The role of background diffusivity and mean subsidence in the temperature stratification in the Mozhaysk reservoir according to the LAKE 2.3 model

Abstract

This paper presents the results of numerical experiments carried out with a one-dimensional hydrodynamic model, LAKE 2.3. To accurately reproduce the cycle of biological processes in a reservoir, correct calculation of the thermodynamic regime is necessary. This paper considers the influence of background diffusion, vertical advection, and the inflows, outflows, and level fluctuations on the formation of a thermal regime in a reservoir using data on the Mozhaysk artificial reservoir as an example. A series of numerical experiments has been carried out to switch on/off these effects in the model and subsequently compare the results with the measurement data. The model adequately reproduces the field observations for the surface water horizon. For the near-bottom horizon, the quality of the simulation results strongly depends on the stratification. Also, in order to correctly reproduce the temperature variability near the bottom, it is necessary to calibrate the parameters of an empirical function that defines the additive background diffusion coefficient. In the future, the calibration of these parameters will make it possible to obtain results that are in better agreement with the field measurements, and thus improve the quality of the model reproduction of the thermal regime and, as a result, improve the accuracy of estimates of methane emissions into the atmosphere from reservoirs.