The Water Issues of the Megacity Tokyo ─Thinking about the World’s Top Megacity Tokyo from the Viewpoint of Water─

One of the important pillars of civil engineering is water-related issues. The JSCE Magazine “Civil Engineering”, No. 7, 2011 featured “International development in the field of water supply and sewage infrastructure – in an attempt to become Water baron”, which takes up the topics of international contributions and business models in the water sector. In this special issue, we would like to feature water issues in metropolitan areas where the majority of the people live.

The water issues brought by urbanization addressed in this special issue cover unsatisfied water demand, ground subsidence resulting from the withdrawal of groundwater, water contamination caused by wastewater that exceeds the processing capacity of nature and intensification of flood damage due to the reduction in rainwater infiltration associated with urbanization. The history of how Japan overcame these problems is the history of the Megacity Tokyo, as well as the history of the water sector in civil engineering itself. It is also the mission of modern civil engineers to find ways to solve the unsettled issue of the concentration of population in areas vulnerable to flood damage such as the areas below sea level, and further give advice to Asian megacities that are vulnerable to flood damage similar to Tokyo, since most of the Asian megacities are located in coastal areas.

Civil engineers are expected to portray the blueprint of the future of water infrastructure after 50 years or 100 years in Japan that is facing a declining population at the forefront of the world, and to think of a way to gradually replace the infrastructure with the renewal of existing facilities, setting the blueprint as a goal. To realize this, it is time to rethink what kind of experiences, knowledge, and education system is needed in order to develop the necessary conceptual ability and technical expertise.