Comparison of different methods with lysimeter measurements in estimation of rice evapotranspiration in Sari Region

One of the important parts of the hydrological cycle is water requirement of plants. Evapotranspiration of plant is an important parameter in irrigation planning. Estimation of evapotranspiration for each vegetation is very necessary action. All of the empirical equations are not suitable for estimating potential evapotranspiration in a region, so the choice of the best method for estimating potential evapotranspiration in each region is necessary. Lysimetric measurements were conducted in 2015 year (during the rice cultivation season (May-September)) in the Khazar Abad area of Sari county. Using lysimetric data, evapotranspiration of rice plant (early maturity variety of Tarom Hashemi) was estimated in Sari county. The Ref-ET software was used to estimate potential evapotranspiration by Penman-Monteith, Penman, Hargreaves-Samani, Blaney-Criddle, Makkink and Turc methods. The actual evapotranspiration (rice evapotranspiration) represents potential evapotranspiration multiplied by crop coefficients (Kc) at different stages of growth. The efficiency of all methods was evaluated using Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and Coefficient of Determination (R-2) statistic parameters. The results showed that the Blaney-Criddle method with RMSE = 0,54 mm, MAE = 0,42 and R-2 = 0,728 has the most consistent with lysimetric data. so the Blaney-Criddle method is the most suitable method for estimating the evapotranspiration of the rice plant in Sari region.