DIMICTIC LAKE (OR RESERVOIR)

A stratified lake or reservoir that experiences two periods of full mixing or (Fall and Spring) Overturns annually. The water in lakes layer in response to differences in the temperatures of surface and deep waters. The surface water will be warmer because of radiant heating by the sun, and the bottom water will be cooler and therefore denser. The waters in these two layers (termed the Epilimnion on the surface and Hypolimnion on the bottom) are separated by a boundary referred to as the Thermocline. This layering is disrupted in response to variation in air temperature associated with changes in the seasons of the year. As the epilimnion cools, it sinks, mixing the water within the lake. Contrast with Meromictic Lake.