‘ SPONGE CITIES’ AB­SORB UR­BAN FLOOD­ING WOES

Pi­lot projects re­tain, re­use rain­wa­ter

China Daily - - FRONT PAGE - By TAN YINGZI in Chongqing, XING YI in Shang­hai and ZHANG XIAOMIN

Flood­ing is one of the most se­ri­ous wa­ter- re­lated is­sues in Chi­nese cities due to rapid ur­ban­iza­tion, land- use changes and the dis­ap­pear­ance of nat­u­ral wet­lands.

To cope with such prob­lems, the na­tion turned five years ago to the con­cept of build­ing “sponge cities” on an un­prece­dented global scale.

In 2015, the State Coun­cil, China’s Cabi­net, launched the Sponge City pi­lot project, in which 30 me­trop­o­lises are tak­ing part.

The aim of the project is that by 2030, some 80 per­cent of ur­ban ar­eas should ab­sorb and re­use at least 70 per­cent of rain­wa­ter, ac­cord­ing to guide­lines is­sued by the State Coun­cil in Oc­to­ber 2015.

Qu Ji­uhui, an aca­demi­cian at the Chi­nese Academy of En­gi­neer­ing, said the con­cept of a sponge city is the Chi­nese ver­sion of low- im­pact de­vel­op­ment, which is com­mon in North Amer­ica.

“It refers to the man­age­ment of rain­wa­ter runoff so that this wa­ter can be stored, used and chan­neled like a sponge,” Qu said.

“It can solve the prob­lem of too much rain­wa­ter flow­ing into the drainage sys­tem, and through eco­engi­neer­ing, plants can also ab­sorb pol­lu­tants and pu­rify the wa­ter, as in na­ture.”

Eco- en­gi­neer­ing refers to the ap­pli­ca­tion of eco­log­i­cal prin­ci­ples to shape and man­age the en­vi­ron­ment, in tan­dem with the de­sign and use of tech­nol­ogy that min­i­mizes dam­age to the en­vi­ron­ment, or which ac­tively helps to pro­tect or sus­tain it.

A multi- lay­ered ar­ray of ar­ti­fi­cial holes and pores at the en­trance to the Shang­hai Lin­gang Sponge City Ex­hi­bi­tion Cen­ter show­cases the sponge city con­cept.

Sit­ting be­side the Dishuihu, a 5.6- squarek­ilo­me­ter ar­ti­fi­cial lake, the cen­ter’s role is to ex­plain the com­pli­cated con­cept of eco­engi­neer­ing and ur­ban plan­ning to deal with flood­ing in big cities.

Lin­gang New City, lo­cated on the coast in Shang­hai and which cov­ers about 100 sq km, was se­lected as a pi­lot sponge city by the cen­tral gov­ern­ment in 2016. Among the 30 pi­lot cities na­tion­wide, it is the largest.

The ex­hi­bi­tion cen­ter, which was un­veiled last year, has set out to demon­strate how the sponge city con­cept has been trans­lated into tan­gi­ble in­fra­struc­ture in the new city.

In the past three years, grass ditches, wa­ter- ab­sorbent side­walks, gar­den rooftops and ar­ti­fi­cial wet­lands and wa­ter pools have been cre­ated to store rain­wa­ter.

Some 36 km of roads have been ren­o­vated and con­crete side­walks re­placed with wa­ter- ab­sorbent bricks to re­duce wa­ter­pool­ing dur­ing heavy rain­fall. In­stead of go­ing di­rectly to drainage, the bulk of the rain­wa­ter is ab­sorbed by the soil in grass ditches along­side the roads.

Retrofits have been com­pleted in Lin­gang at 26 res­i­den­tial neigh­bor­hoods cov­er­ing 200 hectares. This work in­cluded plac­ing small wa­ter stor­age units un­der the earth, adding small stretches of grass in park­ing lots, and build­ing un­der­ground wa­ter pools in ex­ist­ing gar­dens.

The con­struc­tion stan­dards used were writ­ten into the reg­u­la­tions be­ing ap­plied to real es­tate de­vel­op­ment in the city’s new neigh­bor­hoods.

Yu Xiang, di­rec­tor of the cen­ter, said lo­cal peo­ple had asked why holes had been dug in their neigh­bor­hoods and whether the sponge city was ef­fec­tive.

“Since the sponge city was con­structed in Lin­gang, the flood­ing i ssue has been ad­dressed sig­nif­i­cantly, the en­vi­ron­ment has been im­proved and these ques­tions are no longer be­ing asked,” she said.

Parks and univer­si­ties are also im­por­tant parts of the pi­lot pro­gram.

Luchao­gang Park, a sponge park, opened to the pub­lic in Lin­gang in Septem­ber last year. The site’s orig­i­nal ponds were re­tained, with rain­wa­ter chan­neled to them for stor­age.

The cam­puses at higher ed­u­ca­tion in­sti­tu­tions in Lin­gang, in­clud­ing Shang­hai Ocean Uni­ver­sity and Shang­hai Dianji Uni­ver­sity, have been ren­o­vated.

Other Shang­hai dis­tricts are also us­ing the sponge city con­cept to be­gin in­fras­truc­tural im­prove­ment work.

In July, Shang­hai Hongqiao Cen­tral Business Dis­trict, which in­cludes Hongqiao In­ter­na­tional Air­port and Hongqiao Rail­way Sta­tion, an­nounced its sponge city plan for 2020 to 2035.

The aim is to en­sure the dis­trict’s roads are free from flood­ing — even in the event of rain­fall on a scale seen only once ev­ery 100 years. Wa­ter qual­ity in rivers will be im­proved and the ur­ban heat- is­land ef­fect re­duced.

Duan Jin, an aca­demi­cian at the Chi­nese Academy of Sciences who took part in draw­ing up the mas­ter plan for the core area of the Yangtze River Delta demon­stra­tion zone, said the sponge city con­cept would be im­ple­mented in the zone.

Cov­er­ing 2,300 sq km on the lower reaches of the Yangtze, the zone is a pi­lot green de­vel­op­ment and re­gional in­te­gra­tion project for parts of Shang­hai and neigh­bor­ing Jiangsu and Zhe­jiang prov­inces.

“The area has a large and in­tri­cate net­work of wa­ter­ways, so build­ing sponge cities is a ba­sic re­quire­ment to avoid ur­ban flood­ing,” Duan said.

Chongqing de­vel­ops

Mean­while, the south­west­ern metropo­lis of Chongqing has wit­nessed rapid de­vel­op­ment in sponge city con­struc­tion and is look­ing for ways to solve wa­ter prob­lems in ur­ban ar­eas of West China.

By the end of last year, a sponge city cov­er­ing just over 42 sq km had been built in the Liangjiang New Area, Wanzhou and Bis­han dis­tricts and Xiushan county, ac­cord­ing to the mu­nic­i­pal Com­mis­sion of Hous­ing and Ru­ral and Ur­ban Con­struc­tion.

In com­ing years, all con­struc­tion in Chongqing’s main ur­ban ar­eas must meet sponge city stan­dards, ac­cord­ing to the lo­cal au­thor­i­ties.

Jin Jun­wei, deputy head of the Chongqing Sponge En­gi­neer­ing and Tech­nol­ogy Cen­ter, said that in re­cent years con­cerns have arisen in many Chi­nese cities over wa­ter pol­lu­tion, wa­ter short­ages and flood­ing.

“The con­cept of a sponge city is a Chi­nese adap­ta­tion of in­ter­na­tional wa­ter man­age­ment tech­niques. The goal is to man­age flood risks, treat the wa­ter and con­trol the use of re­sources while cre­at­ing a pleas­ant liv­ing en­vi­ron­ment,” he said.

Chongqing has an­nual rain­fall of more than 1 meter, the bulk of which falls in sum­mer and au­tumn. Due to its com­plex land­scape, the city faces chal­leng­ing is­sues such as flood con­trol and drainage.

The qual­ity of wa­ter flow­ing through Chongqing, which is sit­u­ated on the up­per reaches of the Yangtze, is not only im­por­tant to the city it­self, but also to many other parts of the coun­try.

The Yangtze, the world’s third- long­est river, flows 6,300 kilo­me­ters from the glaciers of the Qing­hai- Ti­bet Plateau east through Chongqing, Wuhan, cap­i­tal of Hubei prov­ince, and Nan­jing, cap­i­tal of Jiangsu, be­fore reach­ing the East China Sea in Shang­hai.

More than 400 mil­lion peo­ple get their drink­ing wa­ter from the river, and wa­ter se­cu­rity has be­come a ma­jor na­tional de­vel­op­ment is­sue.

Sit­u­ated in Chongqing Liang jiang New Area, Yue­lai New City, which cov­ers 18.67 sq km, was one of 16 sponge cities on a na­tional pi­lot list of cli­mate- re­silient ur­ban de­signs re­leased in 2016.

The city has es­tab­lished a model sponge sys­tem in moun­tain­ous ar­eas through a num­ber of demon­stra­tion ven­tures. These in­clude the Yue­lai In­ter­na­tional Expo Cen­ter Sponge Re­con­struc­tion Project and the Yue­lai Con­ven­tion Cen­ter Park Re­con­struc­tion Project, which have sig­nif­i­cantly re­duced the amount of pol­lu­tants dis­charged into the Yangtze.

Yang Ping, deputy gen­eral man­ager of Chongqing Yue­lai In­vest­ment Group, said: “Dur­ing heavy rain­fall, the wa­ter is ab­sorbed by por­ous bricks and by plants to pre­vent flood­ing. We col­lect and store most of it, then use the wa­ter for ir­ri­ga­tion or clean­ing.

“The roof of a huge ex­hi­bi­tion hall fea­tures a spe­cial rain­wa­ter col­lec­tion path. Be­fore the wa­ter flows into a pipe, we use a spe­cial de­vice to pu­rify it for the first time be­fore di­rectly dis­charg­ing it into wet­land through the pipe,” he added.

Sur­plus wa­ter is pu­ri­fied again and dis­charged into six reser­voirs. Yang added that the com­pany has been able to save 600,000 yuan ($ 89,105) in wa­ter charges ev­ery year.

Chongqing is also the first of China’s 30 sponge cities to have a smart stormwa­ter con­trol sys­tem.

This dig­i­tal ur­ban drainage sys­tem has been de­vel­oped by Suez, one of the world’s lead­ing wa­ter and waste man­age­ment com­pa­nies. It is used to mon­i­tor, an­a­lyze and pre­dict the op­er­at­ing sta­tus of rain­wa­ter drainage, ur­ban flood­ing risks, eco­log­i­cal ef­fects and meth­ods to re­use rain­wa­ter. The sys­tem also cal­cu­lates and re­ports on how a sponge city per­forms against a set of key in­di­ca­tors.

Ac­cord­ing to Suez, by con­sol­i­dat­ing and an­a­lyz­ing this data, the soft­ware will pro­tect against the risk of flood­ing and also limit pol­lu­tion on the Yangtze.

In Jan­uary 2018, the first phase of the Yue­lai Sponge City Mon­i­tor­ing and In­for­ma­tion Plat­form project was com­pleted and started tri­als. It will be ex­tended to other parts of the Liangjiang New Area.

Dalian ben­e­fits

In 2016, ap­proval was given for Zhuanghe, a county- level city in Dalian, Liaon­ing prov­ince, to be in­cluded in the sec­ond group of pi­lot cities re­ceiv­ing cen­tral gov­ern­ment fi­nanc­ing for sponge city con­struc­tion.

Cov­er­ing 21.8 sq km, the Zhuanghe pi­lot area lies in the south of the city on the lower reaches of a three- river es­tu­ary.

Zhu Qinghui, di­rec­tor of the Zhuanghe Sponge City Con­struc­tion Of­fice, said 143 demon­stra­tion projects in­volv­ing in­vest­ment of about 3.35 bil­lion yuan have been com­pleted in pi­lot ar­eas.

“The con­struc­tion of a sponge city has brought real ben­e­fits, with the rivers be­com­ing cleaner and the en­vi­ron­ment im­prov­ing,” Zhu said.

In 2018, nearly 1,000 relict gulls, a rare and lit­tle- known species, were at­tracted to and spent the win­ter in Zhuanghe for the first time.

Zhu said that in sum­mer last year, the pop­u­la­tion of black- faced spoon­bills, one of the world’s most en­dan­gered species, reached a record 165 in Zhuanghe.

In late Au­gust, un­der the in­flu­ence of Typhoon Bavi, the eighth of the year, rain­fall in Zhuanghe reached 131 mil­lime­ters in a sin­gle day. How­ever, there were hardly any prob­lems, such as flood­ing, in the sponge city con­struc­tion area.

“The source emis­sion re­duc­tion sys­tem, the pipe net­work ter­mi­nal reg­u­la­tory and stor­age sys­tem, as well as the large drainage sys­tem play vi­tal roles,” Zhu said.

In con­struct­ing a sponge city, Zhuanghe, a typ­i­cal county- level city in North­east China, faced dif­fi­cul­ties such as weak man­age­ment and a short­age of cap­i­tal and hu­man re­sources.

As a re­sult, Zhu said a long- term sponge city man­age­ment and con­trol mech­a­nism was set up, in­no­va­tive op­er­a­tion teams in­tro­duced, along with new man­age­ment and con­trol meth­ods. Con­struc­tion was also ac­cel­er­ated.

Zhuanghe learned from the first group of sponge city pi­lot projects how to set up new sys­tems, bid for projects, and con­struct and de­sign in­fra­struc­ture, thus avoid­ing many prob­lems, Zhu added.

The city also launched an in­no­va­tive sponge city plan­ning sys­tem, top- level de­sign frame­work and put for­ward the con­cept of build­ing an “en­ergy- sav­ing sponge city”, which has been widely pro­moted among small and medium- sized cities in North­east China and those in coastal ar­eas.

See­ing the huge po­ten­tial of the Chi­nese mar­ket as more ar­eas be­gan con­struct­ing sponge cities, Ja­panese en­trepreneur Daisuke Itazawa in­tro­duced tech­nol­ogy from his coun­try to man­u­fac­ture wa­ter- re­tain­ing bricks in China.

In 2017, Itazawa took part in set­ting up a joint ven­ture in Dalian.

Pres­i­dent of the Dalian Deta- Shinwa En­vi­ron­men­tal Sci­ence and Tech­nol­ogy De­vel­op­ment Co, lo­cated in the Dalian sec­tion of the China ( Liaon­ing) Pi­lot Free Trade Zone, Itazawa said that in many parts of China there is a short­age of wa­ter re­sources and that con­trol and drainage prob­lems per­sist dur­ing the flood sea­son.

Bricks that re­tain and fil­ter rain­wa­ter have been par­tic­u­larly ef­fec­tive in re­solv­ing such is­sues, he said.

Itazawa added that such bricks pro­duced by his com­pany for use on roads have been a highly pop­u­lar el­e­ment of sponge city con­struc­tion.

He said this con­struc­tion should in­volve long- term prepa­ra­tion and tech­ni­cal re­sources, adding that as it took Ja­pan 50 years to con­trol its wa­ter sys­tem, this il­lus­trates just how hard and long- term such work is.

YUAN JINGZHI / FOR CHINA DAILY

A bird’s- eye view of a small park in Bis­han dis­trict, Chongqing, which has ben­e­fited from the sponge city project. A Tian­jin res­i­dent pours wa­ter ab­sorbed by a road as part of sponge city con­struc­tion. A sponge city con­struc­tion site in Xi’an, Shaanxi prov­ince.

DAILY CHEN XIAODONG / FOR CHINA ZHANG HU / FOR CHINA DAILY

Top: Work­ers build a drainage net­work in Zhangji­akou, He­bei prov­ince. Above: A worker shows how a newly built track ab­sorbs wa­ter in Qian’an, He­bei prov­ince.

PENG ZHAOZHI / XINHUA

Fre­quent flood­ing is no longer a prob­lem in this area of Pingx­i­ang, Jiangxi prov­ince, af­ter com­ple­tion of sponge city con­struc­tion.

LIU CHAN / XINHUA HU LINGYUN / FOR CHINA DAILY

Top: Above left: Above right:

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