Selected Aspects of Lake Restorations in Poland

The work presents the problems of revitalization of water reservoirs in Poland. Lakes are subject to the inevitable process of aging, but as a result of anthropopression, the processes of natural eutrophication have been repeatedly accelerated. The consequence of the supply of excess allochtonic matter to water reservoirs, with the passive character of these landscape elements, is their degradation manifested by a sudden deterioration of water quality. A number of methods for the renovation of natural water reservoirs have been developed. Methods involving the removal of excess nutrients outside the ecosystem are the removal of hypolimnion waters, removal of bottom sediments, flushing the lake bowl, and removal of seston, macrophytes, and fish. The second group of methods consists in reducing the amount of nutrients in the matter circulation in the lake. This includes artificial aeration of lakes, inactivation of phosphorus compounds, treatment of bottom sediments, or biomanipulation. Despite such diversification of existing ways of affecting the aquatic environment, both in Poland and in the world, it is rarely possible to obtain really good effects of the restoration measures undertaken. The most common reason for defeats is the failure to take into account the basic assumption of eliminating excess loads of pollutants reaching the lake from the catchment before commencing its reclamation. Poor effects are also caused by insufficient understanding of the functioning of the complicated lake ecosystem and incorrect selection of revitalization techniques according to the environmental conditions of lakes. Properly conducted reclamation requires collecting research results about the lake and its catchment, recognizing the conditions of the eutrophication process, impartial selection of methods, securing funds for all planned operations, and substantive supervision and monitoring which provides the basis for assessing effectiveness and possible adjustments in the project implementation.