Shade balls are small plastic spheres floated on top of a reservoir for environmental protection and to slow evaporation. Also known as bird balls, they were developed initially to prevent birds from landing on toxic tailing ponds produced by mining operations. They have been used by airports to prevent birds from being attracted to drainage ponds and thus risking collisions with planes.It helps in not evaporating the water by limiting the direct fall of sunlight in those areas.
Because of the Causes of Evaporation. Evaporation occurs when liquid water turns into a water vapor, with about 90 percent of the water going through such a transformation originating from rivers, lakes and oceans. ... Heat is the cause of evaporation