‘Sponge city’ is green, smart and will rule in fu­ture

China Daily (Canada) - - FRONT PAGE -

Wa­ter as a re­source is ir­re­place­able. Yet heavy rain­fall can be­come a dis­as­ter even in mod­ern cities if rain­wa­ter is not drained out in time. This was re­cently ev­i­dent in Shang­hai, Nan­jing and some other cities, es­pe­cially in south­ern China, where streets looked more like the canals of Venice.

The idea of “sponge city”, which emerged in theWest and is grad­u­ally gain­ing pop­u­lar­ity in China, will hope­fully solve this prob­lem. Fol­low­ing the phi­los­o­phy of “solv­ing a city’s prob­lems with its own re­sources”, it aims at stor­ing rain­wa­ter, es­pe­cially dur­ing heavy rain­fall, to pre­vent floods and re­lease it for the ben­e­fit of res­i­dents dur­ing dry times. This will also ease a city’s wa­ter short­age.

The wa­ter dis­tribu­tive sys­tem has three main parts. First, it en­cour­ages the cul­ti­va­tion of “wet­lands” and “mead­ows” in ur­ban gar­dens, which will help col­lect wa­ter in pools, en­able trees and plants to hold wa­ter, and re­plen­ish the un­der­ground wa­ter ta­ble. In case of wa­ter short­age, the wa­ter in the pools can be used di­rectly, while more plants mean higher hu­mid­ity and eva­po­ra­tion which will even­tu­ally lead to higher pre­cip­i­ta­tion lev­els.

Sec­ond, build­ings can col­lect rain­wa­ter, re­cy­cle it and save it in tanks or un­der­ground reser­voirs. Data show that if all the prom­i­nent build­ings in a city in­stall a sys­tem to re­cy­cle and save rain­fall, the rate of wa­ter flow­ing to the ground dur­ing heavy rain­fall and thun­der­storms could drop by 80 per­cent.

And third, a sponge com­mu­nity will com­bine pools, ur­ban “mead­ows” and “wet­lands”, and sponge build­ings within one whole sys­tem. This is a par­tic­u­larly ben­e­fi­cial idea for China which has a tra­di­tion of liv­ing with na­ture— gar­dens are con­sid­ered an in­dis­pens­able part of tra­di­tional Chi­nese ar­chi­tec­ture. Pools, open green spa­ces and trees are key el­e­ments of tra­di­tional Chi­nese com­pounds, all of which help save wa­ter.

Sponge cities save wa­ter and, there­fore, are more en­vi­ron­men­tally friendly. Some cities in for­eign coun­tries have not only adopted the idea of sponge gar­dens, but also built sponge squares. Un­likemet­aled squares that pre­vent wa­ter from re­plen­ish­ing the un­der­ground wa­ter ta­ble, these sponge squares have plants and well-de­signed pipe­lines that help store large vol­umes of wa­ter un­der the Earth’s sur­face. Chi­nese cities too can ben­e­fit by chang­ing its met­aled or tile-bed­ded squares to sponge squares.

Sponge cities will also re­duce pol­lu­tion. Stud­ies show that rain­wa­ter flow in the first 30 min­utes is ex­cep­tion­ally muddy be­cause it car­ries the dust from build­ings and roads. The mud, con­sid­ered a waste by hu­mans, is good nutri­tion for plants and mead­ows. Trees, plants and grass fil­ter ab­sorb the mud and thus fil­ter the wa­ter that flows to the un­der­ground wa­ter ta­ble. And good rain­fall helps cities save piped wa­ter that they use to clean the streets.

In more ways than one a sponge city will be a smart city. Ur­ban man­age­ment of­fi­cials can in­stall de­vices across a city to col­lect real data on rain­fall, ground and un­der­ground flow of wa­ter, and amount of pol­lu­tants, which they can use to deal with emer­gen­cies.

A sponge city fol­lows the phi­los­o­phy of in­no­va­tion: that a city can solve wa­ter prob­lems in­stead of cre­at­ing them. In the long run, sponge cities will re­duce car­bon emis­sion cities and help fight cli­mate change. The idea of green cities will rule in the fu­ture and sponge cities will be part of it. The au­thor is coun­selor of the State Coun­cil and for­mer vice-min­is­ter ofHous­ing and Ur­ban-Ru­ral De­vel­op­ment. This is an ex­cerpt from a speech he de­liv­ered at the re­cent In­ter­na­tional Low Car­bon City fo­rum in Shen­zhen, Guang­dong province.


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