1990 Volume 63 Issue 1 Pages 88-97
Hydrological conditions in Tokyo have been greatly modified by recent urbanization. Extension of impermeable land surfaces, waterworks, drainage or sewerage systems and pumping of groundwater are the main causes of this modification.
Historical changes in the water balance in Tokyo are estimated including natural and anthropogenic processes. Although the result is qualitative and very rough, an extreme deficit in the balance has been obtained for the 1960's. Since the sources of water in rivers depend on the yield from springs, distribution and activity of springs are investigated. About 300 springs were active in 1986, yielding several tens of thousands of cubic meters of water per day.
For the conservation of water quality, yield from groundwater is as important as sewage treatment. A good waterscape also depends on clear river flow.