Potential Evapotranspiration Calculation Using Remote Sensing With Minimal Amount of Ground Data

Potential evapotranspiration is one of the most important components in water balance equation in a watershed or a plain. ETP measurement is a costly and time-consuming process. Therefore, remote sensing allowed us to estimate the surface energy considering the energy balance in a small area in order to calculate evapotranspiration (ET). Thus in this study, the Priestly-Taylor equation associated with Landsat 7 and 8 were taken into account for crop ETP calculation. The remotely sensed ETP algorithm was evaluated against four different ETP calculation approaches including radiation approach (Priestly-Taylor), aerodynamic approach, combination approach (Penman), and temperature approach (Hargreaves). These approaches were conducted using meteorological data obtained from seven stations around the Qazvin plain. Results showed that this algorithm could properly estimate ETP, and had the best relationship with ETP calculated from the Priestly-Taylor equation with R2 of 0.95 and RMSE of 0.6. Also, this algorithm could detect the crop on the ground and presented more actual values of ETP compared with ETPs calculated from meteorological data. Therefore, this algorithm could estimate ETP more accurately by distinguishing the dense of vegetation on the ground.