What is the phenomenon of separate layers of temperature occurring in a lake or reservoir called?

The phenomenon of separate layers of temperature occurring in a lake or reservoir is known as stratification. This process occurs when the water in a body of water forms distinct layers due to differences in temperature and density. Typically, warmer water is found at the surface, and cooler water resides below because cooler water is denser. This layering can lead to different physical and chemical characteristics in each stratum, affecting aquatic life and water quality.

Stratification often occurs in seasonal cycles, particularly in larger lakes, where thermal stratification can create a stable upper layer, or epilimnion, which is warmed by the sun, while the lower layer, or hypolimnion, remains colder and denser. This condition plays a significant role in nutrient cycling and oxygen levels within the water, impacting the entire ecosystem.

While mixing refers to the process of waters intermingling, hydrolysis pertains to the chemical reaction involving the breakdown of substances in water, and circulation generally describes the movement of water within a body. None of these concepts accurately describe the specific layering effect that defines stratification.