METRIC based evapotranspiration mapping of pistachio orchard in the semi-arid region

Agricultural lands under pistachio crop are expanded in the Bahadoran area due to the high profitability of production. Therefore, accurate estimation of pistachio water requirements and efficient use of water is essential where water resources are insufficient. This study evaluates the performance of METRIC in estimating pistachio evapotranspiration in a semi-arid region. The satellite images utilized in this study were consisting of three clouds free LANDSAT TM5 data acquired on 28 April 2010, 17 Jul 2010, and 2 Aug 2010. These images in Tagged Image File Format were downloaded from the U.S. Geological Survey Global Visualization Viewer website. Geometric correction of images was performed by collecting 20 numbers of well-dispersed ground control points. First-order polynomial transformation with nearest neighbor resampling method was applied to each image to fit the image coordinate to the coordinate of ground control points. The accuracy of the geo-referencing was evaluated by calculation of root mean square error and it was controlled to be less than half the size of the original pixel. Then two other scenes were co-registered based on this image and a subset of interest areas was generated from image scenes. Radiometric and atmospheric calibration was performed first by converting original digital numbers to radiance. Results and METRIC estimates the average ET for the image on April 28, July 17, and August 2 at 2.9, 4.2, and 3.1 mm per day, respectively.