On the Irrigation of Terraced Paddy Fields (or Rice Terraces) with Special Reference to the Wajima Region, the Obasute Region and the Hayakawa Valley

Abstract

When making paddy fields on a slope, the paddies, each with a level surface, must be made one by one in the form of a series of shelves or terraces. Paddy fields made in this manner are called “terraced paddy fields” or “shelf paddies” “tanada” in Japanese. Such paddy fields are found in various parts of the mountainous regions of Japan, and may roughly be divided into two categories, depending on the nature of the place where they are found. The first category includes terraced paddy fields that stretch in long, narrow lines along the bottom of small valley among the mountains. To the second category belong those that are found stretching on wide slopes. Terraced paddy fields belonging to the first category are found everywhere in mountainous regions. They are easy to make and their irrigation presents no problems. In the case of terraced paddy fields of the second category, however, because of the general complexity of the relief of the slopes where they are found, their making in such places requires great labor, and their irrigation is a difficult matter.The present writer conducted a study of 26 of the main terraced paddy fields belonging to the second category, and in each case, was convinced of the great pains and resourcefulness required to ensure the supply of irrigation water.In Japan, rice has been the main food crop since ancient times ; and until the Meiji period, it was the practice among farmers to pay their taxes in rice. Rice was the all-important element of economy, both for the central and local feudal lords until the Meiji period. This was the reason that, throughout the nation, the development and expansion of paddy fields were the two main concerns of the rulers as well as the farmers. This state of affairs continued until recent times. The present writer believes that it is possible to consider the existence of terraced paddy fields as one of the manifestations of the history of this type of rice-centered policy in the form of cultural landscapes seen in the land.In the present paper, the writer has chosen three typical regions, and he purposes to describe the development of the irrigation of the terraced paddy fields found in each of these regions.(1) The Wajima Region in the northern part of the Noto Peninsula.This region is the location of “Shirayone no Senmaida” (or “Numerous Small Terraced Paddy Fields of Shirayone”), which in recent years have come to attract the attention of tourists. There are monographs and books which state that the terraced paddy fields in this region are supplied with irrigation water by springs and rain water. The writer, however, has made clear in the present paper the fallacy of these claims. In the Edo period, in order to irrigate the terraced paddy fields in this region, long irrigation canals were dug to draw irrigation water from the upper reaches of rivers among the mountains, while irrigation reservoirs were made among the mountains to provide irrigation water. Examples of these irrigation systems are shown in Figures 1 and 2. The terraced paddy fields in this region are developed on slopes formed as a result of landslides.(2) The Obasute Region in Nagano Prefecture.This region is the location of terraced paddy fields widely reputed as “Tagoto no Tsuki” (or “The Moon Reflected in Each of Many Paddy Fields”). In this region, too, are found terraced paddy fields on slopes formed as a result of landslides. Concerning the terraced paddy fields in this region, there are books which state that they were supplied with irrigation water by springs and rain water, but the irrigation system in this region is not such a simple matter.