That water needs to be collected, as a drier-than-expected rainy season could lead to a drought. At least 750 private and public buildings in Tokyo have rainwater collection and utilisation systems.

Home to more than 30 million people, Tokyo has a water system that depends 70% on surface water (rivers, lakes, and melted snow).

Recent investment in the pipeline infrastructure aims also to reduce waste by leakage to only 3% in the near future.

11. Miami

The US state of Florida is among the five US states most hit by rain every year. However, there is a crisis brewing in its most famous city, Miami.

An early 20th Century project to drain nearby swamps had an unforeseen result; water from the Atlantic Ocean contaminated the Biscayne Aquifer, the city's main source of fresh water.

Although the problem was detected in the 1930s, seawater still leaks in, especially because the American city has experienced faster rates of sea level rise, with water breaching underground defence barriers installed in recent decades.