COMPARISON OF EVAPOTRANSPIRATION MEASURED FROM SURFACE RENEWAL SYSTEMS, EDDY COVARIANCE SYSTEMS, AND BOUNDARY LAYER SCINTILLOMETER OVER A POTATO FIELD IN THE BEKAA VALLEY

Abstract

An accurate estimation of the heat fluxes and evapotranspiration (ET) is important to evaluate water requirements of crops and thereby optimize irrigation management. Familiar ET sensing methods include Eddy Covariance (EC), Scintillometers and Surface Renewal (SR) systems. EC offers accurate data with low percentage of errors. Although it is non-disruptive and fully automated system that is simple to operate and maintain, the EC system has known usability of expensive sensors and energy balance closure discrepancies. Accordingly, Boundary Layer Scintillometer (BLS) and Surface Renewal (SR) are examined as alternatives to EC. In this study, the three methods mentioned above are evaluated to compare each technique’s viability in determining sensible and latent heat fluxes, along with evapotranspiration and energy balance closure. The study was conducted between October and December on a semiarid irrigated potato field in the Bekaa valley, Lebanon. BLS results show good correlation with EC while comparing sensible heat flux with an R2 = 0.73 and RMSE = 27.89 W/m2. While analyzing SR and EC, results show better correlation between sensible heat flux with R2 = 0.75 and RMSE = 21.19 W/m2. The results showed closer agreement for latent heat flux and evapotranspiration, between BLS, EC and SR with BLS values only 5% greater than those from EC and 13% lower than those found using SR while EC values were 18% lower than those found using SR. Future work will need to examine the technical implementation details to maximize the advantages of adopting these alternatives to EC.