CONTRIBUTION OF GROUND WATER SYSTEM TO THE DISTRIBUTION OF GEOTHERMAL STATE

Abstract

Distribution of underground temperature is obtained m Beppu from observations during well drillings. It involves some regional characteristics. The chemical characteristics of ground water are compared with the thermal states. The correspondency shows that the properties of thermal state are mostly related to the flow of thermal water in deep aquifer. Statical heads of ground water observed after or during the drilling works show relatively complicated distributions owing to their differences with depths of holes. They are simplified as being composed of two kinds of piezometric levels respectively corresponding to the upper ground water and the deeper thermal water. Thermal water is diluted owing to the downwards percolation of ground water. Piezometric level of the thermal water has a more gentle gradient than that of the upper ground water. Both levels become nearly equal in the area of alluvial strata near the coast. Control of exploitation of the thermal water is required in upstream region in order to keep the sea wards slope of its piezometric level and preserve the present thermal activity near the coast.