This phenomenon occurs in the summer and spring in reservoirs and lakes when the air temperature is higher than the water temperature thus creating a warm layer on top of the lake and a cold heavy layer on the bottom of the lake/reservoir. The layer in between the top and bottom is known as the Thermocline.
The problem with stratification is that the bottom layer of the lake becomes anaerobic, the pH of the water decreases and toxic and smelly H2S is released by bacteria invoved in decay. And when the weather cools down, the lake turns over and this can result in bad water quality.
To prevent this phenomenon, lake bottoms are aerated using air diffusers in the spring.
Compiled by Rami E. Kremesti M.Sc.