Investigation the Monolayers Performance on Evaporation Reduction from the Water Surface with Regard to Meteorological Parameters

Reservoir dams have had problems despite all the benefits for humans. one of the most important issues is exposing a large amount of water in contact with the air causing a large amount of water to evaporate. Using chemical methods including heavy alcohols is one of the evaporation suppression methods. In this study, three emulsions of octadecanol, hexadecanol, and a combination of octadecanol, and hexadecanol along with Brij-35 and two physical methods of the canopy and floating balls were used to evaluate the performance of different emulsions. A one-way analysis of variance was applied to compare the mean of evaporation in different chemical and physical methods and a two-way analysis of variance was performed to investigate the main and interaction effects of different meteorological parameters on the value of evaporation. The mean comparison of the evaporation in different methods showed that the two physical methods of the canopy and floating balls had better performance than the chemical methods, and the octadecanol was more efficient than the two other chemical methods. The results of one-way ANOVA showed that among the chemical methods, the octadecanol had no significant difference with floating balls at a 99% probability level (P <0.01). Two-way ANOVA indicated that air temperature and relative humidity had the greatest effect on evaporation. Examination of the effect of different levels of meteorological parameters on the performance of evaporation reduction methods showed that at low temperatures, octadecanol had poor performance than the two physical methods but with increasing temperature, its performance improved. In addition, this monolayer had a suitable performance at low wind speeds compared to physical methods. By increasing wind speed, its performance is severely affected and its efficiency decreases. So, at temperatures above 37° C, an increase in wind speed from 3.5 m/s to above 8.7 m/s has increased evaporation by more than 50%. The effects of monolayers and other evaporation suppression methods on the quality characteristics of the water including dissolved oxygen are significant and should be investigated in future research.