台地の開発と水利施設形成過程—播州印南野の場合—

抄録

Innamino upland has the highest density of irrigation reservoirs for paddyfields in Japan. As the upland is made up of sand and gravel beds, water for drinking and irrigation was difficult to be obtained. So it was almost impossible to cultivate the land in ancient time. In the prehistoric age, paddy fields were opened only in a small area near the springs at the foot of the marginal cliffs of the upland. In the Nara period, reservoir irrigation was begun by damming up some of the shallow ravines in the upland. But as the relative height of the upland is large, it was difficult to lead the water from rivers. up to the surface of the upland. At the end of the middle age, when engin eering techinique developed in connection with fortification, the technique was possibly applied to the irrigation work, and there came a new epoch in the reclamation of the upland. At first, the river course of the Kako River was improved and its delta plain was reclaimed. Then it was successfully carried out to lead the water from. the Kako River and its tributaries and the Akashi River up into the reservoirs. constructed on the upland. Thus the upland surface was rather rapidly reclaimed. But as the time-period for supplying river water into reservoirs was ordinarily limited, irrigation water for the newly reclaimed paddy fields on the upland could not be sufficient, so the quarrel for water constantly occurred. At present, a new method of welldrilling irrigation has been applied, while the improvement of irrigation canals and reservoirs has been also promoted. The development of new paddyfields which had been so eagerly promoted in the years of the feudal-clan government, was irresistively ceased in the Meiji era. And, thereafter, conversion of upland fields into paddy-fields was made. Nowadays, the rice-and-ccorn agriculture has become intensive intending to meet the demands of a big city to which the surrouding agricultural villages are being centralized.