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A flood tunnel needs a destination for its water

The Metropolitan Outer Area Underground Discharge Channel takes overflow from smaller rivers and carries it toward the Edogawa River, with a pressure-adjusting tank and pumping facilities along the route. Following the water makes the imposing underground rooms part of a connected drainage system.

5–7 min

Questions you could explore

  • Why does a flood tunnel need a suitable destination as well as enough storage space?
  • How do pumps and river levels affect when stored floodwater can be discharged?

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Cities and transport

From raw water to the drinking-water tap

Clear river water is not automatically safe to drink. Many surface-water treatment plants use a sequence of coagulation, settling, filtration, and disinfection, with each stage tackling different hazards. The exact treatment depends on the source water and the contaminants the utility needs to remove.

4–5 min

From raw water to the drinking-water tap

Cities and transport4–5 minClear river water is not automatically safe to drink. Many surface-water treatment plants use a sequence of coagulation, settling, filtration, and disinfection, with each stage tackling different hazards. The exact treatment depends on the source water and the contaminants the utility needs to remove.

Cities and transport

How can three words identify a three-meter square?

A street address can identify a house but struggle with a park entrance or a remote rescue location. The what3words system assigns three-word addresses to a worldwide grid of three-meter squares; open alternatives such as Plus Codes encode locations with letters and numbers. Comparing the systems raises practical questions about reading a location aloud, confusing similar codes, and depending on a proprietary service.

3–5 min

How can three words identify a three-meter square?

Cities and transport3–5 minA street address can identify a house but struggle with a park entrance or a remote rescue location. The what3words system assigns three-word addresses to a worldwide grid of three-meter squares; open alternatives such as Plus Codes encode locations with letters and numbers. Comparing the systems raises practical questions about reading a location aloud, confusing similar codes, and depending on a proprietary service.

Cities and transport

How does a canal lock lift a boat without lifting machinery?

A boat inside a lock rises when the water around it rises. By filling or emptying the enclosed chamber, a conventional lock brings the boat to the level of the next stretch of canal. The gates contain the water; they do not hoist the boat.

3–5 min

How does a canal lock lift a boat without lifting machinery?

Cities and transport3–5 minA boat inside a lock rises when the water around it rises. By filling or emptying the enclosed chamber, a conventional lock brings the boat to the level of the next stretch of canal. The gates contain the water; they do not hoist the boat.

A flood tunnel needs a destination for its water | Speech Topic | speaking.app