Impact of Micrometeorological Conditions on the Efficiency of Artificial Monolayers in Reducing Evaporation

Monolayer products can potentially provide a cost effective solution for reducing evaporative loss from water storages. Commercial adoption has been low, due to the extreme variability of product performance. In this study, the efficiency of three monolayer compounds (stearyl alcohol, ethylene glycol monooctadecyl ether and the commercial product WaterSavr) in reducing evaporation were tested at three controlled wind speeds inside a glasshouse in class-A evaporation pans. Water levels and micrometeorological conditions were monitored to document the impact of prevailing atmospheric conditions on monolayer performance. The evaporation reduction ranged from 13 to 71 % depending on the product and micrometeorological conditions. The ethylene glycol monooctadecyl ether was most effective reducing evaporation across all wind speeds. Atmospheric conditions markedly affected monolayer products’ performance. All monolayers were most effective when the wind was sufficient to drive evaporative loss but lacked the force to disrupt the condensed monolayer (1.5 m s⁻¹). Continuous wind of 3 m s⁻¹ disrupted the condensed monolayer and substantially decreased the product performance. Without wind, the resistance to evaporation induced by monolayers had little additional effect. When atmospheric evaporation demand was very low, the evaporation suppression efficiency was minimized. High temperatures and high incoming radiation negatively affected the persistence of the condensed monolayer and decreased product performance. These results highlight the importance of analysing micrometeorological conditions when assessing product performance.