Assessment of potential evapotranspiration estimation methods in Mazandaran Province

Potential Evapotranspiration (PET) is one of the important elements in hydrologic cycle which is required to be estimated in many fields such as irrigation، drainage and hydrological studies. This element represents potential losses from moist soil layer and vegetation cover. In this research different methods (Blaney-Criddle، Thorenthwaite، Penman and Hargreaves- Samani) are applied and then their results were compared with Fao Penman-Montieth method (as reference) and the best one is selected and suggested to estimate PET in Mazandaran province. The results show that the Blaney-Criddle has the lowest standard error and the highest correlation with the Fao Penman-Montieth method in the province. The results also show that the Blaney-Criddle method estimated PET about 5% lower than the reference method. Furthermore the results indicate that PET decreases from east to west of the province.