2023 Volume 79 Issue 26 Article ID: 23-26007
The Basic Plan on Water Cycle is a significant plan that specifies the appropriate conservation and use of groundwater. However, the definition of "watershed" in the plan is still an issue. In addition, the significance of the water cycle in man-made systems such as water supply and sewage systems, which have a hydrological continuity with river water, is not mentioned. In this paper, we propose the concept of a "water cycle sphere" that encompasses a river basin, a water supply area, and a sewerage system area, and is considered as a planning area for water cycle planning. Furthermore, the hydrological continuity of the water cycle between artificial and natural systems will be discussed. The case of the Tama River will be presented as an example of how tap water in an urban area becomes reclaimed water after use and becomes an important water resource for maintaining the flow rate of the urban river, and the significance of the water cycle will be presented.
