Abstract
Recent demand of water other than that for agricultural use has been increased because of Japan's industrialization and urbanization. Water dispute has often occurred between agricultural and urban water users, because both have obtained fresh water supply from streams. Thus the increasing demand for urban water has led to the development of new water resources mainly by the construction of multi-purpose dams. Moreover, urban water users have acquired their new water rights not only by controlling the stream discharge but also by the transfer of water rights from agricultural users. In this paper, the author followed the recent changes of water uses in the lower reaches of the Takahashi River.
The agricultural water users in the lower reaches of the Takahashi River have solved the deficiency of water supply during the dry period through the organization of the Tozai Irrigation Association which had integrated small-size users after the river improvements carried out around the 1910's, and through the constructions of Osakabe dam, Godo barrage and Lake Kojima which had expanded the area included within the same water management system after 1950.
It is since the 1960's that large plants have started their operation at the Mizushima district in Kurashiki city and that the new demand of industrial water has occurred in the area of the lower reaches of the Takahashi River. This demand has been also satisfied with the public water-supply system for industry using the new water resources from Komoto dam constructed by the authority of Okayama Prefecture, and from Shinariwagaw a dam by Chugoku electric power company. There is no conflict concerning the position of intakes between those for industrial water-supply and those for irrigation and waterworks in the lower reaches, because the former are located lower than the latter along the river course.
The demand for residential water began to increase somewhat later than that for industrial water. In this case, water rights for residential water have been obtained b Y the partial transfer of water rights for irrigation, since there was no surplus of water for new water rights in the Takahashi River at that time. The volume of water rights transferred from the Tozai Irrigation Association to the residential water-supply was about 20, 000 m3/day.
The following factors may be considered as the general conditions of water right transfers from irrigation to urban use; (1) the deficiency of water supply for irrigation has been solved by the improvement or establishment of irrigation facilities which have changed the form of water management system in the region, (2) the considerable area of agricultural land has been transferred into the urban uses, (3) the water use system for irrigation sustained by farmers in the region has deteriorated due to the outflow of the labor force from farming. In addition to the factors mentioned above, the manager of the Tozai Irrigation Association is the Mayer of Kurashiki city who is also the manager of the residential water-supply system in the district belonging to the Tozai Irrigation Association. Thus the transfers of water rights had been carried out quite easily. However, drastic change of water use system will occurr at the time when there will be no rests of water rights during non-irrigation season in the Takahashi River, provided that the transfers of water rights will be carried out in this manner.
