The World Heritage Sites of Irrigation in Japan

Irrigation and rice cultivation

Rice is the basis of the Japanese diet and a stable supply of water is necessary for its successful cultivation. In Japan, where there are many mountains and few plains, rainwater flows into the sea quickly. For this reason, it is essential that farmers prepare for seasons of low rainfall or possible drought periods, and this is how the irrigation process was implemented. It consists in facilities that capture water from rivers, the underground or lakes and distribute it artificially to rice paddies and other crop fields through canals. Most rice fields in Japan are cultivated by irrigation.

The function of irrigation

To successfully irrigate, it is necessary to guarantee the water source and organize the driving and distribution installations. Currently, the construction of embankments at water sources or dams at rivers allows for a stable collection of water resources.

The water that supplies the rice paddies can follow two paths: one part infiltrates the soil, becoming groundwater and contributing to recharging the water tables; another part flows across the surface, reaching the drainage channels and then the rivers. This movement allows water to continue in the hydrological cycle, collected and reused in other activities, especially in regions near the mouth of rivers, where this water accumulates again and is available for other uses. The proper management of this flow is the key to maintaining the health of the water cycle in the entire basin. As such, we can say that irrigation is not only useful for agricultural production, but that it plays a multifaceted role, including the sustainable management of water resources and the preservation of aquatic ecosystems. In order for this system to work stably and for many years, there has to be a concerted, continuous effort from the local community, including the farmers who benefit from it.

Source: Mynavi Nogyo.

Japan's irrigation facilities

The International Commission on Irrigation & Drainage (ICID) certifies historic irrigation facilities that are considered “World Irrigation Heritage Sites.” Japan stands out in this scenario with a significant number of registered locales, a total of 54 as of the year 2024.

One difference worth noting between irrigation facilities in Japan and other countries relates to the system of local and national government-supported organizations known as Land Improvement Districts (Tochi Kairyō-ku). They are comprised of farmers who benefit from the water and who play a central role in creating and maintaining the installations that supply the land with water resources. This is considered a representative example of Farmer Participatory Irrigation Management, known as PIM in Japan.

Many of these installations were developed before the 17th century, but are still in use because they were maintained by farmers, and it is possible to find this type of structure throughout the country.

Outside of Japan, irrigation is mostly a national initiative, with the construction and management of key facilities led by the government. Japanese facilities are often relatively smaller in scale, which allows for locally-run management.

Reference: Tsugihiro Watanabe. Water Heritage Passed Down in the Community. Mitsukan Water Culture Center, No. 66.