AbstractEvaporation is the main outflow of many water bodies. In hypersaline Lake Urmia (LU), which has experienced significant shrinkage during the last 3 decades, evaporation is the only water outflow. The 15-year daily saline water evaporation pan data collected near the lake indicate that approximately 71% of the annual evaporation occurred from May to September, about 4.15 billion m3/year. To reduce this water loss, three self-assembled layer coatings—fatty alcohols of stearyl and cetyl with stearic acid in hexane solvents, stearyl and cetyl alcohols with stearic acid powder, and stearyl and cetyl alcohols in ethanol solvents—were tested on pools and evaporation pans adjacent to LU in July, when the lake had the highest evaporation rate. Results of 60 h of experiments for each test showed that the coating composed of stearyl and cetyl alcohols with stearic acid in hexane had the best performance and could reduce evaporation by about 52%. This suggests that applying this coating to LU for 5 months/year could reduce the lake evaporation by about 1.5 billion m3, which is more than the total annual supply of the main river flowing into the lake. A short-term study of Artemia urmiana indicated that the coatings did not have a significant effect on their length and weight. However, long-term side effects on human health and the environment need further investigation.