Comparison of evaporation estimation methods applied to the Reservoir of Saveh (Alghadir) Dam, Iran

In this study, several precise models and methods are used for estimating annual and monthly evaporation rates for the reservoir of Saveh (Alghadir) Dam for 13 years (1995-2007). Water budget and evaporation pan, experimental methods, penman type equations, Bowen Ratio Energy Budget (BREB) method, and Complementary Relationship Lake Evaporation model (CRLE) were applied to this study. The maximum and minimum values for the mean annual evaporation rates are estimated between 145 cm (for Debruin-Keijman method) and 175 cm (CRLE model for shallow lakes). Also the long term monthly evaporation pattern from the applied methods are different from the standard method of BREB evaporation. The least difference in the mean monthly evaporation from the BREB results, are for the Mass Transfer, Papadakis, Penman, Brutsaert-Stricker, and Priestley-Taylor methods. However, only the standard deviation of Penman and Mass Transfer methods were very small and the other three methods have relatively large standard deviation from the BREB results. The qualification of the CRLE model have been rejected, and the Thornthwaite, Hamon and Ryan-Harleman methods have also large bias in mean and standard deviation for monthly evaporation rates from the BREB results.