Numerical modeling of inland water bodies is an important tool for understanding their role in local ecosystems and the climate system. While one-dimensional lake models are widely used in geophysical applications due to their efficiency, they have limited ability to describe horizontal processes and basin-scale circulation. In cases of large reservoirs and lakes with complex morphometry, three-dimensional approaches can provide additional insights.

A three-dimensional thermohydrodynamics model with turbulence closure, ice dynamics, and biogeochemical modules for oxygen and methane was applied to several reservoirs in the Volga Basin, including the Rybinsk, Mozhaysk, and Gorky reservoirs. Simulations were forced with in situ data and ERA5-Land reanalysis and evaluated against field observations collected in different years.

The simulations reproduce observed seasonal thermal stratification, mixing, and ice cover, as well as spatial heterogeneity of temperature fields related to reservoir morphometry. Model results show generally good agreement with available profiles and freeze–thaw timing. The use of a three-dimensional framework makes it possible to investigate circulation patterns and horizontal heterogeneity, which may be important for understanding mixing processes and biogeochemical regimes in large inland waters.

These examples illustrate the usefulness of 3D modeling as a complementary approach to widely used 1D lake schemes in studies of hydrophysics and limnology.