Uchikawa Irrigation System was built in the sixteenth century in the midst of Japan’s civil war. The nationally renowned samurai Masamune Date, ordered the development of the castle town’s urban planning as well as the construction of this agricultural irrigation canal with the purpose of protecting his own castle.
For military protection purposes, water continuously flowed through the canal, which surrounded the castle town. The local farmers also took advantage of the canal’s presence and affluent availability of water to produce a large quantity of rice. Therefore, it was said that this canal played a dual role in protecting the lives of the local residents. In Japan, Uchikawa Irrigation System supports a vast beneficiary area, which refers to the area of land that benefits from its presence. Uchikawa Irrigation System was 2.7 meters high, with an average width of 6.8 meters, a depth ranging from 1.5 to 2.4 meters, a length of 9.405 meters, and an average gradient of 1 in 260. After being constructed as an earth canal (partly fenced in with fascine), Uchikawa Irrigation System was filled with water, and always kept full. Since the canal was inside the town surrounding the castle, it was named “Uchikawa,” which literally means, “Inner River.”
Water for the Uchikawa Irrigation System was taken in through the Ozeki Diversion Dam, which had a height of approximately 14.4 meters and a wooden head gate about 9 meters in width. The dam was called Ozeki (which means “Great Diversion Dam”) because of its unprecedented size. Beginning in 1991, the present-day Uchikawa Irrigation System was extensively repaired for the first time in 400 years, through a joint project conducted by the national government Osaki Western Area Irrigation and Drainage Project and the prefectural government Water Environment Renovation Project. After construction was completed, the “Uchikawa Hometown Maintenance Corps,” “Iwadeyama Friendship Liaison Council,” and other groups, cooperated with Uchikawa cleaning crews, environmental liaison councils, sanitation unions, and other groups in order to prune the trees and plants in the area. On February 22, 2006, Uchikawa Irrigation System was listed on the selection of 100 fine canals in Japan called Sosui Hyakusen.