There are about 120 rivers of various sizes flowing through Tokyo, including the Tama and Sumida rivers. Although the water quality of these rivers deteriorated significantly during the period of high economic growth, there has been remarkable improvement since the early 1970s due to the control of pollutants from sources like factories and improvements to sewage systems.
Compared with the early 1970s, the water quality of Tokyo Bay has also improved. However, TMG still has some problems to overcome, such as algal bloom incidents.
TMG will continue to take various measures to conserve and improve the water environment.