Determining the Empirical Relation for Estimating the Evaporation from Open Water Surfaces

  • Maziar Asmani; Kazem Bashirnejad; Payman Bashi Shahabi


Evaporation is an important factor in managing the water resources and it is through the exact calculation of evaporation that effective solutions can be implemented for reducing the effects of droughts as well as protecting the water resources. Correct estimation of evaporation parallel to proper water resources’ management and determination of an empirical relation with an optimal precision can result in the correction of the amounts of evaporation from the pans and obtainment of more precise results within shorter periods of time. Due to the shortage of the evaporimeter stations and absence of sufficient statistics on evaporation, various empirical methods have been suggested by various researchers for estimating the evaporation from the open liquid surfaces. However, the offered empirical relations have a lot of weak points in such a way that the comparison of the results of these relations and the statistics obtained from empirical relations for Dusti Dam is reflective of evident errors. In the present research paper, a laboratory devise will be designed for simulating the different climatic conditions and it was subsequently calibrated and validated using the data recorded in a meteorological station near Dusti Dam. Various experiments were carried out in different climatic conditions and a new empirical relation was offered for estimating the evaporation amounts following the analysis of the laboratory data; the amounts of RMSE, MAD, MSE, MAPE and correlation coefficient (R) obtained based on the proposed relation are respectively equal to 0.684, 0.559, 0.468, 8.165 and 0.96 which are lower in contrast to the other three empirical relations.