Stone Conduits of the Tatsumi Waterway, Stone Well Frame

Tatsumi Waterway is an irrigation channel constructed in 1632 (Kan’ei 9). Of the approximately 11 kilometers running from the upper reaches of the Saigawa River through Kanazawa City to the Ninomaru of Kanazawa Castle, about half—4.8 kilometers—was excavated as a tunnel. For its time, it was an advanced hydraulic engineering project making full use of exceptional civil engineering techniques. The major reason for its construction is said to have been the increased need for fire prevention after the great fire of 1631 (Kan’ei 8). By bringing water into the castle, the moats were transformed into water-filled moats, and the surplus water was used as a water supply for the castle town.

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From Kenrokuen Garden to the Ninomaru within the castle, the water was transported through underground conduit pipes. To cross the moat, the conduit was first laid at a low point, and then the outlet was placed at the higher elevation of the Ninomaru. This technique is known as the “Fusekoshi no Ri” (inverted siphon principle). To make this system work successfully, construction with very high precision and no leakage was essential.  

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The original conduit pipes were made of wood, but between 1841 (Tenpō 12) and 1862 (Bunkyū 2), they were replaced with stone pipes made of Kanaya stone from Etchū (present-day Toyama Prefecture).   Separate from the waterway, many wells were constructed within the castle grounds. Today, only some of them can still be seen, such as those in Gyokusen'inmaru, Takinomaru, and the Sukiya Residence area. Well frames that had been removed and stored during earlier development projects are now displayed around the Tsuru-no-Maru Rest House. These include large wells carved from a single block of Tomuro stone as well as highly decorative ones assembled from eight individual stones.

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