Аннотация:This paper studies the influence of various parameterizations of aerodynam-ic roughness on the description of the thermal regime and heat flux into the atmosphere from the surface of the lake. Three parameterizations were used: modified Charnock formula, the one based on field measurements at the Gorky Reservoir and the one proposed for the Bolshoy Vilyui lake, Mozhaisk and Gorky reservoirs. The formulas were implemented into the three-dimensional model of thermohydrodynamics of an inland reservoir. The numerical experiments with setup corresponding to the Finnish lake Kuivajärvi in an open water period (May to October 2013) were conducted. The parameterization of roughness significantly affects the description of the temperature regime and heat fluxes, especially at the beginning and end of the open water period.