The Shichika Canal of Japan since the twelfth century

This paper is concerned with the history of the Shichika Canal construction works in Japan, which have been carried out since the twelfth century to benefit the people living in the Tedori alluvial fan. The history can be demarcated into three periods. The first period started at the end of the twelfth century and ended in 1903, after Gonbei Eda made a success of digging the five water intake holes at the Akudo Pool, feeding sufficient water to the Togashi and Go channels. The second period began when the Grand Water Gate was completed in 1903 and ended in 1962, when the third period started with the division of the Shichika Canal into three groups. With this grouping, the management and administration of the Shichika Canal have become not only efficient but also effective. Water diversion by means of an inverted siphon from the Shichika Canal to the Miyatake channel has made the canal much more valuable, for, by covering the part of the Kakehashi basin aside from the Tedori and Sai basins, the irrigation area has been increased by approximately 25%.