Investigating the Effect of using Polystyrene sheets on Evaporation Reduction from Water-storage Reservoirs in Arid and Semiarid Regions (Case study: Semnan city)

There are several water storage reservoirs in different cities of Iran. These reservoirs are used to store irrigation water on agricultural lands. Improper use of water resources, pollution of water resources due to the entrance of urban and industrial wastewaters, as well as natural factors such as evaporation from open water surfaces, leads to available water losses. To reduce water evaporation from storage reservoirs and pools, several methods have been proposed such as using physical and chemical materials. One of the physical materials that can be used to control evaporation is floating covers of polystyrene sheets. In this study, the rate of evaporation reduction in the standard Colorado evaporation pan was investigated by adding 3 mm thick, 50 g/m2, 8000 Rials/m2 polystyrene sheets with 60% coverage. Results revealed that this material has proper function in controlling and reducing evaporation. By doing this test from June 2018 to September 2018 for 4 months in Semnan city, it was observed that polystyrene sheets could reduce evaporation by an average of 44%. Other advantages of this material include its cheapness, good durability against sunlight (about 3 years), water environment and no water contamination.