By measuring the water mass balance, weighing lysimeters are considered as the standard for other methods in the determination of evaporation or evapotranspiration. In order to obtain accurate measurements, the lysimeters must be calibrated in situ, to establish the relationship between load cell signal and mass variation of the system. This work had as objective to present construction details of a battery of ten weighing lysimeters, to calibrate them and to test their performance to measure variations of water mass under field conditions. Each lysimeter had 1.4 x 1.9 m surface dimensions by 1.3 m depth, being supported by a lever-load cell scale, whose signal was recorded by an electronic system. The calibration was performed using recipients of known mass quantity, in a range equivalent to 150 mm. The results showed an excellent linearity between mass and voltage variations for all lysimeters and there was no hysteresis. The measurements of evapotranspiration showed a precision as high as 0.1 mm, by averaging readings in intervals of 10 min or longer, which is suitable for most of applications in agrometeorology and agricultural engineering.
balanço hídrico; evapotranspiração; uso consuntivo; water balance; evapotranspiration; consumptive use
