Modeling of Reference Evapotranspiration Using Time Series in order to Protect Water Resources in Arid Regions, A Case Study of Shahroud Station, Iran

Reliable estimations of reference evapotranspiration can be considered as a way to manage water resourses، especially in arid and semi-arid areas. Researches conducted around the world show that the precision of the estimated evapotranspiration values with FAO- Penman- Monteith are closer than the other empirical relations to measured values with lysimeter. In the present study، after calculating monthly reference evapotranspiration for Shahroud synoptic station located in Semnan province، reference evapotranspiration modeling was carried out during 1961-2005 using time series methods. Results showed the suitability of multiple seasonal patterns (SARIMA). Also according to model efficiencies statistics such as MSE، AIC and SBC، SARIMA (2،0،0) * (2،1،0) 12 was determined as the optimum model in Shahroud station.