Scholarly article on topic 'EMergy accounting for the Three Gorges Dam project: three scenarios for the estimation of non-renewable sediment cost'

EMergy accounting for the Three Gorges Dam project: three scenarios for the estimation of non-renewable sediment cost Academic research paper on "Earth and related environmental sciences"

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Abstract of research paper on Earth and related environmental sciences, author of scientific article — Juan Yang

Abstract Dam construction conflicts are typically multidimensional, complex, and dynamic. Until recently, the environmental impact assessment of large dam projects was not fully acknowledged due to the uncertainty of the issue and the current knowledge on the accountability of ecological services. The measurement on the sustainability of the production system with a holistic view are thus of great relevance for the decision makers to implement the sustainable energy policy. In this paper, an integrated EMergy accounting was presented for assessing how the Three Gorges Dam project has performed based on the sustainability criteria. We quantified each EMergy flow component of energy, material and purchased input with available data in an assumed 100-year lifetime run. Special attention is focused on three simplified scenarios for estimating the EMergy cost of sediment. Our results showed that when the EMergy cost of sediment was counted, the Environmental Sustainability Index decreased dramatically with the increasing of the nonrenewable input. The results serve as a reminder of the necessity to apply different transformities for sediment EMergy cost in any hydro project, depending on the unique ecological service of sediment in the local river system. However, due to the high intensity of local renewable EMergy flow, the Environmental Loading Ratios and the Investment Ratios of the Three Gorges Dam system were relatively low. In spite the fluctation, the Environmental Sustainability Index remained higher than that of China in 1996, no matter the sediment EMergy cost was included or not.

Academic research paper on topic "EMergy accounting for the Three Gorges Dam project: three scenarios for the estimation of non-renewable sediment cost"

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Journal of Cleaner Production

journal homepage: www.elsevier.com/locate/jclepro

EMergy accounting for the Three Gorges Dam project: three scenarios for the estimation of non-renewable sediment cost

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Juan Yang

School of Marine Science, China University of Geosciences, No. 29 Xueyuan Road, Haidian District, Beijing, 100083, PR China

ARTICLE INFO

Article history: Received 27 April 2015 Received in revised form 5 October 2015 Accepted 24 October 2015 Available online 10 November 2015

Keywords: EMergy accounting Sediment

Environmental sustainability index Three Gorges Project

ABSTRACT

Dam construction conflicts are typically multidimensional, complex, and dynamic. Until recently, the environmental impact assessment of large dam projects was not fully acknowledged due to the uncertainty of the issue and the current knowledge on the accountability of ecological services. The measurement on the sustainability of the production system with a holistic view are thus of great relevance for the decision makers to implement the sustainable energy policy. In this paper, an integrated EMergy accounting was presented for assessing how the Three Gorges Dam project has performed based on the sustainability criteria. We quantified each EMergy flow component of energy, material and purchased input with available data in an assumed 100-year lifetime run. Special attention is focused on three simplified scenarios for estimating the EMergy cost of sediment. Our results showed that when the EMergy cost of sediment was counted, the Environmental Sustainability Index decreased dramatically with the increasing of the nonrenewable input. The results serve as a reminder of the necessity to apply different transformities for sediment EMergy cost in any hydro project, depending on the unique ecological service of sediment in the local river system. However, due to the high intensity of local renewable EMergy flow, the Environmental Loading Ratios and the Investment Ratios of the Three Gorges Dam system were relatively low. In spite the fluctation, the Environmental Sustainability Index remained higher than that of China in 1996, no matter the sediment EMergy cost was included or not.

© 2015 The Author. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND

license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction

As powerful symbols of modernization, the big dam era started with the construction of the Hoover Dam on the Colorado River in the 1930s. Large dam-building projects were parallelled with improvements in engineering skills and construction technology after the World War II. By the year 2000, the world had built over 45,000 large dams (WCD, 2000). Many people believe that more dams will be needed in the future to meet the increased demands of the increasing population and water consumption. However, in recent years, the value of dams to human society has been questioned because they pose severe environmental and social risks in their life time (Bednarek, 2001; Sikder and Elahi, 2013). Intensive opposition to large dam construction has been aroused in many places. Underpinning many of these augments is the evidence of severe environmental and socioeconomic degradation after river damming (Beck et al., 2012; McCully, 1996; Pearse-Smith, 2012). In

E-mail address: yangjuan@cugb.edu.cn.

response to the dam construction conflict, WCD (World Commission on Dams) released a final report entitled Dams and Development — a New Framework for Decision Making in 2000, presenting its harsh criticism of large dams as well as recommendations on how to deal with the differing interests and conflicts over dam projects (Bird and Wallace, 2001). Since then, applying the WCD's framework was believed to result in better decision-making at the preliminary stage of dam planning (Bosshard, 2013; Pearse-Smith, 2014; Skinner et al., 2009).

There are real and varied benefits that human beings obtain from large dam construction. In China, the annual mean shares for hydropower has remained constant in China, 6.90% in the total energy production during 2000—2011 (Hu et al., 2014). Due to the huge gap between energy supply and demand, the Chinese government has been pressed ahead with plans to build multiple large dams in western provinces. The development of large hydro plants is expected to provide sufficient energy to meet the overall requirements, as well as a notable cutting in CO2 emissions during the power generation. According to the National Development and Reform Commission of China, 366 g of coal produced 1 kWh of

http://dx.doi.org/10.1016/jjclepro.2015.10.110

0959-6526/© 2015 The Author. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

electricity in 2006 (NDRC, 2007). The operation of Three Gorges Dam (TGD) project at full power reduces coal consumption by 31 million tons per year, which prevents 100 million tons of greenhouse gas emissions. The competitive advantages meet the national strategic demand for more economic and cleaner energy supply, in spite of the fact that the lakes created by large dams act as a source of greenhouse gas emissions. In the case of Itaipu Power Plant, the greenhouse gas emissions were estimated as 9.644 x 104t CO2/yr plus 1.175 x 104 t CH4/yr from Itaipu's reservoir (Ribeiro and Silva, 2010).

Except for the success in improving people's life quality, some underestimated environmental consequences of the TGD project have become visible since the reservoir started filling to the height of 135 m in 2003. According to the systematic hydrological data between 1950 and 2010, the significant deposition centre of sediment shifted from the middle and lower reaches (before 2000) to the upper Yichang following the river impoundment in 2003 (Dai and Lu, 2014). Moreover, due to a series of environmental projects and hydropower cascade development in the upper Yangtze River, the sedimentation rate (average 176 Mt per year for the 2008—2010 period) in the reservoir was much lower than expected. However the downstream riverbank erosion in the middle reaches was significantly underestimated in the early EIS (Environmental Impact Statement for the Yangtze Three Gorges Project) Report (Xu et al., 2013). The annual erosion rate downstream averaged 108.8 million m3 from 2002 to 2010, which was greater than the average of 6.25 million m3 per year in 1975—2002 (Lu et al., 2011). Riverbank collapse not only occurred in the midstream but also expanded to the downstream and estuarial zone, coinciding in the sharp decline in sediment load at Datong (the lowest gauging station of Yangtze River) since 2003 (Dai and Lu, 2014). Another underestimated environmental problem in the early EIS report was the water quality deterioration and eutrophication in the reservoir area. The frequency of algal bloom events in the reservoir area increased from three events in 2003 to 26 events in 2010, with a widening affected scope of water body (Yang et al., 2009). In addition, over 80% of the available phosphor and heavy metal pollutants are absorbed in the suspended sediments, which are partially precipitated in the reservoir. When dredging the drainage ditch behind the dam, the pollutants are released into the water. Between 2001 and 2010, the Chinese government budgeted approximately RMB 40 billion yuan for the Water Pollution Prevention Plan for the Three Gorges Reservoir and the upper Reaches of the Yangtze River (Revised), to improve the water quality and reverse eutrophication. However, the target of water quality criteria has not yet been achieved.

These severe environmental impacts are more or less linked to the sediment and nutrient retention after the impoundment. Combined with other disputes in the TGD project, these underestimated consequences urgently require reassessing for a better acknowledgement on the dam project sustainability. Relying only on energy security and CO2 abatement to measure the sustain-ability of the TGD project is not sufficient without considering other uses of environmental services (New and Xie, 2008; Romitelli, 1997; Shen and Xie, 2004; Tilley and Comar, 2006). In the long run, dam projects may be far more destructive and threaten human well-being than the tons of CO2 released (Brown and Ulgiati, 2002). The mentioned drawbacks have also reduced the green power efficiency of large-scaled hydro (i.e., more than 15 m in height or, if 5—15 m high, has a storage capacity of more than 3 million cubic metres) in comparison to small-scaled ones (Hicks, 2004; Pang et al., 2015; Kosnik, 2010).

The environment has a renewable capacity to support economic processes and human welfare. As one of the natural components of river system, sediment provide a variety of ecological services in fluvial geomorphology, biogeochemistry, and engineering, as well

as land ocean interactions (Dai and Lu, 2014). The erosion and sedimentation processes are strongly linked to the change of hydrology of a river after large dam building. Globally, Syvitski et al. (2005) estimated that reservoirs hold over one billion tons of sediment, preventing sediment transport to coastal areas, reducing nutrient delivery to agricultural areas and increasing coastal erosion rates. In the environmental impact assessment of dam projects, Brown and McClanahan (1996) first identified the largest environmental impact of the Mekong River Dam as the loss of sediment delivery to downstream ecosystems.

EMergy analysis, as a feasible method to appraise the total energy embodied in any product or service, has been considerably advanced in the efficiency and sustainability evaluation as well as in the comparison of different production systems (Brown, Ulgiati, 2002; Lima et al., 2012; Pang et al., 2015; Wang et al., 2014; Wang et al., 2015). Due to the unit EMergy baseline could be different in the EMergy method, how to determine the EMergy transformity of sediment flow component in a hydro project is not fully explored yet. In some cases, the EMergy estimate on sediment is based on transformity of the organic energy contained in the sediments (Brown and McClanahan, 1996; Kang and Park, 2002), while in other practices, sediment EMergy was ignored (Pang et al., 2015; Zhang et al., 2014) or calculated as a renewable resource by summing the rainfall and geologic contributions and dividing by the annual flow of sediments (Martin, 2002). Accordingly, the purpose of this study is to quantify each EMergy flow components of the TGD project system under three scenarios with considering the potential cost of sediment. Two important questions to be addressed are how to objectively assess the environmental and ecological disadvantages of sediment after river damming and whether the TGD project yields a net public benefit with sustain-ability criterion within the assumed 100 years life time.

2. System description

The TGD project is located at Sandouping, Yichang, Hubei Province, on the upper Yangtze River. Being the longest river in Asia, the Yangtze River flows for 6418 km from the glaciers on the Tibetan Plateau in Qinghai eastward across southwest, central and eastern China before emptying into the East China Sea. The Yangtze River drains one-fifth of China's land area, and its river basin is home to one-third of China's population. The elevation decreases from above 5000 m to less than 1000 m along the river course.

After a long-term feasibility study and comprehensive design, Three Gorges Dam began construction in 1992. The dam's main structure was completed in 2006, and the first generator started working on July 10, 2003. Before the dam construction, the average discharge of the Yangtze River was 30,166 m3/s. The sediment load was 5.3 x 108 t/yr at the Yichang gauge station near the dam. The Three Gorges Dam controls a drainage area of 1.0 x 106 km2, which is 55% of the total catchment area of Yangtze River, with a reservoir capacity of approximately 20 Gm3. Table 1 shows the main engineering features and multipurpose of the dam project (Zhang, 1998).

Table 1

Features of the Reservoir and Dam buildings of the TGD project.

Engineering structures Item Index

Reservoir Reservoir area 1084 km2

Normal storage elevation 175 m

Total storage 393 x 108 m3

Storage for flood reduction 221.5 x 108 m3

Improved navigation channel 570-650 km

Dam Buildings Maximum height of dam 175 m

Installed capacity 2250 x 104 kW

Annual electric generation 847 x 108 kW h

The TGD project has been one of the most controversial projects in China due to the uncertain environmental and social consequences. The contentious environmental issues surrounding the TGD have centred on water quality, fishery, sedimentation and downstream riverbed erosion, reservoir-induced seismicity and geological instability, human displacement and environment carrying capacity in the reservoir area (Xu et al., 2013). Before construction, the Environmental Impact Statement for the Yangtze Three Gorges Project (EIS Report) was employed by the Chinese government at all levels as an authoritative guideline for the implementation of the TGD project.

3. EMergy accounting method

EMergy analysis was developed by H.T. Odum to provide a method of assessing different systems (Odum, 1996). In a thermo-dynamic viewpoint at the process scale, the total available energy in a product (natural resources) or service is made up of previously transformed energy. Different inputs to a process can be normalized by using the tranformities and converted into the equivalents of one form of energy, usually sunlight.

Within a common evaluation framework, EMergy accounting requires systems diagrams to organize evaluations for all inflows and outflows in a production process. The system diagram in the dam project was firstly proposed by Brown and McClanahan (1996). Because we are interested in the EMergy flows of the TGD project, the system diagram helps to organize data collection and to ensure that all necessary flows are taken into account.

Data, including construction materials, source energy, labour and service in construction as well as in operation and maintenance, and other environmental or economic inputs and outputs were obtained before and after the dam construction. Evaluation table of the actual flows of energy, materials, capital and services was then constructed (Table 2). All EMergy flow components were calculated in their raw units and were converted by the trans-formities calculated earlier or in this paper (see Appendix 1). Moreover, the total sediment silted volume was estimated as the sum of the dead storage capacity and the 10% effective storage capacity of the reservoir in the assumed 100 years life according to the ESI report. Three scenarios for the estimation of sediment Emergy were expected to provide meaningful information on the environmental services of the sediment before the river impoundment. The sediment EMergy cost in the TGD project system was thus estimated as no EMergy involved (S1), EMergy input in terms of contained organic energy (S2) and EMergy input in terms of geopotential (S3). Those details on sediment EMergy calculation in scenario 2 and 3 were also shown in Appendix 1(17).

Three aggregating flows (Nonrenewable, Renewable and Purchased input) were used for the sake of simplicity. To avoid double-counting, only the environmental input of the river geopotential was calculated as the total input of renewable resources (Appendix 1(6)). Afterwards, the EMergy yield ratio (EYR), the investment ratio (Ir), the environmental loading ratio (ELR) and the environmental sustainability index (ESI) were calculated for lending insight into the overall sustainability.

EMergy yield ratio, EYR = Y/(N + F) Investment ratio, Ir = F/(N + R) Environmental loading ratio, ELR =(N + F)/R Environmental sustainability index, EIS = EYR/ELR

Note: F, N, R denote the EMergy flows in terms of purchased input, non-renewable and renewable resources, respectively.

Herein, EYR provides insight into the net benefit of the dam project. Ir measures the feedback of the process fuelling by local resources and imported (or purchased) EMergy flows. ELR measures the impact to the environment around the process. And ESI evaluates the sustainability of a process or system performance.

4. The estimate for the EMergy cost of sediment arrested in the Three Gorges Reservoir

The main EMergy inputs of the dam project come from 4 sources: renewable (R) and nonrenewable resources (N1) from the environment, original ecosystem services of the original submerged land (N2), and purchased inputs for construction and maintenance of the dam project (F) (see Table 2). In addition to producing electricity, the multipurpose dam project is intended to increase the Yangtze River's shipping capacity and to reduce the floods downstream by providing flood storage space. By comparison, the electricity product profit is the largest benefit of the TGD project, which is 4.85 x 1022 sej/yr, approximately 92.7% of the total EMergy benefit. The proportion is much larger than that of flood control (5.9%) or navigation (1.4%).

Table 2 also provides an illustration of how EMergy flow components are calculated. By multiplying the transformities on the fourth column, the main components in raw units were then transformed to solar EMergy units. The sediment EMergy counted in S2 and S3 has increased the nonrenewable input significantly. The total EMergy cost of sediments during the life span of the dam is 49.56 x 1022 sej in terms of the organic biopotential (scenario 2) and 650.53 x 1022 sej in terms of the geopotential (scenario 3) [Appendix 1(17)]. That means the EMergy cost of sediment in terms of the geopotential is approximately 13 times as much as that of organics. The dramatic different estimations of the EMergy cost reflect the potential environmental services of sediment in the downstream Yangtze.

5. The impact of the sediment EMergy flow on the sustainability of the TGD project

The aggregated diagram showed the main EMergy flows of the TGD project system in different scenarios with the nonrenewable estimation (Fig. 1). Two types of nonrenewable resources were calculated: (1) nonrenewable input (N1), including earth and rock used for dam construction, and including or not including sediment cost locked behind the dam structure; (2) the loss of original production and services (N2) of land submerged in the reservoir. When sediment is regarded as a nonrenewable resource input, the N1 EMergy flow increased 3—25-fold in S2 and S3 in comparison with S1, respectively. The EMergy yield of the TGD project (523.1 x 1022 sej) surpassed the former system (12.12 x 1022 sej) dramatically [see Appendix 1(18), Fig. 1].

EMergy indices provide a deep insight into the sustainability of the dam project (see Table 3). The EYR of the TGD project decreased from 6.9 in S1 to 0.7 in S3, indicating that the benefit of the dam project cannot offset the social and environmental cost in S3. ESI was also sensitive to the inclusion of sediment EMergy loss, which declined from 91.1 in scenario 1 to 0.98 in scenario 3. The latter is higher than the ESI of China in 1996 (0.91) (Li et al., 2001). Due to the high intensity of renewable EMergy flow, the ELRs of the TGD in the three scenarios were relatively low in comparison with that of China (10.54) or the original agriculture ecosystem (2.80) (Lan et al., 2002).

Table 2

EMergy accounting table for the TGD project (unit: 1020 sej. The dam life span is assumed as 100 yr).

Items Subclasses Raw unit Transformity Solar EMergy

(sej/unit) (1020 sej)

Renewable (R) 1 water geopotential 7.73 x 1017 J/yr 1.28 x 105 99003.5

EMergy benefit for human society (Y1) 2 Electricity 3.05 x 1017 J/yr 1.59 x 105 48495

3 Flood control 3.82 x 108 $/yr 8.12 x 1012 3100.3

4 Shipping 1.35 x 1016 J/yr 5.3 x 104 715.7

5 Aquaculture total 8.25 x 1014 J/yr 4.40 x 102 0.36 52311.36

Direct and indirect inputs of nonrenewable (N1) 6 Earth and rock 2.68 x 1014 g 1.0 x 109 2680

7-S2 Sediment arrested (S 2) 7.87 x 1018 J 6.3 x 104 4956

7-S3 Sediment arrested (S 3) 5.97 x 1016J 1.09 x 108 65053

Total-N11 2680

Total-N12 7636

Total-N13 67733

EMergy loss of ecosystem production and services(N2) 8 Production of crop land loss 1.16 x 1015 J/yr 8.30 x 104 96.28

9 Production of orchard submerged 6.02 x 1014 J/yr 5.3 x 105 319.1

10 Social disruption 3.75 x 107 people 4.38 x 1015 1642.5

Total 2057.9

Purchased input (F) 11 Concrete 6.78 x 1013 g 5.08 x 108 344.17

12 Steel 6.35 x 1011g 5.07 x 109 32.2

13 Construction investment 8.69 x 109$ 8.12 x 1012 706.03

14 Operation and maintenance 4.35 x 109$ 8.12 x 1012 353.02

15 Electricity transmit service 5.61 x 109$ 8.12 x 1012 455.18

16 Resettlement 9.18 x 109$ 8.12 x 1012 745.48

17 Pollution reduction investment 4.74 x 109$ 3.46 x 1012 163.9

Total 2800

Note: Data sources and calculation details are given in the Appendix 1. The total EMergy used in the dam project in different scenarios are calculated as below. Uj = R + N11 + N2 + F = (99003.5 + 2680 + 2057.9 + 2800)*1020 sej = 1.07*1025 sej. U2 = R + N12 + N2 + F = (99003.5 + 7636 + 2057.9 + 2800)*1020 sej = 1.11*1025 sej. U3 = R + N13 + N2 + F = (99003.5 + 67733 + 2057.9 + 2800)*1020 sej = 1.72*1025 sej.

6. Dissussion

In a free fluvial system, the drainage basin is the production zone where water and sediments are generated, whereas the middle zone is the transfer zone, which contains the main channel for carrying material to be settled in the deposition zone. In this way, nutrients and sediment are supplied to the floodplain, and the floodplain provides a breeding ground for river species and improves water quality through the settlement of sediment and the absorption and re-cycling of nutrients and pollutants. River damming reduces these links and services significantly. The concepts of river continuum, proposed by Vannote et al. (1980), and the flood pulse concept, proposed by Bailey (1991,1995), offer a theoretical view of how impoundments are responsible for major disruptions in the longitudinal gradient of the river network and the lateral connection between the river channel and the floodplain of

Fig. 1. Summary diagram of EMergy flows in the TGD project system in scenario 1, 2 and 3. Renewable, local non-renewable and purchased inflows enter the system for hydroelectric production.

alluvial rivers (Magilligan et al., 2003). Odum H T (1996) also identified the river network as an example of the energy hierarchy. An increase in energy quality often follows the river system organizing downstream, i.e., the river transformity downstream increases as the available energy of river water declines. With the growing acknowledgement of the importance for preserving freeflow rivers (Nilsson et al., 2005), the environmental impacts of sediments and nutrient retention in the reservoir should not be considered in isolation but must be considered with the whole river ecosystem. In this case, the estimate of the EMergy cost of arrested sediment may reflect the residual available energy which used to work in the downstream before the river impoundment.

Renewable power plants are often characterized by high energy return on investment. It explains why a high EYR of 7.6 is common for hydroelectric generation (Brown and Ulgiati, 2002). In this paper, a similar EYR of 6.9 was achieved in scenario 1 without considering the sediment as a non-renewable EMergy cost. Presumably, this estimate in scenario 1 is more reasonable for dam projects on a low sediment-carrying river. However, the Three Gorge Dam was built on the 4th largest sediment-carrying river. The maintenance of downstream ecosystems, i.e., floodplain swamps, marshes, deltas and coastal ecosystems, depends on the re-supplying of sediment to compensate for land subsidence, the re-nourishing of depleted nutrient stocks and the supporting for secondary production with rich organic material. The unique

Table 3

EMergy-based indices for the TGP system in scenario 1, 2 and 3.

EMergy indices Scenarios

EYR 6.9 4.2 0.7

Ir 0.03 0.03 0.02

ELR 0.08 0.13 0.73

ESI 91.1 33.2 0.98

environmental dis-service of sediments could be considerably huge due to the spatial relocation of sediments. Therefore, the sediment EMergy cost in term of organics in scenario 2, reflected the side benefit of the nutrients contained in the sediments, which contributed to the downstream and estuarine and riparian ecosystems. In scenario 3, the EMergy cost in terms of geopotential energy reflected the potential of sediments to work on the river geomorphology. When sediments diffuse in the alluvial plain and deposits, erosion is unlikely to occur. Owing to the predominance of the artificial river course in the middle and lower reaches of the Yangtze River, the EMergy estimate of the sediment cost in scenario 3 may reflect the most important service of sediment in the original downstream zone.

On the other hand, sediments can perform either an ecosystem service or dis-service, depending on the location and what target ecosystem is assessed. The irreversible change in hydrological conditions after river impoundment exacerbates water pollution by trapping pollutants and increasing eutrophication in the TGD reservoir. These unforeseen environmental impacts can be attributed to the combined effects of the release of nutrients contained in the sediments and the slowing tributary flow. That means the available energy (e.g., chemical or gravitational potential energy) retaining in the sediment may cause the mis-directed work on environment. Although hydropower plants do not produce any pollutants, they are characterized as a high ratio of environmental input to output. Additional insight of the ternary diagram (presented by Giannetti et al., 2006) representing the three main EMergy flows revealed the low proportion of purchased input. It showed that the ESI and ELR are very sensitive to the inclusion of sediment EMergy cost (see Fig. 2).

In the future, the mis-directed work of sediment on environment will continue. Consequently, the EMergy derived from economic sources to mitigate the impacts or from environment to dissipate the residual available energy should be increased, though there was not much data for this estimation currently.

7. Conclusion

Sediment arrested in the reservoir represented one of the most remarkable investment from environment in the TGD project. With

ESI= 91.1; ELR= 0.08 0 ^

ESI=33.2; ELR= 0.13 \/

ESN 0.98; ELR= 0.73

0.4 \ // \\\ 06

* >A \V4 *

0.6 // \ \\\ 0.4

0.8 / \ \ \ \ 0.2

1 / \ \ \ \ 0

0 0.2 0.4 0.6 0.8 1

Fig. 2. Emergetic ternary diagram representing the TGD project in scenario 1, 2 and 3.

the transformity of the different type of available energy involved, the estimate for sediment EMergy cost in the TGD project were 49.56 x 1022 sej in terms of organics (S2) and 650.53 x 1022 sej in terms of geopotential energy (S3). The sustainability of the dam project is thus sensitive to the different estimates. However, due to the high intensity of the renewable EMergy flow, the environmental load ratio (ELR) and investment ratio (Ir) of the TGD project remained relatively low in these scenarios. With the ecological services of sediment in Yangtze River taking into account, we concluded that the EMergy in term of geopotential is the most reasonable estimation of sediment for the TGD project. Based on our practice, the selective application of the transformities for estimating sediment EMergy cost is feasible in other hydro projects according to the dominant ecological service of sediment in the local river system.

Acknowledgements

The research was supported by the Fundamental Research Funds for the Central Universities of China (35832012032, 35832015043). Special thanks are addressed to Prof. Qingbin Li (Tsinghua University) for his important contributions. The author appreciates the anonymous reviewers for their valuable comments and criticisms.

Appendix 1

(1) Transformity of sediment geopotential

Avg. discharge = 451 x 109 m3/yr, Avg. sediment discharge = 5.3 x 108 t/yr (Yichang station)

Geopotential of river water:

Energy (J) = (451 x 109 m3/yr)*(1.0 x 103 kg/m3)*(9.8 m/s2) *(175 m) = 7.73 x 1017J/yr

Geopotential of sediments:

Energy (J) = (5.3 x 1011 l<g/yr)*(9.8m/s2)*(175m) = 9.09 x 1014J/yr

Natural EMergy input to the upstream catchment of Yangtze River:

(average annual rainfall: 1100 mm/yr; the upper Yangtze catchment area: 106 km2)

Total annual solar emjoules = (1100 mm/yr x *(100 x 104 km2 x 106)*(1.0 x 106 g/m3) *(8.99 x 104 sej/ g)a = 9.889 x 1022 sej/yr

Transformity of water geopotential = (9.889 x 1022 sej/yr)/ (7.73 x 1017 J/yr) = 1.28 x 105 sej/J.

Tansformity of sediment geopotential = (9.889 x 1022 sej/yr)/ (9.09 x 1014 J/yr) = 1.09 x 108 sej/J.

(2) Electricity (actual installed capacity = 22.5 x

106 kW, Avg.

power = 8.47 x 1010 kWh/yr, according to the TGD project design in 1992)

EMergy benefit = (8.47 x 1010 kWh/yr)*(3.6 x 106 J/kWh) *(1.59 x 105sej/J)b = 48495 x 1018 sej/yr

(3) Aquatic production increase (reservoir surface doubled to a total area of 1.08 x

103 km2; aquatic productivity was assumed as 1 g C/m2/day)

EMergy benefit = (1 g C/m2/day)*(2.5 g OM/g C)*(1674J/g OM) *(365 day/yr)*(0.5)*(1.08 x 103 km2)*(1.0 x 106 m2/km2) *(4.40 x 102 sej/J)b = 0.36 x 1018 sej/yr

(4). Flood control (flood storage capacity: 22.1 x 109 m3/yr, economic benefit from flood control: 2.2 x 109 yuan/yr,

according to the TGD project design in 1992, with the price level in 1992)

EMergy benefit = (2.2 x 109 yuan/yr)/(5.762 yuan/$)* (8.12 x 1012 sej/$)c = 3100.3 x 1018 sej/yr

EMergy of water geopotential = (22.1 x 109 m3/yr)*(1.0 x 103 g/ m3)*(9.8 m/s2)*(175 m)*(1.28 x 105sej/J) =4851.4 x 1018 sej/yr

(5) Navigation improvement (assumed 5.0 x 107 t/yr of freight increase in shipping capacity with retrenched fuel consumption along the 660 km upstream. Source from Guo, 2010)

EMergy benefit = (660 km x 2)*(5.0 x 107 t/yr)*[7.6 g/ (t-km) - 2.9 g/(M<m)]/(1 x 103 g/kg)*(1.04 x 104 kcal/kg)*(4186J/ kcal)*(5.3 x 104 sej/J)h = 715.7 x 1018 sej/yr

(6). River geopotential

Renewable EMergy(sej) input = (451 x 109 m3/yr)*(1.0 x 103 kg/ m3)*(9.8 m/s2)*(175 m)*(1.28 x 105 sej/J) = 99003.5 x 1018 sej/yr

(7) Construction investment (5.01 x 1010 yuan, according to the TGD project design in 1992 with price level in 1992. Source: http://www.gov.cn/gzdt/2013-06/07/content_2421795.htm)

(13) Orchard submerged

EMergy cost = (5.01 x 10 (8.12 x 1012 sej/$)c = 706.03 x 1020

10 yuan)/(5.762 yuan/$)* sej.

(8) Electricity transmit service (according to the TGD project design in 1992 with price level in 1992. Source: http://www. gov.cn/gzdt/2013-06/07/content_2421795.htm)

EMergy cost = (3.23 x 1010 yuan)/(5.762 yuan/$)

(8.12 x 1012 sej/$)c = 455.18 x 1020 sej.

(9) Operation and maintenance (assumed to be half of the construction investment)

EMergy cost = V2*(5.01 x 1010 yuan)/(5.762 yuan/$)* (8.12 x 1012 sej/$)c = 353.02 x 1020 sej.

(10) Concrete use for dam building (Volume = 2.71 x 107 m3, according to the TGD project design in 1992)

EMergy use = (2.71

(5.08 x 108 sej/g)d = 344.17 x 1020 sej.

7 m3)*(2.5 x

16 g/m3)*

(11) Steel use for dam building (Weight = 6.35 x 105 t, according

to the TGD project design in 1992)

Area submerged = 7.35 x 107 m2, according to the Flood treatment and resettlement plan for the Three Gorges Reservoir of the Yangtze River (1994)

Fruits yield = 5594 kg/ha/yr, according to the statistics data in Chongqing, 2001

EMergy loss = (5594 kg/ha/yr)*(1 x 103 g/kg)/(1 x 104 m2/ha)* (7.35 x 107 m2)*(3.5 kcal/g)*(4186 J/kcal)*(5.3 x 105 sej/J)f = 319.1 x 1018 sej/yr

(14) Resettlement (Number of people resettled = 1.25 x 106 people, the immigration cost according to the auditing of TGD project in 2013 at price level in 1993, source: http:// www.gov.cn/gzdt/2013-06/07/content_2421795.htm)

EMergy cost = (5.29 x 1010 yuan)/(5.762 yuan/$) *(8.12 x 1012 sej/$)c = 745.48 x 1020 sej.

(15) Social disruption (assume it is equal to the EMergy value of the population over a 30-year generation) Average EMergy/ Ppl = 4.38 x 1015 sej/yr in 1996

EMergy loss = (1.25 x 106 Ppl)*(4.38 x 1015 sej/yr/Ppl)h*

(16) Earth and rock excavated for dam building (Volume = 1.03 x 108 m3, according to the TGD project design in 1992)

EMergy use = (1.03 x 108 (1.0 x 109 sej/g)g = 2680 x 1020 sej.

m3)*(2.6 x 106 g/m3)*

(17) Sediments (assume silted volume = dead storage capacity + 10% effective storage capacity)

Volume = (1.72 x 1010 m3 +10% x 2.21 x 1010 m3)*(2.0 x 103 kg/ m3) = 3.48 x 1013 kg.

EMergy1 = (3.48 x 1016 g)*(1% OM)*(5.4 kcal/g)*(4186 J/kcal)* (6.3 x 104 sej/J)b = 4955.8 x 1020 sej.

EMergy2 = (3.48 x 1013 kg)*(9.8 m/s2)*(175 m)*(1.09 x 108 sej/ J) = 65053.4 x 1020 sej.

(18) The EMergy loss of income in the submerged regions (Average income = 1017 yuan/person/yr, Zhang, 1998; the number of residents in the submerged region is 8.462 x 105 according to the official report. Source: http://news.xinhuanet.com/ziliao/ 2003-05/30/content_896773.htm)

EMergy loss = (1017 yuan/person/yr)*(8.462 x 105 people)/

EMergy use = (6.35 x 105 t)*(1.0 x 106 g/t)* (5.762 yuan/$)*(8.12 x 1012 sej/$)c = 12.12 x 1020 sej/yr

(5.07 x 109 sej/g)e = 32.2 x 1020 sej.

(12) Crop land loss

Crop area submerged and relocation of cultivated land = 2.1 x 108 m2, according to the general land use planning in Chongqing city (1997-2010), 1996

Grain yield = 3770 kg/ha/yr, according to the statistics data in Chongqing, 2001

EMergy loss = (3770 kg/ha/yr)*(1 x 103 g/kg)/(1 x 104 m2/ha)* (2.1 x 108 m2)*(3.5 kcal/g)*(4186 J/kcal)*(8.30 x 104 sej/J)f = 96.28 x 1018 sej/yr

(19) The investment on pollution reduction (Source from State environmental protection administration (2001): Water Pollution Prevention Plan for the Three Gorges Reservoir and the upper Reaches of the Yangtze River (Revised))

EMergy cost = (3.92 x 1010 yuan)/(8.277 yuan/$)* (3.46 x 1012 sej/$)e = 163.9 x 1020 sej.

Note: Transformities came from the following references. a: Martin (2002); b: Brown and McClanahan (1996); c: Chen and Chen (2009); d: Brown and Ulgiati (2002); Zhang et al. (2009); f: Lan et al. (2002); g: Odum (1996); h: Li et al.(2001). The exchange

rate between Chinese yuan (RMB) and U.S. dollars (USD) used in the paper was 5.762 in 1993 and 8.277 in 2002. Herein, the static investment ignored the yearly EMergy/dollar ratio variation which depended mainly on the EMergy inputs to the country and on GDP.

References

Bailey, R.G., 1991. Design of ecological networks for monitoring global change.

Environ. Conserv 18 (2), 173-175. Bailey, R.G., 1995. Ecosystem Geography. Springer-Verlag, New York. Beck, M.W., Claassen, A.H., Hundt, P.J., 2012. Environmental and livelihood impacts of dams: common lessons across development gradients that challenge sustain-ability. Int. J. River Basin Manag. http://dx.doi.org/10.1080/15715124.2012.656133. Bednarek, A.T., 2001. Undamming rivers: a review of the ecological impacts of dam

removal. Environ. Manage 27, 803-814. Bird, J., Wallace, P., 2001. Dam and development - an insight of the report of the

World Commission on Dam. Irrig. Drain. 50, 53-64. Bosshard, P., 2013. World Bank returns to big dams. World Rivers Rev. 28 (3), 1-15. Brown, M.T., McClanahan, T.R., 1996. Emergy analysis perspectives of Thailand and

Mekong River dam proposals. Ecol. Model. 91, 105-130. Brown, M.T., Ulgiati, S., 2002. Emergy evaluations and environmental loading of

electricity production systems. J. Clean. Prod. 10, 321-334. Chen, B., Chen, G.Q., 2009. Emergy-based energy and material metabolism of the

Yellow River Basin. Commun. Nonlinear Sci. Numer. Simul. 14, 923-934. Dai, S.B., Lu, X.X., 2014. Sediment load change in the Yangtze River (Changjiang): a

review. Geomorphology 215, 60-73. Giannetti, B.F., Barrella, F.A., Almeida, C.M.V.B., 2006. A combined tool for environmental scientists and decision makers: ternary diagrams and emergy accounting. J. Clean. Prod. 14, 201-210. Guo, T., 2010. On shipping benefit of the Three Gorges Project. Port & Waterway

Engineering 443, 104-106 (in Chinese). Hicks, C., 2004. Small hydropower in China: a new record in world hydropower

development. Refocus 5 (6), 36-40. Hu, H., Zhang, X., Lin, L., 2014. The interactions between China's economic growth, energy production and consumption and the related air emissions during 2000-2011. Ecol. Indic. 46, 38-51. Kang, D., Park, S.S., 2002. Emergy evaluation perspectives of a multipurpose dam proposal in Korea. J. Environ. Manag. 66, 293-306. http://dx.doi.org/10.1006/ jema.2002.0594.

Kosnik, L., 2010. The potential for small scale hydropower development in the US.

Energy Policy 38 (10), 5512-5519. Lan, S.F., Qin, P., Lu, H.F., 2002. Emergy Analysis on Ecological Economic System.

Chemical Industry Press, Beijing (in Chinese). Li, S.C., Fu, X.F., Zheng, D., 2001. Emergy analysis for evaluating sustainability of

Chinese economy. J. Nat. Resour. 16 (4), 297-304 (in Chinese). Lima, J.S.G., Rivera, E.C., Focken, U., 2012. Emergy evaluation of organic and conventional marine shrimp farms in Guarafra Lagoon, Brazil. J. Clean. Prod. 35, 194-202.

Lu,J.Y., Huang, Y., Wang, J., 2011. The analysis on reservoir sediment deposition and downstream river channel scouring after impoundment and operation of TGP. Eng. Sci. 9 (3), 113-120. Magilligan, F.J., Nislow, K.H., Graber, B.E., 2003. Scale independent assessment of discharge reduction and riparian disconnectivity following flow regulation by dams. Geology 31 (7), 569-572. Martin, J.F., 2002. Emergy valuation of diversions of river water to marshes in the Mississippi River Delta. Ecol. Eng. 18, 265-286.

McCully, P., 1996. Silenced Rivers: the Ecology and Politics of Large Dams. London, New Jersey.

NDRC (National Development and Reform Commission), 2007-03-07. Three Gorges Dam (in Chinese). Retrieved 2007-05-15.

New, T., Xie, Z., 2008. Impacts of large dams on riparian vegetation: applying global experience to the case of China's Three Gorges Dam. Biodivers. Conserv. 17, 3149-3163. http://dx.doi.org/10.1007/s10531-008-9416-2.

Nilsson, C., Reidy, C.A., Dynesius, M., Revenga, C., 2005. Fragmentation and flow regulation of the world's large river systems. Science 308, 405-408.

Odum, H.T., 1996. Environmental Accounting: Emergy and Environmental Decision Making. Wiley, New York.

Pang, M.Y., Zhang, L.X., Wang, C.B., 2015. Ecological impacts of small hydropower in China: Insight from an emergy analysis of a case plant. Energy policy 76, 112-122.

Pearse-Smith, S.W.D., 2012. The impact of continued Mekong Basin hydropower development on local livelihoods. Cons. J. Sustain. Dev. 7 (1), 73-86.

Pearse-Smith, S.W.D., 2014. The return of large dams to the development agenda: a post-development critique. Con. J. Sustain. Dev. 11 (1), 123-131.

Ribeiro, F.M., Silva, G.A., 2010. Life-cycle inventory for hydroelectric generation: a Brazilian case study. J. Clean. Prod. 18, 44-54.

Romitelli, M.S., 1997. Energy Analysis of Watersheds. Ph.D. dissertation. University of Florida, Gainesville.

Shen, G., Xie, Z.G., 2004. Three Gorges Project: chance and challenge. Science 304, 681. http://dx.doi.org/10.1126/science. 304.5671.681b.

Sikder, M.T., Elahi, K.M., 2013. Environmental degradation and global warming-consequences of Himalayan mega dams: a review. Am. J. Environ. Prot. 2 (1), 1-9.

Skinner, J., Niasse, M., Haas, L. (Eds.), 2009. Sharing the Benefits of Large Dams in West Africa. Natural Resource Issues No. 19. International Institute for Environment and Development, London.

Syvitski, J.M.P., Vorosmarty, C.J., Kettner, A.J., Green, P., 2005. Impact of humans on the flux of terrestrial sediment to the global coastal ocean. Science 308, 376-380.

Tilley, D.R., Comar, V., 2006. Emergy-based simulation to assess Brazil's long-term carrying capacity: environment, electricity and population. Popul. Environ. 27, 307-326. http://dx.doi.org/10.1007/s11111-006-0023-4.

Vannote, R.L., Minshall, G.W., Cummins, K.W., Sedell, J.R., Cushing, C.E., 1980. The river continuum concept. Can. J. Fish. Aquat. Sci. 37,130-137.

Wang, X., Chen, Y., Sui, P., et al., 2014. Efficiency and sustainability analysis of biogas and electricity production from a large-scale biogas project in China: an emergy evaluation based on LCA. J. Clean. Prod. 65, 234-245.

Wang, X., Dadouma, A., Chen, Y., Sui, P., Gao, W., Jia, L., 2015. Sustainability evaluation of the large-scale pig farming system in North China: an emergy analysis based on life cycle assessment. J. Clean. Prod. 102,144-164.

WCD (World Commission on Dams), 2000. Dams and Development: a New Framework for Decision Making. Earthscan, London.

Xu, X., Tan, Y., Yang, G., 2013. Environmental impact assessments of the Three Gorges Project in China: issues and interventions. Earth-Science Rev. 124, 115-125.

Yang, G.S., Ma, C.D., Chang, S.Y., 2009. Yangtze River Conservation and Development Report 2009. Yangtze River Press, Wuhan (in Chinese).

Zhang, L., Pang, M., Wang, C., 2014. Emergy analysis of a small hydropower plant in southwestern China. Ecol. Indic. 38, 81 -88.

Zhang, R., 1998. Yangtze River and Three Gorges Project. Tsinghua University Press, Beijing (in Chinese).

Zhang, X., Jiang, W., Deng, S., Peng, K., 2009. Emergy evaluation of the sustainability of Chinese steel production during 1998-2004. J. Clean. Prod. 17,1030-1038.