Measures and Policies against the Eutrophication for Lake Water Quality in Japan

Lakes and marshes are valuable water resources and natural environments for the human beings, it is necessary to preserve and improve their water quality. Since experiencing severe pollution problems during the 1950s and 1960s, Japan has been strengthening its environmental policy. Regulations over the quality of water were enforced under the Water Pollution Control Law, resulting in the successful reduction of pollutants during the 1970s and 1980s. In this paper, the present status of the special measures for conservation of lakes water quality in Japan, and the measures for reducing influent loads from point and non-point sources, dredging of the sediment contamination on the lake bottom and water purification by means of vegetation, wetland, restoration of the lake’s original landscape and integrated watershed management etc. are discussed.