In the Riukiu Islands aquifers consist of Riukiu limestone, sandstone-tuff beds of Shimajiri formation and Paleozoic limestone.
Among the above, Riukiu limestone will be the best aquifer for developing ground water in future. Riukiu limestone is either porous limestone or calcareous sandstone in Plio-Pleistocene age, forming terraces and hills of islands.
The ground water is counted as fissure ground water, also having a character of bedding ground water. Therefore, as far as the development of ground water in Riukiu limestone is concerned, it is suggested to make a scientific ground water inquiry such as adopting to drill wells after investigation of the depression of bed rocks by using either electrical resistivity method or seismic refraction method.