Numerical Simulation of Temporal Variability of Methane Emissions from Mozhaysk Reservoir

Abstract

Estimates of methane emission from the Mozhaysk reservoir surface were carried out using the mathematical model LAKE2.3. The average emission value is 361 tC per year, the average flux = 37.7 mgC–CH4 m–2 day–1. Comparison of the obtained estimates with in situ measurements revealed, that the methane emission and specific flux according to the model are in good agreement with the observations data. The ebullition makes the largest contribution to the total emission. During the heating period, an increase of methane emission is observed with a maximum before the autumn mixing stage. In the course of numerical experiments with the model, it was found that the amplitude of methane fluxes into the atmosphere is associated with fluctuations in atmospheric pressure, and the most significant emissions peaks associated with water level drawdowns. Effective method for calibrating the diffusion component of the methane flux into the atmosphere is the potential rate of methane oxidation in the Michaelis-Menten reaction, and for ebullition it is the methane generation parameter in bottom sediments — q10. For the described numerical experiments, the article presents the values of the annual emissions of methane into the atmosphere.