There are about 97 hot-spring areas in Taiwan, 70 of which are located in the Central Range metamorphic terrane. Among these 70 spring areas, 13 have maximum spring temperatures >=85°C <=99°C; the rest have >=36°C <=79°C. The five explored thermal areas in this region indicate maximum subsurface temperatures from 173° to 226°C. The Central Range is approximately 185 mi (300 km) long and 25 to 45 mi (40 to 70 km) wide, comprising more than 100 mountain peaks that are 9,840 to 13,100 ft (3,000 to 3,995 m) above sea level. Topographic relief is high, ranging from 1,640 to 4,900 ft (500 to 1,500 m) (^DgrH, elevation difference between a mountain peak and the spring) in 1.25 mi (2 km) (D, horizontal distance between the mountain peak a d the spring) to 8,200 to 9,840 ft (2,500 to 3,000 m) in 6.2 to 8.7 mi (10 to 14 km). High topographic relief facilitates deep circulation of meteoric water and upwelling of thermal water from depth, so that thermal springs mostly occur in deep valleys and production wells are all artesian. Analysis of the topographic effect on hydrothermal systems reveals that ^DgrH's of 2,300 to 7,200 ft (700 to 2,200 m) and D's of 1.25 to 6.2 mi (2 to 10 km) favor occurrence of high temperature thermal areas (max. spr. temp. >=35°C or T_SiO2 >=140°C), whereas ^DgrH's of 2,300 to 5,900 ft (700 to 1,800 m) and D's of 1.25 to 4.4 mi (2 to 7 km) can only form low temperature thermal areas (max. spr. temp. <60°C or T_SiO2 <110°C). A imple model for the hydrothermal system in the Central Range is based on these data.

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