Abstract
Rice terraces are not considered well-conserved if sustainable paddy rice planting cannot be carried out on them. In contrast to farmlands where upland crops or grasses are grown, in Japan, most rice terraces need irrigation systems, that is, irrigation facilities and their operation and maintenance for their conservation to obtain water for paddy rice planting. This paper focuses on the irrigation systems. necessary for conserving the rice terraces and investigates 3 rice terrace areas to clarify the irrigation facilities and their operation and maintenance. The main findings of this study are as follows:(1) A full-set of upstream to downstream irrigation facilities for rice terraces, like for a paddy-field area in the plains, comprises a reservoir, small river, intake works, diversion canals, distribution canals, delivery canals, plot-to-plot irrigation systems, and drain canals.(2) Maintaining the diversion canals and distribution canals requires a lot of work by farmers since the length of these canals per irrigated rice terrace area is rather long.(3) High skill and much working hours are required for supplying plot-to-plot irrigation systems in the rice terrace areas with few intake works from delivery canals.(4) Longer working hours are also required for water management in each plot by mowing levee, preventing water leaks, etc.
