Eddy covariance measurements of the total evaporation during sprinkler irrigation - preliminary results

Abstract

Eddy covariance (ECV) is a direct, accurate and reliable micrometeorological mass transfer method for measuring evaporation and evapotranspiration (ET). It has been used successfully for the last decade to measure evaporation from natural and agricultural plant communities. However, a review of the literature provided no instances of it being used to measure evaporation losses occurring during sprinkler irrigation. Instead, sprinkler irrigation research has focused on using traditional methods acknowledged to have many limitations. Some of these limitations can be overcome by adopting this new technique. In this field study the feasibility of ECV to measure the total evaporation during sprinkler irrigation over the cotton crop is established. The trials were carried out at small scale (area 0.2 ha) at the Agricultural Station at USQ using a low pressure impact type sprinkler irrigation system. Results indicated that ECV technique was clearly able to measure the different rates of total evaporation before, during and after sprinkler irrigation. Using this technique, the average additional evaporation (loss) as a direct result of sprinkler irrigation was measured as about 0.2 mm/hr (50% extra) over the grass surface, 0.36 mm/hr (44%) at the early stage of the cotton crop and 0.30 mm/hr (63%) at the mature stage in comparison with pre irrigation period.