Evaporation Reduction from Water Reservoirs in Arid Lands Using Monolayers: Algerian Experience

The extremely high rate of evaporation from water surfaces in arid and semi-arid areas greatly reduces optimal utilization of water reservoirs. In Algeria, which is at 80% an arid country, water resources are scarce and renewable due to low annual precipitation. Considering the importance of optimal utilization of renewable water resources, about 70 dams with capacity of 7.4 billion m³ were constructed. One of the biggest problems of water in dams in Algeria is the huge amount of water loss through evaporation due to high evaporation rate. Therefore, applying techniques to reduce evaporation are greatly needed. One of the most recommended techniques for reducing evaporation is the application of a thin chemical film on the surface of the water. The present study aims to investigate the effect of this technique under arid conditions. Experiment was conducted for 20 weeks in Touggourt with three Colorado-type evaporation pans. Fatty alcohol with various doses were used in different pans. First pan was filled with water without adding fatty alcohol while in second pan, fatty alcohols was added with recommended concentration (0.3 kg/10⁴ m²/day) and similarly in third pan fatty alcohol was added with concentration (0.5 kg/10⁴ m²/day). The preliminary results of the study indicated that evaporation rate from surface water was reduced overall up to 16 and 22% in the second pan and the third one, respectively as compared to the non covered pan.