The aim of this study is to clarify controllers and period of construction of the many irrigation ponds in the Nara-Basin. The mental reconstruction of those irrigation ponds which have been developed so far drew the following findings.
1. It became clear that most of the irrigation ponds in the Nara-Basin were built during the Edo period. The period of building can be divided into two. The first period is the earlier Edo period, when an economic system placing a great importance on production of rice was established. Landlords built many irrigation ponds in their villages to increase output of rice collected as a tax. The second period was the mid-Edo period when farmers suffered from the lack of water for irrigation, caused by a drought and a tax increase ordered by the Bakufu. Many irrigation ponds were built in villages in response to the farmers' demands.
2. It is the villages governed by smaller Han [provinces] that mainly built irrigation ponds in the earlier Edo period, while it is villages governed by the Bakufu or retainers of a shogun or some feudal lords that built them in the mid-Edo period. Hence we can assume that the period of the construction of irrigation ponds in the Nara-Basin depended upon who governed the villages in the Edo period and that it made a great difference in agriculture and agricultural production between villages.
3. The peak of bulding irrigation ponds in Tenri-shi was the erly Edo period. Most of them were built on level ground below 60 merters msl. As for Tawaramoto-cho, the peak war in the mid-Edo period and the Meiji Era. Almost all irrigation ponds built or expanded at that time were built on level ground. There is a difference of from 50 to more than 100 years between the period of construction of irrigation ponds on level ground in Tenri-shi, located on the upper reaches of a stream, and that in Tawaramoto-cho, located on the lower reaches.
