The Päijänne Water Tunnel (, ) is a water tunnel located in Southern Finland. At , it is the second-longest

tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...

in the world, running at a depth of in the

bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...

. The purpose of the tunnel is to provide

fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salt (chemistry), salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include ...

for the over one million people of the

Greater Helsinki Helsinki metropolitan area (, ) or Greater Helsinki (, ) is the metropolitan area around Helsinki, the capital city of Finland. It also includes the smaller Helsinki capital region, capital region. The terms Helsinki metropolitan area, Greater H ...

area, including the cities of

Helsinki Helsinki () is the Capital city, capital and most populous List of cities and towns in Finland, city in Finland. It is on the shore of the Gulf of Finland and is the seat of southern Finland's Uusimaa region. About people live in the municipali ...

Espoo Espoo (, ; ) is a city in Finland. It is located to the west of the capital, Helsinki, in southern Uusimaa. The population is approximately . It is the most populous Municipalities of Finland, municipality in Finland. Espoo is part of the Helsi ...

Vantaa Vantaa (; , ) is a city in Finland. It is located to the north of the capital, Helsinki, in southern Uusimaa. The population of Vantaa is approximately . It is the most populous municipality in Finland. Vantaa is part of the Helsinki Metropoli ...

Hyvinkää Hyvinkää (; , ) is a town in Finland, located in the southern interior of the country. Hyvinkää is situated in the northern part of the Uusimaa region. The population of Hyvinkää is approximately . It is the most populous municipality in ...

, Järvenpää,

Kerava Kerava (; ) is a town in Finland, located in the southern interior of the country. Kerava is situated in the centre of the Uusimaa region. The population of Kerava is approximately . It is the most populous Municipalities of Finland, municipality ...

Kauniainen Kauniainen (; ) is a town in Finland, located in the southern interior of the country. Kauniainen is situated in the southern part of the Uusimaa region, and it is Enclave and exclave, enclaved by the City of Espoo. The population of Kauniainen ...

Kirkkonummi Kirkkonummi (; , , Sweden ) is a municipality in Finland, located in the southern coast of the country. Kirkkonummi is situated in the western part of the Uusimaa region. The population of Kirkkonummi is approximately . It is the most populous Mu ...

Sipoo Sipoo (; ) is a municipality of Finland. It is part of the Helsinki metropolitan area. The municipality has a population of () and covers an area of of which is water. The population density is . The administrative center of the municipality i ...

and

Tuusula Tuusula (; ) is a municipality in Finland, located in the southern interior of the country. Tuusula is situated in the centre of the Uusimaa region. The population of Tuusula is approximately . It is the most populous Municipalities of Finland, ...

. The former Porvoo Rural Municipality, now merged with the municipality of

Porvoo Porvoo (; ; ) is a city in Finland. It is located on the south coast of the country, on the Gulf of Finland. Porvoo lies in the eastern part of the Uusimaa region. The population of Porvoo is approximately , while the Porvoo sub-region, sub-re ...

, also took part in the building of the scheme but has never drawn water from it for domestic use. The tunnel starts at Asikkalanselkä in Lake Päijänne, the second-largest lake in Finland with an area of . From there, the tunnel slopes slightly downhill allowing water to flow naturally with gravity. Water from the southern portion of Lake Päijänne is of good quality at the tunnel intake, and usually drinkable without processing. The tunnel ends at the Silvola

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

in Vantaa. From the reservoir, water is pumped to water treatment plants in Pitkäkoski and Vanhakaupunki. The construction of the tunnel started in 1972 and was completed in 1982, at a cost of approximately €200 million (adjusted for inflation). In 1999 and 2001, portions of the tunnel required repair due to rock falls. In 2008, the tunnel underwent an extensive renovation. The southern part of the tunnel was reinforced in order to prevent cave-ins. During the renovation, the Vantaa River was used as an alternative water supply for the Greater Helsinki area. The tunnel has a cross section of , wide enough for a truck to pass through, enabling a water flow of per second. It takes approximately nine days for the water to traverse the length of the tunnel. At current water usage rates, treatment plants take water at a rate of about per second for drinking water processing. __NOTOC__

Gallery

Image:Päijänne.png, Location of Lake Päijänne in

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

. image:Aurinkovuori15112014.JPG, Asikkalanselkä in Lake Päijänne, where the tunnel starts. Image:Silvolan tekojärvi 1.jpg, Silvola reservoir, where the tunnel ends. Image:Silvolan tekojärvi.jpg, Aerial view of Silvola reservoir.

References

External links

Finnish Tunnelling Association, Päijänne Water TunnelPääkaupunkiseudun Vesi Oy
{{DEFAULTSORT:Paijanne Water Tunnel Water tunnels Water supply and sanitation in Finland Tunnels in Finland Tunnels completed in 1982 Lake Päijänne 1982 establishments in Finland

Gallery

See also

References

External links