Due to urban expansion, it is difficult to get source of municipal water near the city, hence the catchment of source rivers has moved to outside the city. Diversion and transport of water bring heavy changes on the source river and the end rivers.

This study focuses on the long distance water transport was developed by Kanagawa Prefecture in the Meiji era. Yokohama and Kawasaki cities located in the east of the Prefecture consumes a great amount of water, whereas the water resources are lacking in this area water for these cities has been taken mainly from the Sagami River and transported by aqueducts. The author analysed the statistics of municipal water and sewerage water from 1960 to 1990, and the following results are obtained.

The volume of drainaged water through sewerage into the Tsurumi River surpassed its droughty water discharge, aggravating the water pollution. The flow volume in the lower reaches of the Sagami River is decreasing by the intake for municipal water and relative amount of polluted water has also increased aggravating the water pollution.

In near future, it is assumed that water pollution load will increase with increasing sewerage water in the drainage area, and aquatic environment of the lower of the Sagami River will be changed by the operation of the Sagami Intake Dam and the Miyagase Intake Dam. It is very important to clarify the influence of diversion of water for municipal supply on aquatic environment, and also on water cycle and resouces.