Goitsche lake complex in Central Germany comprises two sub-basins, namely Muehlbeck and Niemegk, with distinct water compositions, which are linked to one another by a channel. The channel owes its nearly constant cross section and flat design of the bottom to the mining activity, which left a void after closure of the mine in the 1990s. The importance of exchange flows through such channels or straits, which are interconnecting water bodies of different densities, lies in the fact that water mass characteristics in sub-basins are determined by these flows, extend of which depends on the exchange rate between the interconnected water bodies. The knowledge of kinematic viscosity, k, and vertical diffusivity, v, along a channel/strait is therefore crucial as this gives us an idea about the amount of heat, mass and dissolved solids transported across it and provide parameterisations for circulation models. By conducting a number of numerical experiments with varying Rayleigh number and aspect ratio, we attempted to give an estimation of effective values for k and v in this channel. From comparison with numerical results of an exchange through a channel at various values for Ra, Pr and aspect ratio, we infer the effective value for kv as it appears in the Rayleigh number.