Abstract
In the 1970s, high economic growth enabled the industrialization of Japan. This led to the alteration and destruction of the natural environment. Furthermore, it caused large changes in the social structure. Urban areas were expanded because of the increasing population and industrialization in cities. On the other hand, rural areas became depopulated with an ageing society and there was a subsequent decline in agricultural and forestry industries. Moreover, Japan is located in the northernmost region of the Asian monsoon zone, and tends to suffer from serious floods due to the heavy rain during the rainy season and frequent typhoons. Volcanic activity has damaged river basins and influenced the water environment of enclosed coastal seas. The various human activities and natural disasters also damaged river basins and generated pollutants. It is thought that these phenomena have had a large impact on the water environment of the Ariake Sea. As a result, approximately 4% water quality in the Ariake Sea was deteriorated by the desolation of river basins. Approximately 75% of the water quality (COD values) of the Ariake Sea was deteriorated by the impact of the change in social conditions. In addition, approximately 25% of the water quality of the Ariake Sea was deteriorated by natural disaster.
