Evaluation of Surface Renewal VS. Eddy Covariance Methods to Estimate Cereal Crops Evapotranspiration

Abstract

This study aims at evaluating the application of using the surface renewal "SR" method against Eddy Covariance "EC" method, for direct estimation of crops evapotranspiration "ETc" of wheat and rice crops, cultivated under the agro-climatic conditions of the old lands in the Nile Delta region in Egypt. Two field experiments were conducted at Qalubia governorate, in 15 feddan experimental field. The assessments were conducted for rice and wheat crops during the agricultural seasons of 2016. During the two seasons, the surface energy fluxes were recorded each 30 min, including net radiation, soil heat fluxes, sensible heat fluxes by EC method, and sensible heat fluxes by SR method. The SR method was calibrated against the EC method, and the determined latent heat fluxes "LE" of the both methods show high correlation with R 2 around 0.98 for both crops. The comparison between ETc-SR and ETc-EC showed statistically good performance, with NRMSE of 11% for rice, and 16% for wheat. The rice results showed that the widely used ETc-FAO was a slight higher than ETc-SR and ETc-EC, by 5% and 0.7%, respectively. Wheat results showed that the ETc-FAO was higher than ETc-SR and ETc-EC by 30% and 32%, respectively. The results of rice and wheat could be promising for further improvement in using the SR method as reliable, accurate, and cost-effective method to estimate ETc for field crops, while more validation is still needed to cover different types of agricultural practices.