We present the first mechanistic model LAKE2.3 for prediction of methane emissions from artificial reservoirs. Estimates of CH4 emissions from the Mozhaysk reservoir (Moscow region) surface provided by the model are demonstrated. The annual emission value was 361 tC-CH4 yr-1, the average flux 37.7 mgC-CH4 m-2 day-1. The methane emission according to the model were shown to be in good agreement with the observation data. The ebullition makes the largest contribution to the total emission (up to 95 %). During the heating period, an increase of methane emission is observed both in the model and empirical data with a maximum before the onset of the autumn overturn. Effective parameter for calibrating the diffusion component of methane flux in the model is the potential rate of methane oxidation in the Michaelis-Menten reaction, and the same for ebullition is the temperature dependence parameter for methane production in bottom sediments – q10.