Lakes provide many crucial functions in different regions of the world: starting with supplying of drinking water and being as underwater environment for aquatic habitats and finishing with being as integral component of local landscape, fishery place or area of recreation and tourism development. Unfortunately nowadays, the problem of eutophication concerns most countries in the world including Baltic countries. The lakes on the grounds of Warmian-Masurian Vivodeship in Poland were used as an example to highlight the genesis and consequences of the problem and to find the possible ways of its solution.