This paper is concerned with the problems on the irrigation structure of the villages in the Nara Basin and to clarify the characters of the villages and their regionalities. The irrigation structure here shows a special phase to have several methods of irrigation, because this is not favored with enough precipitation and, moreover, has none of large rivers and reservoirs.
The author summarizes the essential points as follows :
1. The irrigation structure in this basin differenciates on account of the geographical and historical condtions. 57.53% of the whole villages depend upon several methods of irrigation, and they are located main-ly in the southern part of the basin, while the remaning 42.47% make use of only one method especially in the northern part.
2. In most cases, the control of the irrigation structure is carried out in connection with administrative measures, especially in the case of the control of reservoirs. Some of them, however, keep their oldfashioned characters. This shows the peculiarity of the villages in this basin, but in the villages depending upon irrigation by rivers is naturally different.
3. In this basin, the irrigation arrangement was completely done in an earlier period than in any other basins in our country, but the farmers have been always suffering from troublesome events because of water shortage.
In the middle of Meiji era when cotton fields were changed to rice fields, many irrigation ponds were constructed everywhere.
After that, they could make use of underground water in full grade, and gain enough water for irrigation. However, the irrigation structure was so complicated that larger cost and labor were required.
4. The more the irrigation structure got complicated, the more powerful effect was produced on the mutual connections among villages, and therefore the difference of the strength of rights about irrigation showed the economic strength of villages. But recently, such difference has been gradually decreasing due to the improvement of irrigation structure.

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