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close this bookFreshwater Resources in Arid Lands (UNU, 1997, 94 p.)
close this folder5: The development of groundwater resources on the Miyakojima Islands
View the document(introduction...)
View the documentIntroduction
View the documentOutline of the Miyakojima Islands
View the documentGeology and the hydrological cycle
View the documentOutline of the irrigation project on Miyakojima
View the documentThe construction and concept of the underground dam
View the documentThe Construction of the Cut-off Walls
View the documentThe construction of the intake facilities
View the documentThe storage situation of the Sunagawa underground dam
View the documentConclusion
View the documentBibliography


It is now possible to irrigate 914 ha using the water stored in the Sunagawa Dam (as of March 1996). This area will increase gradually according to the increase in the area of land consolidation and of irrigation facilities installed.

Construction of underground dams applying the same methods used on the Miyakojima Islands has started on the main island of Okinawa and on Kikaijima Island in Kagoshima Prefecture. Building underground dams has thus been verified as an effective way of water-resources development on these remote islands or in areas with no surface water. This method is also effective in arid lands, from the point of view that it can reduce high evaporation and store the fluctuating rainfall.

Figure 7 Changes in Groundwater Levels in the Sunagawa Dam over Time