Abstract
(1) Over almost all the area of Nara Basin, where ancient Japanese civilization flourished, we can find a number of moat-surrounded villages. Especially they are most frequently found in the southern part of the basin, forming one of the typically distributed areas of the moat-surrounded villages in Japan. Many geographical and historical studies have been made to analyse the peculiar shape and distribution of these villages. However, it should be noted that the farmers of this area have suffered from droughts and most of them have no other source of irrigation water for the rice-fields than a pond. The moats are not only used for irrigation, but also for other pusposes, such as draining or putting out a fire.
(2) In building these moats, farmers often made use of a part of rivulets. The water of these rivulets is stored in summer and these rivulets, together with the moats, play an important role as water reservior for rice-planting. These rivulets and moats which surround villages make an important element within the whole irrigation system, and their existence has close relation to the history and climate of this basin characterized by a little rainfall.
(3) The size and depth of the moats is rather small, but water is easily stored and supplied to ricefields, and repeatedly used during summer. But the use of water was strictly administered by responsible persons of the villages.
(4) To secure the irrigation water as much as possible, the moats are to be cleared of muds and dirts in the bottom every year or every other year. The work is done as the co-operative service-work of all the farmers of the village and is the most imporiant irrigation event of the year. Today with the use of underground-water and improvement of irrigation system, necessity of moats has gradually decreased, and it will not be so long before we see the moats buried or turned for other uses.
