Outline of the irrigation project on Miyakojima

In order to reduce the burden of drought and to modernize agricultural management, an irrigation project has been implemented since 1987. The area benefiting from the project is 8,400 ha, which occupies half of the total surface area of the islands and about 90 per cent of the arable land. The total project cost was estimated at ¥89 billion in 1986.

The irrigation project is divided into the following three parts (table 1):

1. The construction of two underground dams, named Sunagawa and Fukuzato, and intake facilities (a number of wells with submergible motor pumps) installed in the storage area of those dams, which will be implemented by the JALDA Project;
2. The construction of farm ponds and the main pipelines, which will be implemented by the Japanese National Irrigation Project;
3. The construction of irrigation facilities on the farm and the field consolidation, which will be implemented by the Prefectural and Local Government Project.

The water sources for the project depend on two underground dams, one experimental underground dam (Minafuku) and one natural groundwater basin (Nakahara). The total amount of developed groundwater resources in this project will be 24 million cubic metres (mcm), which constitutes 40 per cent of the total unused groundwater returning to the ocean per annum, an estimated 60 mcm (table 2).

Table 1 Planned Infrastructure Facilities of Irrigation Project

^a. Estimated costs based on 1986 prices ($1 = ¥150).

Table 2 Water Resources Development Plan

a. mcm = million cubic metres.