High Island Reservoir
Interesting facts
- The eruption that created the columns released an estimated 1,300 cubic kilometres of volcanic ash, ranking the ancient volcano as a supervolcano.
- The rim of its buried caldera, about 18 kilometres across, runs over High Island and extends beneath Kowloon and Hong Kong Island.
- More than 200,000 rock columns are exposed across roughly 100 square kilometres of Sai Kung's coastline and islands.
- Most columnar formations worldwide are dark basalt, but these columns are light-coloured rhyolite containing around 76 percent silica.
- The columns average about 1.2 metres in diameter, and the largest, in the nearby Ninepin Group, reach around 3 metres.
- The welded ash sheet that cracked into columns reaches up to about 400 metres in thickness inside the old caldera.
- The reservoir began holding water in 1978, a year before the wider High Island Water Scheme was completed.
- An Italian contractor built the scheme at a cost of more than 400 million Hong Kong dollars, using grouting techniques advanced for the time.
- About 8 kilometres of aqueducts were built to gather water from streams across Sai Kung and feed it into the reservoir.
Why it is worth it
At the eastern end of Hong Kong's Sai Kung Peninsula, where the reservoir's East Dam meets the open South China Sea, the shoreline is built of stone columns: tightly packed, mostly six-sided pillars of volcanic rock, grey and pinkish in tone, standing in ranks along the coast and rising out of the water. They are the most accessible part of the Hong Kong UNESCO Global Geopark, and among the most striking displays of columnar jointing anywhere in the world.
The columns record a violent episode about 140 million years ago, when a huge volcanic eruption in this area buried the landscape under thick deposits of hot ash. As that layer of welded tuff slowly cooled and contracted, it cracked into a regular honeycomb of polygonal prisms, much as drying mud splits into cells. The columns here are unusually large for acidic volcanic rock, typically more than a metre across, and in places the sequence is over a hundred metres thick. Near the dam some columns are bent into S-shaped curves, a sign that the rock was still deforming under its own weight before it fully set, and the sea has cut caves and arches into the cliffs. Offshore, Po Pin Chau, a sheer sea stack, shows the same structure in cross-section. The geopark that protects the site was inaugurated in 2009 and joined UNESCO's Global Geoparks Network in 2011.
The reservoir itself is a feat of engineering. After mainland China cut off water supplies during the unrest of 1967, the Hong Kong government responded by damming the Kwun Mun Channel, the sea strait that once separated High Island from the peninsula. Designed by Binnie & Partners and built between 1969 and 1979, the scheme used two main dams, three smaller ones and aqueducts collecting stream water from across Sai Kung; with a capacity of about 281 million cubic metres it is still Hong Kong's largest reservoir by volume. A memorial beside the East Dam honours five workers who died during construction.
Getting there
The East Dam lies in Sai Kung East Country Park, about 8 km east of Sai Kung Town, which is the usual starting point; the reservoir is reached by the road built across its dams. Hong Kong International Airport (HKG) is about 46 km away in a straight line.
Plan your visit
We have no confirmed visit data yet. Once it is confirmed, this block also carries the date it was checked.
Nearby places
- Bank of China Tower 22.2 km · skyscraper
- Peak Tram 23.2 km · funicular
- Victoria Peak 24.0 km · scenic-viewpoint
On these lists
From the encyclopaedia
The High Island Reservoir is the largest impounding reservoir by capacity in Hong Kong. Located in the far south eastern part of the Sai Kung Peninsula, it was opened in 1978, helping to alleviate water shortage problems in Hong Kong. Its water capacity is approximately 281 million cubic metres. The area it occupies was originally the Kwun Mun Channel (官門海峽), which separated High Island from the Sai Kung Peninsula.
Wikipedia · CC BY-SA 4.0
22.37530, 114.35100per Wikidata