epilimnion

thumb|Lakes are stratified into three separate sections: I. The Epilimnion II. The Thermocline|Metalimnion III. The [[Hypolimnion The scales are used to associate each section of the stratification to their corresponding depths and temperatures. The arrow is used to show the movement of wind over the surface of the water which initiates the turnover in the epilimnion and the hypolimnion.]]

The epilimnion or surface layer is the top-most layer in a thermally stratified lake.