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Article
Sponge City Construction in China: A Survey of the
Challenges and Opportunities
Hui Li 1,2, Liuqian Ding 1,2, Minglei Ren 1,2 ID , Changzhi Li 1,2 and Hong Wang 1,2, *
1State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water
Resources and Hydropower Research, Beijing 100038, China; lihui@wihr.com (H.L.);
dinglq@iwhr.com (L.D.); mingleiren@163.com (M.R.); lichangzhi@iwhr.com (C.L.)
2Research Center on Flood and Drought Disaster Reduction of the Ministry of Water Resources,
Beijing 100038, China
*Correspondence: wanghong@iwhr.com; Tel.: +86-10-6878-1593
Received: 15 June 2017; Accepted: 7 August 2017; Published: 28 August 2017
Abstract:
Rapid urbanization in China has caused severe water and environmental problems in recent
years. To resolve the issues, the Chinese government launched a sponge city construction program
in 2015. While the sponge city construction initiative is drawing attention and is spreading fast
nationwide, some challenges and risks remain. This study surveyed progress of all 30 pilot sponge
cities and identified a broad array of challenges from technical, physical, regulatory, and financial,
to community and institutional. The most dominant challenges involve uncertainties and risks.
To resolve the issues, this study also identified various opportunities to improve China’s sponge city
construction program. Based on the results, recommendations are proposed including urging local
governments to adopt sponge city regulations and permits to alleviate water quality and urban pluvial
flooding issues, fully measuring and accounting for economic and environmental benefits, embracing
regional flexibility and results-oriented approaches, and focusing on a wider range of funding
resources to finance the sponge city program. Coordination among other government agencies is
critical, and this is true at all level of governments. Only through greater coordination, education,
and broader funding could the sponge city program be advanced meaningfully and sustainably.
Keywords:
green infrastructure; low impact development; public–private-partnership; urban
stormwater management; urban flood
1. Introduction
China’s large scale urbanization started around the 1980’s with a rapid rise in the urban population
from 36.22% in 2000 to 54.77% in 2014 (Figure 1) [
1
]. Consequently, more cities are facing challenges
associated with urban sustainability and urban water issues such as aging/outdated water and
wastewater infrastructures, urban flooding, combined sewer overflow, water quality deterioration,
water scarcity, and a high frequency of extreme weather [
2
–
4
]. Among these, urban flooding is one
of the most frequent and hazardous disasters that can cause enormous impacts on the economy,
environment, city infrastructure and human society [
5
–
7
]. Recent survey shows that 62% of Chinese
cities experienced floods, and direct economic losses amounted to up to $100 billion between 2011 and
2014 [1]. Other research indicates increasing trends to both urban flood disasters as well as economic
and human life losses. To address these challenges, the Chinese government had been searching for
viable options and launched pilot sponge city construction programs.
Water 2017,9, 594; doi:10.3390/w9090594 www.mdpi.com/journal/water
Water 2017,9, 594 2 of 17
Water 2017, 9, 594 2 of 17
1980 1985 1990 1995 2000 2005 2010 2015
20
30
40
50
60
Urbanization rate (%)
Year
Figure 1. China’s urbanization rate from 1980 to 2014.
A sponge city refers to sustainable urban development including flood control, water
conservation, water quality improvement and natural eco-system protection. It envisions a city with
a water system which operates like a sponge to absorb, store, infiltrate and purify rainwater and
release it for reuse when needed [8]. The sponge city program takes inspiration from the low impact
development (LID) and green infrastructure in the US [9,10] and Canada [11,12], sustainable drainage
systems (SusDrain) in the UK [13,14] and other European countries [15,16], and water sensitive urban
design (WSUD) in Australia [17] and New Zealand [18]. It promotes natural and semi-natural
measures in managing urban stormwater and wastewater as well as other water cycles. The primary
goals for China’s sponge city construction are: retaining 70–90% of average annual rain water onsite
by applying the green infrastructure concept and using LID measures, eliminating water logging and
preventing urban flooding, improving urban water quality, mitigating impacts on natural eco-
systems, and alleviating urban heat island impacts [19]. The sponge city program will also create
investment opportunities in infrastructure upgrading, engineering products and new green
technologies.
The sponge city program was launched at the end of 2014, under the direct guidance and support
of the Ministry of Housing and Rural-Urban Development (UHURD), Ministry of Finance (MOF) and
Ministry of Water Resources (MWR). These three ministries are responsible for reviewing, evaluating
and selecting candidate cities recommended by their respective provincial governments, based on a
series of criteria concerning the rationality and feasibility of pilot goals, financing mechanisms and
the effectiveness of supporting measures from local governments. The three ministries are also
responsible for the assessment of pilot city performance. In April 2015, the first group of 16 cities was
selected as the pilot sponge cities; one year later in April 2016, the pilot program was expanded to
another 14 cities. Figure 2 illustrates the locations of these pilot cities. The central government
allocated to each pilot city between 400 and 600 million Chinese Yuan (CNY) each year for three
consecutive years, and pilot cities are encouraged to raise matching funds through public–private-
partnership (PPP) and other financial ventures. The money will be used to implement innovative
water and wastewater management measures that would transform these cities into sponge cities
[20].
Figure 1. China’s urbanization rate from 1980 to 2014.
A sponge city refers to sustainable urban development including flood control, water conservation,
water quality improvement and natural eco-system protection. It envisions a city with a water system
which operates like a sponge to absorb, store, infiltrate and purify rainwater and release it for reuse
when needed [
8
]. The sponge city program takes inspiration from the low impact development (LID)
and green infrastructure in the US [
9
,
10
] and Canada [
11
,
12
], sustainable drainage systems (SusDrain)
in the UK [
13
,
14
] and other European countries [
15
,
16
], and water sensitive urban design (WSUD) in
Australia [
17
] and New Zealand [
18
]. It promotes natural and semi-natural measures in managing
urban stormwater and wastewater as well as other water cycles. The primary goals for China’s sponge
city construction are: retaining 70–90% of average annual rain water onsite by applying the green
infrastructure concept and using LID measures, eliminating water logging and preventing urban
flooding, improving urban water quality, mitigating impacts on natural eco-systems, and alleviating
urban heat island impacts [19]. The sponge city program will also create investment opportunities in
infrastructure upgrading, engineering products and new green technologies.
The sponge city program was launched at the end of 2014, under the direct guidance and support
of the Ministry of Housing and Rural-Urban Development (UHURD), Ministry of Finance (MOF) and
Ministry of Water Resources (MWR). These three ministries are responsible for reviewing, evaluating
and selecting candidate cities recommended by their respective provincial governments, based on a
series of criteria concerning the rationality and feasibility of pilot goals, financing mechanisms and the
effectiveness of supporting measures from local governments. The three ministries are also responsible
for the assessment of pilot city performance. In April 2015, the first group of 16 cities was selected
as the pilot sponge cities; one year later in April 2016, the pilot program was expanded to another
14 cities. Figure 2illustrates the locations of these pilot cities. The central government allocated to
each pilot city between 400 and 600 million Chinese Yuan (CNY) each year for three consecutive years,
and pilot cities are encouraged to raise matching funds through public–private-partnership (PPP) and
other financial ventures. The money will be used to implement innovative water and wastewater
management measures that would transform these cities into sponge cities [20].
With the strong support of the central government along with the enthusiastic participation of
local governments and private sectors, the sponge city program is gaining momentum; however,
the obstacles and challenges should not be overlooked, associated risks should not be ignored, and
future opportunities should be fully recognized.
Water 2017,9, 594 3 of 17
Water 2017, 9, 594 3 of 17
Figure 2. Location of pilot sponge cities.
With the strong support of the central government along with the enthusiastic participation of
local governments and private sectors, the sponge city program is gaining momentum; however, the
obstacles and challenges should not be overlooked, associated risks should not be ignored, and future
opportunities should be fully recognized.
2. General Descriptions of Pilot Cities
China is a vast country with great physical diversity. The climate of China is extremely diverse,
ranging from tropical in the far south to subarctic in the far north and alpine in the higher elevations
of the Tibetan plateau in the southwest. Precipitation is unevenly distributed in time and space.
Temporally, it is almost invariably concentrated in the warmer months; and spatially, it increases
from the northwest inland to the southeast coast, with the annual totals range from less than 20 mm
in northwestern regions to easily exceeding 2000 mm in southern coast of the country (Figure 3). As
sponge city construction involves green planning and LID measures, impacts of annual precipitation
and temperature were considered along with other regional factors when selecting pilot cities. Owing
to the nature and potential benefits of green infrastructures, most pilot cities are located in the central
and southeastern regions, where annual precipitation ranges from 410 to 1830 mm and annual
average temperature from 4.6 to 25.5 °C. In order to gain diverse experiences, a few pilot cities were
also selected in northeastern cold area and in arid areas near the central-north of China.
Similar to other cities in China, pilot cities are facing various urban sustainability and urban
water issues [21]. Ahead of others, these cities are actively seeking solutions in recent years; most are
exposed or engaged in the early stages of green infrastructure planning and LID practices. In
addition, these cities also have a fairly good governance and support basis both technically and
financially. In order to focus on innovation and new approaches, as well as safeguarding success,
each pilot city was designated a pilot area (not smaller than 15 km2). Most LID measures are planned
inside the designated pilot areas, and other green infrastructure planning and gray infrastructure
improvements may expand outside the pilot areas.
Figure 2. Location of pilot sponge cities.
2. General Descriptions of Pilot Cities
China is a vast country with great physical diversity. The climate of China is extremely diverse,
ranging from tropical in the far south to subarctic in the far north and alpine in the higher elevations
of the Tibetan plateau in the southwest. Precipitation is unevenly distributed in time and space.
Temporally, it is almost invariably concentrated in the warmer months; and spatially, it increases
from the northwest inland to the southeast coast, with the annual totals range from less than 20 mm
in northwestern regions to easily exceeding 2000 mm in southern coast of the country (Figure 3).
As sponge city construction involves green planning and LID measures, impacts of annual precipitation
and temperature were considered along with other regional factors when selecting pilot cities. Owing
to the nature and potential benefits of green infrastructures, most pilot cities are located in the central
and southeastern regions, where annual precipitation ranges from 410 to 1830 mm and annual average
temperature from 4.6 to 25.5
◦
C. In order to gain diverse experiences, a few pilot cities were also
selected in northeastern cold area and in arid areas near the central-north of China.
Similar to other cities in China, pilot cities are facing various urban sustainability and urban
water issues [21]. Ahead of others, these cities are actively seeking solutions in recent years; most are
exposed or engaged in the early stages of green infrastructure planning and LID practices. In addition,
these cities also have a fairly good governance and support basis both technically and financially. In
order to focus on innovation and new approaches, as well as safeguarding success, each pilot city
was designated a pilot area (not smaller than 15 km
2
). Most LID measures are planned inside the
designated pilot areas, and other green infrastructure planning and gray infrastructure improvements
may expand outside the pilot areas.
Table A1 in Appendix Apresents the regional characteristics of and general information on the
30 pilot cities including precipitation and climate, sizes of the designated pilot areas, existing conditions
of stormwater management systems, proposed goals of the sponge city construction, and the total
capital investment in the three-year period. As indicated in Table A1, all 30 cities set up clear goals
Water 2017,9, 594 4 of 17
on runoff volume control, urban drainage standards as well as waterlogging and flood prevention
standards. However, the first group of 16 cities had less clear standards on rainwater resourcing,
stormwater runoff pollution control, and wastewater recycling, comparing to the second group of
14 cities. Note that Table A1 only listed the primary goals of sponge cities. There are other secondary
goals set up by sponge cities based on the specific conditions of each city.
Water 2017, 9, 594 4 of 17
Figure 3. Annual precipitation distribution in China.
Table A1 in Appendix A presents the regional characteristics of and general information on the
30 pilot cities including precipitation and climate, sizes of the designated pilot areas, existing
conditions of stormwater management systems, proposed goals of the sponge city construction, and
the total capital investment in the three-year period. As indicated in Table A1, all 30 cities set up clear
goals on runoff volume control, urban drainage standards as well as waterlogging and flood
prevention standards. However, the first group of 16 cities had less clear standards on rainwater
resourcing, stormwater runoff pollution control, and wastewater recycling, comparing to the second
group of 14 cities. Note that Table A1 only listed the primary goals of sponge cities. There are other
secondary goals set up by sponge cities based on the specific conditions of each city.
3. Materials and Methods
3.1. Study Design
This study utilized a descriptive design to survey pilot sponge cities. The survey consists of a
literature review, information collection and review, field visits to pilot cities, and interviews with
the public. All 30 pilot cities were included in the survey. Information collected in this survey relates
to current implementation efforts and challenges to the further spreading of the sponge city program.
The survey was organized by four challenge categories: technical/physical, legal/regulatory,
financial, and community/institutional challenges. It was designed to collect both quantitative and
qualitative information regarding the benefits of sponge city program, the type of challenges that it
may encounter, and if/how these challenges can be overcome; however, more qualitative information
was gained due to the nature of this study.
The goal of the survey was to identify challenges to sponge cities at the local, provincial and
national levels of government, and provide concrete and provocative recommendations on how these
challenges can be overcome. The flow chart of our survey is shown in Figure 4.
Figure 3. Annual precipitation distribution in China.
3. Materials and Methods
3.1. Study Design
This study utilized a descriptive design to survey pilot sponge cities. The survey consists of a
literature review, information collection and review, field visits to pilot cities, and interviews with the
public. All 30 pilot cities were included in the survey. Information collected in this survey relates to
current implementation efforts and challenges to the further spreading of the sponge city program.
The survey was organized by four challenge categories: technical/physical, legal/regulatory, financial,
and community/institutional challenges. It was designed to collect both quantitative and qualitative
information regarding the benefits of sponge city program, the type of challenges that it may encounter,
and if/how these challenges can be overcome; however, more qualitative information was gained due
to the nature of this study.
The goal of the survey was to identify challenges to sponge cities at the local, provincial and
national levels of government, and provide concrete and provocative recommendations on how these
challenges can be overcome. The flow chart of our survey is shown in Figure 4.
Water 2017,9, 594 5 of 17
Water 2017, 9, 594 5 of 17
Figure 4. Flow chart of the survey work.
3.2. Data Collection Procetures
Extensive data and information were collected primarily from three sources (1) reviewing
application packages and annual progress reports submitted by each pilot sponge city; (2) literature
review; (3) field visits to pilot cities.
To compete for pilot sponge cities, each candidate city submitted an application package for
review, evaluation and selection. The packages generally include a three-year sponge city
implementation plan and other supporting documents such as long-term sponge city planning,
future regulatory frameworks, and related research. The implementation plans are important
documents, which contain variety of valuable information such as physical conditions; existing
issues; proposed scopes and goals; proposed projects including green, gray, and non-structural
measures; schedule of projects; responsible organizations; and financial arrangements. Annual
progress reports are other significant resources for evaluating the progress as well as assessing and
analyzing the success of the sponge city program.
The literature review was focused on recent publications, journal articles, and conference/forum
presentations in China. Using the PRISMA (Preferred Reporting Items for Systematic Reviews and
Meta-Analyses) methodology of literature review, 90 articles and presentations were retrieved from
the CNKI [22], WANFANG [23], CSCD [24], and VIP [25] databases, as well as several conference
sites in China including the 2016 International Low Impact Development Conference, in Beijing,
China, 2016 International Conference on Green Infrastructure and Resilient City in Shenzhen, China,
and the International Conference on Sustainable Infrastructure 2016 in Shenzhen, China. A total of
70 articles/presentations were included in the initial review, and 20 were excluded from the review
after reading the whole content because they did not match the objectives of the literature review and
the inclusion criteria. The key words used to search the materials were: urban flooding, urban water
safety, green infrastructure, low impact development, sponge city construction, sustainable urban
planning, rainwater resourcing, wastewater recycling, storm runoff pollution, socio-economic impact
of urbanization, urban eco-system. The literature search was for publications starting from the year
2002 to the year 2016.
In addition, the research team also conducted field trips to 22 sponge cities from July 2015 to
April 2017. Some field trips were accomplished during sponge city annual reviews and inspection or
Figure 4. Flow chart of the survey work.
3.2. Data Collection Procetures
Extensive data and information were collected primarily from three sources (1) reviewing
application packages and annual progress reports submitted by each pilot sponge city; (2) literature
review; (3) field visits to pilot cities.
To compete for pilot sponge cities, each candidate city submitted an application package for review,
evaluation and selection. The packages generally include a three-year sponge city implementation
plan and other supporting documents such as long-term sponge city planning, future regulatory
frameworks, and related research. The implementation plans are important documents, which contain
variety of valuable information such as physical conditions; existing issues; proposed scopes and goals;
proposed projects including green, gray, and non-structural measures; schedule of projects; responsible
organizations; and financial arrangements. Annual progress reports are other significant resources for
evaluating the progress as well as assessing and analyzing the success of the sponge city program.
The literature review was focused on recent publications, journal articles, and conference/forum
presentations in China. Using the PRISMA (Preferred Reporting Items for Systematic Reviews and
Meta-Analyses) methodology of literature review, 90 articles and presentations were retrieved from
the CNKI [
22
], WANFANG [
23
], CSCD [
24
], and VIP [
25
] databases, as well as several conference
sites in China including the 2016 International Low Impact Development Conference, in Beijing,
China, 2016 International Conference on Green Infrastructure and Resilient City in Shenzhen, China,
and the International Conference on Sustainable Infrastructure 2016 in Shenzhen, China. A total of
70 articles/presentations were included in the initial review, and 20 were excluded from the review
after reading the whole content because they did not match the objectives of the literature review and
the inclusion criteria. The key words used to search the materials were: urban flooding, urban water
safety, green infrastructure, low impact development, sponge city construction, sustainable urban
planning, rainwater resourcing, wastewater recycling, storm runoff pollution, socio-economic impact
of urbanization, urban eco-system. The literature search was for publications starting from the year
2002 to the year 2016.
In addition, the research team also conducted field trips to 22 sponge cities from July 2015 to
April 2017. Some field trips were accomplished during sponge city annual reviews and inspection or
were organized by conferences, while others were conducted with expert consultation activities. Total
Water 2017,9, 594 6 of 17
of 156 pilot projects were visited, numerous photos and field notes were taken, and over 200 people
were surveyed including scholars, practitioners, government officials, urban dwellers, and local
stakeholders. The outline of the survey questions is presented in Table 1.
Table 1. The outline of the survey questions.
Technical:
Design and construction codes and standards
Performance and sustainability of sponge city measures
Technology and materials
Monitoring techniques and standards
Education and training
Operation and maintenance
Legal:
Local, provincial and national rules, ordinance, policies, regulations, laws and guidelines
Municipal structure for maintenance and ownership
Opportunities
Financial:
Full life cycle and maintenance costs of sponge city measures
Social, economic and environmental benefits of sponge city measures
Financial sources
Private sector’s interests
Incentives
Community/Institutional:
Public knowledge, interests, and involvement of sponge city construction
Community education
Aesthetics
Cooperation between agencies and communities
Available information
3.3. Data Analysis
Data and information were organized based on four challenge categories identified in the
beginning. The data from application packages and annual progress reports were primarily used
for analyzing technical/physical challenges along with legal/regulatory and financial challenges.
The information retrieved from the literature review contains a fair number of expert and
practitioner opinions and was largely used for analyzing the technical/physical, legal/regulatory,
and community/institutional challenges. The data obtained from field visits contained first-hand
knowledge and was used for analyzing all four categories.
4. Major Challenges
The survey results show that despite the promising benefits that the sponge city program
could provide to urban environment, many challenges were present, which may inhibit wide-scale
implementation and the long-term success of the sponge city program. The following sections present
the primary challenges that were identified in this survey.
4.1. Technical Challenges
(1) Ambitious goals without sound research basis
The original goal of the sponge city construction was defined as runoff-volume-focused LID
to retain 60–90% runoff on sites. One year later in 2016, it was expanded to a full array of urban
sustainability goals by adding restoration of eco-systems, improving deteriorated urban water bodies,
reducing urban heat island impacts, and building smart urban water cycle. Although the concept and
Water 2017,9, 594 7 of 17
practices of LID were introduced into China more than a decade ago [
26
], and recent research has
been carried out on sustainable urban stormwater management [
27
,
28
], the research foundation for
sponge city construction on such a large scale is rather weak. The rapid implementation of sponge city
measures with such ambitious goals is largely based on very little research domestically and locally.
A sponge city is an integrated approach that involves a broad range of concepts such as multi-scale
conservation and water system management, multi-function of ecological systems, urban hydrology
and runoff control frameworks, and impacts of urbanization and human activities on the natural
environment. Lacking a sound research foundation can unnecessarily restrict the potential positive
effects of this new urban water cycle management approach. To successfully implement sponge cities,
appropriate definition of goals and adequate research to understand this new approach, along with
sufficient knowledge are necessary.
(2) One model to fit every part of the country
Although the basic theories and primary concepts of the sponge city approach are
largely applicable to any climate, geographical/geological, hydrological and soil conditions;
the implementation strategies and the selection of specific measures should be considered with
local conditions. The current practices, however, exhibits a pattern of using one model for every part
of the country. Table 2presents LID strategies proposed by four pilot sponge cities.
Table 2. LID strategies for various cities.
Data Qian’an Baicheng Shenzhen Yuxi
Annual Temp. (◦C) 11.5 4.6 22.4 19.2
Annual Rainfall (mm) 672 410 1837 909
Annual Evap. (mm) 1100 1840 1675 1801
Runoff Control (%) 80 85 70 82
Runoff Control (mm) 28.0 25 31.3 23.9
Rain Resourcing (%) 7 6 ≥8 10
Green Roof (%) 6 5 ≥30 12.6
Depressed Green (%) 35 36.4 ≥10 35.4
Permeable Paver (%) 46.5 46.2 ≥70 38.2
As illustrated in Table 2, although the natural weather and geographical/hydrological conditions
for these four cities vary drastically, the LID strategies proposed by these cities remain similar.
For example, Baicheng City is located in a cold and arid region (as shown in Figure 2) with an
annual temperature of 4.6
◦
C (Celsius), annual rainfall and annual evaporation of 410 and 1840 mm,
respectively. The urgent issues for this city are water quality deterioration, water body shrinking,
and water resources shortage. However, the LID strategies this city proposed will not alleviate these
problems; instead, green roof, depressed green space and permeable pavement all have a potential to
increase evaporation/evapotranspiration, and consequently, worsen the situation. Shenzhen, on the
contrary, is a lowland coastal city located in a tropical region. It suffers from a high groundwater table,
poorly drained soil, sea water intrusion, land salinization and heavy seasonal storms. Depressed green
space and permeable pavements are clearly not suitable for it, and 30% of green roofs may not be
economically viable. The success of a sponge city approach depends on local conditions and cannot
be transferred in a standardized way to another context, as it might not prove as successful as local
conditions change. The sponge city strategies should be developed based on a careful assessment of
local conditions and potentials along with special issues, and mitigate these problems by leveraging
the local potential and regional resources.
(3) In need of guidance and education/training
Up to recently, complete local, provincial and national guidance, design standards and codes
were not available. A national level guideline was published at the end of 2014, and a few city-level
Water 2017,9, 594 8 of 17
guidelines were completed through 2015 to 2016 by some pilot sponge cities. These guidelines,
however, are rather simple and general. They are, by large, merely the translation and combination of
similar guidelines widely used in the US and do not consider variations in regional and local conditions
such as soil, climate and topography variances. Lack of design standards and codes has limited the
ability of local communities to implement sponge city projects based on local conditions.
In addition, the most common technical challenge is perhaps an overall lack of education/training,
knowledge, and experience of sponge city planning, design, construction, maintenance,
and maximizing benefits at all levels of government and all related professions across the board.
In addition to local practicing staff and management personnel, the development and consulting
industries also lack sufficient knowledge of sponge city concepts and practices, resulting in an industry
culture that is either skeptical of the sponge city approach or one that produces poor planning
and design.
(4) Inappropriate strategies causing further problems
The lack of knowledge and guidance, design standards and codes, as well as appropriate education
and training may result in the poor planning and implementation of certain sponge city measures in
some incidences. For example, an existing drainage ditch, which used to run along the foot of a hill,
was covered with rain gardens and concrete grates (a few meters of rain garden and a few meters of
grate alternation); the small openings on the grate are around 3 cm in diameter. The design concept is
to filter the mud and debris from hill-flow; however, it neglected the sudden and greater damaging
nature of the hill-flow. The new design severely restricted the runoff collecting capacity of the original
open ditch; consequently, it may cause additional damage to the roadway traffic, bypassers, and even
damage to the newly installed rain gardens.
Other frequent problems involve excessively using green measuresor constructing green measures
at inappropriate or unnecessary locations. For example, some sponge parks are largely in undeveloped
natural areas with over 75% of land covered by trees, plants and greens, and another over 10% of open
water. Despite the lightly-developed nature, these parks are fully loaded with various LID measures
including pervious pavement, rain gardens, dry creeks, depressed green spaces, infiltration swales,
and even underground retention tanks. In another incidence, a 10 km long, two-lane roadway features
large rain gardens on each side of the road with retention chambers underneath each rain garden,
pervious pavers line the sidewalks, and depressed green spaces are planned beside the sidewalks.
It appears that many LID measures are built in undeveloped/underdeveloped areas such as parks
and large open spaces, while in urban and old town centers, where retrofit and restoration are really
needed, sponge city interventions are largely avoided.
In other incidences, infiltration-related LID measures have been constructed on mountain sides
with no consideration of mud-slides; an infiltration reservoir was built on top of karst bedrock with no
protection from groundwater; green roofs were planned in arid areas with no concern for water scarcity;
and rain gardens and depressed green spaces were designed in coastal areas with high groundwater
tables and sea water intrusion problems with no knowledge of the suitability of the plants.
(5) Unavailable green products and materials
In recent decades, the green infrastructure industry has been booming in the US and Europe,
and many products and materials have been developed to assist green infrastructure implementation.
These range from LID products including rain garden systems, tree planting systems, green/blue roof
systems, tree root protection modular, landscape/sports/playground solution systems; blue products
including vortex flow control device and inlet filter device; and different monitoring equipment. Many
of these pre-made, ready-to-install products are designed and tested to meet industrial standards.
Besides easy to design and install and easy to operate and maintain, these products also achieve
stable/consistent performance and, in certain cases, provide standard monitoring components.
In China currently, sponge city products and materials are mainly imported or introduced from
Water 2017,9, 594 9 of 17
abroad such as computer software and design and implementation techniques. Counterparts of the
ready-to-install systems/modular/devices are largely unavailable. Table 3exhibits the availability
of various green infrastructure systems/modular/devices. Absence of similar green infrastructure
products and materials may greatly hinder the progress of sponge city construction, or reduces the
effectiveness of the sponge city program.
Table 3. Availability of various green infrastructure systems/modular/devices.
Products AVLB LMTD UNAV Remarks
Cistern/Rain Barrel √Simple small-size above ground barrels
available without control apparatus
Rain Garden System √
Tree Planter System √
Green/Blue Roof System √Include green and blue roof modular
Infiltration Planter System √
Pervious Pavement √
Various products available, but quality and
durability are uncertain
Underground Infiltration √
Underground Detention √Very limited small-scale, small-sized
products available.
Water Quality Control √refers to vortex flow control device, inlet
filter device, etc.
Monitoring Equipment √Mostly copy versions of international
products, and generally in poor quality and
poor accuracy
Notes: AVLB = Available; LMTD = Limited; UNAV = Unavailable.
(6) Insufficient performance data
As a new approach, long-term performance data for sponge city measures is not available in most
regions of China. Local communities are uncertain when implementing sponge city measures as part of
the development process. In addition, the information on life cycle costs and operation/maintenance
requirements under different flow regimes, soil types and climates is also unavailable. As a remedy,
computer models have been used to predict the unavailable information, which appears difficult to
use to convince public and local governments. Currently, there is not enough information on how well
some sponge city measures will perform in long-term service and what it may take to maintain their
various functions.
(7) Unaddressed operation and maintenance difficulties
Compared to traditional stormwater management systems, sponge city measures may require
more frequent, periodic maintenance. Maintenance requirements vary depending on the specific
measures, their functions and local conditions. These tasks may be as simple as weeding a vegetated
swale and removing debris from curb cuts, or as complex as maintaining a large-scale wetland or an
underground storage tunnel with multiple functions. One unique maintenance challenge posed by
sponge city measures is that they are often scattered around a large area, and some are located on
private property, making it difficult for public agencies to ensure that proper maintenance is carried
out. Sometimes sponge city projects may be filled in or removed during other projects by private
owners. This, in turn, presents great difficulties for the sustainability of sponge city construction.
Water 2017,9, 594 10 of 17
4.2. Physical Challenges
(1) Geographical location
Some sponge city measures may not be suitable in certain locations due to the physical
characteristics of the land, climate, or other conditions. For example, infiltration-related practices
should not be used in areas where infiltration is not desirable, such as poorly drained soil, high
groundwater tables, steep slopes, landslide hazard areas, floodplains, contaminated soils, and wellhead
protection areas, unless special measures are employed. In arid and semi-arid areas, certain practices
that increase evaporation are also not desirable. These restrictions create challenges to sponge
city construction.
(2) Land scarcity in urban areas
China is a densely-populated country. Land is highly valuable, especially in developed urban
areas. Whereas traditional systems in urban areas convey stormwater via underground pipes, sponge
city practices, which allow stormwater to infiltrate into the ground or be stored on-site, may require
additional land space; this may present a challenge when designing new developments or retrofitting
existing urban areas. It is in developers’ financial interests to maximize the amount of buildable land,
while minimizing the costs. Setting aside space for sponge city measures sometimes may conflict with
other development goals. Space limitations can also present a challenge when installing sponge city
measures in the right-of-way along public streets. There are multiple demands for space in the right of
way, including stormwater treatment, bicycle lanes, sidewalks, utilities, parking and traffic lanes.
(3) Climate
It is known that certain sponge city measures are not effective in managing stormwater in cold,
hot or arid climates. In some regions of China, where the ground is frozen half of the year or permafrost
exists, the potential for water to infiltrate into the ground is reduced. This limits year-round functioning
and presents challenges to local governments.
(4) Soil conditions
One very specific challenge is the lack of understanding of soil characteristics, soil
conservation/restoration, and plant–soil–water relations. Clay soils are a substantial impediment to
LID because the full effect is hard to achieve. This problem has not been addressed in China and
remains poorly understood. To compensate, projects in regions with poorly drained soil must be
designed with underdrains, thereby reducing the benefits of the systems. Sponge city measures in clay
soils need further investigation, standard development and championing to tout the benefits.
4.3. Financial Challenges
(1) Uncertainty of life cycle costs and benefits
Although the design and construction costs for sponge city projects are quite clear, the life cycle
costs including operation and maintenance are unknown. In certain cases, even the life-spans of certain
sponge city projects are uncertain. In current practices, sufficient funding for initial construction is
allocated, however, funding needs for future operation and maintenance are not addressed. In addition,
due to the uncertainty of the life-span and life-cycle performance, the life-cycle benefits—including
environmental, ecological and social benefits—cannot be assessed appropriately. For an investment
without a clear picture of the future benefits, the financial risk is rather high for both public and
private entities.
(2) Challenges in public–private partnership
As the demand for infrastructure investment climbs around the globe, public–private partnerships
(PPPs) are increasingly playing a crucial role in bridging the gap. In Western countries, these
Water 2017,9, 594 11 of 17
partnerships—in which the private sector builds, controls, and operates infrastructure projects subject
to strict laws, regulations and government oversight—tap private sources of financing and expertise to
deliver large infrastructure improvements. When managed effectively, PPPs not only provide much
needed new sources of capital, but also bring significant discipline to project selection, construction,
and operation. Successfully forming and managing PPPs, however, is no small feat.
As a new approach, sponge city construction is pushing its funding resources through PPPs,
another new venue in China. Due to the nature of sponge city projects, the PPPs are mostly performance
based. This survey identified following challenges: (1) The regulatory environment. There are no
specific laws governing PPPs, and there is no independent PPP regulating agency in China. To better
regulate PPPs and attract more private funding, a more robust regulatory environment, with clear
laws and an independent regulating agency are essential; (2) Lack of information. The PPP program
lacks a comprehensive database regarding the projects/studies to be awarded under PPPs. An online
database, consisting of all the project documents including feasibility reports, concession agreements
and the status of various clearances and land acquisitions would be helpful to all bidders; (3) Project
development. The project development activities, such as detailed feasibility studies, land acquisition,
and environmental/forest/floodplain clearances, are not given adequate importance by the concession
authorities. The absence of adequate project development by authorities leads to misunderstood
interests by the private sector, mispricing, and many times delays at the time of execution; (4) Lack of
institutional capacity. The limited institutional capacity to undertake large and complex projects at all
levels of government, especially at the local level, hinder the translation of targets into projects.
Other issues involve risk transfer, financial implications, contractual matters, politics, management
and accountability. For example, some well financed pilot cities are capable of completing all sponge
city projects with their own funding; for some political reasons, they are forced into using PPPs against
their will and public interests. It defies the purpose of PPPs and can induce unnecessary costs to the
public and increase managing difficulties for local governments.
4.4. Legal and Regulatory Challenges
Locally, challenges include local ordinances; building codes; plumbing and health codes;
restrictions involving street width, drainage codes, and parking spaces; and restrictions on the use of
reclaimed stormwater. Municipal codes and ordinances often favor gray over green infrastructure. A
challenge that may be both technical and legal is that green infrastructure is often located on private
property, and public agencies face difficulties ensuring that proper maintenance is occurring and
will continue long-term. At the provincial level, water and land-use policies and property rights
can be complicating factors. For example, downstream water rights may be impacted if upstream
water management practices reduce the quantity of water to downstream users. The lack of national
guidelines and performance standards are a complicating factor.
4.5. Public Acceptance Challenges
Contrary to traditional stormwater management systems, which are generally buried
underground, sponge city systems are mostly built above ground and scattered in large regions;
some located in private land interfering with public life. Therefore, public opinion and acceptance of
sponge city construction can easily hinder its success. Considering the importance of public acceptance,
the education efforts in China are deficient both in quality and in scale. More educational efforts are
needed for a broad array of groups including political leaders, administrators, agency staff, planning
and design professionals, developers, builders, landscapers, and the public. To achieve public outreach
goals and shift public perceptions, a complete education program involving the technical training of
municipal staff and lessons in sponge city concepts for the public are in demand. These lessons must
be incorporated into formal and informal education programs for institutions and communities to
fully understand the sponge city concepts.
Water 2017,9, 594 12 of 17
4.6. Inter-Agency Cooperation and Data Sharing Challenges
Since sponge city construction involves a broad field of knowledge including stormwater,
water quality, the eco-system, transportation, neighborhood retrofitting, and energy management,
inter-agency and community cooperation is critical. While the partnerships and cooperation between
agencies leverage efficiencies and economic benefits, they require significant patience and finesse. So
far, the inter-agency cooperation and working across functions has not always been easy in China due
to the difficulty of working across divisions, agencies, and political boundaries with diverse groups
and diverse interests. It seems that some agencies compete to be a dominant party and reluctant to
cooperate, whereas others view it as someone else’s responsibility. Consequently, holistic efforts are
hard to coordinate, focus and keep moving forward.
Lack of inter-agency cooperation also leads to difficulties in data and information sharing.
It hinders research and innovations. In some situations, repetitive efforts were directed to collect the
same data or information, while in others, research funding was awarded to organizations solely
because they owned the critical data that was needed for the research.
5. Future Opportunities
As a new approach for urban water cycle management, the success of China’s sponge city
construction relies on the identification of challenges and adaption of effective improvements.
To achieve a bright future, the following critical improvement opportunities are identified.
5.1. Taking an Integrated, Watershed Scale Approach
Sponge city construction aims at resolving various problems associated with urbanization at
multiple scales, and ultimately at establishing greener and more holistic urban environments. Some
earlier efforts defined the sponge city as runoff-volume-focused LID measures, and set up volume
control criteria as the sole control parameter. It narrowed the sponge city concept; thus, some pilot cities
focused on discretized LID measures at the source level and lessened the importance of connectivity
at multiple scales. Taking an integrated, watershed-scale approach and focusing on the connectivity
of the source–community–region–watershed scales can prevent the segmentation and isolation of
the system and focus on the full benefits of sponge city approach—such as natural conservation,
flood reduction, eco-service enhancement, and water resource protection—and ultimately promote a
healthier watershed [29].
5.2. Enhancing Guidance and Design Standards for Local Conditions
The success of sponge city approach relies on the understanding of local issues, conditions, and
potentials. It is essential to carefully assess specific problems in the city and resolve these by leveraging
the local potential and regional resources. Currently, the lack of guidance and design standards from
national, provincial and local levels make the following elements of sponge city projects difficult:
assessment, planning, design, construction, operation/maintenance, and monitoring/evaluation. To
ensure the success of sponge city construction, it is urgent that national and provincial guidelines
be completed to help local governments develop local sponge city construction manuals/design
standards. These documents should be based on a careful assessment of local conditions and potentials
with input from local developers, planners, and engineers. Various education programs should also
be established to provide training to government officials, public works employees, planning and
design professionals, and the public. In addition, there is a strong demand for performance, costs and
life-cycle data from pilot demonstration projects/practices in various natural conditions.
5.3. Promoting Government Leadership and Inter-Agency Cooperation
Leadership at all levels of government along with inter-agency cooperation is another key element
essential for the effective implementation of sponge cities. Local leadership and knowledge of local
Water 2017,9, 594 13 of 17
conditions, as well as the potential benefits of sponge cities, need to grow. Agencies should work
together to identify the needs for changing current municipal building codes, street/transportation/
parking ordinances, conflicting agency policies, and other uniquely local management constraints.
Provincial leadership is necessary to clarify sponge city definitions and water rights implications, and to
integrate and reconcile multiple local and provincial agency policies that impact sponge city practices.
National leadership can take many forms without creating a one size fits all approach that stifles
provincial or local flexibility. Flexible performance criteria can help promote the performance of
this new approach [
30
]. Standard-setting, permitting and enforcement agencies need to recognize
that the sponge city approach often demands more time and different performance milestones than
traditional approaches.
5.4. Establishing Locally Based Legislation Framework
Another important element to China’s sponge city construction is locally based legislation that is
formulated based on local conditions. These laws and regulations should consider the following:
(1)
Establish decision-making processes surrounding land development activities that protect the
integrity of the watershed and preserve the health of water resources.
(2)
Require that new developments, redevelopments and all land conversion activities maintain the
natural hydrologic characteristics of the land to reduce flooding, stream bank erosion, siltation,
nonpoint source pollution, property damage, and to maintain the integrity of stream channels
and aquatic habitats.
(3) Establish minimum post-development LID management standards and design criteria and control
of stormwater runoff quantity and quality; establish minimum design criteria for the protection
of groundwater resources; establish minimum design criteria for measures to minimize nonpoint
source pollution from stormwater runoff.
(4)
Establish design and application criteria for the construction and use of structural
stormwater control facilities that can be used to meet the minimum post-development LID
management standards.
(5)
Encourage the use of LID practices such as reducing impervious cover and the preservation of
green space and other natural areas to the maximum extent practicable.
(6)
Establish provisions for the long-term responsibility for and maintenance of sponge city facilities
to ensure that they continue to function as designed and pose no threat to public safety;
(7)
Establish provisions to ensure that there is an adequate funding mechanism including
guarantee for the proper review, inspection and long-term maintenance of the sponge city
facilities implemented.
(8) Establish administrative procedures and fees for the submission, review, approval or disapproval
of sponge city plans, and for the inspection of approved active projects, and long-term follow up.
5.5. Finding Innovative Ways to Create More Funding Options
While PPP is gaining interest in both developed and developing countries, it alone may not be
able to raise enough funding to support China’s large-scale sponge city construction. Additional and
more innovative funding opportunities and mechanisms at all levels are in demand, including better
integration between national agencies to cost-share national funds for local sponge city projects. China
should adopt a model which takes into consideration the various local conditions. Different cities
should select different economic strategies concerning their varied natural conditions and economic
situations. Other funding sources such as tax-increments, development charges, value-capture taxes,
loans, and bonds should be explored based on local conditions. Meanwhile, PPPs should be utilized as
a way of developing local private-sector capabilities through joint ventures with large domestic and/or
international firms, as well as providing sub-contracting opportunities for local firms. Ultimately,
the economic strategy of a city should be beneficial to the local public and local economic growth.
Water 2017,9, 594 14 of 17
Furthermore, incentives, both financial and non-financial, are in strong need at the provincial and
local levels to encourage the adaptation of the sponge city approach. The incentives can range from
instituting tax incentives, utility rate reductions, and/or regulatory credits. Non-monetary incentives
that can encourage sponge city implementation include development incentives such as streamlined
permitting and transfer of development rights, regulatory credits, and watershed trading for sponge
city projects.
5.6. Continuous Research
In-depth research into sponge city concepts and practices is needed in various areas. At the
national level, the following research should be conducted: developing computer models and
tools to assist planning, design, and monitoring and performance evaluation purposes; assessing
urban soils across the country for the suitability of sponge city practices; completing design,
operation, maintenance and decision support guidelines; and establishing a national database for
sponge-city-related data, information, technology, and demonstration. At the provincial and local
scales, the following research should be carried out: assessing sponge city impacts on watersheds;
developing incentives to encourage the sponge city; conducting cost of service studies and fiscal impact
analyses to determine the impact on the fiscal health and viability of the community; conducting triple
bottom-line (social, economic, and environment) analysis to identify means for saving and/or funding
sponge city practices as opposed to gray infrastructure. Additionally, many other studies are also
in demand.
6. Conclusions
As a new urban water planning and management approach, China’s sponge city construction
initiative is entering the third year and is quickly taking root in cities across the country. This research
surveyed 30 pilot sponge cities and identified a wide array of challenges that may hinder the progress
of the sponge city program. These challenges are classified into four categories: technical and physical,
legal and regulatory, financial, as well community and institutional. The results show that these
challenges come in various shapes and sizes depending on the local context; however, risks and
uncertainties appear in each pilot sponge city, especially uncertainty about the outcomes, standards,
techniques, and procedures. While significant challenges remain, important opportunities are opening
for safer, greener, more holistic urban environments. Based on this study, the following conclusions
are reached. (1) broad and diverse coalitions are necessary for discovering the benefits, exploring the
possibilities, piloting the projects and probing system-wide changes; (2) increased research efforts
into the techniques, levels of performance, range of multiple benefits, life cycle analysis of costs,
and other key areas of sponge city implementation are needed; (3) greater coordination is needed
among agencies and at all levels; communication among stakeholders, government officials and staff,
and practitioners is also in need of improvement; (4) similarly to all new things, this new approach will
require investment, coordination and patience. The development of green solutions that are acceptable
in modern cities will take time. Time is needed for professional training and public education; time
is needed for stepwise learning including learning from previous experiences. With the appropriate
guidance and adjustments, it obstacles can be overcome, resulting in fewer technical, legal, financial,
and cultural barriers. As understanding grows and methods improve, risks will be reduced.
Acknowledgments:
This research was supported by the IWHR Research & Development Support Programs
(No. JZ0145B322016; No. JZ0145B042017). We are grateful for the efforts of editors and reviewers and believe that
the valuable comments reviewers provided are beneficial to this paper.
Author Contributions:
Hong Wang served as lead and corresponding author, and designed the proposal;
Liuqian Ding perfected the thoughts; Hui Li, Minglei Ren and Changzhi Li collected the data; Hui Li and
Hong Wang analyzed the data; Hui Li wrote the paper; Hong Wang and Liuqian Ding provided editorial
improvements to the paper.
Conflicts of Interest: The authors declare no conflict of interest.
Water 2017,9, 594 15 of 17
Appendix A
Table A1. Regional characteristics and general information of pilot sponge cities.
No Pilot
Cities
General Information Goals of Sponge City Construction
Investment
(Billion-RMB)
Water Quantity Water Quality Water Disaster Prevention
Annual
Average
Rainfall
(mm)
Annual
Average
Evapor.
(mm)
Temperature (◦C) Pilot Area
(km2)
Existing
Drainage
Capacity
(a)
Ex. Flood
Control
Capacity
(a)
Average
Annual
Runoff
Contl (%)
Rain Water
Resourcing
(%)
Water
Quality
Control
SS (%)
Wastewater
Recycling
(%)
Drainage
Standard
(a)
Pluvial
Flood
Standard (a)
Fluvial
Flood
Standard (a)
Annual
Average
Average
High/Low
1 Qian’an 672 1100 11.5 26/−5 21 0.5–1 20–50 80 7 – 30 2 20 50 4.493
2 Baicheng 410 1840 4.6 38/−32 21 1–3 10/20 85 6 60 25 3–5 20 50 4.230
3 Zhenjiang 1063 1277 16.1 29/3 22.0 2–5 20–50 75.0 8 60 25 2–5 30 100 3.060
4 Jiaxing 1194 1313 17.2 29/5 18.4 0.5–1 50 75.0 – 40 25 2–5 30 100 1.948
5 Chizhou 1483 1444 12.7 24/1 18.5 1–2 10–20 80.0 – – 20 2–5 20–30 50–100 4.045
6 Xiamen 1530 1651 21.3 29/14 45.5 2–5 50 75.0 5 – – 2–5 50 50 6.474
7 Pingxiang 1600 – 18.1 30/6 28.8 2–3 – 80.0 – – – 2–3 30 50 4.600
8 Jinan 665 1526 14.8 28/−1 39 1–5 <100 75 – – – 2–10 30–50 50 7.600
9 Hebi 665 2016 14.1 28/−1 29.8 1 50 70 – – – 2–5 30 100 3.476
10 Wuhan 1257 950 17.2 30/4 38.0 10 50–100 75.0 – 50 – 5–10 50 200 10.278
11 Changde 1366 – 17.5 29/5 41.2 2–5 50 80.0 8 75 – 2–5 30 100 17.350
12 Nanning 1298 1367 22.6 29/14 60.2 2 20–50 75.0 – 50 20 2–5 20 100 9.519
13
Chongqing
1107 1193 18.0 7/35 18.7 2–5 50–100 80.0 5 50 – 3–5 50 100 7.047
14 Suining 928 950 17.8 28/7 25.0 1–3 20–50 80.0 – – – 2–5 30 50 5.760
15 Gui’an 1158 1200 15.3 24/5 19.1 – – 85.0 10 56 – 2–5 30 100 4.760
16 Xixian 520 1481 14.3 27/1 17.8 – – 80 – >60 30 2–5 50 50–200 3.123
17 Fuzhou 1360 970 19.7 28.8/10.6 36.9 1–2 20 75.0 2 45 2 3–5 20–50 20–200 7.800
18 Zhuhai 1766 1469 23.0 32.2/−3 52.0 1–3 20–50 70.0 10 50 15 3–5 30–50 100 10.656
19 Ningbo 1517 830 17.2 29/6 31.0 1–3 20–100 80.0 22 60 40 3–10 50 100–200 6.042
20 Yuxi 909 1801 19.2 22/10 20.9 – 20 82.0 10 50 20 3–5 30 100 4.873
21 Dalian 736 1551 9.1 22/−8.1 21.8 1–3 50 75.0 5 50 25 >2 20 50 2.898
22 Shenzhen 1837 1675 22.4 29/16 24.9 1–5 20–50 70.0 ≥8 60 30 3–5 50 200 3.529
23 Shanghai 1191 1420 15.7 29/5 79.0 2–5 200 80.0 8 80 20 5 100 200 8.560
24 Qingyang 510 1425 9.5 23/−8.4 29.6 1 20 90.0 5 60 – 2–5 30 100 4.735
25 Xining 460 1364 6.2 14.9/−0.3 21.6 – 50–100 88.0 2 60 50 2–5 50 100 6.375
26 Sanya 1392 2361 25.5 28.8/21.6 20.3 – – 70.0 5 – 20 2–5 30 100 4.040
27 Qingdao 776 1401 12.2 25.1/−1.2 25.2 2–3 50 75.0 8 65 30 2–5 50 100 4.870
28 Guyuan 458 1099 6.1
24.7/
−
14.3
23.0 – – 85.0 10 40 30 2 30 50 3.654
29 Tianjin 511 1639 13.5 27.2/−2.4 39.5 1–3 50 80.0 5 65 60 3–5 20–50 50–200 7.490
30 Beijing 573 1164 11.7 26/−4.7 19.4 3–5 50 84.4 3 42 75 2–10 50 100 3.937
Note: No. 1–16 are the regional characteristics and general information of the first group of pilot sponge cities and No. 17–30 are those of the second group of pilot cities.
Water 2017,9, 594 16 of 17
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