| Abstract |
The exploitation in the Beppu hydrothennal system started in the 1880s, and by the 1920s the number of wells increased to about 1,000. This caused the seawater to intmde into the thennal aquifer at the coast, and to draw the piezometric pressure of the thennal aquifer down. The second flurry of exploitation was during 1960s to 1970s, by which the number of wells incresed to ever 2,300 and the discharge increased from about 450 kg/s to about 650 kg/so The increase of discharge was mainly due to the increase of the chloride water discharge at highland. By this, the subsurface flow rate of the chloride water towards the lowland has decreased and also the steam-heated shallow water intrudes into the chloride water layer. |