During the period 1920-1932 the expansion of rice fields in Hokkaido went on extensively and rapidly. Remarkable changes can be seen in the distribution of the fields. In this paper, the author explains the expansion and distribution of the rice fields in relation to the nature of the land.
(1) Before 1920 the expansion of rice fields was confined, as a whole, to the valley floors and alluvial plains along the foot of the hills and mountains where it was relatively easy to get irrigation water from the tributaries of the Ishikari River.
The first large scale irrigation system from main stream was established by Fukagawa Doko Kumiai Fig. 2, one of the associations for the irrigation. In this period, the reclamation of rice fields in the central part of the plain was carried on by Shinoro Heison Doko Kumiai No. 2, Fig. 1.
(2) After 1920 the expansion of rice fields in the plain had progressed on a large scale, together with the construction of large scale irrigation systems, complete pumping facilities, and many irrigation reservoirs for uplands. These works were brought about by several Doko Kumiai under the financial support by the national government.
(3) Although the expansion of rice fields in the peaty and swampy lands took place since 1930, the full-scale development in these lands was delayed until after World War II.
(4) The full-scale reclamation during the time of land owner system was carried out by the Doko Kumiai, and after the War it was brought about directly by the agency of the national government.