The bio-diversity of this region is very rich: about 500 species of plants and 500 species of animals have been recorded. More than 400 brooks and rivers flow into Lake Biwa. In recent years, more than 30 million people visited the Lake area annually. Lake Biwa water is used as drinking water for 14 million people and for irrigation purposes.
The rapid economic development that began in the 1960s led to drastic changes, and in the late 1970s the Shiga Prefecture started programmes to clean the water.