Holding on to the rains

A rainstorm caused chaos in Beijing on June 23 paralyzing the city’s traffic and turning the city’s underpasses into treacherous hazards for drivers.

In the wake of the torrential rains that have hit the city this summer the municipal authority indicated on July 18 that the drainage systems of all underpasses in Beijing will be improved and underground catchment facilities will be constructed to collect rainwater.

Water is an extremely precious resource for Beijing, and this is an applaudable change of mindset by the authorities who used to regard rainwater as wastewater destined for the sewers.

The population in Beijing reached 19.61 million this year, hitting the 18 million mark 10 years earlier than the development plan drawn up in 2005 predicted. The fresh water per capita in the city has now shrunk to 100 cubic meters, one-tenth the international standard, making it one of the thirstiest cities on earth.

Rainwater conservation has become a hot topic for cities around the world and the longest waiting list in New York is for rainwater barrels. The city handed out 1,000 free barrels to water-conscious residents in April.

In Tokyo the capacity of the drainage system can be adjusted to collect as much water as possible and the green areas of the city are designed nearly 1 meter lower than the surrounding asphalt and concrete surfaces in order to let rainwater recharge the city’s groundwater.

Singapore is another excellent example. Apart from importing fresh water from abroad, the city-state ensures an adequate water supply by collecting almost every drop of rainwater in catchments.

It took Paris one and a half centuries to complete the 2,400 kilometers of drainage tunnels and more than 6,000 underground reservoirs that serve the city’s needs today.

In contrast, the drainage system of central Beijing has only been tinkered with now and then when necessary since Ming Dynasty (1368-1644). Moreover, the city mainly relies on several small reservoirs in the mountainous areas to the north and its nearly depleted groundwater to satisfy its exploding demand for water.

Only one out of 49 underpasses in Beijing, Fuxingmen underpass, is equipped to collect rainwater. As for the will-be-built catchments, insightful and meticulous calculation is needed to match them with the existing drainage system and rainfall levels, because holding water is self-evidently more difficult than draining it.

Building more underpass water catchments will not only ease the city’s traffic nightmares during the rainy season but also enable this valuable natural resource to be used to quench the thirst of the water-guzzling metropolis.

It is a good beginning, but Beijing still has a long way to go to ensure it makes the most of its rainwater.

Source: China Daily

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