Reference evapotranspiration in the experimental basin of Gameleira, PE, using lysimeter and indirect methods

Abstract

The estimate of the evapotranspiration is very important for the determination of the water balance, especially in agricultural areas under irrigation, with direct impact on the irrigation management. This paper evaluates the reference evapotranspiration (ETo) in the experimental basin of the Gameleira  rivulet – PE, using an hydraulic weighing lysimeter and indirect methods. The lysimeter has a surface area of 1.52 m², depth of 0.80 m and ratio of border and surface area of 18%. Tests presented resolution of 0.1543 mm of ETo, average positional error of 2.31% and calibration with coefficients of determination higher than 0.9993. The statistic analysis was performed in daily and five days time scales between the lysimeter (standard) and the  indirect methods: Class A pan, Camargo, Makkink, Solar Radiation, Jensen-Haise, Hargreaves-Samani, Blaney-Criddle, Penman and PenmanMonteith. The methods of Jensen-Haise and Class A pan overestimated the values of the ETo compared to the lysimeter. The ETo estimated by the Solar Radiation  method had the best performance in relation to the lysimeter values.