مطالعه تطبيقي روشهاي برآورد تبخير و تعرق پتانسيل در جلگه مازندران

The basis for estimation of water requirement of agricultural crops in the most methods is the calculation of potential evapotranspiration (ETO) amounts. Annual and monthly ETO amounts were calculated in the Mazandaran Plain, using five 1methods, Modified Penman (FAO), Penman - Monteith (FAO), Blanney - Criddle (FAO), Hargreaves and Makkink (FAO) and the long - term data of ten station in the region between 1970 to 1999.•The variables used in the study were: mean temperature, mean minimum and mean maximum temperature, mean relative humidity, mean wind speed and daylight hours of the station. Among the methods, Penman-Monteith (FAO) and Hargreaves methods were selected, beacuse of the FAO suggestion and their data accessibilities. Then the related ETO maps were drawn for the region. The greatest amount of ETO belong to the central part of the region with about 1200 mm. Toward the west and east decrease to about 1100 mm and again increase toward the east to about 1200 mm. The difference of ETO amounts in the region increase in the warm months, beacuse of different reactions of various land covers against the sunshine and decrease in the cold months. July have the greatest and January have the least amounts of ETO.