A study is made of the thermal structure in stratified water by using a onc-dimcnsional two layer mathematical model. The model accounts for the nonlinear interaction between the large flux of thermal diffusion and the buoyancy gradients produced by atmospheric and solar surface heating. The objective is to determine the water temperature at any time and position by using available meteorological data and the physical characteristics of the water body. Calculated water temperatures are compared with the measured values. The comparison shows the expected similarity.