Investigation of the performance of experimental equations in estimating evaporation losses from the pan in the area of Shahid Rajaei Dam Lake

Evaporation is one of the most effective and massive loss factors in water resources, and with its accurate calculation, effective solutions can be implemented to reduce the effects of drought and to protect and efficiently manage water resources. In this research, the common experimental relationships in estimating the daily and monthly evaporation rate for four stations of Suleiman Tange, Mohavvateh Edareh Sari, Farim Sahra and Telmadarreh were investigated and evaluated based on the observed data of the evaporation pan, and the best experimental relationships for estimating the daily and monthly evaporation values was introduced. For this purpose, the 10-year statistics of the measured values of evaporation from the pan with the values calculated from the experimental methods of Meyer, Marciano, Shahtin, Hefner, Ivanov, and the American civil engineering office, with two-time scales, daily and monthly, with the aim of estimating losses due to evaporation it was compared from the lake level of Shahid Rajaei Sari Dam. Then, the performance of empirical relationships was evaluated based on MSE, R2 and EF statistics. The results of the evaluation of the experimental relationships of evaporation calculation showed that Meyer's method is the best relationship for estimating daily evaporation in the studied stations. After Meyer's empirical relation, Ivanov's relation was introduced as the best relation. The values of MSE, R2 and EF statistics in the estimation of monthly evaporation using Meyer's relation at Suleiman Tangeh station, which is the closest station to Shahid Rajaei dam, were obtained as 436.9, 0.97, and 0.3, respectively. Also, among the experimental methods used in this study, the American Civil Engineering Bureau method was determined as the weakest equation for estimating monthly evaporation at Suleiman Tangeh station.