World Facts

The Longest Tunnels In The World

Stretching for 137,000 meters, the Delaware Aqueduct is the longest tunnel in the world.

Tunnels are underground passageways dug through an enclosed area like soil or rock. A tunnel may be used as a foot passage or for vehicles, trains, or as a canal. Some tunnels are used to supply water for consumption or hydro-power. Military forces may build tunnels underground to access the enemy’s territory while secret tunnels may also be built by civilians to smuggle goods. Special tunnels may also be built along the wildlife’s paths to facilitate the crossing of human-made barriers. The length of a tunnel is determined by its purpose and the nature of the enclosed area in which the tunnel is dug.

Delaware Aqueduct

Delaware Aqueduct is the newest aqueduct in the New York City. It takes water from Rondout Reservoir to the Hillview Reservoir. The construction of the aqueduct began in 1939 and was completed in 1945. It carries almost half of the New York's water supply every day. The tunnel is 85 miles long and has a width measuring 13.5 feet. It goes through the counties of Ulster, Orange, Dutchess, Putnam, and Westchester. The water tunnel leaks about 36 million gallons of water daily through the leaks. A $1 billion project was initiated in 2013 to repair the leaks. A 2.5 mile long bypass tunnel is also being constructed to address the leak problem. The Delaware Aqueduct is expected to be shut down to connect the bypass to the main aqueduct. Shutting it down will deprive the city nearly half of its water supply.

Päijänne Water Tunnel

Päijänne Water Tunnel is a 75-mile long water tunnel located in Southern Finland. It supplies water to thousands of households in the cities of Helsinki, Vantaa, and Kerava among others in southern Finland. The tunnel starts at Lake Päijänne, the second largest lake in Finland, and slopes downhill to allow water to flow naturally. The tunnel ends at Silvola reservoir in the Greater Helsinki Area. The water is then pumped into the water treatment plants. The building of the tunnel began in 1972 and was officially opened in 1982. The tunnel went through extensive renovation in 2008 with the southern part of the tunnel reinforced to avoid curve-ins.

Orange–Fish River Tunnel

Orange–Fish River Tunnel supplies water for irrigation and household use. It is located in central South Africa. The Eastern Cape Town experienced water shortage for a long time because of such little rain that fell in the area. The reduction of the water levels in the nearby dam only worsened the situation. The Orange–Fish Tunnel was constructed to restore the area and to make irrigation of the large farms possible. The main reason for its construction was to tap water from the Gariep Dam to Eastern Cape for household use and irrigation. The construction of the Orange–Fish River Tunnel began in 1966, and it was officially opened in 1975. When completed, the tunnel measured 51.4 miles in length. It has a diameter of 17.6 feet but ranges in depth between 262 feet and 1,247 feet. The tunnel can be sealed off completely using the four inlets to allow for de-watering for maintenance purposes. Regular maintenance is carried out on the tunnel to ensure it operates efficiently and also to control leaks

Which Are The Longest Tunnels In The World?

RankNameLocationLength (Miles) TypeYear
1Delaware Aqueduct New York state, United State85.1Water supply1945
2Päijänne Water Tunnel Southern Finland, Finland74.6 Water supply1982
3Dahuofang Water Tunnel Liaoning Province, China53.0Water supply2009
4Orange–Fish River Tunnel South Africa51.4Water supply1972
5Bolmen Water Tunnel Kronoberg/Scania, Sweden51.0Water supply1987
6Tunel Emisor Oriente Mexico City, Mexico38.8Waterwaste2006-2012
7Guangzhou Metro Line 3 Guangzhou, China37.5Metro2005-2010
8Gotthard Base Tunnel Central Swiss Alps, Switzerland35.5Railway Twin Tube2016
9Beijing Subway Line 10 Beijing, China35.5Metro2008-2012
10Seikan Tunnel Tsugaru Strait, Japan33.5Railway Single Tube1988

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