Water from Heaven:

The Tianmu Historic Trail has long been a popular hiking route for visitors aiming to get out into the mountains around Taipei City. If you head downward from the Aifu 3rd Street Trailhead near Corpus Christi Church on Yangmingshan (Mt. Yangming), before long you will see a large gate by the path that is closed tightly all year round. It leads directly to the restricted area of the Caoshan Waterway System, and in the past only regular maintenance patrols were permitted to enter.

Hikers follow the Tianmu Historic Trail, also known as “Water Pipe Road.” (MOFA file photos)

Testament to a century of modernization

Behind the gate is a spring that supplies water to tens of thousands of people in Tianmu and other parts of the Shilin and Beitou Districts. It is known as the “Yang San” or “Yangmingshan No. 3” water source.

The story began in the early years of the era of Japanese rule in Taiwan (1895‡1945). The Japanese played an ­important role in developing water supply and sewerage systems for modern urban areas. In Taipei, they commissioned the Scottish engineer William Kinninmond Burton, known as the father of Taiwan’s modern water supply, to build the “Taipei Waterway water source area” (today’s Taipei Water Park). However, as the city’s population grew, the supply from this site proved inadequate for the increasing number of residents. That was when the next stage in the development of water facilities in Taipei got underway.

One of Burton’s disciples, Tojiro Sano, found four major water sources on Yangmingshan. One of these was the “Sapphire Spring” (a.k.a. Yangming Spring), located on the side of Mt. Shamao at 300 meters above sea level, which feeds the Caoshan Waterway System.

This three-way collaboration involving Taiwan, Japan, and the UK produced a site rich in historical significance. However, because it is critical for the daily life of citizens, access to it was restricted. It was only in 2020, when the Covid-19 pandemic closed international borders and drove a surge in domestic tourism, that the area was opened to the public, albeit on a strictly limited basis, with advance application required for entry.

(left) The “Yang San” or “Yangmingshan No. 3” spring is located next to the entrance to the Tianmu Historic Trail.

(right) This closed gate protects the sources that supply water to tens of thousands of residents of Taipei’s Shilin and Beitou Districts. 

History, nature, and architecture

The guide for our visit is Chen Shengbin, manager of the Taipei Water Department’s Yangming water purification plant. Following a small path that maintenance patrol staff walk daily, the first thing we see is an arched bridge aqueduct built in the Japanese era.

Two types of material are used in the channels that carry water across this bridge. One of the channels transports water from the “Yang Yi” or “Yangmingshan No. 1” water source near Zhuzihu. Flowing down from a higher elevation, its water creates high pressure in the aqueduct, so steel pipe is used. The water from the Yang San water source, on the other hand, flows across level ground, generating lower water pressure, so a simple concrete culvert was constructed to carry it across the bridge. Owing to the use of these different materials, the right and left sides of the walkway on the aqueduct have different surfaces. On the side with the steel pipe, stone slabs were laid down that can be removed individually, facilitating access to the pipe for future maintenance, while the culvert was covered with a single slab of cast concrete.

(left) This aqueduct bridge carries water from two different sources in separate channels made of different materials (concrete and metal). Hence the left and right sides of the footway covering the channels have different surfaces.(right) Chen Shengbin, manager of the Taipei Water Department’s Yangming water purification plant.

An aeration chamber, built to aerate spring water.

Meanwhile, from the mountain face beside the bridge there comes the sound of rumbling water as a nameless waterfall gushes down into the Song River, a tributary of the famous Huang River (“Sulfur River”). Because the spring water that feeds the waterfall contains sulfur, it exudes a faint sulfurous odor and the rocks over which it passes have all been stained a reddish-brown color.

With its rare combination of majestic landscapes and historical significance, along with the reinforced concrete architecture of years gone by and a water supply system that does not rely on pumps, this place fully deserves the name “living historic site.”

(left) Next to the aqueduct, an unnamed waterfall roars down. Because the spring water that feeds the waterfall contains white sulfur, it has a faint sulfurous odor.

(right) The small stone building that houses the Sapphire Spring is built from locally sourced andesite, an igneous rock.

(left) The Yuanshan Water Shrine, a Shinto shrine at the outlet of the Caoshan Waterway System, preserves features from its construction in the 1930s, including stone lanterns, the shrine name stele, and guardian lion-dogs, giving the site an otherworldly atmosphere.

(right) The Caoshan Waterway network includes various water transport facilities. The photo shows an octagonal distribution well, located beside the Yuanshan Water Shrine. It was used to regulate the volume and pressure of water conveyed from the Sanjiaobu Power Station.

Natural rock filter

The pièce de résistance of the scenery here is a small stone-block structure erected at the end of the bridge in order to protect the water source. The material for the building was obtained locally, being cut from andesite, an igneous rock. The name above it—Yongquan Terrace (“Spring Terrace”)—was bestowed by then Taipei mayor Kozaburo Tabata when construction of the Caoshan Waterway System was completed in 1932.

When the locked doors to Yongquan Terrace are opened, inside we see the “Sapphire Spring,” also known as “Asia’s Number One Spring.” The abundantly flowing spring water has been filtered through many layers of rock in the volcanic Datun Mountain Range, which, as Chen Shengbin explains, makes it extremely pure. Light refracted off the mineral-rich “hypersthene hornblende andesite” rock wall gives the spring water a mysterious sapphire-blue luster.

The mineral content (hardness) of this water that has been filtered through andesite has been measured at about 150 parts per million (ppm), putting it somewhere between the 30‡40 ppm of ordinary tap water and the 500 ppm of mineral water. “We call that moderate hardness,” explains Chen.

The natural water of the Sapphire Spring can be consumed directly without processing. Hailed by the Japanese as “Asia’s Number One Spring” and “a water source bestowed by heaven,” the spring’s water is comparable to France’s Volvic mineral water, which is likewise filtered through volcanic rock. This easily accessible high-quality water is one of the highlights of our journey to the Caoshan Waterway System. 

(left) The sulfur-laden spring water that feeds the Huang River stains the rocks over which it passes a reddish-brown color.

(right) The natural spring water of the Sapphire Spring, known to the Japanese as “Asia’s Number One Spring” or “a water source bestowed by heaven,” is fit to drink untreated.