Accuracy of evapotranspiration determinations by the bowen ratio method

Abstract

Evapotranspiration rates determined from meteorological data by the Bowen ratio method were tested against rates obtained from weighing lysimeters. The tests were conducted on an irrigated field (73 by 92 meters), where the minimum fetch was 27 m. Air-temperature and vapor-pressure differences obtained as 15-minute averages at heights of from 5 to 40 cm above the crop surface were used to calculate evapotranspiration. The results indicate that the Bowen ratio method can be used successfully to determine the evaporative flux for short periods, which can be summed for longer periods. During daylight periods, the absolute errors were less that. 0.02 cal cm−2 min−1 (or ly min−1), while the relative errors were less than 5 percent. © 1965 Taylor & Francis Group, LLC.