Comparing the Estimates of Reference Crop Evapotranspiration in Qazvin Plain Using SEBAL and METRIC Models

Increasing crop production depends on supplying crop water demands, thus, accurate estimation of crop water requirement helps not only to crop production, but also is effective in the management of water resources. Based on this, the purpose of the present research was to investigate the estimates of reference evapotranspiration from SEBAL and METRIC models using satellite imageries of Landsat 7 and 8 and Terra in the Qazvin plain. In the first step, the estimates of METRIC and SEBAL models with a total of 10 images obtained from MODIS sensor, Terra satellite, and ETM sensor, Landsat 7 satellite, were evaluated using lysimeter data for grass reference crop in 2001. Estimates of MODIS sensor with r =0.88, RMSE =1.91, and SE =0.85 mm/day and Landsat ETM with r =1.00, RMSE =0.91, and SE=0.09 in METRIC model were closer to the lysimeter data compared with the SEBAL model. In the next step, the results of the METRIC and SEBAL models obtained from OLI & TIRS sensor images of Landsat 8 satellite were evaluated with the results of METRIC model on ETM due to lack of lysimeter data at the time of checking. Evaluation of the results indicate that the METRIC model with r=0.96, RMSE=0.28 and SE=0.29 mm/day may be recommended as a superior model compared with SEBAL model, for estimating reference crop evapotranspiration in the Qazvin plain.