|Title||In Hong Kong, too much water — and too little — leads to creative solutions|
|Date||2018-01-23 PM 5:41:32||Hit||242|
When it comes to water, Hong Kong is in a paradoxical situation.
This city of more than 7 million people has few reliable sources of drinking water. There¡¯s no major river or natural lake to draw from. Groundwater is scarce and difficult to reach. And the city¡¯s hilly terrain makes it difficult to create reservoirs. Under such a crunch, Hong Kong depends heavily on water imports from China¡¯s Guangdong province.
On the other hand, Hong Kong is one of the wettest cities in Asia. The city regularly sees tropical storms drop heavy rains. The runoff rushes down from the mountains into the city¡¯s dense urban core, causing frequent flooding and waterlogging in low-lying areas where land has been reclaimed from the sea.
Instead of flushing its scarce freshwater supplies down toilets, Hong Kong uses seawater. The water is pumped from 42 treatment plants on the coast through a massive network of pipes carrying water into businesses and residences just for toilet flushing. Using seawater for this purpose reduces the city¡¯s freshwater consumption by 20 per cent.
This system got started in 1957, as Hong Kong¡¯s growing population began straining its water supply, and riots over water access became common. The experiment was seen as a success and inspired city planners to expand the concept to other districts.
Hong Kong¡¯s other problem — heavy rains — has pointed the city to a different set of water solutions. And the best place to find them the Happy Valley Recreation Ground£¬it has 11 fields£¬Just below the fields is a massive underground storage tank. During heavy rains, the tank fills with runoff flowing down from the mountains, and temporarily holds it there to prevent it from inundating the city below. The tank can hold 60,000 cubic metres of water, or roughly the equivalent of 24 Olympic-sized swimming pools.
¡°Sponge cities¡± refers to a range of strategies for controlling flooding in urban areas. Some allow for more rain to soak into the ground, through rain gardens or permeable pavements. Others, like Happy Valley, are more engineered solutions.
The water storage scheme cost HKD 1.7 billion (USD 218 million) to build and was completed in March of this year. It¡¯s not the first such system in Hong Kong. The first one, built in 2004 beneath a football and rugby ground, holds almost twice as much water. But the Happy Valley water storage is more advanced technologically.
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