Estimating evapotranspiration in green landscape by usingSEBAL Method (Case Study: Mellat Park of Mashhad)

Since the design of water systems in many countries such as Iran are according to water systems criteria of 50 years ago, this issue should be reconsidered on adaptability with atmospheric changes. Energy balance algorithm for the earth by using MODIS satellite images with interval of 10 days and spatial resolution of 250×250 meter was used, to estimate the amount of evaporation and transpiration of green landscape in Mellat Park of Mashhad. The evapotranspiration in Mellat park of Mashhad (per square meter) in the end of the growing season was about 1210.6 mm. In the other side, the values of reference evapotranspiration are calculated by the FAO 56 Penman-Monteith at the end of the growing season reached to 1563.3 mm, showing an increase of 22.5 percent compared to the estimated one. The relationship between evaporation and transpiration of the estimated plant was significant by FAO 56 Penman-Monteith in SEBAL Method, with the correlation coefficient of 0.7637. Using the relationship based on vegetation index is useful to make a connection between evaporation and transpiration of the estimated source plant (by method of FAO 56 Penman-Monteith) and the real evaporation and transpiration. RMSE and MAE decreased from 2.62 to 1.27 and 1.83 to 0.91 respectively. Therefore RMSE and MAE for the real estimated evaporation and transpiration was estimated by multiplying crop coefficients related to landscape and during entire growing season and was equal to 1.2 and 0.93 respectively.