ECOLOGICAL FOOTPRINT OF HYDROPOWER*
GENERATION CHAINS
RUAN SHIPING
Dr., engineer, Nanjing Hydraulic Research Institute (NHRI), China
XU SHIKAI
Dr., professorate senior engineer, NHRI, China
TONG ZHONGSHAN
Dr., senior engineer, NHRI, China
WANG YONG
Engineer, NHRI, China
ZHANG YING
Master, NHRI, China
1. INTRODUCTION
Preserving our natural environment and development of society are
complementary to each other. During the early stage of the society, due to the
underdeveloped economic and small population, nature resources are in little
demand and the environmental impact of the human race on was slighter. With
the development of economic and the increase of population, the contradiction of
increasing energy demand with the limited bio-capacity becomes more and more
evident, which has become the key factor and primary problem restricting
economic and social development.
Hydropower is important for the development of the society. As a resource, it
cycles in natural world, so its development and utilization will certainly have an
impact on the ecological environment and the impact degree corresponds to the
amount of nature it occupies to produce. Take China’s hydropower for example, in
the period of 1980-2000, 34 high dams over 100m have been/have been being
finished. Since the new century, 28 dams over 100m have been being/will be
constructed, among which arch dam of the Jinping Hydropower Station grade 1
reaches new height of 305m. They, no doubt, will play greater role in the
developments of China. But on the other hand, with the raising of the
environmental awareness of the whole society, many issues such as effects of
*
Supported by Key Projects in the National Science & Technology Pillar Program during
the Eleventh Five-Year Plan of china (Grant No: 2006BAC14B03).
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hydropower project on ecological environment, establishment of eco-water
resources become increasingly concerned [1].
Ecological footprint theory was employed to estimate the effects of
hydropower generation chains on the needs of carrying capacity of natural
resources and services, of the earth ecosphere and the results were
changed into quantitative biologically productive area, i.e., ecological
footprint of the hydropower generation chains.
2.
THEORY OF ECOLOGICAL FOOTPRINT
Ecological footprint concept was firstly used by Wackernagel and Rees
(1996), it associates human resource consumption to six different land categories
(cropland, pasture, forest, fishing ground, built-up land for infrastructure, fossil
fuel land to absorb anthropogenic carbon emissions) [2]. Through following the
tracks of consumption of energy and natural resources of a region, these
consumption patterns provide information of areas, showing each type of land
necessary for providing these material resources. By comparison of these
different areas providing natural resources, we can quantifiable judge the scope
within which that area’s capacity to provide can be developed. Ecological
footprint theory has been widely used all over the world in various zone scales
and various social fields and the interesting areas include the footprints of the
earth [3,4], the footprints of nations and regions[5], the footprint of cities and the
footprint of industries[6].
3.
ECOLOGICAL FOOTPRINT OF HYDROPOWER GENERATION CHAINS
Ecological footprint is defined as land areas to meet the needs of human
being consumption and waste absorbability [7]. In this paper ecological footprint of
hydropower generation chains is defined as biologically productive areas of
requirement for resources use and waste absorbability in the period of
hydropower project construction.
Ecological footprint includes three functions of ecological system: space
occupation of resources supply, waste absorbability and basic establishment.
Ecological footprint of hydropower generation chains consists of two parts: direct
and indirect biologically productive areas occupation. The former is biologically
productive areas of the main structures and their accessorial permanent hydraulic
structures, such as forest, cropland, fisheries area and pasture, and is transferred
as built-up land. The latter is land occupation about construct facilities, equipment,
construct materials, workers and the land to absorb the GHG from reservoir during
the hydropower generation (shown in Fig.1). Because of the lack of energy
consume data, dam retire was not ignored in this study.
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Ecological footprint of hydropower
generation chains
Occupied area
Direct
Indirect
Building materials
Machinery
Energy
Fossil fuel land
Fossil fuel land
Workers
Cropland
Pasture
Forest
Fishing ground
Built-up land
Fossil fuel land
GHG from
resevior
built-up land
Fossil fuel land
EFopr
EFcon
Fig.1 Ecological footprint of hydropower generation chains
Ecological footprint of hydropower generation chains is the sum of ecological
footprints during project construction and during project operation, and expressed
as:
EFhp  EFcon  EFopr
[1]
where EFhp is ecological footprint the hydropower chains in global hectare (gha);
EFcon is ecological footprint of EFhp during project construction, gha; and EFopr is
ecological footprint of EFhp during project operation, gha.
EFcon and EFopr can be calculated with following formulas:
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EFcon   Areai * Eqfi * Yfi
[2]
i 1
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EFopr   Areai * Eqfi * Yfi
[3]
i 1
where Areai is the land area of the ith type, ha; Eqf i is the equivalence factor the
ith type land, it represents the world average potential productivity of the ith type
land relative to the world average potential productivity of all bioproductive area,
gha/ha； Yf i is the yield factor the ith type land, it describe the extent to which a
biologically productive area in a given country is more (or less) productive than the
global average of the same bioproductive area, dimensionless。The values can be
acceded from reference [8].
Formula [2] and [3] can be simplified according to the main environmental
impacts of the project during the life-cycle of the project.
During the construction stage, main environmental impact is the GHG from
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the generation and transportation chains of building materials such as steel and
cement. So formula [2] can be written as:
EFcon  AreaFossil * Eqf Fossil *Yf Fossil
[4]
where the subscript “Fossil” means fossil fuel land reserved to absorb the GHG.
Immediately after power-dams are filled, carbon dioxide and methane form
during the decomposition of organic matter. In dams, the source of organic matter
may be submerged pre-existing biomass, dissolved organic carbon and
particulate organic carbon (DOC and POC) swept down from neighboring onshore
areas, as well as biomass generated within the dam itself. At the oxic water level,
CO2 is produced through aerobic decomposition of DOC and POC, with methane
oxidization generated at lower water levels. For organic matter in anoxic
sediments, bacterial decomposition takes place through methanogenesis,
resulting in CH4 and CO2.Simplified formula [3] can be expressed as:
EFopr  AreaBuild * Eqf Build * Yf Build + AreaFossil * Eqf Fossil * Yf Fossil
[5]
where the subscript “Build” means submersed bioproductive area; and the
subscript “Fossil” means fossil fuel land reserved to absorb the GHG from
reservoir.
4. Estimating the ecological footprint of hydropower Generation chains in China
Tab.1 presents statistics data of steel and cement consumption and the
embodied GHG of more than 100 hydropower stations in China.
Tab.1 Steel and cement consumption and the embodied GHG of hydropower
stations in China [9]
Earth-rock
Concrete
Building material
Items
Embodied CO2
dams
dams
consumption
Installed
1.81×103MW 2.428×104MW
capacity
Steel
90kg/kW
90 kg/kW
90 kg/kW
90×3.63kg/kW
Cement
680kg/kW
810 kg/kW
800 kg/kW
800×0.925 kg/kW
Footprint calculation of fossil fuel adopted waste assimilation and the ocean
absorbs C of 1/3 [10]. The absorbability rate of average forest was 5.2t/ha.yr to CO2,
and 1.42t/ha.yr to C [6].
Due to a high variation in the productivity of land inundated by hydropower
reservoirs and the lack of data documenting their distribution, this area receives a
world average equivalence factor of 1.0 and a yield factor of 1.0[8].
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Take the generation chain of 1kW.h hydropower for example (assuming a
lifetime of 100 years). The ecological footprint can be calculated as follows:
EFcon  AreaFossil * Eqf Fossil * Yf Fossil
 (1  1/ 3)(90  3.63  800  0.925) / 5.2 105 1.1 1.0
=0.0015(gha)
where Eqf Fossil =1.1; Eqf Fossil =1.0.
The average value of inundated area of large and medium-scale hydropower
stations in China is 1.1×10-2m2/kW.h, the CO2 emission is 7.63gCO2-equiv./kW.h;
the CO2 emission of small-scale power stations is 180.3gCO2-equiv./kW.h, and the
weighted average CO2 emission is 173.3gCO2-equiv./kW.h [9].
EFopr  AreaRes * Eqf Res * Yf Res + AreaFossil * Eqf Fossil * Yf Fossil
=1.1 10-2  1.0  1.0 
(1  1/ 3)(173.3 106 )
5.2 / 365 / 24
 0.2056(gha)
where Eqf Res =1.0; Yf Res ＝1; Yf Fossil ＝1.
So the ecological footprint of 1kW.h hydropower is 0.2071gha. If we assume
a load factor of 0.6, the value will be 0.3452gha, i.e, and the generation of 1kW.h
hydropower needs 0.3452gha bioproductive land for the nature service to supply
the demand of space occupation of resources supply, waste absorbability and
basic establishment.
5.
CONCLUSIONS
This paper qualified the indirect environmental impact of hydropower
generation chains, gave the value of China 0.3452gha/kW.h. The result shows
that the GHG emission during the operation stage is the main factor on
environmental impact and which during the building stage is negligible.
REFERENCES
[1]Wu Jianhua, Shang Yuming, Li Zantang, Ruan Shiping, Luo Chao. Model and
its applications of effects of hydropower project construction on ecological
environment，XXXI IAHR Congress, 2005, Seoul, Korea.
[2]Frey, S. Ecological Footprint (EF) Feasibility Study on a Personal Computer
5
[EB/OL]. http://mitpress.mit.edu/journals/JIEC/supplements/JIE10/Frey_supp.pdf.
2006
[3]Wackernagel, M., Onisto L., Bello P. National natural capital accounting with
the ecological footprint concept [J]. Ecological Economics. 1999, 29(3):375-390.
[4]WWF. Living planet report 2004 [EB/OL]. http://www.panda.org/news_facts/
publications/general/livingplanet/lpr04.cfm, 2004.
[5]Erb, K.-H. Actual land demand of Austria 1926–2000, a variation on ecological
footprint assessments [J]. Land Use Policy, 2004, 21 (3):247 - 259.
[6]Barrett, J., Vallack, H., Jones, A., Gary, H. A Material flow analysis and
ecological footprint of York [EB/OL]. http://www.york.ac.uk/inst/sei/ecofootprint/
york- footprint.html. 2004.
[7]Lenzen, M., Lundie, S., Bransgrove, G., Charet, L., Sack, F. Assessing the
ecological footprint of a large metropolitan water supplieris lessons for water
management and planning towards sustainability [J]. Journal of Environmental
Planning and Management. 2003, 46 (1): 113-141.
[8]Monfreda, C, Wackernagel, M., Deumling, D. Establishing national natural
capital accounts based on detailed Ecological Footprint and biological capacity
assessments [J]. Land Use Policy. 2004, 21(3): 231-246.
[9]Ma Zhonghai. Study on GHG emission of some main energy resources in
China [D].China Institute of Atomic Energy, 2002.
[10] Wackernagel, M., Monfreda, C., Moran, D., Goldfinger, S., Deumling, D. and
Murray, M., National footprint and biocapacity accounts 2004: the underlying
calculation method [EB/OL]. http:// www.footprintnetwork.org, 2004.
Abstract: Hydropower, which is a clean energy, plays an important part in the
national economy and the society development. However, over the past decade,
the effects of hydropower generation chains on ecological environment have been
paid good attention to from project research to project practice and have greater
advances so that the functions of hydropower projects have greatly changed.
In this paper, ecological footprint theory and life-cycle assessment were
introduced to account for the environmental burdens associated with the creation
of 1 kW.h of energy by taking into account mass and energy flows at each step of
the procedure, the ecological footprint concept and model of hydropower
generation chains were developed. Such an analysis quantifies the indirect
emissions attributed to the different economic sectors that contribute to the
creation of the hydropower.
Key words: hydropower generation chains, ecological footprint, life-cycle
assessment
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