Water resources are sources of life for all main constituent, and those are indirectly sources of activity for economic agent. The construction technology of underground dam is a means which makes it possible to supply groundwater resources stably to agricultures and households in an island. When we regard some islands with which the ocean is dotted as one economic bloc and one living area, since those islands are isolated geographically, the disutility that water resources are not supplied should be conquered. And it is the composite of construction technology that realizes this subject. About the application possibility of underground dam construction, geological structure is not suitable for construction in any islands other than Miyakojima main island in Okinawa Miyako Islands. Therefore, it is rational to supply water for agriculture which is collected in the underground dam in Miyakojima main island to surrounding islands. With some underground dams and addition equipment of the bridge applied to islands, distribution of the groundwater resource will be stably supplied to those islands. Furthermore, the total utility of main constituent in islands will be maintained in a high position.
