Long-term changes associated with exploitation of the Beppu hydrothermal system, Japan

Exploitation of the Beppu hydrothermal system started mainly in the lowland areas as early as the 1880s, and by the 1920s the number of wells had incr eased to about 1000. This caused the piezometric head of the thermal ground water to draw down, and seawater to intrude into the thermal groundwater aq uifer near the coast. A second flurry of exploitation occurred during the 1 960s-70s, by which time there were over 2300 wells, and the mass and heat f lows had increased due mainly to the discharge of high-temperature chloride waters in the highland areas. This caused a decline in piezometric head of the deep chloride water, a decline in the subsurface flow of chloride wate r towards the lowlands, and intrusion of steam-heated shallow water into th e chloride water layer. (C) 2000 CNR. Published by Elsevier Science Ltd. Al l rights reserved.