸𝐸𝐸𝐸𝐸𝐸 = 0,01 * 𝑄𝑄𝐸𝐸 * 𝑇𝑇 … … … 𝑒𝑒𝑒𝑒 7 donde: Qo = radiación solar global extraterrestre según el mes (mm evaporación equivalente día -1 ) T = Temperatura media del aire (°C) ND = Número de días del período considerado El método de Linacre utiliza la temperatura promedio del día, el porcentaje de humedad relativa, la elevación de la ubicación del estudio y la latitud en grados [20] Eto = evapotranspiración (mm d -1 ) Tmed = temperatura promedio ( o C) To = temperatura punto de rocío ( o C) Z = altura (msnm) L = latitud ( o ) %HR = porcentaje de la humedad relativa El método de Turc para humedad relativa menores al 50% se utiliza la siguiente ecuación [21]: Para humedad relativa mayores al 50% se utiliza la siguiente ecuación: 𝐸𝐸𝐸𝐸𝐸𝐸 = 0,013 * * 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 + 15 1 * (𝑅𝑅𝑅𝑅 * 23,8846 + 50) … … … 𝑇𝑇𝑒𝑒 11 donde: Eto = evapotranspiración (mm d -1 ) Tmed = temperatura promedio ( o C) Rs = radiación solar ( 𝑀𝑀𝑀𝑀 𝑚𝑚 ! * 𝑑𝑑 )El método de Ivanov utiliza la temperatura media y el porcentaje de humedad relativa para estimar la evapotranspiración potencial[20]:Tmed = temperatura promedio ( o C) %HR = porcentaje de humedad relativaLa evapotranspiración real se mide con base en la ecuación del balance hídrico se tiene[22]: 𝐸𝐸𝐸𝐸𝐸𝐸 = 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑒𝑒𝑒𝑒𝐸𝐸𝐸𝐸𝐴𝐴 − 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑠𝑠𝐴𝐴𝑠𝑠𝑒𝑒 ± 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑒𝑒𝑒𝑒 𝑒𝑒𝑠𝑠 𝑠𝑠𝐴𝐴𝑒𝑒𝑠𝑠𝑠𝑠 … … … 𝑒𝑒𝑒𝑒 13 donde:…”