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How to measure the ecological compensation threshold in the upper Yangtze River basin, China? An approach for coupling InVEST and grey water footprint

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Defining a reasonable and feasible watershed ecological compensation threshold is the key to protecting watershed ecological functions and maintaining the sustainable utilization of watershed ecosystems. However, many studies have obtained compensation values that are too high to promote the implementation of ecological compensation policies. This study chose the upper reaches of the Yangtze River as the research area, taking water resources closer to people’s daily needs as the evaluation object. Based on the InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) model and grey water footprint method, the ecological compensation threshold model for water resources was established. Combined with the eco-compensation priority sequence coefficient identification of protected areas and beneficiary areas and allowed for the measurement of the watershed ecological compensation value in 2015 and 2020. Finally, compare the advantages and disadvantages of different ecological compensation calculation methods, compare the gap between different watershed ecological compensation standards and the theoretical threshold globally. The results showed that from 2015 to 2020, the value of the water content in the upper reaches of the Yangtze River increased, while the value of the grey water footprint decreased. The classified watershed ecological compensation beneficiary areas were mainly concentrated in the central-eastern and southern parts of the upper Yangtze River, while the ecological compensation protected areas were concentrated in the western and northwestern parts. The mean absolute values of the watershed ecological compensation thresholds for each prefecture-level city and state ranged from 0.43 to 24.63 billion CNY in 2015 and from 0.67 to 41.60 billion CNY in 2020, which were close to the actual values. Among the different land-use types, the water conservation service value per unit area of shrubs was the highest. The lower limit value of watershed ecological compensation calculated using the grey water footprint method was closer to the amount of compensation in practice than was the commonly used opportunity cost method. The findings of the study can help improve the watershed ecological compensation mechanism in the upper Yangtze River region, promote win–win cooperation among transboundary watershed areas, and form a harmonious and stable green development model.
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How to measure the ecological
compensation threshold in the
upper Yangtze River basin,
China? An approach for coupling
InVEST and grey water footprint
Dongjie Guan
1
, Lei Wu
1
, Lidan Cheng
2
*, Yuxiang Zhang
1
and
Lilei Zhou
3
1
School of Smart City, Chongqing Jiaotong University, Chongqing, China,
2
Chongqing Geomatics and
Remote Sensing Center, Chongqing, China,
3
School of Civil Engineering, Chongqing Jiaotong
University, Chongqing, China
Dening a reasonable and feasible watershed ecological compensation
threshold is the key to protecting watershed ecological functions and
maintaining the sustainable utilization of watershed ecosystems. However,
many studies have obtained compensation values that are too high to
promote the implementation of ecological compensation policies. This study
chose the upper reaches of the Yangtze River as the research area, taking water
resources closer to peoples daily needs as the evaluation object. Based on the
InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) model and
grey water footprint method, the ecological compensation threshold model for
water resources was established. Combined with the eco-compensation
priority sequence coefcient identication of protected areas and
beneciary areas and allowed for the measurement of the watershed
ecological compensation value in 2015 and 2020. Finally, compare the
advantages and disadvantages of different ecological compensation
calculation methods, compare the gap between different watershed
ecological compensation standards and the theoretical threshold globally.
The results showed that from 2015 to 2020, the value of the water content
in the upper reaches of the Yangtze River increased, while the value of the grey
water footprint decreased. The classied watershed ecological compensation
beneciary areas were mainly concentrated in the central-eastern and southern
parts of the upper Yangtze River, while the ecological compensation protected
areas were concentrated in the western and northwestern parts. The mean
absolute values of the watershed ecological compensation thresholds for each
prefecture-level city and state ranged from 0.43 to 24.63 billion CNY in
2015 and from 0.67 to 41.60 billion CNY in 2020, which were close to the
actual values. Among the different land-use types, the water conservation
service value per unit area of shrubs was the highest. The lower limit value
of watershed ecological compensation calculated using the grey water
footprint method was closer to the amount of compensation in practice
than was the commonly used opportunity cost method. The ndings of the
study can help improve the watershed ecological compensation mechanism in
OPEN ACCESS
EDITED BY
Ke Zhang,
Hohai University, China
REVIEWED BY
Ehsan Elahi,
Shandong University of Technology,
China
Yuechen Li,
Southwest University, China
Chuanhao Wen,
Yunnan University, China
*CORRESPONDENCE
Lidan Cheng,
cldheipingguo@163.com
SPECIALTY SECTION
This article was submitted to
Hydrosphere,
a section of the journal
Frontiers in Earth Science
RECEIVED 08 July 2022
ACCEPTED 23 August 2022
PUBLISHED 12 September 2022
CITATION
Guan D, Wu L, Cheng L, Zhang Y and
Zhou L (2022), How to measure the
ecological compensation threshold in
the upper Yangtze River basin, China?
An approach for coupling InVEST and
grey water footprint.
Front. Earth Sci. 10:988291.
doi: 10.3389/feart.2022.988291
COPYRIGHT
© 2022 Guan, Wu, Cheng, Zhang and
Zhou. This is an open-access article
distributed under the terms of the
Creative Commons Attribution License
(CC BY). The use, distribution or
reproduction in other forums is
permitted, provided the original
author(s) and the copyright owner(s) are
credited and that the original
publication in this journal is cited, in
accordance with accepted academic
practice. No use, distribution or
reproduction is permitted which does
not comply with these terms.
Frontiers in Earth Science frontiersin.org01
TYPE Original Research
PUBLISHED 12 September 2022
DOI 10.3389/feart.2022.988291
the upper Yangtze River region, promote winwin cooperation among
transboundary watershed areas, and form a harmonious and stable green
development model.
KEYWORDS
InVEST model, water conservation services, grey water footprint, ecocompensation
priority sequence, ecological compensation threshold
1 Introduction
With accelerated urbanization worldwide, economic
development brings rapid population growth (He et al., 2021),
and the demand for industrial and domestic water increases
(Florke et al., 2018;Garrick et al., 2019). Additionally, climate
change in nature brings extreme weather effects that exacerbate
water scarcity by causing water resources to be unevenly
distributed in time and space (Greve et al., 2018;Schilling
et al., 2020;Schilling et al., 2020). In many developing
countries, due to technological constraints, the long-term
economic development model based on high energy
consumption and pollution has caused damage to the regional
ecological environment, resulting in the decline of ecosystem
functions and frequent problems such as water and
environmental pollution (Bekturganov et al., 2016;Best, 2019;
Wang et al., 2021). And a healthy watershed ecosystem is the
basis for abundant natural resources and social wealth for human
beings (Grill et al., 2019). China has attached great importance to
the protection of water ecology and the environment in recent
years and has actively adopted environmental protection
measures and implemented economic transformation and
industrial restructuring to gradually change the situation of
water pollution and water shortages (Chen and Qian, 2020;
Wan et al., 2022). According to Tang et al. (2022), Chinas
wastewater treatment rate has exceeded 90% in the past
20 years, and signicant results have been achieved in surface
water environmental pollution management. Although there is
still a trend of deteriorating water quality in some watersheds, the
direction of water pollution management is reasonable. The
Yangtze River, the longest river in Asia and one of the most
famous rivers in China, is rich in water resources and plays an
important role in Chinas history, culture and economy,
especially in the upper reaches of the Yangtze, where it has
extremely important ecological and economic and social values
(E et al., 2018). For thousands of years, the Yangtze River has
spanned the east and west of China, serving multiple functions
such as transportation, water supply and ecological safety barrier,
making it ChinasGolden Waterwayand an important link in
the Silk Road(Xu et al., 2021;Yang et al., 2021). However, as in
many developing countries, the erosion and water pollution
problems caused by the crude economy in the past have
greatly hindered the path of green development (Xu et al.,
2022). For the sustainable development of water resources, the
Chinese government has introduced a series of related policies
such as the Outline for the Development of Yangtze River
Economic Belt and the Yangtze River Protection Law, making
the restoration of the Yangtze River ecological environment a top
priority (Liu and Yuan, 2022). The upper Yangtze River is the
most fragile area of the basins ecological environment, and its
water ecological environment security is the basis of the
ecological environment quality of the whole basin and the key
to ensure the smooth implementation of the relevant national
strategic plans (Wang et al., 2022). How to reconcile economic
development and the sustainable use of ecosystem services is a
major long-term challenge. The ecological protection of water
resources in the upper reaches of the Yangtze River can be
strengthened through the establishment of an ecological
compensation system, which can help alleviate the
contradiction between rapid local economic development and
excessive resource use, and can narrow the large gap between the
economic development level of the eastern and western parts of
China. (Jiang et al., 2022).
Ecological compensation, also known as payment for
environmental services, has become a hot topic in the 21st
century as a mechanism for transforming environmental
externalities and nonmarket values into internal real nancial
resources for environmental stakeholders, and its theoretical and
practical research has been widely used in countries around the
world (Engel et al., 2008;Farley and Costanza, 2010;Gastineau
et al., 2021). The application of ecological compensation in
different contexts is not entirely consistent and is generally
agreed upon as a voluntary and quantiable transaction
between the compensating party and the compensated party,
an institutional arrangement that regulates stakeholder interests
primarily through economic means (Wen et al., 2011). Its
purpose is to protect the sustainability and stability of
ecosystem services and to promote the harmonious
development of humans and nature. Funding sources
currently include government nancial compensation
supplemented by market compensation, with an increasing
number of nongovernmental organizations (NGOs)
participating as market-based mechanisms are improved
(Kinzig et al., 2011). Ecological compensation in China is in a
preliminary stage and is piloted in several regions, such as
transboundary compensation involving the Xinan River
(Sheng and Han, 2022) and Chishui River (Qiu and Zhai,
2014) and market trading involving Zhejiang Province (Wang
H. et al., 2010). Among them, watershed ecological compensation
has been gradually promoted in China to protect the ecological
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Guan et al. 10.3389/feart.2022.988291
benets of shared water resources and mitigate transboundary
water pollution conditions (Gao et al., 2019). Ecological
compensation for highly spatially integrated and connected
watersheds requires upstream and downstream consultation
for joint protection, and how to formulate ecological
compensation scientically and rationally for watersheds is the
key to making sound ecological management decisions within
watersheds (Gao et al., 2020). Academic research on ecological
compensation has mainly focused on the determination of
ecological compensation areas and the calculation of
ecological compensation criteria.
How to identify protected areas and beneciary areas is the
primary issue in establishing ecological compensation
mechanisms, and this information directly determines the
science and effectiveness of compensation. Related studies,
e.g., Gastineau et al. (2021), discussed the mechanism of the
spatial distribution, environment and land cost factors affecting
the location of ecological compensation. Hu et al. (2022) used a
mathematical model to determine the changes in spatial and
temporal patterns of wind erosion prevention services provided
by desert ecosystems from recharge areas to benet areas from
the perspective of ecosystem service ows. Villarreal-Rosas et al.
(2022) also considered the impact of land-use change on spatial
and temporal changes in the supply, demand, and ow of
ecosystem services in different beneciary sectors from the
perspective of ecosystem service ows. Schirpke et al. (2014)
applied a spatially explicit modeling approach to determine the
specic location distribution of beneciary areas and protected
areas for ecosystem services. Garau et al. (2021) focused on the
spatial distributions of service supply and demand characteristics
among water ecosystems to help identify sources of conict and
improve stakeholder group coordination. Yu and Xu. (2016)
helped identify the supply and demand of services by
constructing a complete framework of ecological
compensation mechanisms to identify recipients and payers.
Burdon et al. (2022) constructed a new stakeholder-driven
participatory mapping approach to analyze the logical
relationship between stakeholders and natural capital from
multiple perspectives. Xi and Jing (2021) used the ecological
footprint method to distinguish ecological decit areas from
ecological surplus areas and found that eastern China was
mostly classied as an ecological decit area, while central
and western China were mostly classied as an ecological
surplus area. However, identifying the location of protected
areas and beneciary areas for ecosystem services, as well as
identifying those who use and protect them, remain key
challenges in the eld (Bagstad et al., 2013). Many studies
have used a separate modeling framework to distinguish
ecological compensation areas, identifying ecological
compensation protected areas and beneciary areas primarily
through stakeholder and natural resource participation.
The measurement of ecological compensation standards is
the core issue, and reasonable ecological compensation standards
are directly related to compensation effects and policy feasibility.
Many studies have carried out large-scale, high-specication
calculations of ecological compensation standards to maintain
the use of their natural resources (Hou et al., 2021). For example,
under the full consideration of the service functions of each
ecosystem, the ecosystem service value before and after the
change in regional land use/cover has been evaluated, and the
inuencing factors and temporal and spatial changes have been
analyzed to provide optimized information on ecosystem services
for land-use planning (Aziz, 2020;Ma et al., 2020;Wu et al., 2020;
Anley et al., 2022). There are many other methods used to
measure ecological compensation for various ecosystems. Gu
(2017) established an ecological compensation standard
evaluation model for the Zhoushan Islands New Area using
the theory related to ecological compensation for tourism and
the ecological footprint composition method. Fu et al. (2017)
established an ecological compensation standard calculation
system for the sustainable development of watershed
agriculture based on the convertibility of energy and price.
Rao et al. (2014) considered the spatial variation in ecological
services by establishing the criteria of marine ecological damage
compensation to suppress unsustainable development that
causes ecological damage. One of the most frequently used
models to calculate ecosystem services is the InVEST
(Integrated Valuation of Ecosystem Services and Trade-offs)
model, which has had good applications in hydrological
ecosystem services (e.g., Cong et al., 2020;Benra et al., 2021;
Zhang et al., 2021;McMahon et al., 2022). There are also many
studies on watershed ecosystems that use water quality and
quantity as the basis for compensation measurements, and in
the context of rapid global economic development, which has
resulted in a large increase in urban water demand and a large
amount of unreasonable sewage discharge, it is urgent to consider
the water environment as a compensation target; furthermore,
ecological compensation based on pollution damage can be used
to better control and monitor the quality of the water
environment (Liu et al., 2016;Guan et al., 2021). Related
research also includes the water footprint theory that can be
used to quantify the supply and demand of water ecosystem
services, which can be divided into green water (rainwater stored
in the soil), blue water (surface and groundwater) and grey water
(polluted water in production) (Chapagain and Hoekstra, 2011;
Pacetti et al., 2021). Applying the Total Pollutant Control-Water
Resource Value model, the concept of diluted water was
introduced to quantify the basin ecological compensation
criteria by combining the total pollutant and water resource
value (Guan et al., 2018). In addition, the integrated pollution
index method was used to calculate the transboundary water
quality compensation standard (Hao et al., 2021), calculate the
compensation index of pollution loss in a watershed based on the
pollution loss rate and energy value method (Guan et al., 2021),
and establish a pollutant abatement differential game model for
transboundary watersheds to obtain the optimal compensation
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strategy (Jiang et al., 2019a). The study of ecological
compensation in watersheds is dedicated to proposing a
reasonable ecological compensation standard measurement
method based on water allocation and water quality control,
and the grey water footprint approach can adequately integrate
water quality and quantity (Chai and Chen, 2022). The
application of the grey water footprint to ecological
compensation in watersheds is still very limited. There are
several methods for measuring ecological compensation
standards, but the results of these methods often correspond
to a xed ecological compensation standard value, and the results
often differ signicantly from the actual watershed compensation
values, making it difcult to provide direct guidance for actual
compensation cases. The ecological compensation threshold can
be used to calculate the ecological compensation standards of
different time periods and different judgment standards in the
same area, and a range interval can be obtained to represent the
uctuating interval of ecosystem service value within the
ecosystem carrying capacity of the study area, which can be
judged by integrating more factors.
How to combine the upper and lower limits of ecological
compensation to calculate the ecological compensation threshold
is a difcult problem. However, the ecological compensation
threshold is closely related to ecological benets, and both
ecological benets and ecological impacts must be considered
when setting ecological compensation threshold. If the ecological
compensation threshold is set too high, ecological policies cannot
be achieved, and if the ecological compensation threshold is set
too low, ecological environmental protection effects cannot be
achieved. However, ecological compensation actions in the past
have often been criticized for low levels of achievement, where
planned conservation actions were only partially achieved or not
achieved at all, while development activities were clearly still
underway. Brown et al. (2013) investigated the compliance of
245 conditions related to ecological compensation in 81 case
studies in New Zealand according to the Resource Management
Act of 1991, and the results showed that 35.2% of the
requirements were not met. Therefore, determining a
reasonable ecological compensation threshold has become a
pressing issue for the integrity of ecological compensation
mechanisms. For example, Simmonds et al. (2020) categorized
the pathways to achieve specic biodiversity characterization
targets as net gain, no net loss, or (rarely) managed net loss by
specifying different types and amounts of ecological
compensation to ensure the achievement of different targets.
De Mello et al. (2021) developed a novel offsetting
methodological approach for the compensation of legal
reserves. If landowners fail to meet the legal requirements on
their land, they may compensation in other equivalent
properties. Hou et al. (2021) found that grassland ecological
compensation policy improved grassland quality to a small
extent and had a positive impact on income, but it
exacerbated existing income inequalities among local
pastoralists. Jiang et al. (2019b) constructed a stochastic
differential game model to analyze transboundary pollution
control options between ecological compensation beneciary
areas and protected areas and found that the ecological
compensation mechanism provided long-term, effective
incentives only when the marginal losses of environmental
damage in the compensating region were more than twice
those of the compensated region. Qin and Wang (2022)
constructed an evolutionary game model to dene the
ecological compensation threshold, which showed that from
the governments perspective, the social benets must exceed
$10.69 million per year; however, from the perspective of
enterprises, government subsidies should be less than
$21.38 million per year. Therefore, using a combination of
ecological benets and ecological impacts to measure the
ecological compensation threshold is a valid and reasonable
approach.
Although the determination of ecological compensation
areas and the calculation of ecological compensation criteria
have been richly discussed, the following two fundamental
aspects have long been left to be enriched and are also the
main research questions of this study. 1) How can ecological
compensation protected areas and beneciary areas be
reasonably determined? 2) How can the ecological
compensation threshold model be constructed and how can
the upper and lower thresholds of ecological compensation be
accurately grasped? To solve these two problems, this study
adopts quantitative methods. 1) The concept of eco-
compensation priority sequence is invoked, and the InVEST
model is applied to obtain the non-market value of ecosystem
services, which is divided by the local GDP to obtain the ratio.
Revised it in combination with the income of farmers of major
related interest groups, to judge the ecological compensation
protected areas and benet areas according to the priority. 2)
According to water conservation and grey water footprint value,
a watershed ecological compensation threshold model is
constructed. From the perspectives of watershed ecological
resource value and water quality and water quantity damage
value. It indicates that the ability of the region to supply the value
of the water conservation service is directly taken as the upper
limit of ecological compensation, and the grey water footprint
compensation result of the zero-sum modelis introduced as the
lower limit of ecological compensation. Thus, the spatial
differences and evolutionary patterns of this ecological
compensation threshold are claried. The conclusion can
assist the establishment of the ecological compensation system
in the upper Yangtze River, provide a reference for the
management of regional ecological land types, and contribute
to the conservation and sustainable use of water resources.
The rest of this study is structured as follows. In Section 2, the
natural conditions of the upper Yangtze River and the policy
background of ecological compensation are introduced, and the
method of constructing the ecological compensation threshold
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model is explained. In Section 3, the specic results generated by
each phase of the method are analyzed. In Section 4 discusses the
comparative analysis of compensation cases and results of
different ecosystems, different calculation methods and
different river basins. The last part of section 5 is the
conclusion and prospect.
2 Data and methods
2.1 Study area and data sources
The upper reaches of the Yangtze River refer to the reach from
the source of the Yangtze River to the main stream of the Yichang,
with a total length of approximately 4,511 km, accounting for
approximately 70% of the total length of the Yangtze River. The
main tributaries include the Yalong River, Minjiang River, Jialing
River and Wujiang River, covering nine provinces (municipalities
and autonomous regions), including Qinghai, Tibet, Sichuan,
Gansu, Shaanxi, Yunnan, Guizhou, Chongqing and Hubei,
accounting for approximately 58.9% of the total area of the
Yangtze River basin (Hong et al., 2019), as shown in Figure 1.
This plays an important role in the safety of water resources and
the water environment as well as the sustainable development of
the economy and society in the Yangtze River basin. However,
rivers in the basin are prone to natural disasters due to their large
gap, changeable climate and landforms. For example, global
climate change causes ooding in the lower reaches of the river
when rainfall is abundant in summer, and the melting of glaciers
and the decline of the snow line make it a fragile ecological
environment and sensitive area with global strategic
signicance. In addition, long-term human disturbance has
reduced the ecosystem function of the river basin, which has
seriously weakened the water conservation function of the system.
It is imperative to establish and improve an ecological
compensation mechanism for water conservation in the upper
Yangtze River basin. By 2016, the Yangtze River Economic Belt
Development Outlineaimed to guide the coordinated
development of ecological environmental protection and the
green economy in the Yangtze River Economic Belt. Following
the promulgation of the Guiding Opinions on Establishing and
Improving the Long-term Mechanism of Ecological
Compensation and Protection in the Yangtze River Economic
Beltin 2018, a special fund was set up to subsidize the ecological
protection of the Yangtze River Economic Belt to ensure that the
ecological compensation mechanism of the Yangtze River
Economic Belt could be effectively realized for a long time. In
December 2020, the National Peoples Congress meeting passed
the Protection Law of the Peoples Republic of China,which
continuously strengthens the protection of the ecological
environment in the Yangtze River basin (Qiao et al., 2021). The
data from 2015 to 2020 were selected for analysis, and the 5 years
centered on the construction of an ecological civilization and the
improvement of environmental quality were regarded as the new
stage of environmental protection implementation. Analyzing and
calculating the changes in ecological compensation in river basins,
evaluating the effects of environmental protection
implementation, and promoting the sustainable and healthy
development of environmental protection were objectives of
this research.
The data sources used in the study are as follows: 1) Land
use remote sensing monitoring data: The land use remote
sensing monitoring data were selected from the Resource
and Environment Science and Data Center of the Chinese
Academy of Sciences (https://www.resdc.cn/) with a spatial
resolution of 1 km. The downloaded raw data were spliced
andcroppedasrequiredforthestudy area, and the blank values
were interpolated. 2) Soil data: Soil data in which soil hydraulic
conductivity saturation rates were calculated from sand
content, clay content, chalk content soil organic matter and
soil salinity by soil-plant-air-water (SPAW) model. And the rest
of the data were obtained from the Cold and Arid Regions
Science Data Centre (http://www.ncdc.ac.cn/auth/register)1:
1 million data of Chinas soil in 2017. 3) Meteorological data:
The meteorological data mainly include annual average
precipitation, sunshine hours and monthly average
temperature data for each prefecture-level city, and are
obtained from the daily dataset of Chinese meteorological
element station observations provided by the Resource
Science and Data Centre of the Chinese Academy of
Sciences (https://www.resdc.cn/), and collated according to
the stations included in the upper Yangtze River study area.
4) DEM data: The DEA data is mainly used to calculate the
number of catchment areas and percentage of slope in the study
area through ArcGIS hydrological analysis to obtain
topographic index data. The data were obtained from the
topographic and geomorphological data from the Resource
Science and Data Centre of the Chinese Academy of
Sciences (https://www.resdc.cn/) with a spatial resolution of
90 m. 5) Socio-economic data: Socio-economic data include
data on population, GDP, grain output, crop sown area,
economic forestry output, afforestation area and shery
output of each prefecture-level city (autonomous prefecture)
in 2015 and 2020, as well as data on nitrogen fertilizer
application, livestock breeding, industrial and domestic
wastewater emissions of various pollutants, total water
resources, etc. From the regional 2015 and 2020 Statistical
Yearbook, National Economic and Social Development
Statistical Bulletin, Environmental Statistics Bulletin and
Water Resources Bulletin, as well as from applications to
relevant authorities for public access.6) Vector data: All
administrative boundary data, vector data of ecological
function reserves and water systems were obtained from the
Resource Science and Data Centre of the Chinese Academy of
Sciences (https://www.resdc.cn/), and the vector data within the
upper reaches of the Yangtze River were obtained by
intersecting and cropping with ArcGIS software.
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2.2 Methodology
2.2.1 Model of water content in the upper
Yangtze River
In this study, the InVEST model was used to assess the water
content in the upper reaches of the Yangtze River. The input data
required for calculating water yield in the water supply module of
the InVEST model include the maximum soil root depth data,
average annual precipitation data, plant available water data,
average annual potential evapotranspiration data, land use/cover
data, watershed vector data, different surface cover types
corresponding to the biophysical coefcient table and Zhang
coefcient, which has a value of 4.433 (Liu J. et al., 2019).
WR min (1,0.TI3)×min (1,K
c300)×min (1,249V)×WY
(1)
TI log DASoildepth ×θ (2)
where WR denotes the water content (mm); TI denotes the
topographic index; Kcdenotes the soil hydraulic conductivity
saturation rate (mm/d); Vdenotes the ow rate coefcient; WY
denotes the water supply (mm); DA denotes the number of
catchment area grids obtained by watershed vector data statistics;
Soildepth denotes the soil depth (mm) extracted from the soil
database; and θis the slope percentage calculated from the study
area digital elevation model (DEM) in ArcGIS based on slope
analysis.
2.2.2 Calculation of grey water footprint in the
upper Yangtze River
Based on the ecological and environmental loss value of
water resources in the basin, an ecological compensation
calculation approach based on water quality and quantity
was considered to quantify the relationship between
compensation beneciary areas and compensation
protected areas in the basin. The grey water footprint
focuses on water quality and pollution discharge and
represents the volume of fresh water needed to dilute
pollutants to meet water quality standards (De Girolamo
et al., 2019). It can be regarded as the cost of water quality
improvement and effectively combines water quality and
quantity to be considered in the calculation of the loss
value of the environment. Referring to the formula of the
grey water footprint described in the Water Footprint
Evaluation Handbook(Hoekstra and Chapagain, 2007),
which is determined by the pollutant that produces the
largest grey water footprint in agricultural, industrial, and
domestic uses. The three grey water footprints are added
together to obtain the total regional grey water footprint value.
2.2.2.1 Agriculture grey water footprint
The agricultural grey water footprint includes planting and
breeding. Nitrogen pollution is the main problem faced by rivers
in China (Rong et al., 2016), so nitrogen fertilizer application
(e.g., total nitrogen, TN) was chosen as the main pollutant in the
plantation industry. The large amount of chemical oxygen
demand (COD) and TN contained in the excrement of
representative livestock (cattle, sheep, pig and poultry) was
chosen as the main source of pollution in the breeding
industry. Finally, the grey water footprint produced by
different pollutants was compared, and the maximum was
taken as the agricultural grey water footprint. The calculation
formulas are as follows:
Hp(TN)a×K
CTN Co
(3)
Hb(i)Sb(i)
CiCo
(4)
Sb(i)
4
e1
Ne×Fecal discharge ×fecal pollutant content ×fecal loss rate+
urine discharge ×urine pollutant content ×urine loss rate
(5)
HAmaxHb(COD),Hb(TN)+Hp(TN) (6)
where Hp(TN)denotes the plantation industry grey water
footprint; ais the rate of nitrogen fertilizer loss; Kis the
amount of nitrogen fertilizer used; CTN denotes the water
quality standard concentration of TN; Cois the natural
background concentration; Hb(i)denotes the breeding
industry grey water footprint of the ipollutant; Sb(i)is the i
sum of emissions of pollutants; Neindicates the number of e
species of livestock and poultry; Ciindicates the water quality
standard concentration of the icategory of pollutants; and HA
indicates the agricultural grey water footprint.
2.2.2.2 Industrial grey water footprint
Industrial grey water footprint two major pollutants, COD
and ammonia nitrogen, were selected as representatives, and the
maximum values were taken after separate calculations using the
following equations:
HImaxHI(COD),H
I(NH3N)(7)
HI(i)SI(i)
CiCo
(8)
where HIdenotes the industrial grey water footprint, and SI(i)
denotes the industrial emissions of pollutant category i.
2.2.2.3 Domestic grey water footprint
The domestic grey water footprint was also calculated using
two types of pollutants, COD and ammonia nitrogen, as
indicators, and the formulas are as follows:
HDmaxHD(COD),H
D(NH3N)(9)
HD(i)SD(i)
CiCo
(10)
where HDrepresents the domestic grey water footprint, and SD(i)
represents the domestic emissions of pollutants in category i.
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2.2.2.4 Regional grey water footprint
The regional grey water footprint is the sum of the industrial,
agricultural and domestic grey water footprints of the entire
region.
HGHA+HI+HD(11)
where HGdenotes the total regional grey water footprint.
According to the primary emission standard in the
Comprehensive Emission Standard for Pollutants (GB8978-1996),
CCOD, max=0.06 g/m
3
and C(TN),max=0.015 kg/m
3
.Accordingtothe
natural background concentration, Cnat is 0 (Bai and Sun, 2018), the
nitrogen fertilizer leaching rate was selected as 13.82% (Pang et al.,
2021). The values of livestock excretion were obtained from the
Technical Report on the Survey of Pollution in the National Scale
Livestock and Poultry Breeding Industry.
2.2.3 Eco-compensation priority sequence
calculation in the upper Yangtze River
The eco-compensation priority sequence (ECPS) refers to the
ratio of the regional nonmarket value of ecosystem services per unit
area to GDP per unit area, which indicates the demand intensity of
ecological compensation in different regions (Wang N. J. et al.,
2010). The value of water conservation services is mainly reected in
the value generated by water storage and water conservation. The
value of water content services for each grid was simulated using the
shadow engineering method to build water facilities with a storage
capacity comparable to the ecosystem water content, and the unit
cost required to build such water facilities was used to estimate the
unit value of water conservation services. With reference to the
results of Gao et al. (2020), the price index discount showed that the
value was 7.29 CNY/m
3
in 2015 and 10.92 CNY/m
3
in 2020. Taking
the main stakeholders in the compensation area into account in
ecological protection, the participation of ecological stakeholders can
make the compensation priority more reasonable (Sterling et al.,
2017). The farmerscollective is the most closely related to the
natural ecosystem and is the main compensation object in ecological
compensation. To distinguish the main compensation protection
areas and beneciary areas in the upper reaches of the Yangtze River,
the per capita disposable income of rural residents was substituted
into the ECPS for correction. According to the ECPS, the
compensation carrier was divided, and the area higher than the
average value was dened as the protected area, while the area lower
than the average value was dened as the beneciary area. The
specic expressions are as follows:
ECPS VNGN (12)
VN VS(13)
V(WR ×a)(14)
fiFFi(15)
ECPSECPS ×fi(16)
where ECPS is the eco-compensation priority sequence; GN is
the GDP per unit area of administrative district (CNY/ha); VN is
the water conservation services value per unit area (CNY/ha); V
is the total ecosystem water conservation services value (CNY/
ha); Sis the area of the prefecture (ha); WR denotes the water
content (m
3
); ais the unit price of water conservation services
(CNY/m
3
); iis the different prefecture; fiis the correction factor
of the corresponding prefecture; Fiis the annual disposable
income per farmer in the corresponding prefecture (CNY); F
is the average annual disposable income of farmers in the study
area (CNY); and ECPSis the corrected eco-compensation
priority sequence.
2.2.4 Model of the ecological compensation
threshold in the upper Yangtze River
Using the InVEST model to evaluate the water content of the
study area in 2015 and 2020, the upper limit of compensation in the
study area was based on the ecological benetsandusedtoreect the
water storage and preservation value of the water ecosystem in the
upper reaches of the Yangtze River; specically, the water
conservation value was chosen to measure it. The lower limit of
compensation in the study area was based on the loss value of the
ecological environment, the cost of maintaining and improving
water quality and quantity was the basis for evaluating the loss of
water resource value in the basin, and the grey water footprint
method was chosen to measure it. The market value of freshwater
resources in each region was chosen, and the zero-sum model (Liu
H. G. et al., 2019) was used to set all ecological compensation in the
basin to be self-consistent; that is, all administrative districts in the
basin compensated each other, and the ecological compensation
demand intensity coefcients of each prefecture-level city were
combined to make the lower limit value closer to the actual
situation. The ecological compensation demand intensity
coefcient t
i
wasthenobtainedbyECPScalculation.
The specic expression for the upper limit of the threshold is
as follows:
Ri upper V(17)
The per capita ecological surplus (decit) of water resources
in the whole basin is as follows:
εWjHj,G
Pj
(18)
The per capita ecological surplus (decit) of water resources
in the region is as follows:
εjWjHj,G
Pj
(19)
The specic expressions for the lower limit of the threshold
are as follows:
Mjεjε·Pj·m(20)
tiarctanECPSπ(21)
Ri lower Mj×ti(22)
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where population isPj,Mjis the ecological compensation
standard of region j,mis the weighted average value of
freshwater resources per unit, Riupper is the upper limit of
ecological compensation of prefecture-level municipalities (10
8
CNY), tiis the demand intensity coefcient of ecological
compensation of prefecture-level municipalities, πis the
circumference, and Ri lower is the lower limit of ecological
compensation of prefecture-level municipalities (10
8
CNY).
3 Results
3.1 Results of the upper and lower limits of
ecological compensation in the upper
Yangtze River
3.1.1 The upper Yangtze River water
containment
The water yield module of the InVEST model was applied to
obtain the water yield of the upper Yangtze River ecosystem, as
shown in Figure 2. In 2015, the unit water yield of the upper
Yangtze River ranged from 0 to 1,667.13 mm, and in 2020, the
unit water yield of the upper Yangtze River ranged from 0 to
1840.22 mm, with the range interval increasing by 173.09 mm.
The water yield of a watershed was mainly inuenced by
precipitation and evapotranspiration. The higher the
precipitation, the higher the water yield, and the higher the
evapotranspiration, the lower the water yield in the area. The
spatial distribution characteristics of the results show a gradual
increase in water yield in the upper Yangtze River from
northwest to southeast. The high value of water yield was
concentrated in the southeast of the upper Yangtze River and
near the Chengdu Plain, where precipitation was abundant, while
the low value is mainly distributed in Qinghai, Tibet and Gansu,
where evapotranspiration was high and precipitation was low.
Land use/cover type, soil properties, elevation and slope also
directly or indirectly inuence water yield.
The water content was further obtained from the water yield,
as shown in Figure 3. The water content per square kilometer of
the upper Yangtze River ranged from 0 to 1,359.74 mm in
FIGURE 1
Location map of the upper Yangtze River. (A) Geographical location of the Yangtze River Basin; (B) Geographical location of the study area; (C)
Water resources and ecological function protection areas in the study area.
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2015 and from 0 to 1,427.64 mm in 2020, an increase of 67.9 mm.
The water content calculated by the InVEST model was the
regulated amount of water in the soil layer obtained by
combining surface runoff based on the water yield. It
indicates that in addition to rainfall and evapotranspiration,
the inltration and water-holding capacity of the soil also
determines the amount of water content. The gure shows a
spatial distribution of water content gradually increasing from
northwest to southeast, with obvious spatial variability. The
regions with high water content were distributed in central
Sichuan and northern Guizhou and southern Chongqing,
which have high water yield, are dominated by hilly and
mountainous areas with dense vegetation and have better
water holding capacity. The areas with low water content are
mainly located in the north and west, where the water yield is low
and the main vegetation is grassland, making the soil layer weak
in its ability to retain precipitation. The land use/cover type was
very important to the precipitation retention and buffering, and
thus determines the size of water content.
3.1.2 The upper Yangtze River grey water
footprint
According to the calculation formula of the grey water
footprint, the average annual grey water footprint of different
sources was obtained. Because the numerical values of different
sources were quite different, the method of arc tangent function
normalization was used to map the original data to the interval of
[0,1], and the formula was x=ATAN(x)×(2/π); this approach
benets the comparative analysis of grey water footprint
structures in different areas, as shown in Figure 4. The
FIGURE 2
The upper Yangtze River water yield. (A) water yield in 2015; (B) water yield in 2020.
FIGURE 3
The upper Yangtze River water content. (A) water content in 2015; (B) water content in 2020.
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comparison between different sources clearly showed that the
agricultural grey water footprint accounted for the largest share,
followed by the domestic grey water footprint, and the industrial
grey water footprint was the smallest. The difference between the
agricultural grey water footprint and the other two was large,
indicating that nonpoint source pollution caused by agriculture is
the main problem affecting water pollution in the Yangtze River
basin.
As shown in Figure 5, spatial distribution of the total grey
water footprint values in different regions. To better compare the
changes in the greywater footprint, the range of values from
180 million to 50.62 billion m
3
for 2015 and from 100 million to
37.10 billion m
3
for 2020 were combined to unify the intervals,
which were classied into ve intervals using natural
breakpoints. In terms of time change, the grey water footprint
value from 2015 to 2020 decreased by 80 million to
13.52 billion m
3
. And in terms of spatial change, most areas
also show a transition from a dark high numerical range to a light
low numerical range. This reects the effectiveness of the upper
Yangtze River in following green development and energy
conservation and emission reduction during this period. The
spatial distribution of the two results was characterized by high
values on both sides and low values in the middle, with the lower
grey water footprint interval concentrated around the Chengdu
Plain, including Suining, Neijiang, Zigong, Leshan, and Yaan. In
the northwest region is less populated and economically
underdeveloped, yet all regions have a high grey water
footprint, except for Haixi Prefecture. Combined with
Figure 4, the industrial and domestic wastewater emissions in
Yushu Prefecture, Guoluo Prefecture, Changdu city, Aba
Prefecture, and Ganzi Prefecture were low, but the breeding
and raising of more livestock and a large amount of livestock
excretion among the sources of pollution required more
freshwater resources in nature to dilute, and were thus mainly
affected by agricultural pollution. As a result, the grey water
footprint was relatively high. These areas belong to the source
area of the Yangtze River basin, and the protection of water
resources is very important in these regions; thus, the prevention
and control of agricultural nonpoint source pollution should be
strengthened.
3.2 Upstream of the Yangtze River
ecological compensation, protected areas
and beneciary areas were identied
In this study, we considered the relationship between the
ratio of water conservation value and the economy and
determined the ecological compensation protection cities and
beneciary cities in the upper Yangtze River according to the size
of the ECPS (Wang N. J. et al., 2010). The mean ECPS values were
calculated to be 0.74 in 2015 and 1.07 in 2020. Areas with ECPS
values greater than 0.74 in 2015 were ecological compensation
protected areas in the basin, and those below 0.74 were ecological
compensation beneciary areas. The areas with ECPS values
greater than 0.74 in 2015 were ecological compensation protected
areas, and those with values lower than 0.74 were ecological
compensation beneciary areas. Similarly, those with ECPS
values greater than 1.07 in 2020 were protected areas, and
those with values less than 1.07 were beneciary areas. The
FIGURE 4
Source structure of the upper Yangtze River grey water footprint.
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intervals greater than the mean and those less than the mean was
graded using the natural breakpoint method, respectively, and
the results were divided into six intervals, as shown in Table 1,
and the spatial distribution results are shown in Figure 6. From
2015 to 2020, the number of low beneciary areas increased,
mainly transformed by low protected and medium-benet areas.
In terms of spatial location, most of the beneciary areas were
concentrated in the middle, east and south of the upper reaches of
the Yangtze River, and high-benet areas were mostly
concentrated in the Chengdu-Chongqing area. Most of the
protected areas were concentrated in the west and northwest
of the upstream basin. The classication result was in line with
the general socioeconomic development law. The cities in the
central-eastern region with better economic development enjoy
the water-conserving ecosystem services supplied by the upper
reaches and should pay compensation to the western upper
reaches to account for some of the economic development
benets sacriced by the protected areas due to the protection
of water resources to ensure the long-term stability of ecosystem
services, coordinate and alleviate the development conicts
between regions, and maintain a harmonious winwin
situation in the basin.
3.3 Results of ecological compensation
thresholds in the upper Yangtze River
The threshold model was constructed to obtain the upper and
lower threshold limits of ecological compensation for each
administrative region in the upper reaches of the Yangtze River
in 2015 and 2020 (Figure 7). The lower threshold limits for
2015 and 2020 were based on the grey water footprint and
water resources. A value less than 0 indicated that the region
had a negative externality, that is, its own freshwater resources
were insufcient to solve the pressure of environmental pollution
discharge and encroached on the freshwater resources of other
regions; as a result, this region must pay ecological compensation
to the regions with a water resource surplus. A value greater than
0 indicated a surplus of regional water resources, meaning the
region has positive externalitiesand can supply water to areas with
FIGURE 5
Grey water footprint values in the upper Yangtze River. (A) Grey water footprint values of prefecture-level cities in 2015; (B) Grey water footprint
values of prefecture-level cities in 2020.
TABLE 1 Eco-compensation priority sequence intervals.
Regional level High beneciary Moderate beneciary Low beneciary
2015 0.0003830.148850 0.1488510.381618 0.3816190.736054
2020 0.0006520.124698 0.1246990.350619 0.3506201.070166
Regional level Low Protection Moderate Protection High Protection
2015 0.7360541.201863 1.2018645.049350 5.0493519.419619
2020 1.0701663.459581 3.4595828.116419 8.11642024.100103
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water resource decits and obtain ecological compensation in
return. In terms of spatial distribution, the lower limit of the 2-
year ecological compensation threshold tended to be that the
compensation benet areas were clustered in the western region
and the compensation payment areas were clustered in the eastern
region. Among them, the cities of Yushu, Guoluo and Longnan
were transformed from compensation payment areas to
compensation benet areas in 2015; specically, there were less
FIGURE 6
The upper Yangtze River eco-compensation priority sequence. (A) ECPS in prefecture-level cities in 2015; (B) ECPS in prefecture-level cities in
2020.
FIGURE 7
Total ecological compensation threshold in the upper Yangtze River. (A) The lower limit of the total threshold of prefecture-level cities in 2015;
(B) The lower limit of the total threshold of prefecture-level cities in 2020; (C) The upper limit of the total threshold of prefecture-level cities in 2015;
(D) The upper limit of the total threshold of prefecture-level cities in 2020.
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total water resources in 2015, but the value doubled by 2020,
causing the regions to transition from having a water decit to
having a water surplus.
The upper limit of the threshold in 2015 and 2020 was obtained
based on the water content, which reects the total value of water
conservation ecosystem servicesintheregion.Thehigherthe
threshold value is, the stronger the water retention and storage
capacity are, and the more important it is to protect the water
resources; a lower threshold value indicate the ecological
environment needs to be improved to increase the water
retention capacity. From 2015 to 2020, the values of the upper
threshold levels increased signicantly, and the overall water
conservation ecosystem service function of the upper Yangtze
River improved signicantly. Ganzi, Aba, Liangshan, Chongqing,
and Zunyi maintained high water conservation ecosystem service
values for the 5 years, while the urban clusters around Chengdu and
Kunming had low water conservation ecosystem service values that
increased. Comparing the upper and lower thresholds in 2015 and
2020, the upper and lower thresholds of Ganzi, Aba, and Liangshan
were all in the higher range. This result means that they had high
water conservation value, and at the same time, the surplus of water
resources was abundant, which enabled these regions to benet
other areas in the basin. The upper threshold and lower thresholds of
Chengdu and Kunming were both low and categorized the areas as
high beneciary areas in the basin, which was in line with the eco-
compensation priority sequence and the general rule. Among them,
Chongqing and Zunyi have good ecological environment quality of
water conservation, so the upper threshold was higher. Additionally,
due to the high demand for fresh water in economic development,
the lower threshold was paid.
The unit compensation threshold of each prefecture-level
city in the upper Yangtze River was compared, and since the
difference between the upper and lower thresholds was large
(note: the upper thresholds were larger than the lower thresholds
in each region), the upper and lower thresholds were represented
by line graphs, and the maximum and minimum values of each
type of threshold were marked, as shown in Figure 8. In 2015, the
lower threshold range of the unit area of each prefecture-level city
and state in the upper reaches of the Yangtze River
was 254.55637.04 CNY/ha, with an absolute average value
of 90.94 CNY/ha, and the upper threshold range was
55.1127903.05 CNY/ha, with an average value of
10,663.48 CNY/ha. In 2020, each prefecture-level city and
state in the upper reaches of the Yangtze River state unit area
threshold lower limit ranged from 357.19 to 1,016.45 CNY/ha,
the absolute value of the average value was 165.71 CNY/ha, the
upper limit ranged from 188.21 to 54,006.75 CNY/ha, and the
average value was 17,929.34 CNY/ha. The absolute value of the
total compensation threshold in the upper reaches of the Yangtze
River ranged from 0.430 to 24.626 billion CNY in 2015 and from
0.671 to 41.602 billion CNY in 2020.
Figure 8 shows that the trend of the peak distribution points of
the threshold in 2015 and 2020 was generally consistent, with the
peak range in 2020 being larger than that in 2015. In the comparison
of the threshold lower limit, the number of prefecture-level cities
with unit compensation values less than 0 was greater than that of
prefecture-level cities with unit compensation values greater than 0;
that is, there were more areas paying ecological compensation than
receiving ecological compensation.
The highest value of the unit lower limit ecological
compensation was in Changdu city in 2015 and in
Shennongjia in 2020, while the lowest values of unit lower
limit ecological compensation were in Gannan Prefecture and
Bijie city. The comparison of the threshold upper limit showed
that the overall threshold upper limit of each administrative
region in 2020 was signicantly higher than that in 2015, where
the changes were obvious and the values exceeding 10,000 CNY/
ha were in Leshan, Meishan, Chengdu, Deyang, Yaan, Yibin,
Ziyang, Zigong, Zunyi, Chongqing and Enshi, and most of the
regions were in the Chengdu city cluster.
4 Discussion
4.1 Water conservation service values in
different ecosystems in the upper Yangtze
River
Ecosystem services include water conservation, food production,
climate regulation, carbon sequestration and oxygen release,
biodiversity and other ecosystem service functions (Tian et al.,
2019). For watershed ecosystems, the water content service
occupies a more important position than other ecosystem services,
and the global water scarcity problem causes people to pay close
attention to water content services (Liu J. et al., 2019). As the water
source area of the Yangtze River, the protection of water conservation
in the upper reaches of the Yangtze River is an important guarantee
for the safety of water resources in the whole basin and the whole
country. In common cases of watershed ecological compensation
implementation, water price is often used to assess compensation
values, and the value of water conservation services should be close to
the actual situation than accounting for all ecosystem service values;
thus, inated compensation standards can be reduced and the process
becomes more feasible. Discussing the service value of water
conservation in different ecosystems can clarify the relationship
between them, and provide reference for the improvement of
ecological environment and land space planning.
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Referring to the classication method of the China
Ecosystem Assessment and Ecosystem Security Database
1
and
the Resource and Environmental Science and Data Center of the
Chinese Academy of Sciences
2
, the upper reaches of the Yangtze
River can be divided into eight ecosystem types: forest
ecosystem, shrub ecosystem, grassland ecosystem, desert
ecosystem, wetland ecosystem, farmland ecosystem, urban
ecosystem and other ecosystems. And count the changes of
the area ratio and water conservation service value of each
ecosystem, as shown in Figure 9. The results showed that urban
ecosystems and forest ecosystems in the upper Yangtze River
increased from 2015 to 2020, while the rest of the ecosystems
decreased to different degrees, with the scrub ecosystem area
decreasing the most. The ecosystem type of the upper Yangtze
River is mainly grassland, followed by forest and farmland, with
the sum of the three exceeding 80% of the total area of the study
area. And inuenced by the increase of precipitation, the value
of water connotation services per unit in 2020 increased
compared to 2015. From the perspective of environmental
improvement, just considering the water conservation
services value per unit area of only four types of ecosystems,
namely wetland, forest, grassland and scrub, the ranking from
high to low as scrub >forest >grassland >wetland.
Corresponding to the previous results (Figure 2,Figure 3),
the water yield and water conservation are increasing from
northwest to southeast. The grassland, desert and wetland
ecosystems mainly distributed in the northwest area of the
upper reaches of the Yangtze River have low water
conservation service value per unit, while the southeast area,
which is dominated by forest and shrub ecosystems, has dense
vegetation, which is not conducive to the formation of surface
runoff, and developed roots are conducive to soil and water
conservation, so the water conservation service value is high.
FIGURE 8
Ecological compensation unit threshold in the upper Yangtze River. (A) Lower limit of unit threshold in prefecture-level cities; (B) Upper limit of
unit threshold in prefecture-level cities.
1 The Chinese terrestrial ecosystem classication system in the China
Ecosystem Assessment and Ecosystem Security Database (https://
www.ecosystem.csdb.cn/ecosys/eco_classes.jsp).
2 The 2015 data on the spatial distribution of terrestrial ecosystem types
in China from the Resource and Environmental Science and Data
Center of the Chinese Academy of Sciences (https://www.resdc.cn/
data.aspx?DATAID=198).
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FIGURE 9
Distribution of different ecosystems in the upper Yangtze River and water conservation service value. (A) different ecosystems in 2015; (B)
different ecosystems in 2020; (C) Area proportion of different ecosystems; (D) water conservation service value of different ecosystems.
FIGURE 10
Comparison of opportunity cost and grey water footprint in the upper Yangtze River.
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4.2 Comparative analysis of grey water
footprint and opportunity cost methods
In determining ecological compensation criteria, many
studies have used the opportunity cost approach to determine
the economic benets lost by farmers to provide ecosystem
services and used this value as a lower bound for ecological
compensation. Economic losses result from the restriction of
industrial development in ecological reserves to implement
ecological compensation policies, and they include the
opportunity costs of participating in reforestation,
reforestation, ecological public welfare forests and water
source protection. The study assumed that after participating
in the ecological compensation policy, farmers would not be
able to obtain economic benets in the short term, so the
benetsprovidedbytheland-usetypebeforeparticipatingin
ecological compensation could be characterized as the
opportunity cost of participating in the ecological
compensation policy, and again, the results of the
opportunity cost were multiplied by the results of the
opportunity cost and were multiplied by the demand
intensity coefcient t
i
of ecological compensation. The grey
water footprint was analyzed in comparison with the results of
the opportunity cost approach, as shown in Figure 10.
In Figure 10, the opportunity cost compensation value and
the grey water footprint compensation value corresponded to
different axes. The range of unit opportunity cost compensation
values for 20152020 for each region is 110.39808510.25 CNY/
ha. Since the unit grey water footprint compensation values were
calculated only for 2015 and 2020, the average value was
multiplied by the number of years to obtain a range of
ecological compensation values per unit grey water footprint
for 20152020 of -1,297.50-4,188.46 CNY/ha. The ecological
compensation value of unit opportunity cost to each
prefecture-level city (state) is greater than that of grey water
footprint, which indicates that the grey water footprint approach
adopted in this study was closer to the actual feasible
compensation value. The gure reects that the compensation
value curves generated by the two methods uctuated with
similar trends among the prefecture-level cities, such as Ganzi,
Yaan, Longnan, and Diqing, which showed signicant peaks in
both compensation methods. Most of the regions with negative
grey water footprints also corresponded to relatively low
opportunity cost values, such as in Xiangyang, Bijie,
Chuxiong, Suining, Nanchong, Guangan, and Bazhong city.
These areas with a small loss of opportunity cost have a great
demand for economic development, thus generating a greater
grey water footprint, resulting in water decits and the need to
pay ecological compensation to balance development within the
basin. Both approaches have their advantages, with the
opportunity cost being able to compensate as much as
possible for the economic loss of farmers who must protect
ecological land, and the economic development aspirations of the
region being considered more than the grey water footprint. The
grey water footprint is more reective of the polluter pays
principle, which considers the cost of pollution control more
than the opportunity cost. The opportunity cost mainly considers
the change of land use type, but less considers the ecological value
of water resources in the watershed. The grey water footprint
better reects the degree of pollution caused by different
industries. For example, non-point source pollution caused by
agriculture has a greater impact on the water environment, taking
the stakeholder relationship into account more comprehensively.
In addition, the grey water footprint introduces a zero-sum
model to calculate ecological compensation, which makes the
results have positive and negative values. It can represent the
compensation subject-object relationship in the basin, which can
reect more information than the opportunity cost method of
calculating ecological compensation.
4.3 Comparative analysis of theoretical
ecological compensation thresholds in
the upper reaches of the Yangtze River
and ecological compensation in different
river basins
In global watershed ecological compensation, many
countries are early to address the issue of inter-basin benet
distribution and ecological compensation. There have been more
cases of successful improvement of the watershed ecological
environment by means of ecological compensation (Table 2).
These experiences can be used as a reference for establishing
ecological compensation in watersheds in China. Table 2 shows
that the compensation effects of various watershed ecological
compensation cases are mainly centered on water quality
improvement, which is the main purpose of watershed
ecological compensation. And due to the nature of rivers, the
relationship between ecological compensation recipients and
payers in a watershed is often upstream and downstream.
Comparing the existing watershed ecological compensation
standards with the theoretical threshold in this study, the
overall theoretical value of the upper threshold was higher,
while the theoretical value of the lower threshold was close to
the actual watershed compensation amount because the upper
threshold represented the value of water conservation services in
the region. In practice, the ecological value of the area is not used
as the evaluation criterion, but the compensation is based on the
degree of loss. The actual compensation standard is often not a
unique price but rather a range of compensation values based on
a combination of multiple instruments, as different watersheds
have different social environments and varying degrees of
pollution.
In recent years, the practice of ecological compensation in
Chinas watersheds has developed rapidly, and funding has
increased signicantly, but the effects of compensation are not
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Guan et al. 10.3389/feart.2022.988291
yet obvious. The domestic compensation cases in Table 2 also
show that the compensation funds are more dependent on
government nance, and the compensation funds come from
a single source. The survey shows that the proportion of funds
invested from social parties has not yet reached 1% of the total
ecological protection compensation funds in China (Wu et al.,
2019). Although local governments at all levels have been actively
experimenting with market-based and diversied ecological
compensation mechanisms in recent years. For example, The
Xinan River (Ren et al., 2021) and Jinhua River (Zhang, 2011)
are the rst examples of cross-provincial watershed ecological
compensation and water rights trading in China, respectively,
and both have achieved good results. However, to further
promote it, it is necessary to provide corresponding legal
system protection and policy support, standardize the
methods of market compensation and compensation fund
accounting, and promote the transition of watershed
ecological compensation work from basic research to technical
guidance and policy (Feng et al., 2018). International watershed
ecological compensation has been developed earlier than in
China, and it is easy to see that governments have a major
role in funding ecological compensation for larger projects.
Examples include the treatment of eutrophication in Lake
Biwa waters in Japan, the New York City plan in the
United States of America and the construction of sewage
treatment plants in the Elbe River basin in Germany and the
Czech Republic (Smith and Porter, 2010;Sauer et al., 2015;Yu
2016). This type of ecological compensation for larger watersheds
requires the coercive power of government to coordinate between
people, sectors and enterprises. When ecological compensation is
initiated by the market, it is mostly motivated by a conict
between economic interests and environmental protection, as in
the case of mineral water companies in France, NGOs in Costa
Rica, local funds in Ecuador (Jiang and Chen, 2016). A common
feature of these types of compensation is that they occur in small
watersheds, where the amount of compensation is small, and
TABLE 2 Research on international watershed ecological compensation.
Countries Watershed Time Compensation
mechanism
Payers and
recipients
Compensation
standard
Effect
China (This
study)
The upper Yangtze
River
20152020 Government-led Beneciary areas
and protected
areas
The average annual compensation
threshold ranges from $19.08 to
$2,125.15 per hectare and total
compensation threshold ranges from
$82 million to $4.92 billion
Strengthened partnerships
between regions to
effectively ensure water
quality and quantity
China Xinanjiang 20122017 Central and local
government-led
Zhejiang and
Anhui
Based on the calculation of
transboundary water quality, it was
about $59 million to $89 million per
year
The water quality has been
improved
China Jinhua River 2000 Government-led Yiwu city and
Dongyang city
Yiwu paid $30 million for the right to
use about 50 million m
3
of water in the
reservoir
The water shortage
downstream was alleviated
Japan Biwa Lake 19992006 Government-led Central
government and
local government
The total investment of Lake Biwa
treatment was $7.22 billion, with an
average annual investment of
$898 million
The water quality has been
improved
United States Croton-Catskill-
Delaware
Watershed System
1994 Government-led Downstream and
upstream
The implementation of a watershed
protection plan cost about $507 million
It saved the funds for
building water purication
plants
Germany Elbe 2000 Government-led Germany and
Czech Republic
It cost about $4.83 million to build a
municipal sewage treatment plant at
the border
The water quality was
basically up to standard
France Rhin-Meuse Basin 1990 Market-led Company and
farmer
Perrier Vittel S. A paid the water source
farmers $230 per hectare per year
Reduce the cost of water
quality improvement
Costa Rica National
Watershed
19972008 Market-led and
government subsidies
Downstream and
upstream
The compensation paid by water users
to upstream stakeholders wad about
$22 to $81.6 per hectare per year
The water quality and
economic development
were ensured
Ecuador Cayambe-Coca
Basin
1998 Government-led and
market transactions
Downstream and
upstream
Paid the upstream households $6 to
$12 per hectare per year through
residential water fees
Protected the upstream
ecological reserves
Note: Selected currency conversion rates. 1CNY, 0.1486 USD, 1DM, 0.5370 USD, 1JPY, 0.00767.
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Guan et al. 10.3389/feart.2022.988291
where government subsidies make it possible to fund the
compensation more adequately. Combined with the
international experience of watershed ecological
compensation, the upper Yangtze River basin involves several
administrative regions, and the implementation of watershed
ecological compensation should establish a horizontal
compensation mechanism, which makes local governments
compensate each other. The compensation can be combined
with market mechanisms, NGOs can be encouraged to jointly
initiate compensation projects, and the sources of compensation
can be broadened to ensure sufcient funds. In addition, we
should improve the ecological compensation system and form a
legal basis to promote the participation of various stakeholders to
promote the harmonious coexistence between humans and
nature and to ensure the sustainable development of water
resources in the upper reaches of the Yangtze River.
5 Conclusion
The water yield per unit in the upper reaches of the Yangtze
River was 01,667.13 mm and 01840.22 mm in 2015 and 2020,
respectively, with the range interval increasing by 173.09 mm.
The water content per unit area was 01,359.74 mm and
01,427.64 mm, with the range interval increasing by 67.9 mm
from 2015 to 2020. The source structure of the grey water
footprint indicates that the agricultural grey water footprint
accounts for the largest proportion, followed by the domestic
grey water footprint, and the smallest is the industrial grey water
footprint. Nonpoint source pollution is the main problem facing
water pollution in the Yangtze River basin. The highest value of
the grey water footprint from 2015 to 2020 was reduced by
13.52 billion m
3
, the total amount of the grey water footprint was
reduced, and environmental protection initiatives became more
effective.
The eco-compensation priority sequence was divided into
ecological compensation protected areas and ecological
compensation beneciary areas according to the relationship with
the mean. Most of the beneciary areas were concentrated in the
central-eastern and southern parts of the upper reaches of the Yangtze
River, especially in the Chengdu-Chongqing urban agglomeration.
Most of the protected areas were concentrated in the western and
northwestern parts of the upper watershed. The classication results
conformed to the general economic development law. Finally, the
lower limit of the threshold for each prefecture-level city and state in
2015 ranged from 254.55 to 637.04 CNY/ha, and the upper limit
ranged from 55.11 to 27,903.05 CNY/ha. The lower limit of the
threshold for each prefecture-level city and state in the upper Yangtze
River in 2020 ranged from 357.19 to 1,016.45 CNY/ha, and the
upper range was 188.2154,006.75 CNY/ha. The absolute mean range
of the total compensation threshold was 0.4324.63 billion CNY in
2015 and 0.67 to 41.60 billion CNY in 2020. From 2015 to 2020, the
ecological compensation threshold of the Yangtze River basin
improved overall.
The value of water conservation services per unit area in the
different ecosystems in descending order was scrub >forest >
grassland >wetland. The grey water footprint and opportunity
cost compensation value curves uctuated similarly at the
prefecture level, but the compensation value of opportunity cost
wasalmostalwaysmuchlargerthanthecompensationvalueof
the grey water footprint. Compared with the actual ecological
compensation standards adopted in different river basins, the
overall theoretical threshold lower limit was closer to the actual
river basin compensation amount than was the upper limit,
indicating that the compensation accounting based on the
ecological damage degree was more in line with the actual situation.
In summary, the threshold model of ecological compensation
in the upper reaches of the Yangtze River was constructed by
using the InVEST model and greywater footprint. The results
proved that this method has certain applicability and reference
value. There are also some shortcomings. First, this study
calculates the non-market value and market value of
watershed ecological compensation as upper and lower limits
separately, but the actual ecological compensation is often a
combination of market value and non-market value. Second, the
ecological compensation of the grey water footprint regards the
upper Yangtze River as a complete basin, lacking consideration of
the impact on the middle and lower reaches of the basin. Thirdly,
due to the limited data acquisition, the lack of the supplement of
actual measurement data and the survey of peoples willingness
to compensate, resulting in the gap between the research results
and the reality. In future studies, more inuence factors can be
added to optimize the parameter selection of the ecological
compensation threshold model. And considering the
correlation of the whole basin, we can try to calculate the
ecological compensation threshold for the whole Yangtze
River and discuss the benet relationship between upstream
and downstream. Supplementing the eldwork data and
questionnaires in the study area makes the parameters more
localized and enhances the feasibility of the results.
Data availability statement
The original contributions presented in the study are
included in the article/supplementary material, further
inquiries can be directed to the corresponding author.
Author contributions
DG: Conceptualization; Methodology; Funding acquisition;
Investigation; Project administration; Supervision; Validation;
Writingoriginal draft, review, and editing. LW:
Conceptualization; Methodology; Data curation; Investigation;
Frontiers in Earth Science frontiersin.org18
Guan et al. 10.3389/feart.2022.988291
Formal analysis; Software; Validation; Visualization; Writing
original draft, review, and editing. LC: Conceptualization;
Methodology; Investigation; Formal analysis; Writingreview
and editing. YZ: Data curation; Investigation; Writingreview
and editing. LZ: Data curation; Project administration;
Supervision; Validation; Writingreview and editing.
Funding
This work is partially supported by National Natural Science
Foundation of China (42171298), Late Project of National Social
Science Foundation in China (20FJYB035), the Ministry of
education of Humanities and Social Science project
(20YJA790016) and Natural Science Foundation of Chongqing
in China (cstc2020jcyj-jqX0004).
Conict of interest
The authors declare that the research was conducted in the
absence of any commercial or nancial relationships that could
be construed as a potential conict of interest.
Publishers note
All claims expressed in this article are solely those of the
authors and do not necessarily represent those of their
afliated organizations, or those of the publisher, the
editors and the reviewers. Any product that may be
evaluated in this article, or claim that may be made by its
manufacturer, is not guaranteed or endorsed by the
publisher.
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