Along the slopes of the Ailao Mountains in Yunnan Province, Southwest China, ethnic groups such as the Hani and Yi have developed an impressive landscape of terraced paddy fields over the past several hundred years. Their intensive terraced rice cultivation stands in striking contrast to shifting cultivation, the predominant mode of agriculture in tropical mountain areas. This study aims to clarify how terraced rice cultivation has been developed and sustained over many years in the Ailao Mountains from the viewpoint of agricultural technology. In terraced rice cultivation, considerable effort is paid to the preservation of paddy fields. In the dry season, most of the terraced paddy fields are kept inundated even when no crop is grown. This dry season irrigation helps to prevent the collapse of the terrace, in close relationship with various farming works. The long-distance channel irrigation systems maintained by local groups have secured a dry season water supply.In the wet season, on the other hand, protection of paddy fi elds from excess water is the major concern. Many kinds of drainage facilities can be observed both in the irrigation channel and in the terraced paddy field. Irrigation in terraced rice cultivation is designed not only for supplying water to rice plants but has various other purposes as well. In addition to the protection of terraced paddy fields, the unique practice of year-round irrigation plays many important roles, including storing water, maintaining favorable soil conditions for rice growth and providing a habitat for various edible aquatic animals. In conclusion, the terraced rice cultivation in the Ailao Mountains has been sustained by various types of technology, related in particular to irrigation and drainage, which have special bearing in the terraced paddy field.
