Effects of Exploitation in the Beppu Hydrothermal Field, Japan

Abstract

Exploitation of the Beppu Hydrothermal System began mainly in the lowland areas as early as the 1880s, and by the 1920s, 1000 wells were extracting about 400 kg/s of geothermal water for domestic uses. This caused (1) intrusion of seawater into the hydrothermal aquifer near the coast, (2) a decline in piezometric head along the coast, and (3) declines in water level and temperature in the shallow aquifer. During the 1960s and 1970s, many wells were drilled over the entire area of Beppu; the number of wells increased to over 2300 and the discharge increased to about 650 kg/s. In particular, high temperature chloride-type waters have been extracted predominantly in the highland areas. This has resulted in: (4) decreased pressure in deep chloride waters, which has caused a reduction in the flow rate of chloride water from highland to lowland areas, and (5) intrusion of steam-heated shallow waters into the chloride waters, which has lowered the chloride concentration and raised the bicarbonate and/or sulfate concentrations.