雲南省哀牢山地の多民族棚田地域における灌漑システム

Abstract

Ethnic groups such as the Hani and Yi have created an impressive landscape of terraced rice paddy fields along the slopes of the Ailao Mountains during the past several hundred years. Sustainable agricultural ecosystem of the terraced paddies has been highly appreciated by many scholars. Most of the previous studies, however, have been confined to examples of the Hani. Other ethnic groups who also cultivate terraced paddies but in different ecological niches have rarely been studied. Ailao Mountains have a long history of multi-ethnic co-existence with highly developed terraced paddy agriculture. Ecosystem of terraced paddy agriculture, especially --as its essential part-- irrigation system needs to be investigated in this regional context. This study attempts to show how irrigation water is exploited and managed in a watershed where two ethnic groups (the Hani and Yi) inhabit, especially in relation to the location environment of their villages. The result shows that irrigation system varies greatly between villages in the upper and mid-watershed, mainly reflecting different hydrological environments. In the upper watershed, abundant and ubiquitous water is easily available for irrigation. Most of the terraced paddies are irrigated by a channel network composed mainly by short channels that runs vertically to the terrains contours. Since water shortage is very rare, few social organizations exist that are devoted to water management. In the mid-watershed, because of the limited water resources near their settlement, most of the terraced paddies are irrigated by long-distance irrigation channels diverting water from streams farther up the watershed. Irrigation water of the channels is managed in more organized way, with social organizations composed of water users and complicated customary rules. Since each long-distance channel passes through several villages in its upper reaches, frequent conflicts over water rights have occurred between upstream villagers and water users of the channels. In Dabei, one of the villages in the mid-watershed, villagers try to avoid the conflicts by means both of appointing some patrolling men from upstream villages and of delaying rice planting. Considering suitable hydrological conditions for terraced paddy agriculture in the upper watershed, there is no doubt that rice terrace development in the upper watershed precedes that by long-distance channels in the mid-watershed. In the light of present ethnic distribution, it is assumed that the Hani played a major role in the early stage of rice terrace development in the upper watershed, and in the subsequent rice terrace expansion to the mid-watershed, the Yi became the major constructors. Important implication of this study is that difference in irrigation system and formation of water use order are not simply adaptation to different elevations, but also a result of eco-historical process in the region, determined both by rice terrace expansion according to the hydrological environment and by timing of each ethnic group's involvement in the development.