Lake Miedwie is a eutrophic reservoir characterized by strong oxygen deficiencies in the hypolimnion, as well as high concentrations of nutrients (particularly phosphorus) and a significant recent increase in algae biomass. The water quality in the lake depends on pollutant inflow from the watershed, rate of biological activities, and accumulations of pollutants in bottom sediments.

The lake has very good natural conditions, described by class I of vulnerability for degradation. Decreasing the level of anthropogenic stress should allow the natural self-purification of lake water. Thus changes in the type of land and waste management in the watershed should improve the water quality in Lake Miedwie.