A simple one-dimensional model has been developed for calculating the development of thermal structure in water bodies under specified meteorological conditions, as a function of their inherent optical properties (spectral absorption coefficients, scattering coefficient). Penetration of radiant solar energy is modeled with a previously derived equation relating attenuation of irradiance in narrow wavebands to absorption coefficient, scattering coefficient and solar angle. Evaporative and other heat exchange processes at the surface are taken into account. Vertical heat transfer is calculated by making use of a recently published parameterization of the eddy diffusion coefficient. The calculations show marked changes in thermal structure as absorption and scattering are varied over a range of optical water types from coastal seawater to highly colored and turbid inland water. In general terms, increasing the color and/or turbidity shifts the zone of shortwave energy absorption more toward the surface and leads to warmer but shallower mixed layers. ¿ American Geophysical Union 1988