The current territory of Izumisano City, in the southwest of Osaka Prefecture, used to be a manor, the highest-ranking noble of the court in the 14-15th century. The Yukawa Irrigation Canal played an important role in the development of the manor. The irrigation system is estimated to be built at least about 800 years ago, as evidenced by two paintings from the early 14th century depicting Izumisano City. The attached archives passed down by a headman in Izumisano City show that the irrigation canal was definitely connected to Junitani-ike Pond in 1446, and a map drawn in 1761 depicts the irrigation canal as it is today. The Yukawa Irrigation Canal is approximately 2.9 km long, and the difference in elevation is only 3 to 5 m.

The Yukawa Irrigation Canal terminates at Junitani-ike Pond, and a spillway is located in the canal in front of the final entrance to prevent water in excess of the amount used from flowing into Junitani-ike Pond. The Yukawa Irrigation Canal used to have a natural boulder as its intake and is constructed along the cliff face from the fan to the low plane. The structure of the irrigation canal has been modified to a three-sided concrete revetment, but part of it was a masonry revetment, and academic excavations have confirmed that the masonry revetment was the original form of the irrigation canal. The excavations have also confirmed that the original structure of the irrigation canal was partially filled and levelled around the base of the terrace, and both sides were piled with locally available natural stone without processing. There is no evidence of a wooden canal. As the modern era approached, the method of piling stones around the canal changed to that of stone walls that used standardized stones and piled the stones through horizontal joints.

The Yukawa Irrigation Canal and the Junitani-ike Pond irrigated about half of the manor by the first half of the 15th century and played an important role in the development of rice paddies. Local people were grateful for the bounty of water brought by the Yukawa Irrigation Canal and dedicated a dance to the local shrine that managed the irrigation canal in spring and summer to pray for a bountiful harvest. This tradition is still carried on today. The Yukawa Irrigation Canal still supports local water conservancy and life today.

In this context, the Yukawa Irrigation Canal and Junitani-ike Pond are highly appraised by the national government as important elements of the construction of the manor, and the manor and its hydraulic heritage are introduced at the Izumisano City Museum. Currently, elementary and junior high schools in Izumisano City conduct fieldwork around the Yukawa Irrigation Canal as part of their extracurricular classes, and tourism volunteers lead guided walks around the area. Local volunteers also hold study groups and stroll. And Izumisano City and local breweries cooperated to produce Sake using rice grown in the water of the Yukawa Irrigation Canal, which helped revitalize the region.

*More details of the structure are available in the attached documents.

The structure made outstanding contribution to enhancing food production, livelihood opportunities, rural prosperity, and poverty alleviation in a region

The development of the Yukawa Irrigation Canal irrigation system has promoted irrigation of the manor, and the water is still used for agricultural purposes in the area today.

The route of the Yukawa Irrigation Canal to the Junitani-ike Pond has been the same since the Middle Ages, and although much of the canal has been modified with three-sided concrete revetments, some of the revetments still retain the original stone masonry from the time of construction. The irrigation area is still being enriched by the branch line from the waterway.

The structure was an example of engineering marvel or excellence at the time of its construction;

The Yukawa Irrigation Canal is about 2.9 km long, with the difference in elevation only about 3 to 5 m, and is designed so that no more water is taken from the Yukawa Irrigation Canal than is used before it flows into the Junitani-ike Pond. These features show the deployment of the high technology of the time. The Yukawa Irrigation Canal used to have a natural boulder as its intake and is constructed along the cliff face from the fan to the low plane. The structure of the irrigation canal has been modified to a three-sided concrete revetment, but part of it was a masonry revetment, and academic excavations have confirmed that the masonry revetment was the original form of the irrigation canal. The excavations have also confirmed that the original structure of the irrigation canal was partially filled and levelled around the base of the terrace, and both sides were piled with locally available natural stone without processing. There is no evidence of a wooden canal. As the modern era approached, the method of piling stones around the canal changed to that of stone walls that used standardized stones and piled the stones through horizontal joints.

The structure bears the stamp of a cultural tradition or a civilization of past;

The Yukawa Irrigation Canal was constructed by the highest-ranking noble of the court to develop his private land called a manor and can be regarded as a living site that shows the history of this area.

Engineering utility vis-à-vis designed utility

The Yukawa Irrigation Canal was constructed to irrigate the "Hinenosho", a private estate in Izumisano City, or a manor of the highest-ranking nobles of the court, and tax revenues from the local farmers in the manor were the income of the aristocrat. Therefore, the irrigation of the manor through the Yukawa Irrigation Canal was crucial in order to obtain stable tax revenues.

Present State of Conservation

The Yukawa Irrigation Canal has supported the water supply of the Hineno district of Izumisano City since its beginning of the canal 800 years ago. Currently, the Hineno Land Improvement District of Izumisano City, organized by farmers in the Hineno area, is responsible for the daily management of the waterway and reservoir, and since it is also a designated historic site, the city, prefectural and national government departments in charge of cultural properties are also involved in its preservation and utilization. The riverbanks have been repaired with concrete, but in some areas, the natural stone masonry revetment that was used at the time of construction is still in place. The irrigation canal is still in use today, and the restoration and maintenance of the waterway landscape and the specifications for the restoration of the water supply system of the Yukawa Branch Canal are being carried out with financial assistance from the national and municipal governments while efforts are being made for cooperative management with the land improvement district and local residents. In addition, the enhancement of a tour route along the waterway is hoped.