1、T H EI M A G I N EI FW A T E RS E R I E SCircular Cities:A circular water economyfor cleaner, greener, healthier, more prosperous citiesB R I E F I N GP A P E R J U LY2 0 2 1Cover: Aleksandr Markin, Getty Images Inside: Getty ImagesContentsImagine if1 The challenges that cities face2 The design of c

2、ities is the issue3 The circular water economy within cities104 A portfolio of circular water solutions5 Getting started6 A circular water approach for cities: An evolution in thinkingAcknowledgementsEndnotesDisclaimerThis document is published by the World Economic Forum as a contribution to a proj

3、ect, insight area or interaction. The findings, interpretations and conclusions expressed herein are a result of a collaborative process facilitated and endorsed by the World Economic Forum but whose results do not necessarily represent the views of the World Economic Forum, nor the entirety of its

4、Members, Partners or other stakeholders. 2021 World Economic Forum. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, including photocopying and recording, or by any information storage and retrieval system.Circular Cities: A circular wate

5、r economy for cleaner, greener, healthier, more prosperous cities2July 2021Circular Cities:A circular water economy for cleaner, greener, healthier, more prosperous citiesThe Imagine IfWater SeriesThis is the first in a series of papers that highlight new ways of thinking about global water resource

6、s. This ImagineIf Water Series aims to inspire, provoke and invite new ideas. The worlds water resources are a system already pushed to the edge. At the same time, water is connected to a diverse set of burning economic, social and environmental issues. In todays context, where the world strives to

7、restart its engines while addressing multiple economic and social priorities, it is necessary to see wateras a catalyst and as a key to unlocking multiple wins spanning these pressing issues to achieve a more equitable and sustainable global economy.Circular Cities: A circular water economy for clea

8、ner, greener, healthier, more prosperous cities3Imagine ifImagine if cities of the future could enhance humanitys quality of life, becoming healthier places to live, more resilient to climate-related shocks, more sustainable, supporting vibrant hubs of economic activity, innovation and job opportuni

9、ties.Imagine if cities were recognized as global climate champions in the “race to net-zero” carbon economy. Circular cities, where the use and reuse of water and wastewater resources are optimized, can unlock the true value and potential of urban areas and propel the world towards achieving this vi

10、sion.1The challenges that cities faceUrban areas around the globe are becoming less liveable due to water stress, exacerbated by climate change. This needs to change right now.Over the next three decades, the worlds population living in urban areas is projected to swell to nearly7 billion people, wh

11、ich will be more than two thirds of all humanity. HYPERLINK l _bookmark0 1 Yet in this time cities will be less liveable due to climate change, unstable weather patterns and extreme meteorological events.Cities face a real challenge with increasing water stress, as some are already running out of wa

12、ter. In 2018, Cape Town was poised to become the first major global city to hit “Day Zero”, the day when the taps would be turned off due to drought, high demand and inadequate supply. The metropolis came close. It isnt alone Istanbul, Mexico City and Chennai have all faced water crises recently.One

13、 in four cities representing over $4 trillion in economic activity are already water stressed. HYPERLINK l _bookmark0 2 This is also true of 70% of the worlds megacities. HYPERLINK l _bookmark0 3 If the world continues with business as usual, HYPERLINK l _bookmark0 4 45 cities, each with over 3 mill

14、ion residents, will face extremely high-water stress by 2030; and by 2050, the number of urban dwellers facing acute water shortages could climb to over 1 billion. HYPERLINK l _bookmark0 5Water problems are not limited to droughts; the number of extreme rainfall events is also growing due to more en

15、ergy in the atmosphere. These produce intense precipitation, resulting in increased urban flooding. HYPERLINK l _bookmark0 6 Extensive cityscapes consisting of concrete, tarmac and buildings create higher flood flows within metropolitan areas. HYPERLINK l _bookmark0 7 In 2020, Jakarta saw the highes

16、t daily rainfall since records beganin 1866: floods killed 19 people and 62,000 people were evacuated. HYPERLINK l _bookmark0 8At the same time, cities are becoming hotter. Nine of the planets 10 warmest years have taken place since 2005, with the five warmest all occurring since 2015. HYPERLINK l _

17、bookmark0 9 By 2050, more than 970 cities will experience average summer temperature highs of 35C. Right now, only 354 cities are this hot. HYPERLINK l _bookmark0 10 By 2050, heat waves will affect more than 1.6 billion people in urban centres. HYPERLINK l _bookmark0 11 Towards the end of the centur

18、y, cities could warm by as much as 4.4C on average. HYPERLINK l _bookmark0 12 Builders predominantly construct citiesusing concrete, which traps this warmth and creates an urban heat island effect, increasing temperatures.Climate change is exacerbating these impacts, making them more frequent and in

19、tense. Adding to this, rapid urbanization is escalating demand for and pressure on city resources. Every month, 5 million people migrate to urban centres around the globe, much of this in the developing world. HYPERLINK l _bookmark0 13 This means increasing demand for water and energy, as well as mo

20、re human waste and water pollution.This puts increasing strain on wastewater treatment plants and utilities, and the riverine systems into which water is often discharged.Water pollution is making waterways sick and deteriorating the environment, potentially having adverse effects on human health. O

21、ver 80% of the worlds wastewater is still released into the environment without treatment: HYPERLINK l _bookmark0 14 roughly 30% inhigh-income countries; 62% in upper middle-income countries; 72% in lower middle-income nations; and a staggering 92% in low-income countries. HYPERLINK l _bookmark0 15T

22、his level of pressure on urban ecosystems is not sustainable.Circular Cities: A circular water economy for cleaner, greener, healthier, more prosperous cities5Over 80%of the worlds wastewater is still released into theenvironment without treatment92%in low-income countries72%in lower middle-income n

23、ationsIf the world continues with business as usual,45 citieswith over 3 million people each will face extremelyhigh-water stress by 203030%in high-income countries62%in upper middle-income countriesBy 2050, the number of urban dwellers facing acute water shortages could climb to over1 billionOne in

24、 four cities representing over$4 trillionin economic activity are already water stressedThis is also true of70%of the worlds megacitiesCircular Cities: A circular water economy for cleaner, greener, healthier, more prosperous cities62The design of cities is the issueWhen it comes to urban areas, wat

25、er is used in a linear way. It is captured, used and disposed of a system that must change rapidly in a climate-conscious world.In the 21st century, the design, development and building of cities is not fit for purpose. Grey infrastructure is predominantly used to capturerainfall and runoff to chann

26、el water from upstream dams, distant watersheds or groundwater extraction and pipe it into cities. It is then shifted out using drainage systems and channelled waterways built using concrete and human engineering.Therefore, most city water follows a linear path: cities capture it, use it and then di

27、spose of it, treated or untreated, into waterways that eventually flow into the ocean. This approach to water infrastructure in urban areas is not sustainable in the long-term because it does not value water asa finite resource that is unpredictable in its supply. Without changes in design, cities w

28、ill become less liveable in the second half of this century.By 2050, the world will add 1 million square kilometres of urban space, HYPERLINK l _bookmark0 16 stretching across tensof thousands of cities globally a surface area larger than Egypt. The current urban development model means this expansi

29、on is likely to be concrete and grey infrastructure.This business-as-usual approach has other consequences. Reducing heat in ever expanding concrete jungles is a challenge. Cooling as an industry consumes up to 30% of global electricity and generates 8% of greenhouse gas emissions worldwide. By 2030

30、, the number of air conditioners will increase by two-thirds from the 2 billion units currently installed. HYPERLINK l _bookmark0 17 Electricity demand for cooling in buildings could also rise by as much as 50% globally. HYPERLINK l _bookmark0 18 The strain on cities will be palpable.Hotter cities a

31、lso impact economic activity. The costs of lower labour productivity worldwide due to rising temperatures is expected to hit humanityhard, with an accumulated financial loss due to heat stress amounting to $2.4 trillion by 2030. HYPERLINK l _bookmark0 19Circular Cities: A circular water economy for

32、cleaner, greener, healthier, more prosperous cities73The circular water economy within citiesClosing the loop on water use will insulate cities from future climate-related shocks.In a post-COVID-19 world, it is necessary to redesign cities: building back better and greener should be the new imperati

33、ve. The worlds 50 largest economies have pledged $14.6 trillion to long-term recovery measures, with $341 billion earmarked for green initiatives. HYPERLINK l _bookmark1 20 At the same time, green finance is reaching new heights, with traded green bonds now valued at over $2.3 trillion. HYPERLINK l

34、_bookmark1 21Rethinking water infrastructure must be at the forefront of this agenda. It plays an incredibly vital role in creating a more sustainable cityscape. The quality and amount of water an urban area uses, reuses and exchanges with the wider watershed is intrinsically linked to the health of

35、 the local environment.Circular cities with water at the core where they manage water in cycles and maintain it at its highest possible intrinsic value within the urban environment should be a fundamental aim. This puts less stress on natural ecosystems. It also insulates cities from external enviro

36、nmental stresses. Cities need to adapt and become resilient to the impacts of climate change already manifesting themselves today and projected to become worse namely heatwaves, flooding, unpredictable rainfall and imminent Day Zeros.The main goal needs to be closing the loop on water use. Cities mu

37、st look to reuse all materials in water and water itself, minimizing wastefrom drinking, sanitation, irrigation, heating and cooling. In a circular city there is no such thing as wastewater. Each metropolis would tap this resource fully, as a rich source of energy andnutrients including carbon, nitr

38、ogen, phosphorus, heat, organic waste and biosolids as many are crucial to urban living.Managing water efficiently in cycles within an urban area will insulate a city from climate change, decoupling a citys economic growth from water use, allowing cities to grow significantly withoutconsuming more w

39、ater. By the middle of this century, the circular economy has the potential to reduce water consumption from primary resources by 53%. HYPERLINK l _bookmark1 22Cities would also benefit from using water to enhance natural capital throughout urban spaces. Ponds, bioswales, creeks and lakes, which als

40、o boost biodiversity, are more desirable places to live and work next to, enhancing the quality of life and mental well-being of city dwellers.Investments in better water management can drive operational savings. They are value-creating investments with short payback periods; they also have environm

41、ental benefits. This money could be used to reinvest in new water infrastructure that is more geared towards the circular economy.For instance, research on the opportunities associated with efficient wastewater management found that by deploying readily available technologies, $40 billion in savings

42、 could be made across the US, Europe and China, and that nearly 50% of electricity-related emissions from the global wastewater sector could also be abated. HYPERLINK l _bookmark1 23Cities with ambitions to become more circular could additionally unlock significant amounts of green and climate finan

43、ce to build new water infrastructure that is not an environmental, social and governance (ESG) risk, but an asset. This will also future-proof urban growth in a more sustainable world.Such water investments would also create jobs in a circular economy. The recycling industry employsmore than 1.5 mil

44、lion people worldwide. HYPERLINK l _bookmark1 24 New jobs will be in blue-green industries and reworking city water ecosystems. New job titles that will emerge include “green rooftop water manager”, “city wetland executive”, “urban cooling supervisor”, and “circular water director”.Cities cannot ach

45、ieve full-blown circularity overnight. It involves replumbing entire neighbourhoods and cities, even watersheds. But some urban areasare starting to make progress through their circular water initiatives. It will be vital to increasingly bring these together in one place: much greater value is gener

46、ated when one districts waste is anothers resource and vice versa.Circular Cities: A circular water economy for cleaner, greener, healthier, more prosperous cities8BOX 1Learning from Singapore and its circular water economySingapore, a city-state with no natural aquifers, is at the forefront of the

47、circular water economy. Reclaimed water satisfies 40% of current water demand. HYPERLINK l _bookmark1 25 Called NEWater, it is projected to expand to 55% by 2060. Public acceptanceof drinking recycled water is a challenge that the country has overcome through widespread education. It has even produc

48、ed a beer fromrecycled water. HYPERLINK l _bookmark1 26 Water reuse is one of the most important pillars for Singapore to provide safe and reliable water sources in the future. HYPERLINK l _bookmark1 27 The city collects stormwater in reservoirs within city boundaries; it is also rolling out 300,000

49、 smart water meters by 2023. HYPERLINK l _bookmark1 28 Singapore has become a global hydro-hub, pioneering new water technologies and jobs. HYPERLINK l _bookmark1 29Stormwater managementRainSeaTreatment of used water at 4 water reclamation plantsIndirect potable use5 NEWater factoriesDirectnon-potab

50、le use through 515-km transmissionCollection of rainfall in 17 reservoirs2 desalination plantsnetworkCollection of used water in 3,500 km of sewers and deep tunnel sewerage systemsIndustryAdapted from: Public Utilities Board, SingaporeTreatment of raw to potable water at 8 Public Utilities Board wat

51、er treatment plantsTransmission and distribution network (5,500 km)HouseholdsBOX 2The 50L Home CoalitionAs more cities face the risk and uncertainty of severefuture of water by reimagining city infrastructure water shortages and potential Day Zero scenarios,and changing the narrative on domestic wat

52、era group of private sector leaders has come togetherconsumption. As part of its efforts, The 50L Home with the 2030 Water Resources Group, WorldCoalition is generating new ideas and opportunities Business Council for Sustainable Developmentto accelerate innovations in homes and acrossand World Econ

53、omic Forum to form the 50L Homeurban infrastructure and ecosystems to enhance Coalition an initiative that aims to reinvent thewater circularity and water reuse.Circular Cities: A circular water economy for cleaner, greener, healthier, more prosperous cities94A portfolio of circular water solutionsM

54、any innovations already exist around the world. Cities must deploy these at scale and interconnect them to achieve a circular water economy.Water capture and storageSponge cities will act as a water buffer Shanghais mission to improve the citys resilience to climate change prompted the Chinese megac

55、ity to rewrite its urban-drainage strategy, putting nature- based solutions first. It has deployed sponge city districts, which store vast amounts of stormwater until needed. This type of blue-green infrastructure was tens of billions of US dollars cheaper than the grey solutions initially proposed.

56、 HYPERLINK l _bookmark1 30Cities must use captured rainwater for cooling Blue-green infrastructure can offset urban heat islands. For instance, Potsdamer Platz in Berlin,with its green roofs, buffer ponds and stormwater cisterns, reduces summer temperatures by 2C. HYPERLINK l _bookmark1 31 The evapo

57、transpiration of planted trees in Mexico City can reduce urban air temperatures by 1C. HYPERLINK l _bookmark1 32City water sources will save energy on cooling Toronto and Paris have deployed free cooling from urban water sources to cool buildings. Climespace takes 50% of its cooling needs from the R

58、iver Seine, meaning 35% less electricity, 50% less CO2 emissions and 65% less water consumption than traditional air conditioning. HYPERLINK l _bookmark1 33WastewaterWastewater use is key to circular city movementWastewater is the largest untapped city waste category as big as all solid waste types

59、combined. HYPERLINK l _bookmark1 34 It has up to 14 times more embedded chemical and thermal energy within it compared to tap water. HYPERLINK l _bookmark1 35 For a city of 4 million people, the value of the carbon, ammonia and phosphorus recovered from wastewater could be worth $300 million a year.

60、 HYPERLINK l _bookmark1 36 However, the adoption of circular water infrastructure requires up-front investments and legislation.Reward dry factories that are less water-intense The circular water economy is progressing well at city factories. There is a strong trend towards dry factories, where they