Tokyo pushes water down 'Pantheon Power on the ground', lake glides in the river

Tokyo has 107 large and small rivers, with a total length of 858km. In the snowy season, the water flow of these rivers rises, pouring into Tokyo Bay. If accompanied by typhoons causing heavy rain, Tokyo will be heavily flooded.

"Power Pantheon" underground

Huge storage tank of G-Can project - (Photo: insidejapan).

For generations, the three rivers Tone, Are and Edo have always been the terror of the people of Tokyo every time the rainy season comes. This area is called the Nakagawa Delta , which lies below the water level of the Endo River and many other small rivers.

The area is known as Japan's floodplain because it is frequently affected by the amount of water melted by snow in other places as well as heavy rains of hurricanes.

Since 1960, Tokyo began to expand in this direction and by the 1980s, the entire agricultural area here was replaced by permanent houses, industrial plants, creating a fever of land. But authorities did not pay much attention to flooding here.

In 1991, Typhoon Mireilles was the strongest in 30 years, leaving 52,000 households in an area of ​​100km ² in the area. 52 people were killed.

In 1993, the Japanese Government decided to build a suburban urban drainage canal , also known as G project . It took 13 years for Japan to complete this project with a budget of 3 billion USD. Now, many people around the world call this "Pantheon Electric underground" due to the pillar system that makes the building look like a giant temple.

This system consists of 5 cylinders, each 75m high, 32m in diameter - just the size to accommodate a spacecraft, buried underground and connected by a 6.3 km long pipeline, diameter 10m, located deep below the ground 50m.

Part of the 75x32m container cylinder of G-Can project - (Photo: insidejapan).

The pipeline carries water to a giant 25m, 177m long, 78m wide tank - wider than a football field. The ceiling of the tank is supported by 59 concrete columns, each weighs 500 tons.

Every time there is heavy rain or hurricanes, the canal system leads into 5 pillars. From here the water is brought into a giant tank. When the tank was full, four engines of the Boeing 737 were used to push the water to the Endo River, in a flood-free location, to Tokyo Bay. The capacity of four pumps is 200m ³ / second, which drains an Olympic standard pool within about 10 seconds.

In 2008, the area suffered a very heavy rain and Project G worked well, successfully pumping 12 million cubic meters of water to the Endo River, avoiding flooding in the area.

Takashi Komiyama, the head of the pump station at the giant tank, said that since putting it into use, Project G has been used 70 times in total, reducing the number of houses and acreage by two thirds. flooding.

In addition to the period of anti-flood operation, during a break , "Pantheon Power underground" becomes a tourist sightseeing address. Of course tourists can only go to certain places. Each week, there are only 9 tours, each tour has 25 guests so they want to have a place, they have to book more than 1 month.

Construction of reservoirs regulating underground rivers

In addition to "Pantheon Power" , Japanese people still have many other underground works to combat flooding. In 2016, the reservoir regulating the Furukawa River was completed. The lake is 3.3 km long with a diameter of 7.5 m, containing 135,000 m ^{3 of} water.

This 3.3km long reservoir is located underneath the Furukawa River and curves in the shape of the river.

G-Can project diagram - (Graphic: Viet Thai).

When the Furukawa River overflows due to heavy rain, the water will follow the discharge road, flowing in a vertical pipe 52m high into the ground, going into the reservoir. When the rain rains, the amount of water in the Furukawa River decreases, the water in the reservoir is pumped back into the river, downstream down 2 km away.

The project was started in 2008 after a series of storms and hurricanes in 2004 flooded Azabu Juban subway station, prompting people to ask the government to take measures to cope with this situation.

The underground regulating reservoir at the Furukawa River is not the first of its kind in Japan. Previously in 2008, after 11 years of construction, Kandagawa underground storage facility was completed.

Even this reservoir is larger than Furukawa, 4.5km long, 12.5m in diameter, used to store water from the Kandagawa, Zenpukujigawa and Myoshojigawa rivers. Maximum capacity of 540,000m3 of the lake is 100% used when the area is stormed in September 2013 and used 5 times in 2013.

By the end of 2013, in Japan 11 underground regulating reservoirs were completed, with a capacity of 2 million m3. In addition, Japan is also building five underground regulating reservoirs in five other rivers. At the same time, plans to build a pipeline connecting the underground regulating reservoir of the Kandagawa River with the Shirakogawa River are also being carried out.