Revealing Water Stress by the Thermal Power ... - ACS Publications

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Revealing Water Stress by the Thermal Power Industry in China Based on a High Spatial Resolution Water Withdrawal and Consumption Inventory Chao Zhang,*,† Lijin Zhong,*,‡ Xiaotian Fu,‡ Jiao Wang,‡ and Zhixuan Wu§ †

School of Economics and Management, Tongji University, 1239 Siping Road, Shanghai 200092, China World Resources Institute China Office, 9 Dongzhong Street, Beijing 100027, China § School of Environment, Tsinghua University, Beijing 100084, China ‡

S Supporting Information *

ABSTRACT: This study reveals the spatial distribution of water withdrawal and consumption by thermal power generation and the associated water stress at catchment level in China based on a high-resolution geodatabase of electric generating units and power plants. We identified three groups of regions where the baseline water stress exerted by thermal power generation is comparatively significant: (1) the Hai River Basin/East Yellow River Basin in the north; (2) some arid catchments in Xinjiang Autonomous Region in the northwest; and (3) the coastal city clusters in the Yangtze River Delta, Pearly River Delta, and Zhejiang Province. Groundwater stress is also detected singularly in a few aquifers mainly in the Hai River Basin and the lower reaches of the Yellow River Basin. As China accelerates its pace of coal mining and coal-fired power generation in the arid northwest regions, the energy/water priorities in catchments under high water stress are noteworthy. We conclude that promotion of advanced water-efficient technologies in the energy industry and more systematic analysis of the water stress of thermal power capacity expansion in water scarce regions in inland China are needed. More comprehensive and transparent data monitoring and reporting are essential to facilitate such water stress assessment.

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INTRODUCTION

vulnerable ecosystems in northwest China among policymakers, researchers, media, NGOs, and the general public.8,9 Some previous studies have touched upon quantitative analyses for water withdrawal and/or consumption of the thermal power industry in China, such as life cycle water use by power generation,5 and water demand projection for thermoelectric power generation in the future.10−12 However, the existing studies could be challenged because of insufficient data. China has not promoted a transparent statistic and reporting system for water withdrawal and consumption in the thermal power industry and the results in existing studies varied between different methods. For example, the estimate about the percentage of air-cooled power capacity in six northwest provinces (Xinjiang, Inner Mongolia, Ningxia, Gansu, Shaanxi, and Shanxi) built on selected samples by Yuan and colleagues11 is higher than the estimate based on a detailed plant-by-plant survey by Zhang and colleagues17 resulting in overestimation for water saved by air-cooled power plants. The water demand for thermoelectric power generation projected by Cai and

The thermal power industry has large water requirements primarily for cooling needs.1,2 Water use by power plants and its associated environmental problems are focal points of a growing number of studies in the energy−water nexus.3,4 In China, thermoelectric power generation is responsible for roughly 10% of the national total freshwater withdrawal, ranking as the second largest water user after irrigation.5 To meet growing electricity demands for economic development, China is accelerating the construction of large coal mines and coal power plants in its arid northwest regions where most coal reserves are located. In these regions, China is also building long-distance, ultrahigh voltage electricity transmission projects to deliver electricity to consumers in the east.6 The latest Action Plan for Energy Development Strategy 2014−2020 issued by the Chinese State Council in November 2014 proposed to build nine clusters of large coal-fired power plants (each with a capacity larger than 10 GW) in northern and northwestern regions (i.e., Xilin Gol, Ordos, North Shanxi, Central Shanxi, East Shanxi, North Shaanxi, Hami, East Junggar, and East Ningxia).7 These ambitious goals for the coal-fired power industry have raised wide concerns about potential negative impacts on scarce water resources and © XXXX American Chemical Society

Received: November 1, 2015 Revised: January 12, 2016 Accepted: January 20, 2016

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DOI: 10.1021/acs.est.5b05374 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

Policy Analysis

Environmental Science & Technology Table 1. Water Withdrawal Factors of Thermoelectric Power Generating Technologies (m3/MWh) fuel type coal

cooling methoda

generation technology 1000 MW (ultrasupercritical) 600 MW (supercritical)

300 MW (subcritical)

100−250 MW

less than 100 MW

mean

low estimate

high estimate

number of observationsb

OT RC dry OT RC dry OT RC dry OT RC dry OT RC dry

82.8 2.11 0.31 100.6 2.061 0.334 103.1 2.37 0.367 103.1 2.70 0.59 103.1 3.09 1.0

74.2 2.05 / 92.8 1.63 0.211 82.9 1.96 0.252 82.9 2.11 0.50 82.9 2.18 0.864

88.4 2.17 / 105.9 2.323 0.456 127.2 2.84 0.517 127.2 3.68 0.68 127.2 4.19 1.08

7 4 1 4 91 42 4 218 25 / 29 2 / 5 4

water withdrawal permits ref 19 ref 19 water withdrawal permits ref 19 ref 19 water withdrawal permits ref 19 ref 19 assumed to be same as 300 MW units ref 19 ref 19 assumed to be same as 300MW units water withdrawal permits water withdrawal permits

data sources

natural gas

steam cycle combined cycle

RC OT RC

4.54 34.07 0.946

4.54 27.25 0.568

4.54 79.5 2.84

/ / /

ref 23 ref 23 ref 23

recovered gases

steam cycle

RC

4.03

3.77

4.46

3

combined cycle

RC

2.09

1.79

2.44

4

ref 24 and feasibility report of proposed projects ref 24−26

nuclear

steam cycle

OT (seawater)

178

87

227

/

ref 23

biomass

steam cycle

RC

4.54

3.58

5.35

14

ref 27

municipal solid waste

steam cycle

RC

7.95

6.79

10.0

7

water withdrawal permits

waste heat

steam cycle

RC

9.61

6.11

12.78

7

feasibility report of proposed projects

a

OT = once through; RC = recirculating. “/” Means these factors are estimated based on other factors or directly extracted from other references. b

colleagues12 is based on the average water withdrawal intensity per kWh of electricity at provincial aggregate level, without distinguishing the differences in water withdrawal and consumption intensities of different cooling technologies and unit sizes. Furthermore, most existing studies analyzed the energy−water nexus by jurisdiction (either at national or provincial scale) rather than at catchment or river basin level. The United States has applied high resolution spatial analyses to understand and address water problems associated with the thermal power industry.13−16 Instead of water withdrawal and/ or consumption, some studies apply “water stress”, the ratio of water withdrawals to local available water resources, to analyze the water problems between supply and demand. The catchment scale analyses provided a good match between the location of water users (e.g., power plants) and the local available water resources helping policy makers understand the impact on local water resources from thermoelectric power generation more accurately and develop more practical and integrated water−energy management plans. A majority of China’s coal reserves and planned large coalfired power plants are located in water scarce areas.8,17 To help China’s decision-makers better understand the actual water problems induced by thermoelectric power generation and develop appropriate water management policies, this study aims at developing a comprehensive geodatabase for electric

generating units (EGUs) and thermal power plants (covering over 3000 units and 98.7% of the total installed thermal power capacities in China) with their fuel types, generation technologies, cooling technologies, water withdrawal and consumption, types of water sources, and geographic locations. Based on this geodatabase, we apply the World Resources Institute’s (WRI) Aqueduct Water Risk framework to analyze the baseline water stress and groundwater stress associated with thermoelectric power generation at catchment scale for 2011. The high resolution spatial analysis maps the spatial distribution of thermal power plants, the cooling technologies adopted, thermoelectric water withdrawal and consumption, and the water sources used by power plants. Key regions subjected to high water stress in China where thermal power development should be adjusted are identified.

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DATA SOURCES AND METHOD

Geodatabase of EGUs and Power Plants. A facility-level inventory of EGUs with water withdrawal and consumption is of high value for energy−water nexus studies. We collected large amounts of relevant information from various sources and compiled a data set of EGUs covering fuel type, nameplate capacity, commissioning date, cooling technology, types of water sources, and detailed geographic location. Major data sources include: B


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Environmental Science & Technology Table 2. Water Consumption Factors of Thermoelectric Power Generating Technologies (m3/MWh) fuel type coal

cooling methoda

generation technology 1000 MW (ultrasupercritical) 600 MW (supercritical)

300 MW (subcritical)

100−250 MW

less than 100 MW

mean

low estimate

high estimate

number of observationsb

OT RC dry OT RC dry OT RC dry OT RC dry OT

0.228 1.688 0.31 0.28 1.65 0.334 0.343 1.89 0.417 0.556 2.16 0.59 0.556

0.190 1.64 / 0.18 1.30 0.211 0.170 1.57 0.250 0.270 1.69 0.50 0.27

0.370 1.736 / 0.39 1.86 0.456 0.488 2.27 0.591 0.930 2.94 0.68 0.93

20 / 1 75 / 42 142 / 25 16 / 2 /

RC dry

2.47 0.59

1.74 0.5

3.35 0.68

/ 4

ref 19 80% of the withdrawal factors ref 19 ref 19 80% of the withdrawal factors ref 19 ref 19 80% of the withdrawal factors ref 19 ref 19 80% of the withdrawal factors ref 19 assumed to be the same as 100−250 MW units 80% of the withdrawal factors ref 19

data sources

natural gas


RC OT RC

2.76 0.379 0.795

2.12 0.076 0.178

4.16 0.871 1.136

/ / /

ref 23 ref 23 ref23

recovered gases


RC RC

3.22 1.68

3.01 1.43

3.57 1.95

/ /

80% of the withdrawal factors 80% of the withdrawal factors

nuclear

steam cycle

OT (seawater)

1.514

0.379

1.514

/

ref 23

biomass

steam cycle

RC

3.63

2.86

4.28

/

80% of the withdrawal factors

municipal solid waste

steam cycle

RC

6.36

5.43

8.0

/


waste heat

steam cycle

RC

9.61

6.11

12.78

/


a

OT = once through; RC = recirculating. “/” Means these factors are estimated based on other factors or directly extracted from other references. b

plants list are not included in the MEP EGUs list and CEC EGU samples. We treated these plants as single EGUs and did not make further disaggregation. Technological information on these small plants is mainly supplemented by other materials as described in data source 4 listed above. We then used Google Earth to locate all power plants. Different types of cooling systems can also be distinguished from the satellite images providing a reliable way to verify or identify the cooling technology of EGUs. For a small proportion of small-sized power plants that cannot be found on the satellite images, we used the geographic coordinates of the administrative district where the plant is located at for approximation. Water source information on many large and medium-sized EGUs is reported in data source 2. For other EGUs and plants, data source 4 was used to identify water sources. Water Withdrawal and Consumption Factors. There have been a number of review articles on water withdrawal and consumption factors (ratios of water withdrawal/consumption per unit of generated electricity) of different electric generation technologies based on data from U.S. power plants.1,21−23 In this study, China specific factors are extracted from various data sources presented in Table 1 and Table 2. The Energy Efficiency Benchmarking Report19 by CEC gleans individual power plants’ operational performance providing water withdrawal factors of EGUs by different cooling technologies and

1. A list of more than 3000 coal-fired EGUs with installed capacity and commissioning date compiled by the Chinese Ministry of Environmental Protection (MEP).18 2. The Energy Efficiency Benchmarking Report compiled by the China Electricity Council (CEC),19 which includes power generation technologies, water withdrawal factors, and water sources for more than 600 selected medium and large-sized coal-fired EGUs. 3. A list of power plants larger than 6 MW with installed capacity and electricity output compiled by CEC.20 Power plants smaller than 6 MW are not covered in our analysis, which account for less than 1% of the total installed thermoelectric power capacities. 4. Other data sources include water withdrawal permits issued to power plants, technical proposal and environmental impact analyses of power plant projects, literature about water use in Chinese power plants, web pages of utility companies, and media reports. Useful information is extracted from these sources and integrated into the inventory. We cross checked the different data sources listed above and created a consolidated data set. First, we matched the information from the MEP EGUs list, the CEC EGU samples, and the CEC power plants list to identify the technology type of each EGU. Some small-sized power plants in the CEC power C


Policy Analysis

Environmental Science & Technology

Figure 1. (a) Water withdrawal by thermal power generation at catchment level in 10 major Chinese river basins defined by the Chinese government: Songhua River Basin (Songhua), Liao River Basin (Liao), Hai River Basin (Hai), Yellow River Basin (Yellow), Huai River Basin (Huai), Yangtze River Basin (Yangtze), Southeast Rivers (SE), Pearl River Basin (Pearl), Southwest Rivers (SW), and Northwest Rivers (NW); (b) Water consumption by thermal power generation at catchment level; (c) baseline water stress caused by thermal power generation at catchment level; (d) groundwater stress caused by thermal power generation plotted at 0.5° × 0.5° resolution.

sizes. The 10th and 90th percentile of the samples are used as low and high estimates for water withdrawal factors in this study, respectively. When the sample size is smaller than ten, the minimum and maximum values are used instead. The water withdrawal factors of once-through cooling plants reported by CEC do not include once-through cooling water but actually refer to water withdrawal for all other processes (e.g., boiler water makeup, slag removal, and flue gas desulfurization). Therefore, these factors approximately reflect water consumption intensities of once-through cooling plants. We extracted water withdrawal factors of coal-fired EGUs using once-through cooling from a number of water withdrawal permits issued by the Changjiang (Yangtze River) Water Resources Commission. Supporting documents attached to

these permits provide detailed water withdrawal data of actual operation. As no detailed water use information is available for natural gas-fired and nuclear power plants in China, we use harmonized estimates from Meldrum and colleagues23 as approximation. Thermal power plants using recovered gases, biomass, municipal solid waste, and waste heat only account for a small part of electricity output in China and we defined their water use factors by literature review, water withdrawal permits, and technical proposals of proposed projects. Water consumption factors are not directly reported in the above-mentioned data sources. For recirculating cooling EGUs (except natural gas-fired and nuclear power) we assume a typical consumption-to-withdrawal ratio of 0.8 for approxD


Policy Analysis


groundwater withdrawal relative to its sustainable recharge rate over a given aquifer.35 Sustainable groundwater use requires that the abstraction rate should not exceed groundwater recharge rate. Following this definition, a groundwater stress indicator relevant to thermoelectric power generation (GWSTHE) over a certain aquifer is calculated as follows:

imation. This typical ratio is determined according to the median values of water consumption and water withdrawal of pulverized coal power generation with cooling tower from Meldrum and colleagues.23 In terms of dry cooling EGUs, it is assumed that their water consumption factors are equal to their water withdrawal factors. More details of the data sources of water withdrawal and consumption factors used in our calculation are described in the Supporting Information (SI). Water Stress Indicators. Water stress can be measured by the ratio of water withdrawals to available water resources, which is also known as the withdrawal-to-availability (WTA) ratio28 or criticality ratio.29 A number of indices have been developed based on this concept such as the Water Supply Stress Index (WaSSI) by Sun and colleagues.30 More complex measurements made extensions to the basic indices by incorporating environmental water requirements,31 considering variations in monthly or annual flows,32 or taking changes of water demand driven by population growth into account.33 In this study, we use the Aqueduct’s global water risk maps developed by the World Resources Institute (WRI)34 to analyze the water stress driven by thermal power generation. The Aqueduct maps define Baseline Water Stress (BWS) as the ratio of total annual water withdrawal to average annual available blue water (open water source) in a catchment35 as follows: BWS =

GWSTHE =

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DESCRIPTIONS OF THE INVENTORY The total installed capacity of thermal power generation in China for 2011 (including nuclear power) amounted to 780.91 GW. Electricity output reached 3.99 billion megawatt hours (MWh).20 The geodatabase compiled in this study covers 98.5% (769.06 GW) of the total installed capacity and 98.1% of the total electricity production (3.91 billion MWh). Coal-fired power plants play a dominant role in China, accounting for 93.0% of the total installed capacity in the geodatabase. Natural gas, nuclear power, and other fuels (such as biomass, municipal solid waste, recovered gases, industrial waste heat, etc.) account for 2.7, 2.2, and 2.1%, respectively. A total of 3116 thermal power plants are included in our geodatabase. Data at EGU level are collected and compiled for 954 medium and largesized power plants, which cover 89% of the total installed capacity. We distinguish 4 types of cooling technologies in the geodatabase, that is, once-through cooling, recirculating cooling, dry cooling, and seawater cooling. Dry cooling is regarded as the most important water conservation technology for thermal power plants in northern China and has been widely adopted over the past decade.17,38 Water withdrawal and consumption of dry cooling power generation can be reduced by more than 75% compared with conventional recirculating cooling towers.39 Seawater is widely used for cooling in many large coastal coal-fired power plants and all nuclear power plants in China. Almost all seawater-cooled power plants adopt once-through cooling systems except two pilot projects using an innovative seawater recirculating cooling technology.38 Seawater cooling can save both freshwater withdrawal and consumption and does not have energy penalties like dry cooling.17 The geographic locations of all thermal power plants distinguished by cooling technologies are plotted in Figure S1 in the Supporting Information (SI). Water resource availability is a key determinant for the choice of cooling technologies. Most dry-cooling power plants are located in the Yellow River Basin and the Hai River Basin of northern and northwestern China. These two river basins cover 7.8 and 3.3% of China’s territorial area but only account for 2.4 and 1.3% of the national total freshwater resources,40 respectively. Inner Mongolia Autonomous Region and Shanxi Province have the largest fleet of dry-cooling plants, which contributed 51 and 61% of their thermal power output, respectively. Most once-through

(1)

in which Ut2010 is the total annual water withdrawal in 2010, Ba represents available blue water as an estimate of surface water availability minus upstream consumptive use, and mean[1950,2010](Ba) is the mean value of blue water supply from 1950 to 2010. The long time series are used to reduce the effect of multiyear climate cycles and to ignore complexities of short-term water storage (e.g., dams, floodplains), which makes BWS a measurement of chronic water stress.35 The BWS indicator is similar to the WTA ratio in definition. Following the definition of BWS, baseline water stress driven by thermal power generation can be calculated by substituting total water withdrawal with water withdrawal for thermoelectric power generation in eq 1. This indicator, which we name as BWSTHE, reflects the magnitude of total thermoelectric water withdrawal (TWWTHE) compared to the average blue water supply in a catchment as shown in eq 2. The hydrological catchment used in Aqueduct is defined as areas of land draining to a single outlet point. A total of 1117 catchments within China are identified in the Aqueduct map according to the Global Drainage Basin Database (GDBD).36 These catchments belong to 10 major river basins defined by the Chinese government as shown in Figure 1(a). BWSTHE =

TWWTHE mean[1950,2010](Ba)

(3)

in which Rg is the groundwater recharge from soil and surface water bodies, GWWTHE is the groundwater withdrawal for thermoelectric power generation. Rg data were from Doll and colleagues37 computed in a global hydrological model WaterGAP (IRR70_S) with the spatial resolution of 0.5°. Values above one indicate where unsustainable groundwater withdrawal could affect groundwater availability and groundwaterdependent ecosystem.

Ut 2010 mean[1950,2010](Ba)

GWWTHE Rg

(2)

BWSTHE presents a general view of water stress related to thermoelectric power generation. However, information about water sources is not included in the BWSTHE. In many water scarce places in northern China power plants use alternative water sources including groundwater and reclaimed wastewater instead of surface water. Excessive abstraction of groundwater could lead to negative environmental impacts such as groundwater depletion and land subsidence. On the Aqueduct’s global water risk maps, groundwater stress measures the ratio of E


Policy Analysis


Table 3. Installed Capacity, Electricity Output, And Calculated Water Withdrawal and Consumption of Thermoelectric Power Generation in China in 2011 cooling technology installed capacity(GW) electricity output (billion MWh) freshwater withdrawala (billion m3) freshwater consumptiona (billion m3) seawater withdrawal(billion m3)

once-through cooling

recirculating cooling

dry cooling

seawater coolingb

sum

116.13 0.628 62.51 (53.00,73.19) 0.22 (0.12, 0.33) -

424.98 2.070 5.20 (4.12, 6.51) 4.16 (3.28, 5.15) -

97.40 0.465 0.18 (0.12, 0.23) 0.18 (0.12, 0.23) -

130.57 0.747 0.33 (0.15, 0.43) 0.33 (0.15, 0.43)

769.06 3.911 68.23 (57.40, 80.37) 4.89 (3.67, 6.16) 76.73

a

Calculation results based on low and high estimates are presented in parentheses/italics. bSeawater-cooled power plants also use freshwater in many processes such as boiler water makeup, slag removal, and flue gas desulfurization.

Figure 2. Electricity output and freshwater consumption disaggregated by cooling technologies at river basin level in 2011. Error bars indicate low and high estimates of total freshwater consumption.

was very different from that of water withdrawal. In general, northern regions had more consumptive water use than southern regions. Catchments with more than 0.2 billion m3 of water consumption are mainly located in the lower reaches of the Yellow River Basin, the Hai River Basin, northern part of the Huai River Basin, and the lower reaches of the Yangtze River Basin. Electricity output and corresponding water consumption in major river basins disaggregated by cooling technology is presented in Figure 2(a) and (b). Shandong, Jiangsu, and Henan provinces ranked as the top three in terms of water consumption for thermal power generation. Dry cooling technology made significant contributions to reducing both water withdrawal and water consumption in Inner Mongolia, Shanxi, and other northwest provinces. Similar water saving effect is achieved by seawater cooling technology in Guangdong and Zhejiang provinces. Water consumption for power generation exceeded 1 billion m3 in the Yangtze River, Yellow River, and Huai River basins and was high in the Hai River Basin as well. In terms of water withdrawal, 67% (44.8 billion m3) of the national total occurred in the Yangtze River Basin because of large capacity, once-through cooling. More details of water withdrawal at province and river basin level are provided in the SI. Spatial Distribution of Baseline Water Stress Induced by Thermoelectric Power Generation (BWSTHE). It is commonly accepted that moderate and severe water stress occurs when the water withdrawal to availability ratio is above 20 and 40%, respectively.28,29 These thresholds are also used in the Aqueduct maps to define medium and high water stress. We present the baseline water stress related to thermoelectric

cooling power plants are located in the Yangtze River Basin and the Pearl River Basin, the top two Chinese river basins with the largest amount of freshwater resources. Jiangsu Province and Shanghai have the largest capacities of once-through cooling plants, most of which are located alongside the Yangtze River. Seawater-cooled plants are located along China’s coastline from the northeastern regions (the Liao River Basin) to the southern regions (the Pearl River Basin). Seawater-cooled power plants play a dominant role in Guangdong and Zhejiang provinces, contributing 67 and 69% of their thermal power output, respectively.

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RESULTS Spatial Distribution of Water Withdrawal and Water Consumption by Thermoelectric Power Generation. We estimated that the freshwater withdrawal for thermal power generation in China was 68.2 (57.4, 80.4) billion m3 in 2011, equivalent to 11.2 (9.4, 13.2) % of China’s total freshwater withdrawal (610.7 billion m3),40 and consumptive freshwater use was 4.89 (3.67, 6.16) billion m3, equivalent to 1.5 (1.1, 1.9) %. We also revealed that seawater plays an important role as an alternative unconventional water source for the power industry in China with seawater withdrawal reaching 76.7 billion m3, exceeding that of freshwater. (See Table 3) Spatial distributions of water withdrawal and water consumption by thermoelectric power generation are presented in Figure 1(a) and (b). Catchments with more than 1 billion m3 water withdrawal for power generation are all located in southern China. The lower reaches of the Yangtze River Basin had the largest amount of water withdrawal (15.6 billion m3) of all catchments. The spatial distribution of water consumption F


Policy Analysis


Liao River Basin (Liao), and Yangtze River Basin (Yangtze) where water withdrawal by thermal power plants is less than one percent of available freshwater resources at catchment level. There are very few thermal power plants in the less-populated Southwest Rivers (SW) and the southern part of the Northwest Rivers (NW). Water Source Structure. Water source information is collected for 1041 power plants covering 91.4% of the total generation capacity, 98.6% of freshwater withdrawal, and 85.2% of freshwater consumption in our geodatabase. Besides seawater, we distinguished four types of freshwater sources: surface water, groundwater, mine water, and reclaimed municipal wastewater. Surface water accounts for a dominant 96.4% (65.79 billion m3) of the total freshwater withdrawal since all once-through (freshwater) cooling plants, which have large volumes of water withdrawal, use surface water. Groundwater (1.2%), mine water (0.1%), and reclaimed municipal wastewater (0.9%) only account for small fractions of water withdrawal. However, in terms of consumptive water use, these alternative water sources play important roles in meeting water demands for thermal power generation in river basins experiencing water shortages in northern China. As shown in Figure 3, the Hai River Basin and the Yellow River

power generation (BWSTHE) at catchment level in Figure 1(c). Catchments colored in deep red show places where water withdrawal by power plants exceeds 20% of local water availability. In other words, thermoelectric power generation alone may lead to moderate water stress in these catchments. There are three regions where the contribution of thermoelectric power generation to water stress is notable: (1) from the North Hai River Basin (Hai) to the East Yellow River Basin (YL) in northern China where serious water scarcity has long been recognized; (2) catchments in the Northwest Rivers (in Xinjiang Autonomous Region and Gansu Province) where coal mining and coal power industry are expanding rapidly; and (3) the developed coastal city clusters in eastern and southern China, especially the Yangtze River Delta, the Pearl River Delta, and eastern coastal regions in Zhejiang Province. Northern China is one of the developed regions with the highest population density in the country and it has long been recognized as the thirstiest region as well. For instance, the average annual per capita water resource in the greater Hai-YL region, where Beijing, Tianjin, Hebei, and Shanxi provinces are located, is only about 190 m3,41 far below the widely accepted threshold of absolute water scarcity (i.e., 500 m3 per capita annually).42 On the other hand, abundant coal reserves in Shanxi Province and high population density and large electricity demands in northern China lead to the concentration of coal-fired power plants in this region, which aggravates the local water stress. BWSTHE in two major catchments in this region exceeds 0.2 (colored in deep red in the figure), that is, the Fen River catchment running across Shanxi Province and the northeast part of the Hai River Basin where Beijing and Tianjin are located. Second, large amounts of new coal reserves have been discovered in the past decade in northwest China, which stimulated the booming development of coal mining and the coal-fired power industry.43 Promoted by China’s national energy development plan,44 many large coal power plants have been constructed in northwestern regions. For example, the installed capacity of thermoelectric power generation in Xinjiang had increased by about 3.4 times from 2007 to 2012 (from 6.6 GW to 22.6 GW). A growing proportion of electricity output in northwest China is exported to northern and central China. Unfortunately, most coal reserves in northwest China are located in arid catchments. The rapid expansion of the water intensive power industry is causing increased pressure on local water resources and could potentially lead to further water-related environmental degradation of the fragile ecosystems in northwest China. Third, the most developed coastal city clusters in southern China are also hotspots of China’s electricity−water nexus. These city clusters are located in the Yangtze River Delta, the northeastern coastal areas of Zhejiang Province, and the Pearl River Delta where many large thermal power plants are located. Different from the above-mentioned two regions in northern and northwestern China, water resources are relatively abundant in southern China. Therefore, many power plants alongside major rivers (e.g., the Yangtze River and the Pearl River) use once-through cooling technology. Although the amount of consumptive water use is small compared to water availability, large volumes of water withdrawal for power generation could cause water stress and negative impacts such as thermal pollution to freshwater aquatic environments.45 In contrast to the above-mentioned regions, BWSTHE is rather low in most places in the Songhua River Basin (SH),

Figure 3. Structure of sources of freshwater consumption at river basin level in 2011. Error bars indicate low and high estimates of total freshwater consumption.

Basin both have large volumes of groundwater consumption, 0.222 and 0.197 billion m3, respectively. In the Northwest Rivers, groundwater is the largest source (44%) of water consumption. Consumptive use of reclaimed municipal wastewater exceeds 0.1 billion m3 in the Yellow (0.156 billion m3), Hai (0.148 billion m3), and Huai (0.114 billion m3) river basins. Reclaimed wastewater is the most important unconventional freshwater source for the thermal power industry, as promoted by nation-wide policies in China.46 In the Yangtze River and Pearl River basins and the Southeast Rivers, where water resources are relatively abundant, almost all power plants use surface water. Spatial Distribution of Groundwater Stress (GWSTHE). While utilizing reclaimed wastewater or mine water helps to relieve water shortages, groundwater abstraction can pose stress on aquifers and cause associated adverse environmental impacts.47,48 Many places in northern China are experiencing serious groundwater depletion due to unsustainable over abstraction.49,50 Although irrigation is the largest user of G



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groundwater in northern China,51 the contribution of thermoelectric power generation to groundwater stress should not be neglected. As shown in Figure 1(d), thermoelectric power generation has led to high (10 < GWSTHE < 20) and extremely high (GWSTHE > 20) groundwater stress in quite a few aquifers mainly in the Hai River Basin and the lower reaches of the Yellow River Basin. Some arid catchments in the northwest part of Xinjiang Autonomous Region (in the Northwest Rivers) and the northern part in the Huai River Basin are also experiencing considerable groundwater stress due to power generation. Most power plants using groundwater in northern China are old or small-sized ones constructed more than 10 years ago when strict regulations on groundwater abstraction had not yet been implemented. More recent water resources management policies do not allow newly built power plants in northern China to use groundwater as main water sources.46,52 Therefore, relieving the groundwater stress associated with thermoelectric power generation depends on retiring old plants and shifting to alternative water sources such as reclaimed wastewater. Uncertainties and Limitations. The accuracy of this bottom-up water withdrawal and consumption inventory and associated water stress analysis for China’s thermal power industry depends on, to a large extent, the water withdrawal/ consumption factors used in the calculation. We collected data from various sources and quantified the uncertainties of these factors. Generally speaking, water intensities of Chinese coalfired power plants are close to those of U.S. plants reported in some review articles.23,53 Factors used in this studies have more classifications for different sizes of EGUs. Although some assumptions and approximations were made when Chinese specific data were not available, they only have a small effect on the calculation results. The overall coverage of this study is broad, however, information on water sources for many smallsized plants can be difficult to obtain. Therefore, 1.4% of freshwater withdrawal and 14.8% of freshwater consumption cannot be assigned to any specific type of water source. This limitation may lead to some underestimation of the groundwater stress in northern China since a considerable amount of the undetermined water withdrawal there may come from groundwater. While our analysis has high spatial resolution, water stress is not investigated in any temporal dimension. Water stress tends to be higher in summer when higher electricity demands meet lower river flows and higher water temperature.54,55 Refining the inventory needs a more detailed plant-level survey supplementing spatial-temporal data, for example, continuous daily data that can reflect seasonal fluctuations of water withdrawal and water consumption. Such efforts can deepen the analysis and make it possible to answer more policyrelevant questions, for example, water-related vulnerability of the power sector exacerbated by climate change in China. Furthermore, some other environmental stresses related to water resources, such as thermal stress from heated oncethrough cooling water and water pollution from power plant effluents, are beyond the scope of this study. Although these impacts are generally evaluated in environmental impact assessment reports for individual power generation projects, a comprehensive, system-level analysis of more water-related environmental impacts of thermoelectric power generation in China is yet to be developed.

Policy Analysis

DISCUSSIONS

This study presents an in-depth analysis on the spatial characteristics of the electricity−water nexus in China and reveals the spatial pattern of water stress caused by thermoelectric power generation at catchment level. A major strength of this study is the construction of a high spatial resolution water withdrawal and consumption inventory with water source information for China’s thermal power industry at EGU level. A geodatabase with high spatial resolution can provide more precise analyses and uncover many hidden water problems since water resources endowments vary tremendously by region and catchment. For example, it shows that a number of arid catchments in Xinjiang Autonomous Region in the Northwest River are subjected to relatively high water stress driven by thermoelectric power generation as coal mining and the coal power industry are expanding rapidly in those areas. However, if the analysis is conducted at provincial aggregate level, this problem will likely be overlooked. The total freshwater resources in Xinjiang seem to be abundant (about 100 billion m3 per year) but are distributed extremely unevenly.34 The spatial mismatch between water resources and major coal reserves could lead to notable water shortage for energy production in China’s northwest regions. Lack of data has been recognized as a big challenge for analyzing the various links between energy and water.23 Similar to other countries, energy data are collected in more detail than water data in China. Systematic data collection and reporting in China’s energy sector has facilitated numerous studies and played a significant role in policy-making processes. In contrast, water use data are not well collected or reported and are filled with large uncertainties as many of them are estimations based on qualitative observations rather than quantitative calculation. The unequal quality of energy and water data could also put water at a disadvantage in decision-making, if the impacts of energy development on water resources cannot be evaluated explicitly.56 This study integrates and combines a wide range of data that are publicly available and fills the gap of understanding the status quo of water-for-electricity in China. Nevertheless, much more effort should be devoted to make water use data in China’s power industry more transparent and accessible. We recommend the following measures: first, setting and promoting more comprehensive standards on measuring and reporting water use data for all types of thermal power plants. A consistent and unified measuring and reporting framework is essential to ensure data from different plants and authorities are comparable. Current data available from different sources are usually inconsistent with each other due to the vague definitions of water use, for example, consumptive and nonconsumptive water use is not distinguished explicitly in many cases. Second, water resources management authorities should implement real-time monitoring of water withdrawal and wastewater discharge by thermal power plants. Such monitoring should cover a wide range of indicators that are informative for decision making, including the volume of water, cooling water temperature, key water quality indicators, as well as sources of water. Constructing a monitoring network for water use by power plants (possibly for water use by all purposes) is the most important component of capacity building in water resources management. Third, data sharing between water and energy authorities should be particularly encouraged and promoted as a basic measure to integrate H



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energy planning and water resources management. Last but not least, making more high-quality data available to the public could also create added-values through facilitating more research activities and enhancing public understanding of the energy−water nexus. In terms of policy implications for managing the electricity− water nexus in China, our results show the urgent need for evaluating the impact of newly built plants on water resource as most regions with rapid growth in thermal power industry have already been experiencing high water stress. Strict water conservation measures are essential for newly built power plants, especially in those three groups of regions (the Hai River Basin and the lower reaches of the Yellow River Basin, Xinjiang Autonomous Region, and Yangtze River Delta and Pearl River Delta) identified with high water stress in this study as well as many places in northern and northwestern regions where groundwater withdrawal by power plants is high. The Chinese government has already made many efforts to save water in the thermal power industry during the past decade,46,57 such as implementing market-access rules to encourage larger generating units with higher energy efficiency and lower water intensity58 and promoting water conservation technologies17,59 in the entire power industry. Technological measures should also be differentiated in different regions. In northern and northwestern China, major approaches for freshwater conservation are adopting dry cooling technology and using reclaimed municipal wastewater or mine water for cooling. It has been estimated that dry cooling technology saved nearly 1 billion m3 of water consumption in China in 2012, which was equivalent to more than half of the total water use of Beijing.17 The latest energy development policy required that most advanced water conservation technologies should be further adopted in new coal-fired power plants in northern and northwestern regions.44 In coastal city clusters in southern China, promoting advanced seawater utilization technologies, including seawater recirculating cooling and seawater desalination for power plant boiler water makeup, could be the appropriate solution.38,60 Furthermore, existing policies mainly focus on technology choice at plant level. A more water-constrained and energythirsty future in China is calling for systematic analysis of the energy−water nexus at various spatial scales, that is, national, regional, river basin, and catchment level.13 Evaluating potential water risk should be integrated into energy planning at various levels. Water resources availability should be considered as one of the key determinants for allocating incremental generation capacities so as to avoid unsustainable water use incurred by rapid expansion of the thermal power industry. Detailed water stress analysis is especially important for northwestern China, such as Xinjiang Autonomous Region, where coal-fired power capacity is still expanding fast.

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Policy Analysis

AUTHOR INFORMATION

Corresponding Authors

*(L.Z.) Phone: +86 10 6416 5697; fax: +86 10 6416 7567; email: [email protected] *(C.Z.) E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Chao Zhang is supported by National Science Foundation of China (71503182), “Chenguang Program” of Shanghai Education Development Foundation (14CG20) and Tongji University Sustainable Development and New-Type Urbanization Think Tank. Lijin Zhong, Xiaotian Fu, Jiao Wang from the World Resources Institute are supported by the Hewlett Foundation, Irish Aid, Dutch Ministry of Foreign Affair, Danish Ministry of Foreign Affair and Swedish International Development Cooperation Agency.

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REFERENCES

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.5b05374. Descriptions of the data sources, uncertainty analysis of baseline water stress (PDF) More detailed calculation results at river basin and province level (XLSX) I


Policy Analysis

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Revealing Water Stress by the Thermal Power ... - ACS Publications

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