The 5 Longest Tunnels In The World

Many tunnels are feats of engineering and civil planning. They enable people to pass through otherwise impassable terrain. Vitally, they also make it possible to move water from areas where it naturally occurs to dry and otherwise thirsty cities. In fact, all the longest tunnels in the world are aqueducts.

1 - Delaware Aqueduct

License: Creative Commons

The Delaware aqueduct was built over a period of six years, between 1939 and 1945, and is still the longest tunnel in the world, at a length of 137 kilometres. It carries about half of New York’s water supply from the immense Rondout Reservoir (pictured above), carrying as much as 4.9 billion litres of water every day.
Unfortunately, the Delaware aqueduct also leaks anywhere between 40 million and 130 million litres of water every day. In an effort to curb losses, a $1 billion repair project was started in January 2013.

2- Päijänne Water Tunnel

Clocking in second at 120 kilometres in length is the Päijänne Water Tunnel, or “Päijännetunneli” as it is known in Finland. Running 100 metres under a surface of bedrock, it carries fresh water from Lake Päijänne, which is Finland’s second largest lake, to various cities in Southern Finland, such as Helsinki, Espoo, Vantaa and Sipoo.
An incredible feature of the tunnel is that it relies exclusively on gravity to carry the water. It naturally flows along a slightly sloped path.

3 - Dahuofang Water Tunnel

Completed in 2009, the Dahuofang Water Tunnel is in China’s Eastern Liaoning Province. This tunnel is 85.3 kilometres in length and carries water from high-altitude reservoirs to the heavily industrialized and dry area of Shenyang.
Immense tunnel boring machines (TBMs) with drill bits of 8 meters in diameter took four years to finish building the tunnel.

4 - Orange–Fish River Tunnel

Arriving at number 4 just below the Dahuofang Water Tunnel is the Orange-Fish River Tunnel in South Africa, which is 82.8 kilometres long. The immense tunnel diverts water underneath the Suurberg Mountain to the arid regions of the Great Fish River and the Eastern Cape.
Its inlet tower begins at Gariep Dam at Oviston, pictured above. Oviston is actually an acronym for the Afrikaans words Oranje-VISrivier TONnel. Travelling between 80 and 380 metres underground, the tunnel has a diameter of 5.3 meters.

5 - Bolmen Water Tunnel

Built over a 12-year period between 1975 and 1987, the Bolmen Water Tunnel comes in at number 5 at 82 kilometres in length. It carries water from the Bolmen Lake, pictured above, to the dry Scania province in Sweden. 700,000 people have fresh drinking water thanks to the Bolmen Water Tunnel. The planning and construction of the tunnel showed impressive foresight on the part of city planners, beginning as it did in the 1960s when the population of the province of Scania had just begun to burgeon.

    Author Bio:
    This post was provided courtesy of Jeff who is interested in all of the world’s most fascinating engineering marvels. He wrote this article on behalf of Hans von der Heyde – a South African engineering company providing industrial engineering solutions, machines and tools.
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