Article

Cradle-to-grave greenhouse gas emissions from dams in the United States of America

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Abstract

Hydropower is traditionally considered to be one type of “clean” energy, and has been heavily developed in many regions of the world. Nevertheless, this assumption is increasingly being challenged by recent findings that a large amount of methane and other greenhouse gases (GHGs) are emitted during reservoir creation, turbine operation, and dam decommissioning. Via a critical review of existing hydropower life cycle assessments and reservoir emission studies, we compared the GHG emissions of various types of dams based on their structural type, size, primary function, and geographical location during their construction, operation, and decommissioning phases. Means to improve dam performance and reduce related GHG emissions were identified. It was found that dams with reservoirs usually have much higher GHG emission rates than diversion dams. GHG emissions are mainly generated at the construction and maintenance stages for small-scale run-of-river dams, whereas decomposition of flooded biomass and organic matter in the sediment has the highest GHG emission contribution to large-scale reservoir-based dams. Generally, reservoir-based dams located in boreal and temperate regions have much lower reservoir emissions (3–70 g CO2 eq./kW h) compared with dams located in tropical regions (8–6647 g CO2 eq./kW h). Our analysis shows that although most hydroelectric dams have comparable GHG emissions to other types of renewable energy (e.g., solar, wind energy), electricity produced from tropical reservoir-based dams could potentially have a higher emission rate than fossil-based electricity.

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... Positive and negative feedbacks refer to reservoirs as carbon sink and carbon source to the climate system, respectively. Hydropower is considered a lowcarbon, clean energy source with significant positive effects in slowing down the global greenhouse effect (Song et al., 2018). In contrast to natural rivers and lakes, carbon buried in reservoir sediments is much larger (Phyoe and Wang, 2019). ...
... It is essential to estimate greenhouse gases emissions from reservoirs over their entire life cycle on a global scale to confirm whether the reservoir carbon cycle is generally a positive or negative feedback loop to the climate system. Current studies have been conducted using Life Cycle Assessment to quantify and compare greenhouse gas fluxes from reservoirs (Briones Hidrovo et al., 2017;Song et al., 2018). Yet, lack of long-term monitoring data and difficulty of quantifying emissions from some process indicators make it difficult to measure reservoir life-cycle emissions accurately. ...
Article
Reservoirs account for about 10% of the freshwater stored in lakes worldwide. These reservoirs are home to ‘reservoir ecosystems’, that is, the aquatic and non-aquatic interactive ecosystems associated with artificial lakes where water is stored, typically behind a dam, for human purposes. While reservoir ecosystems provide various ecosystem services for sustainable development, their significance in research and policy has not been well understood and not well defined in the 2030 United Nation’s (UN) Agenda for Sustainable Development. To advance understanding of reservoir ecosystems and their impact on policy, here we provide an overview of research on reservoir ecosystems and link it to UN SDGs and their Targets. Based on 5,280 articles published in the last three decades, we applied network visualization to construct a framework for research addressing reservoir ecosystems. The framework covers four major themes: (1) ecosystem structure and function, (2) environmental pollution and stress effects, (3) climate impacts and ecological feedbacks, and (4) ecosystem services and management. We have found that sustainable reservoir ecosystems synergistically support 121 Targets of UN SDGs (71% of all). Reservoir ecosystems have both negative and positive implications for 15 targets (9%) and negative trade-offs for only 3 targets (2%). Thirty SDG Targets (18%) are unrelated to sustainable reservoir ecosystems. The synergies and trade-offs exist in three fields, securing basic material needs (SDGs 2, 6, 7, 14 and 15), pursuing common human well-being (SDGs 1, 3, 4, 5, 8 and 10), and coordinating sustainable governance policies (SDGs 9, 11, 12, 13, 16 and 17). Exploring these linkages allows better integration of reservoir ecosystems into the UN SDGs framework and guides sustainable management of reservoir ecosystems for sustainable development.
... The role of irrigation reservoirs in the carbon footprint of agricultural systems has thus far been overlooked despite the potential for high emissions from these systems, especially those that receive elevated nutrient loading from agriculture 9,12 and those that experience elevated water level fluctuations. 13,14 Irrigation and water supply dams only represent 14.7% of dams in the U.S., 15 but in Spain the main use of around 60% of reservoirs is irrigation. 16,17 In spite of this, most studies estimate the life cycle emissions of irrigation based just on energy use and infrastructure requirements, 3,18−20 although one recent study also considered CO 2 and N 2 O degassing from groundwater use, along with changes in soil N 2 O emissions. ...
... Operation emissions are typically higher in the case of hydroelectric reservoirs, especially if electricity consumption for backups is included in the estimate. 15 Emissions from the construction and maintenance of diversions and desalination plants were expressed on a water use basis. 38 EFs for the construction of modern ponds were based on plastic consumption, and those of channels and ditches on concrete consumption (SI). ...
Article
Irrigation in the Mediterranean region has been used for millennia and has greatly expanded with industrialization. Irrigation is critical for climate change adaptation, but it is also an important source of greenhouse gas emissions. This study analyzes the carbon (C) footprint of irrigation in Spain, covering the complete historical process of mechanization. A 21-fold total, 6-fold area-based, and 4-fold product-based increase in the carbon footprint was observed during the 20th century, despite an increase in water use efficiency. CH4 emissions from waterbodies, which had not previously been considered in the C footprint of irrigation systems, dominated the emission budget during most of the analyzed period. Technologies to save water and tap new water resources greatly increased energy and infrastructure demand, while improvements in power generation efficiency had a limited influence on irrigation emissions. Electricity production from irrigation dams may contribute to climate change mitigation, but the amount produced in relation to that consumed in irrigation has greatly declined. High uncertainty in CH4 emission estimates from waterbodies stresses a need for more spatially resolved data and an improved empirical knowledge of the links between water quality, water level fluctuations, and emissions at the regional scale.
... CPEs and ELMs differed significantly by stream type within the TGDRA, as shown in Fig. 7. Several variables, such as land use, human characteristics, and the model used may have led to these differences in findings (Song et al., 2018;Cook and Overpeck, 2019;Huang et al., 2019). Scenario-based clean production change models are ubiquitous (Guo et al., 2021). ...
... Reservoirs exert great and harmful effects on global clean production, studies have revealed, with results from the last 30 years exposing their benefits and downfalls (Xiang et al., 2021b). The life cycle assessment technique has been utilized to measure and evaluate reservoir cleaning capacities (Briones Hidrovo et al., 2017;Song et al., 2018). Thus, those who oversee water supplies must differentiate between various types of resources (Xu et al., 2020;Arif et al., 2021a). ...
Article
Although environmental illiteracy threatens the functioning of landscapes throughout the world, it is frequently ignored. The traditional wisdom assumes that suspicions will evaporate when the public and government authorities are provided with new information. Despite significant efforts to enhance riparian corridor output, limited data are available on the effect of environmental literacy metrics (ELMs) on clean production elements (CPEs) across various streams (e.g., main rivers and tributaries) within impoundments. This study examined such effects within the China Three Gorges Dam Reservoir area (TGDRA) by collecting 336 transects that assessed the breadth of effects on 58,000 km² in 2019. The network visualization revealed 7234 papers published over the last 121 years, each of which focused on themes such as plant cover, regeneration, exotics, erosion, habitat, and stressors. The bar graph showed that the general public lacked understanding of environmental literacy (e.g., knowledge, attitudes, and behavior), which influenced plant cover elements most in tributary zones but had little direct effect on regeneration. Locals' environmental literacy had the greatest impact on CPEs, with Pearson correlation coefficients ranging from −0.69 < r < 0.96 in the main river zones. Moreover, public employees' environmental literacy had a stronger correlation with CPEs (−0.58 < r < 0.83) within the main river regions. Farming systems, exposed soil, dominant grass regeneration, and instream structures, including pollution, were among the most notable CPEs within the TGDRA. According to hierarchical approaches, CPEs and ELMs change substantially across stream types. CPEs and ELMs vary significantly around main rivers and tributaries, requiring efforts to raise the public understanding of the worldwide impacts of stream health on humans.
... Values > 1.3 are bold Grey 1981;Lytle 2002). Nevertheless, in recent decades, human actions have accelerated the occurrence of extreme climatic events, mainly by the emission of greenhouse gases (Cai et al. 2014), and dams can contribute greenhouse gases while they are filling (Song et al. 2018). Our concern is that the frequency of occurrence of these events is expected to increase in upcoming years, not only affecting Brazil but also affecting other regions. ...
Article
Extreme climatic events, such as flooding and drought, can abruptly modify the amplitude of the river level of a river, promoting new environmental conditions and impacting aquatic communities. Furthermore, an increasing frequency of extreme droughts in dammed rivers is expected because dams homogenize the flood pulse and decrease the river level. In this study, we evaluated the effects of extreme river-level oscillations on the benthic macroinvertebrate communities in a floodplain river. We analysed 47 years of river-level data and 17 years of benthic macroinvertebrate data. Our findings indicated that (1) extreme river-level oscillations promoted environmental conditions that were distinct from the regular oscillation; moreover, environmental characteristics were more heterogeneous in extreme oscillations than regular oscillations; (2) extreme oscillations were associated with a decreased richness, density, and diversity of benthic macroinvertebrates, promoting the dominance of tolerant taxa. Furthermore, in the studied river, a large hydroelectric power plant was built 19 years ago, which (3) decreased the river-level downstream, accentuating the occurrence of extreme drought, which has become more common after damming. We emphasize the importance of long-term biological monitoring considering the more frequent occurrence of extreme river-level oscillations in response to factors such as dam building and climate change.
... Decommissioning projects in the energy sector can relate to offshore gas production infrastructure [43], dams [44], wave energy [45], heat pumps systems [46] and nuclear reactors [47]. Remarkably, despite their growing importance and their growing costs in several industrial sectors (e.g., nuclear and offshore oil & gas decommissioning), until now, decommissioning projects have been mostly overlooked by scholars working on the economics and management of energy infrastructure. ...
Article
Empirical research involving projects is an important and common way to advance knowledge in the energy sector, and there are well-established approaches for qualitative analysis of single or few cases (1–10 cases) as well as quantitative analysis of large databases (from 50+ cases). However, the “middle-ground” of analysing 10–50 cases is an unknown territory, and very few approaches exist to deal with numbers of cases that lie in the range of 10–50. This paper shows how this “middle-ground” can be explored through Qualitative Comparative Analysis (QCA). This is a method that can be applied to energy infrastructure projects (such as construction, operations, and decommissioning of power plants) in order to study causal inference (e.g. factors associated with outcomes). This paper demonstrates the potential of QCA by showing its application on an energy infrastructure phenomenon with an intermediate number of cases, that of nuclear decommissioning projects. These projects are becoming increasingly important to society and have multibillion US dollar budgets. Moreover, their characteristics need to urgently be matched with their project performance in order to avoid even further cost overruns. The application of QCA to 24 European nuclear decommissioning projects shows that a combination of characteristics (such as a streamlined governance structure and the presence of a storage facility for radioactive material on site) might be contributing to lower cost overruns. This paper concludes by showing how QCA can be applied to other energy infrastructure phenomena with a similar intermediate number of cases.
... In most cases, power plants located in tropical regions generate from 7 kgCO 2 eq/MWh up to 4326 kgCO 2 eq/MWh (Tremblay 2005a, b;Gagnon 1997;Mallia and Lewis 2013;Song et al. 2018). However, reservoir biomass GHG emissions are much lower in boreal and temperate climates. ...
Article
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PurposeRivers control biophysical processes that underpin essential ecosystem services. Myanmar’s rivers provide great opportunities for increasing energy supply at low costs from hydropower plants and make important contributions to the national economy. However, associated environmental impacts, as well as input and output flows of hydropower developments, remain less well understood. In this paper, we report on an investigation of the overall environmental effects of five hydropower plants in Myanmar, using a life-cycle impact assessment (LCIA) approach. The primary objective of the paper is to generate detailed life-cycle inventory data and quantify the environmental impacts of the existing five hydropower plants in Myanmar.Material and methodThis paper reports on a “cradle to grave” LCIA for five hydropower plants in which environmental impacts associated with construction, operation and maintenance, transportation, and decommissioning of large-scale hydropower plants in Myanmar were systematically assessed.ResultsConstruction, transportation, operation and maintenance phases are most sensitive to global warming, mineral resource depletion, acidification, freshwater aquatic ecotoxicity, human toxicity and photochemical ozone creation. There is heterogeneity in hydropower plants’ effects on the environment, based on the size of the power plant.Conclusion Strategic selection of hydropower projects is suggested to enhance resilience in environmentally sensitive areas. It is concluded that more comprehensive and rigorous environmental and social impact assessment (ESIA) is needed, not only for mega-dams but also for the smaller-scale hydropower plants. Graphical abstract
... Bako et al. (2014) reported soil degradation as a result of the dams' water penetration and heavy metal containment in areas around the Zobe dam in Nigeria. Air pollution as a result of green gas emission of decomposable materials in the reservoir was investigated in several research efforts conducted in past several years (Tremblay et al., 2004;IRN, 2007;Mendonça et al., 2012;Deemer et al., 2016;Fearnside, 2016;Song et al., 2018). ...
Article
Purpose Dams require high-volume of construction materials and operations over the life cycle. This paper aims to select a proper type of dam structure that can significantly contribute to the sustainability of dam projects. Design/methodology/approach This research proposes a complementary fuel consumption and carbon dioxide (CO 2 ) emission assessment method for the alternate dam structure types to assist decision-makers in selecting sustainable choices. Related equations are developed for two common earthen and rock-fill dam structures types in Iran. These equations are then successfully applied to two real dam project cases where the significance of the achieved results are assessed and discussed. Findings The achieved results of the case studies demonstrate a high deviation of up to 41.3% in CO 2 emissions comparing alternate dam structure scenarios of earthen and rock-fill dam structures. This high deviation represents an important potential for CO 2 emission reduction considering the high volume of the emission in large dam projects. Originality/value The life cycle emission assessment of the alternate dam structures, proposed in this research as a novel complementary factor, can be used in the decision-making process of dam projects. The results in this research identify high potential sustainability improvement of dam projects as a result of the proposed method.
... Decisions about dams, whether to build dams, modify dams or remove dams, are fundamentally decisions about managing trade-offs between different water uses with varying human and ecological impacts and, therefore, feature many of the characteristics of other environmental conflicts (Gleick, 2018). Dam decisions involve complex tradeoffs specific to each river system (Roy et al., 2018;Song et al., 2018), have significant impacts on public resources and involve many stakeholders with diverse and often conflicting interests . Dam removal proponents cite the benefits of removal for public safety, restoring fish habitat and overall ecosystem health (Mullens and Wanstreet, 2010;Fox et al., 2016;Magilligan et al., 2017). ...
... For instance, marshes in the drawdown zone of the Three Gorges Reservoir account for ~19% of total reservoir emissions 138 and the water column acts as an N 2 O source for the first 1.5 days of rewetting before switching to a sink for the remainder of wet-dry cycles. These results suggest that newly created (or recreated) flood zones, with organic-rich sediments and frequent variations in water levels, could also become hotspots for GHG emissions after dam removal 107 . This idea is evidenced by the magnitude of hypothetical CO 2 -equivalent emissions from the largest ten reservoirs in the USA once they are decommissioned 139 : after 100 years of damming, postdeconstruction emissions would exceed those of the reservoir's lifetime emissions by nine times. ...
Article
Full-text available
The increased use of hydropower is currently driving the greatest surge in global dam construction since the mid-20th century, meaning that most major rivers on Earth are now dammed. Dams impede the flow of essential nutrients, including carbon, phosphorus, nitrogen and silicon, along river networks, leading to enhanced nutrient transformation and elimination. Increased nutrient retention via sedimentation or gaseous elimination in dammed reservoirs influences downstream terrestrial and coastal environments. Reservoirs can also become hotspots for greenhouse gas emission, potentially impacting how ‘green’ hydropower is compared with fossil-fuel burning. In this Review, we discuss how damming changes nutrient biogeochemistry along river networks, as well as its broader environmental consequences. The influences of construction and management practices on nutrient elimination, the emission of greenhouse gases and potential remobilization of legacy nutrients are also examined. We further consider how regulating hydraulic residence time and environmental flows (or e-flows) can be used in planning and operation from dam conception to deconstruction.
... Dam releases effectively become the new river regime, modifying natural regimes extensively over multiple timescales (Hwang et al., 2021) and dampening some of the impacts of climate change while amplifying others (Chalise et al., 2021). These operations have major implications for safety (Burgherr & Hirschberg, 2014), health (Steinmann et al., 2006), commerce (Wang & Zhang, 2012), ecosystems (Kennedy et al., 2016;Richter & Thomas, 2007), water quality (Reis et al., 2019), flood control (Boulange et al., 2021), international treaty governance (Cosens et al., 2018), and even greenhouse gas emissions (Song et al., 2018). Many of these constraints are physically insurmountable or have critical safety or legal implications that make them a higher priority than hydropower generation. ...
Article
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Hydroelectric power has unusual technical characteristics that could become more valuable as the penetration of variable generation renewables grows, but its use for electricity generation is constrained by complex physical, safety, and socioenvironmental considerations. Hydroelectricity can therefore be difficult to represent in national‐scale energy models, and is frequently presumed to be either overly flexible or inflexible. While a few grid models address this complexity via detailed hydraulic process models, more simplified optimization and dispatch models could benefit from the use of empirical parameter values. In this study, we combine a new data set comprising 7.8 million flow‐hours of data from 2011 to 2016 at 158 dams across the United States with monthly and hourly generation data from the U.S. Energy Information Administration (EIA) to elucidate such empirical constraints for the continental United States. We introduce an approach for estimating power generation from hourly water discharge, then present regionally resolved interannual seasonal and diurnal generation patterns; frequency analyses of ramp rates; minimum and maximum generation rates; daily reversals; and load duration curves, all available interactively with a new data visualization tool. We suggest that due largely to hydropower's role as power generation that also serves non‐energy purposes, it acts as a predictable variable generator with constrained dispatchability, more like a supply side analog to demand response resources than like a battery. This observation is particularly relevant for high penetration renewable energy scenarios, given hydroelectric generators' expected value for grid stabilization and load balancing.
... In addition, over 3700 large hydroelectric dams with a total capacity of more than 1000 GW are to be constructed in the next few decades, which will increase current hydropower generation by more than 70% (Zarfl et al. 2015). Though these dams play a key role in meeting the increasing energy demand, they pose a great risk to sustainable fisheries (Limburg and Waldman 2009;Song et al. 2019) as well as the wellbeing of fish-dependent communities (Zarfl et al. 2015;Winemiller et al. 2016;Limburg and Waldman 2009;Song et al. 2018;Chen et al. 2016). Dams can substantially decrease fish populations by fragmenting migration corridors (Hall et al. 2011;Beasley and Hightower 2000), degrading habitat quality (e.g., changes in temperature and discharge) (Johnson et al. 2007;Piffady et al. 2013;Zhao et al. 2012), and causing severe turbine injuries (Schaller et al. 2013;Stich et al. 2015). ...
Article
Full-text available
While hydroelectric dams play a significant role in meeting the increasing energy demand worldwide, they pose a significant risk to riverine biodiversity and food security for millions of people that mainly depend upon floodplain fisheries. Dam structures could affect fish populations both directly and indirectly through loss of accessible spawning and rearing habitat, degradation of habitat quality (e.g., changes in temperature and discharge), and/or turbine injuries. However, our understandings of the impacts of dam life span and the initial fishery conditions on restoration time and hence the dynamic hydropower (energy)-fish (food) nexus remain limited. In this study, we explored the temporal energy-food tradeoffs associated with a hydroelectric dam located in the Penobscot River basin of the United States. We investigated the influence of dam life span, upstream passage rate, and downstream habitat area on the energy-food tradeoffs using a system dynamics model. Our results show that around 90% of fish biomass loss happen within 5 years of dam construction. Thereafter, fish decline slowly stabilizes and approaches the lowest value at around the 20th year after dam construction. Fish restoration period is highly sensitive even to a short period of blockage. The biomass of alewife spawners need 18 years to recover with only 1-year of blockage to the upstream critical habitats. Hydropower generation and loss of fish biomass present a two-segment linear relationship under changes in dam life span. When the dam life span is less than 5 years, generating 1 GWh energy cause around 0.04 million kg loss of fish biomass; otherwise, the loss of fish biomass is 0.02 million kg. The loss of fish biomass could be significantly decreased with minimal energy loss through increasing upstream passage rate and/or the size of downstream habitat area.
... However, while there is considerable uncertainty regarding the current emitted quantities [5], the robustness of uncertainty analysis can greatly influence emissions of greenhouse gases from hydropower reservoirs, compared to other non-hydropower reservoirs [28,30]. Given quite a significant number of reservoir-based, non-powered reservoirs highlighted above, it is crucial to understand the relative scale and significance of their GHG emissions [35]. ...
Article
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Greenhouse gas (GHG) emissions from reservoirs are responsible for at most 2% of the overall warming effects of human activities. This study aimed at incorporating the GHG emissions of a reservoir (with irrigation/sugar production as its primary purpose), into the carbon footprint of sugar produced from irrigated sugarcane. This study adopts a life-cycle assessment (LCA) approach and encompasses the cradle-to-gate aspect of the international organization of standardization ISO 14040 guidelines. Results show that total carbon footprint of refined sugar could be as high as 5.71 kg CO 2-eq/kg sugar, over its entire life cycle, depending on the priority of purposes allocated to a reservoir and sugarcane productivity. Findings also reveal that the dammed river contributes the most to GHG emissions 5.04 kg CO 2-eq/kg sugar, followed by the agricultural stage 0.430 kg CO 2-eq/kg sugar, the sugar factory 0.227 kg CO 2-eq/kg sugar, and lastly the transportation stage 0.065 kg CO 2-eq/kg sugar. The sensitivity analysis shows that carbon footprint CF of sugar production is largely influenced by the rate of biomass decomposition in the impounded reservoir over time, followed by the reservoir drawdown due to seasonal climatic fluctuations. Significant amounts of GHG emissions are correlated with the impoundment of reservoirs for water resource development projects, which may account for up to 80% of total GHG emissions to the reservoir's primary purpose. Sugar production expansion, coupled with allocating more functions to a reservoir, significantly influences the CF of sugar per service purpose. This study is an indicator for policymakers to comprehend and make plans for the growing tradeoffs amongst key functions of reservoirs.
... It has wide application in agricultural, adaptation and mitigation. In the mitigation aspect, hydropower can help reduce emission of greenhouse gases (Song, Gardner, Klein, Souza, & Mo, 2018;Varun et al. 2012). It can also improve social resilience and increase agricultural yield, particularly within the aspects of utilization of small-hydropower plants. ...
Article
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Over the past few decades, fossil fuels replacements have shown leaps and bounds of progressions. Hence, various nations have initiated the adoption of biomass energy, solar energy, wind energy and hydropower energy. Yet, these currently developing technologies have constantly faced dual pressure from both the economic growth and environmental protection. Hydropower has become a key candidate for considerable utilization in various countries due to its numerous social, economic and environmental benefits. In this paper, a short review was carried out to analyse the development of various hydropower plants and compare its utilization over the conventional fossil fuels. The main setback for the adoption of this technology is that large hydropower plant demands for huge deforestation. This would direly result in the destruction of critical ecosystems, migration of large population at downstream and other catastrophic outcomes such as flash floods and landslides. However, this singular setback could be alleviated with the utilization of small or micro hydropower plant. This technology, in particular, was found to have minimal destruction effects to the environment and is able to produce affordable energy to the rural areas as it has proven in many countries.
... As a result, a variety of measures and facilities have been applied to ensure urban safety (Havko et al. 2017), including dams (Lempérière 2017), dikes (Loon-Steensma and Schelfhout 2017), low-impact development techniques (Baek et al. 2015), etc. However, most measures may intensify the conflicts between cities and natural environment (Kumar et al. 2018;Song et al. 2018;Null et al. 2014), and these measures are often costly and failed to take strong effect. To propose efficiency disaster prevention measures, the safety levels and the characteristics of disasters should be researched carefully. ...
Article
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City is an important foundation for human development. Natural disasters, whose impact on cities was influenced by disaster risk, urban vulnerability and resistance, have always posed serious threats to human development. It is important to identify the key factors in urban disaster preventing and urban securing to reduce the losses of disasters and ensure the urban safety. However, it is difficult to assess the urban safety comprehensively, as the characteristics of disasters and cities varied a lot, resulting in the limited efficiency of urban disaster prevention and management. As a result, we built an index system to improve the urban safety assessment method. By taking six types of urban disasters (urban flood and waterlogging, drought, low temperature, sandstorm, earthquake, and rockfall, landslide and debris flow disasters) into consideration, based on the open access data and the convenient methods to calculate weights and indices, this evaluation system is of applicability and simplicity, and it can overcome the low efficiency shortcoming of the current assessment methods. The index system was then applied to 596 cities in the mainland of China to validate its effectiveness and accuracy and understand the situation of urban safety of China. The interaction mechanisms among the three characteristics of urban disasters (disaster risk, urban vulnerability and resistance) were analysed qualitatively and quantitatively, and the ‘compensate effect’ between urban vulnerability and resistance was found. According to the result of the urban safety assessment, the safety situations of most cities in China were not satisfactory, but there was great potential to improve them. Since the major natural disasters and safety degrees varied in different cities, these Chinese mainland cities were classified into six different regions based on our results, and the key points of disaster management in each region were pointed out, in order to help the government to promote Chinese cities’ safety.
... Hydropower is currently the largest source of renewable energy in the United States of America (USA), accounting for 44% of the total renewable energy generation in 2017 (EIA, 2018a;Song et al., 2018;Uría-Martínez et al., 2015). This energy is generated by around 2300 hydroelectric dams, with an installed capacity ranging from 50 W to 6495 MW (Samu et al., 2018). ...
... A recent study has investigated GHG emissions from 12 hydropower reservoirs in China and found that these systems emit more GHGs than the global estimated emissions for hydroelectricity generation (Kumar et al., 2019). Similar studies were also conducted for hydro power systems in India and the USA (Kumar et al., 2018;Song et al., 2018a;Sharma, 2016a, 2016b). ...
Article
Globally, electricity systems are responsible for two-thirds of total greenhouse gas (GHG) emissions. This area has become one of the main focuses for a wide range of scientific communities, and a large number of articles have been published that reported GHG emissions from the electricity sector using different approaches. Even though some review articles have been published on particular GHG emissions approaches, such as life cycle assessment (LCA), studies that investigated overall approaches are much rarer. A scoping review of these GHG emissions accounting approaches has thus been conducted in this study to explore their limitations and indicate possible future scope. From the review, it was found that the majority of the studies considered the LCA approach to investigate GHG emissions from electricity systems. Although the time-varying carbon intensity approach has potential features, it has received less attention. Furthermore, this review has highlighted some issues that need to be addressed by any new or existing approach that would deal with GHG emissions accounting in the near future. In addition, this review would be helpful for policymakers and electricity authorities when selecting appropriate approaches in accounting GHG emissions from the electricity system.
... The potential for reduced CO 2 emissions were explored under scenarios where existing coal-fired plants were transitioned to carbon-capture technologies with 95% reduction in CO 2 emissions per MWh [71]. Greenhouse gas emissions (CO 2 equivalent) were estimated for hydropower operations and maintenance, including tailwater and reservoir emissions, based on values reported in Song et al. [72]. Acreage requirements per MW for different technologies were compiled from Refs. ...
Article
Cities drive the majority of global human resource consumption and serve as hubs of major infrastructural networks. To offset their resource demands, cities derive goods and resources from regions well outside urban boundaries inducing stress and impacts on distal ecosystems. As cities grow, these stressors are likely to increase, depending on choices about how resource demands will be addressed through new infrastructures; hence, city governance is extremely important to future global sustainability. However, to support effective decision-making and infrastructure transitions, developing tangible city-scale alternative future scenarios is needed. We present a methodology for developing plausible spatially explicit alternative futures for city infrastructures and discuss the tradeoffs in land, energy, carbon, and water resources among alternative future pathways. We first estimate future city populations and urban boundaries and characterize future land cover scenarios. Future population along with residential housing and commercial characteristics are used to estimate current and future electricity and water demand. We characterize the energysheds of cities, which then become the spatial template for designing future electricity production scenarios. Future electricity mixes and spatial distributions of powerplants provide wide-ranging tradeoffs in carbon reduction, water use reduction, and land usage. Additionally, we explore future alternatives for meeting water supply demands. Herein, we emphasize the importance of translating scenarios into physical on-the-ground relevance in order to ensure transparent communication among city- and utility-governance. Unless spatially explicit future infrastructure scenarios are provided, we believe city-level goals will become difficult to implement, or even worse, result in unintended consequences on regional natural resources.
... Decisions about dams, whether to build, modify, or remove them, are fundamentally decisions about managing trade-offs between different water uses with varying human and ecological impacts and, therefore, feature many of the characteristics of other environmental conflicts (Gleick, 2018). Dam decisions involve complex tradeoffs specific to each river system (Roy et al., 2018;Song et al., 2018), have significant impacts on public resources, and involve many stakeholders with diverse and often conflicting interests . Dam removal proponents cite the benefits of removal for public safety, restoring fish habitat and overall ecosystem health (Mullens and Wanstreet, 2010;Fox et al., 2016;Magilligan et al., 2017). ...
Article
Full-text available
Decisions about dams, like other environmental conflicts, involve complex trade-offs between different water uses with varying human and ecological impacts, have significant impacts on public resources, and involve many stakeholders with diverse and often conflicting interests. Given the many upcoming dam decisions in New England and across the United States, an improved understanding of public preferences about dam decisions is needed to steward resources in the public interest. This research asks (1) What does the public want to see happen with dams? and (2) How do public preferences regarding dam removal vary with demography and politics? We address these questions using data from three random sample statewide telephone polls conducted in New Hampshire over 2018 that asked people for their preferences concerning dam removal versus maintaining dams for specific benefits—property values, hydropower generation, industrial history, or recreation. Respondent age, education, gender, and political party were tested among the possible predictors. We find that majorities (52% or 54%) of respondents favor removing dams rather than keeping them for industrial history or property values, and a plurality (43%) favor removal over keeping them for recreation. A plurality (46%) prefer keeping dams, however, if they are used to generate hydropower. Respondent background characteristics and political identity affect these preferences in ways resembling those for many other environment-related issues: women, young or middle-aged individuals, and political liberals or moderates (Democrats or independents) more often support dam removal. Education, on the other hand, has no significant effects. The results quantify levels of general public support for dam removal in New England, illustrating the use of public opinion polling to complement input from public meetings and guide decisions. More broadly, they contribute a new topic to existing scholarship on the social bases of environmental concern.
... The study defines electricity generation per capita as the dependent variable and classifies it into two categories: fossil fuel electricity and lowcarbon electricity (electricity from nuclear, solar, tide, wind, geothermal, biofuels and waste). It excludes hydroelectricity from low-carbon electricity, first considering that reservoir water releases a large amount of carbon dioxide, methane and other greenhouse gases (Song et al., 2018). Second, water-abundant countries have exploited hydro energy because its electricity generation cost is lower than that of fossil fuel. ...
Article
This study focuses on Brazil, Russia, India, China and South Africa (BRICS countries), which contribute over 40% of global CO2 emissions. Using panel co-integration tests, fully modified OLS and seemingly unrelated regressions, the study contributes to the literature by revealing that public debt securities foster the transition from fossil fuel electricity towards low-carbon electricity, whereas private credit is mostly profitless for electricity production transition. The explanation is that environmental pressure urges public capital to play a vital role in electricity transition, while bank loans are reluctant to leave the electricity from fossil fuel for considerable returns. The installed capacity of electricity stations drives the association between financial capital and electricity production. Financial markets in China and South Africa play a more significant role in electricity transition than the other countries. Low-carbon electricity transition requires transformation of financial markets in all these countries.
... This issue appears problematic since one of the purposes of dam reservoir construction is hydroelectricity, which is considered a clean energy source. However, this attribute might become obsolete since a recent study showed that tropical dam reservoirs have greater greenhouse gas emission potential than emissions from electricity generated from fossil fuels (Song et al., 2018). ...
Article
Construction of dams and transformation of rivers, not only affects river-related and adjacent habitats, but also establishes new threats to surface freshwater resources globally. Predicted climate changes and increase of mean annual temperature will affect thermal regimes of dam reservoir ecosystems, severely altering their functioning. Analyzing three projections of representative concentration pathway (RCP 4.5, 6.0 and 8.5) for period of 2061-2080, we found that mean annual temperature at dam reservoir locations will increase by 3.06 °C to 4.74 °C from present. The highest projected increase of temperature was identified for dam reservoirs located in high latitudes of Northern Hemisphere, and therefore dam reservoirs located there will be most significantly affected. Numerous consequences of temperature increase are already recorded. Further increase will amplify unfavorable effects on numerous ecosystems, including dam reservoirs which are built on the purpose of the human population development. Our study indicates a threat for artificially stored water globally, with special attention to high latitudes in northern hemisphere and latitudes close to 200S meridian in southern hemisphere.
... Reservoirs of large hydropower plants located in tropical regions usually generate from 8 gCO 2 eq./kWh up to 6,647 gCO 2 eq./kWh due to the decomposition of biomass and organic matter (Song et al., 2018). However, run of river (RoR) hydropower plants do not need flooding reservoirs and therefore decay of biomass is negligible. ...
Chapter
The aim of this chapter is to provide an overview of social, economic, and environmental impacts of renewable energy. Based on available literature, this chapter identifies the impacts of key renewable energy sources including solar, wind, hydro, and biomass in addition to solid waste. The most common impacts were identified for these renewable energy sources include impacts on land use, employment generation, and social aspects of quality life. This chapter considered both negative and positive aspects of the impacts and indicates that the impacts of renewable energy generation from different renewable energy sources very in terms of types and extent. The extent of impacts may differ according to the types of renewable energy sources, size of the energy generation plant, technology for energy generation, and socioeconomic context of a country.
... Some studies also paid attention to the indirect carbon emissions or the life-cycle (from cradle to gate or from cradle to grave) carbon footprint of hydropower. A majority of these studies are based on the method of process analysis [9][10][11][12][13]. It is found that the indirect carbon emissions caused by the hydropower project are significant. ...
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Hydropower is the largest renewable source of electricity generation, the carbon emissions of which have attracted a lot attention. However, the system boundaries of existing studies are either incomplete or inaccurate. Therefore, this study provides a systems accounting framework for evaluating both the direct and indirect carbon emissions from a hydropower plant. It is based on the hybrid method as a combination of the process analysis and the input-output analysis. To demonstrate the framework, a case study for a typical pumped storage hydropower plant (NPSHP) is carried out. The total carbon emissions are estimated as 5828.39 kt in the life-cycle of the case system. The end-of-use stage causes the largest carbon emissions (38.4%), followed by the construction stage (34.5%), the operation stage (25.6%), and the preparation stage (1.5%). The direct carbon emissions are mainly released from sediments in the end-of-use stage and the surface of reservoirs in the operation stage (94.8%). The indirect carbon emissions are 2.8 times higher than the direct carbon emissions. The material, machinery, energy, and service inputs respectively account for 7.1%, 14.7%, 15.9%, and 62.3% of the total indirect carbon emissions by the case system. The indicator of EGOC (electricity generation on carbon emission) for the NPSHP is calculated as 26.06 g CO2-eq./kWh, which is lower than that of most other power plants.
... Human presence (e.g., accommodation and sanitation facilities for workforce There are also GHG emissions relating to the construction of pump/turbine units, manufacturing of cement and steel, transport of materials and personnel, flooding of forested landscapes, and clearing of vegetation for roads [11,50,51]. ...
Article
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Because generating electricity significantly contributes to global greenhouse gas emissions, meeting the 2015 Paris Agreement and 2021 Glasgow Climate Pact requires rapidly transitioning to zero or low-emissions electricity grids. Though the installation of renewables-based generators—predominantly wind and solar-based systems—is accelerating worldwide, electrical energy storage systems, such as pumped storage hydropower, are needed to balance their weather-dependent output. The authors of this paper are the first to examine the status and potential for pumped storage hydropower development in 24 Pacific Rim economies (the 21 member economies of the Asia Pacific Economic Cooperation plus Cambodia, Lao PDR, and Myanmar). We show that there is 195 times the pumped storage hydropower potential in the 24 target economies as would be required to support 100% renewables-based electricity grids. Further to the electrical energy storage potential, we show that pumped storage hydropower is a low-cost, low-greenhouse-gas-emitting electrical energy storage technology that can be sited and designed to have minimal negative (or in some cases positive) social impacts (e.g., requirements for re-settlement as well as impacts on farming and livelihood practices) and environmental impacts (e.g., impacts on water quality and biodiversity). Because of the high potential for pumped storage hydropower-based electrical energy storage, only sites with low negative (or positive) social and environmental impacts such as brownfield sites and closed-loop PSH developments (where water is moved back and forth between two reservoirs, thus minimally disturbing natural hydrology) need be developed to support the transition to zero or low-carbon electricity grids. In this way, the advantages of well-designed and -sited pumped storage hydropower can effectively address ongoing conflict around the social and environmental impacts of conventional hydropower developments. Noting the International Hydropower Association advocacy for pumped storage ydropower, we make recommendations for how pumped storage hydropower can ustainably reduce electricity-sector greenhouse gas emissions, including through market reforms to encourage investment and the application of standards to avoid and mitigate environmental and social impacts.
... In addition, over 3700 large hydroelectric dams with a total capacity of more than 1000 GW are to be constructed in the next few decades, which will increase current hydropower generation by more than 70% (Zarfl et al. 2015). Though these dams play a key role in meeting the increasing energy demand, they pose a great risk to sustainable fisheries (Limburg and Waldman 2009;Song et al. 2019) as well as the wellbeing of fish-dependent communities (Zarfl et al. 2015;Winemiller et al. 2016;Limburg and Waldman 2009;Song et al. 2018;Chen et al. 2016). Dams can substantially decrease fish populations by fragmenting migration corridors (Hall et al. 2011;Beasley and Hightower 2000), degrading habitat quality (e.g., changes in temperature and discharge) (Johnson et al. 2007;Piffady et al. 2013;Zhao et al. 2012), and causing severe turbine injuries (Schaller et al. 2013;Stich et al. 2015). ...
Presentation
The trapped sediments in reservoirs is a matter of concern in the decommissioning of dams: the flux of sediment during and after removal, increase in availability of potential toxic contaminants, the influence of deposited sediments on downstream habitat and other site-specific considerations. The significant volume of sediments accumulated over the years and the carbon content can also lead to methane emissions, potentially contributing to climate change and influencing the life cycle greenhouse gas emissions from hydroelectric power. Many factors can affect the greenhouse gas (GHG) emissions from trapped sediments, such as sedimentation rate, rate of mineralization, CO2:CH4 ratio, carbon content, among others. The behavior of these parameters for different conditions are still unknown, especially in a dam removal scenario. However, by using a Monte-Carlo analysis applied to published studies evaluating the life-cycle impacts of hydropower plants and methane emission from decomposition of sediments, we found that even in an optimistic scenario with low rates of sedimentation and mineralization, the carbon emissions from the decommissioning of dams may represent 20% of the GHG life-cycle of hydropower plants; in the worst scenario it may account for up to 90%. Such variation is the consequence of a wide range, 10-60 million tons of CO2e, in the dam decommissioning stage. These results demonstrate the need for further analysis to identify the conditions that drive the methanogenesis process post-removal and for strategies to reduce this impact. Best practices for sediments management could be a strategy to reduce the GHG emissions from dam removal, especially when anoxic conditions may be dominant.
... The contribution to GHG emissions related to reservoir construction, meaning those from the activities related to dam construction (raw material extraction, equipment manufacturing, transportation, and building process of dam), is estimated to be (2.3-37.9) gCO2eq/kWh [27]. [28] 235 [28] In paper [26], an average global emission of 173 kg CO2/MWh and 2.95 kg CH4/MWh was estimated after the emissions from over 1400 hydroelectric power plants were analyzed. ...
Article
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In order to evaluate the greenhouse gas (GHG) emissions from a reservoir or from several reservoirs in a country or a climatic zone, simpler or more complex models based on measurements and analyses of emissions presented in the literature were developed, which take into account one or more reservoir-specific parameters. The application of the models in the assessment of GHG emissions from a multipurpose reservoir gave values that are more or less close to the average values reported in the literature for the temperate zone reservoirs. This is explained by the fact that some models only consider emissions caused by impoundment and not degassing, spillway emissions , and downstream emissions, or those that use different calculation periods. The only model that calculates GHG emissions over the life cycle that occur pre-impoundment, post-impoundment, from unrelated anthropogenic sources and due to the reservoir construction is the model used by the G-res tool. In addition, this tool is best suited for multipurpose reservoirs because it allocates GHG emissions for each use, thus facilitating the correct reporting of emissions. The G-res tool used to calculate GHG emissions from the Stânca-Costești Multipurpose Reservoir shows that this is a sink of GHG with a net emission of −5 g CO2eq/m 2 /yr (without taking into account the emissions due to dam construction).
... SNG production process using electricity generated from solar photovoltaic (case 4) or onshore wind (case 5) was more sustainable based on CO 2 emissions. Here, although hydropower is renewable energy, relatively high CO 2 emissions were presented because the pump operation requires significant amount of energy in a pumped storage hydropower plant [76]. Scenarios considering degradation in WE had higher CO 2 emissions for all cases compared to those without degradation, implying that technological developments in WE systems for less or no degradation had a positive effect on economic feasibility as well as environmental impact. ...
Article
Synthetic natural gas (SNG) production from captured CO2 and H2 produced by water electrolysis using renewable energy is of increasing interest for low-carbon fuel production, CO2 utilization technology, and unstable renewable energy storage. In this study, the effect of voltage degradation in a water electrolyzer, a core technology for SNG production, on the unit production cost of SNG production and CO2 emissions, with different water electrolysis types such as alkaline electrolysis (AEL), proton exchange membrane electrolysis (PEMEL), and solid oxide electrolysis (SOEL), was identified through techno-economic and environmental assessment. In particular, the energy efficiency, unit production cost of SNG, and CO2 emissions were identified based on the change in the power consumption caused by voltage degradation. Moderate voltage loss results in a decrease in energy efficiency from 53.8% to 48.8% in AEL, 55.3% to 47.0% in PEMEL, and 76.3% to 51.2% in SOEL. Moreover, respective SNG unit production costs of 140.3–170.2 USD MWh⁻¹, 157.5–203.1 USD MWh⁻¹, and 153.1–353.5 USD MWh⁻¹ for AEL, PEMEL, and SOEL, respectively, were obtained, showing an increase in SNG production cost due to the voltage degradation. Furthermore, total CO2 emissions for the SNG production process were investigated considering voltage degradation as well as electricity generation sources.
Article
Rapid deployment of wind energy plays an important role in China's proposed energy transition to carbon neutrality before 2060. Greenhouse gas (GHG) emissions are, however, unavoidable during the entire life cycle of wind energy from manufacturing to disposal. It is important to estimate these GHG emissions and the emission intensity for programs of energy transition. We developed simplified LCA models and engineering-based models to provide a comprehensive estimate of the GHG emissions intensity and total emissions from onshore wind energy in China at provincial and national scales. We showed that in 2019, the GHG emission intensity per unit power generation was 19.88 g CO2 eq/kWh (provincial intensity ranges from 13.59 to 34.50 g CO2 eq/kWh). The results show that onshore wind energy in China has an emission intensity more than 98% lower than traditional fossil fuels and the mitigation effect can reach 84%–98% compared to the energy mix in 2020. We further investigated the effects on emission intensity of shifting the turbine mix towards larger sizes, reducing wind curtailment and using advanced designs to improve efficiency. Advanced design of turbines can further decrease GHG emission intensity by 21.6%, more than the scenario of reducing curtailment (5.4%), while the emission intensity could be reduced by 2.1% under the scenario of shifting the turbine mix towards larger sizes. The results will aid future energy-mix scenario design and policy formulation.
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Damming rivers addresses a range of society's needs, but at the cost of fragmentation and other negative effects on freshwater ecosystems. This article examines hydropower development and fish conservation in the Upper Yangtze River Basin to explore strategies for managing dams more sustainably at the basin scale. We highlight the need to limit the effects of hydropower dams on freshwater biodiversity, and that protecting fish in reserves could be one of the most effective approaches to limiting the ecological effects of dams on fish. However, in the Yangtze River basin there are dams on the rivers in all but 1 of the 14 fish reserves mapped in this study, thus compromising the effectiveness of the reserves. In addition, the removal of some dams may not be as effective as suggested. Thus, we propose that limiting dam construction in protected tributaries is a ready-to-adopt conservation strategy. However, the adoption of this policy by the Chinese government will be determined by which of two competing policy changes (i.e. gradual or sudden) in the policy subsystem of dam construction will prevail. In this paper we illustrate how greater triage in the Upper Yangtze River Basin can deliver services to people and conserve freshwater biodiversity.
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Continuous dams may lead to great variation in greenhouse gas (GHG) emissions from rivers, which contribute more uncertainty to regional carbon balance. This study is among the first to determine water–air interface GHGs (CO2, CH4, and N2O) in a river with continuous dams in plateau city. Combined static-chamber gas and meteorological chromatography were utilized to monitor the GHGs emission flux at the water–air interface within four continuous dams in the Huoshaogou River in the Qinghai–Tibet Plateau, China. A variation coefficient (VC) and amplification coefficient (AC) were designed to detect the influence of continuous dams on GHG emissions. Results indicate that (1) cascade dams presented an amplifying effect on GHGs emissions from the water-air interface. The VCs of three types of GHGs are 3.7–6.7 times higher than those of the undammed area. The ACs of three types of GHGs are 2.7–4.1 times larger than environmental factors; (2) the average GHG emission fluxes in some dams are higher than that of the first dam, indicating that an amplifying effect may have been accumulated by some continuous dams; (3) EC, pH, Twater, Tair and TDS are found to be principle influencing factors of GHG emission and light intensity, Twater, TOC (plant), TN (sediment) and TOC (sediment) are found to be associated with accumulative changes in GHG emission.
Article
Human economic activity must be decarbonized within several decades to avoid dangerous levels of global warming, with the US passenger fleet a major source of CO2. Decarbonization likely requires an ultimate shift to completely electrified transportation, but given the current reliance of electricity generation on fossil fuels, the optimal deployment schedule of low-carbon vehicles is not known. A simple model is developed for the turnover of the vehicle fleet from the current conventional to an all battery-electric vehicle fleet, including the lifecycle emissions for vehicle production, fuel, and electricity generation. Hybrid-electric vehicles are included as a transitional technology. This model represents the US fleet and both the present and future electrical grid at the county scale, and a range of imposed vehicle market share transition scenarios are considered. To limit cumulative vehicle emissions over the 2017 to 2070 interval, an early, rapid adoption of low-carbon vehicles, either as hybrid or pure electric vehicles, must take place, with an ultimate transition to the battery-electric technology. However, hybrids are found to be an effective transitional technology, and even preferable over the short-term in many areas. Furthermore, some degree of behavioral change, in the form of reduced vehicle miles, must accompany this transition to fully meet climate targets.
Chapter
IPCC AR6 WG2 Chapter 4: Water
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Further reservoir-based hydropower development can contribute to the United Nations’ sustainable development goals (SDGs) on affordable and clean energy, and climate action. However, hydropower reservoir operation can lead to biodiversity impacts, thus interfering with the SDGs on clean water and life on land. We combine a high-resolution, location-specific, technical assessment with newly developed life cycle impact assessment models, to assess potential biodiversity impacts of possible future hydropower reservoirs, resulting from land occupation, water consumption and methane emissions. We show that careful selection of hydropower reservoirs has a large potential to limit biodiversity impacts, as for example, 0.3% of the global hydropower potential accounts for 25% of the terrestrial biodiversity impact. Local variations, e.g. species richness, are the dominant explanatory factors of the variance in the quantified biodiversity impact and not the mere amount of water consumed, or land occupied per kWh. The biodiversity impacts are mainly caused by land occupation and water consumption, with methane emissions being much less important. Further, we indicate a trade-off risk between terrestrial and aquatic biodiversity impacts, as due to the weak correlation between terrestrial and aquatic impacts, reservoirs with small aquatic biodiversity impacts tend to have larger terrestrial impacts and vice versa.
Article
This study evaluated changes in the aquatic environment and river water quality due to construction of the Yeongju Multipurpose Dam (YMD) in the Naeseong Stream Basin, Republic of Korea, over eight years. This study evaluated water quality characteristics immediately after dam construction in the target area with aquatic environmental values and important water quality parameters using classification schemes. The drastic formation of new lentic systems in the upstream dammed pool presented exponential algal growth and high potential availability of nitrogenous compounds depending on seasonally. The results of the river system analyzed with the water quality index focused on eutrophication (WQIEUT) and trophic state index of the Republic of Korea (TSIKO) provided adequate complementary information for specific water quality background within the extensive basin for future management. From the results, inflow and accumulation of anthropogenic organic matter as potential eutrophic factors in the upstream dammed pool were significant in the short-term period. However, the downstream lotic systems adjacent to the dam presented the temporary disturbance by physical factors. Furthermore, potential microbial factors were significant in the outlet in the basin depending on seasonally. These results using classification schemes can aid accessible decision-making for water quality management to prevent eutrophication in the dammed pool of upstream or best management practices (BMP) with microbial source tracking (MST) approaches in the downstream area.
Technical Report
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This chapter assesses observed and projected climate-induced changes in the water cycle, their current impacts and future risks on human and natural systems and the benefits and effectiveness of water-related adaptation efforts now and in the future.
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Hydropower, which contributes to around 16% of global electricity and more than 72% of renewable electricity, is expected to play an important role in the deep decarbonization of the energy sector. However, the idea that hydropower is a carbon-neutral energy alternative on par with solar and wind is controversial. Research, mainly from limnology and climate modeling, shows that depending on the characteristics of the hydro project, it could be a significant source of GHG emissions. This aspect has been ignored in most life cycle assessment (LCA) studies, affecting the effective use of LCA results, especially in comparative assessments. This paper aims to provide a comprehensive and critical review on this topic by conducting a systematic literature review on hydropower LCA studies published since 2010. We found that there is inconsistency in how LCA is used for hydropower projects. While the emissions associated with the engineering work are well addressed, efforts to accurately estimate and model reservoir GHG emissions are constrained by limited data availability, difficulties in accurately quantifying highly variable carbon fluxes, and inconsistent modeling approaches. A huge range of emissions values is reported in the reviewed literature, from 1.5 to 3747.8 g CO2 eq per kWh. Reservoir-based hydropower shows high variability, which is mainly dictated by reservoir-related GHG emissions. Reservoir GHG emissions could be more than 90% of the life cycle emissions, especially for hydropower in a tropical region. The regionalized aspect is a key factor to be considered in extrapolating reservoir GHG emissions.
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Studies of emissions of greenhouse gas (GHG) such as CO2 and CH4 in hydroelectric reservoirs are very important in the debate on whether hydropower can be classified as a ‘clean energy’ source. In this study, GHG emissions in the Topocoro reservoir in Colombia during the first five years after filling were evaluated and related with hydropower generation. The floating static chamber and inverted funnel methodology were used for the collection of GHG and the gas chromatography with flame ionization detector (FID) – methanizer and electron capture detector (ECD) methodology for its detection in the laboratory. The results showed emission values between 256,613 and 654,643 tCO2eq/year. The intensity of gases was also determined in a range between 81 and 148 gCO2eq/kWh, depending on the evolution of the filling and the power generation in the reservoir. The results suggested that as the filling percentage of the surface of the reservoir increases, there will be more GHG emissions, due to the biotic and abiotic decomposition of organic matter. At the same time, higher energy production will be generated. HIGHLIGHTS A tropical reservoir in Colombia was monitored for five years during the post-filling phase.; The floating static chamber and inverted funnel methodology were used.; It analyzed the relationships of the GHG with energy production and power density in the reservoir.; This is the first investigation carried out in Colombia to determine the net emissions in a reservoir.;
Article
We developed a three-dimensional model to study the dynamics of carbon dioxide (CO2) emission from a subtropical drinking water reservoir. The quantitative effects of dissolved CO2 concentration on phytoplankton growth were coupled in an inorganic carbon module. Water quality monitoring was carried out to calibrate and validate the model. The simulated surface CO2 concentrations showed no significant difference between seasons (p > 0.05). Regarding the spatial distribution, high CO2 concentrations were observed in the inflow and dam regions (p < 0.05). Four scenarios of different atmospheric CO2 pressures and eutrophic levels were simulated to test the following hypotheses: (1) eutrophication will reverse the carbon budgets in reservoir systems and (2) rising CO2 levels will increase phytoplankton biomass. The results showed that water quality improvements will promote the emission of CO2 into the atmosphere. Simultaneously, the elevated CO2 in the air will stimulate algal biomass, especially in nutrient-rich systems. The systematic analysis of carbon cycling revealed the different internal transformation rates under different scenarios and showed that 32% of carbon was removed via CO2 emission and carbon burial. The interaction provides a novel direction to understand the feedback loops between aquatic ecosystems and increasing CO2 pressure in the future.
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Purpose Low-carbon emissions are usually related to hydropower energy, making it an attractive option for nations with hydropower potential as it enables them to meet increasing electricity demand without relying on burning fossil fuels. In fact, the new wave of hydropower plant construction is occurring mainly in tropical areas where an additional environmental impact must be considered: biogenic greenhouse gas (GHG) emissions due to the degradation of biogenic carbon in reservoirs. Peru is planning to install up to 2000 MW in hydropower until 2021, but the input and output flows, as well as the environmental impacts that these generate, have not been explored. Hence, a set of three hydropower plants built in the past decade located in the Peruvian Andes were analyzed from a life cycle perspective. The main objective of the study is to generate detailed life cycle inventories for each of these three hydropower plants with the aim of obtaining specific information for current conditions in Peru. Methods The life cycle assessment methodology was applied to compute the environmental impacts. Data collection was based mainly on primary data obtained directly from the hydropower companies, although biogenic emissions were modeled considering local net primary productivity conditions and other site-specific conditions. Although the calculation of GHG emissions related to hydropower plants was a priority, considering the important policy implications of decarbonizing the Peruvian electricity grid, other environmental categories, such as eutrophication or the depletion of abiotic resources, were also considered. The IPCC method was used to calculate GHG emissions, whereas a set of eight additional impact categories were computed using the ReCiPe 2016 method. Results and discussion Results show that GHG emissions per unit of electricity generated were in the lower range of emissions observed in the literature, in all three cases below 3 g CO2eq/kWh. Biogenic emissions represented less than 5% of the total GHG emissions despite their location in a tropical nation, due to the arid conditions of the landscape in the Andean Highlands, as well as the mild temperatures that are present in the reservoirs. In terms of stratospheric ozone depletion, a GHG with ozone depletion properties, N2O, was the main source of impact. Conclusions The results are intended to be of utility for an array of applications, including relevance in decision-making in the energy sector and policy-making at a national level, considering the implications in terms of meeting the nationally determined contributions to mitigate climate change in the frame of the Treaty of Paris.
Chapter
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This chapter assesses current climate change impacts on the global and regional water cycle, projected water-related risks for human and natural systems, and adaptation options and effectiveness across scales.
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Collectively, reservoirs created by dams are thought to be an important source of greenhouse gases (GHGs) to the atmosphere. So far, efforts to quantify, model, and manage these emissions have been limited by data availability and inconsistencies in methodological approach. Here, we synthesize reservoir CH 4 , CO 2 , and N 2 O emission data with three main objectives: (1) to generate a global estimate of GHG emissions from reservoirs, (2) to identify the best predictors of these emissions, and (3) to consider the effect of methodology on emission estimates. We estimate that GHG emissions from reservoir water surfaces account for 0.8 (0.5–1.2) Pg CO 2 equivalents per year, with the majority of this forcing due to CH 4. We then discuss the potential for several alternative pathways such as dam degassing and downstream emissions to contribute significantly to overall emissions. Although prior studies have linked reservoir GHG emissions to reservoir age and latitude, we find that factors related to reservoir productivity are better predictors of emission.
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Aging infrastructure coupled with growing interest in river restoration has driven a dramatic increase in the practice of dam removal. With this increase, there has been a proliferation of studies that assess the physical and ecological responses of rivers to these removals. As more dams are considered for removal, scientific information from these dam-removal studies will increasingly be called upon to inform decisions about whether, and how best, to bring down dams. This raises a critical question: what is the current state of dam-removal science in the United States? To explore the status, trends, and characteristics of dam-removal research in the U.S., we searched the scientific literature and extracted basic information from studies on dam removal. Our literature review illustrates that although over 1200 dams have been removed in the U.S., fewer than 10% have been scientifically evaluated, and most of these studies were short in duration (<4 years) and had limited (1–2 years) or no pre-removal monitoring. The majority of studies focused on hydrologic and geomorphic responses to removal rather than biological and water-quality responses, and few studies were published on linkages between physical and ecological components. Our review illustrates the need for long-term, multidisciplinary case studies, with robust study designs, in order to anticipate the effects of dam removal and inform future decision making. For further resources related to this article, please visit the WIREs website.
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The character and importance of uncertainty in dam safety risk analysis drives how risk assessments are used in practice. The current interpretation of uncertainty is that, in addition to the aleatory risk which arises from presumed uncertainty in the world, it comprises the epistemic aspects of irresolution in a model or forecast, specifically model and parameter uncertainty. This is true in part but it is not all there is to uncertainty in risk analysis. The physics of hazards and of failure may be poorly understood, which goes beyond uncertainty in its conventional sense. There may be alternative scenarios of future conditions, for example non-stationarity in the environment, which cannot easily be forecast. There may also be deep uncertainties of the type associated with climate change. These are situations in which analysts do not know or do not agree on the system characterisation relating actions to consequences or on the probability distributions for key parameters. All of these facets are part of the uncertainty in risk analysis with which we must deal.
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Tropical dams are often falsely portrayed as 'clean' emissions-free energy sources. The letter by de Faria et al (2015 Environ. Res. Lett. 10 124019) adds to evidence questioning this myth. Calculations are made for 18 dams that are planned or under construction in Brazilian Amazonia and show that emissions from storage hydroelectric dams would exceed those from electricity generation based on fossil fuels. Fossil fuels need not be the alternative, because Brazil has vast potential for wind and solar power as well as opportunities for energy conservation. Because dam-building is rapidly shifting to humid tropical areas, where emissions are higher than in other climatic zones, the impact of these emissions needs to be given proper weight in energy-policy decisions.
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Interest in the advancement of hydrokinetic energy conversion (HEC) technology has grown substantially in recent years. The hydrokinetic industry has advanced beyond the initial testing phase and will soon install demonstration projects with arrays of full-scale devices. By reviewing the current state of the industry and the cutting edge research this paper identifies the key advancements required for HEC technology to become commercially successful at the utility scale. The primary hurdles are: (i) reducing the cost of energy, (ii) optimizing individual turbines to work in concert considering array and bathymetry effects, (iii) balancing energy extraction with environmental impact, and (iv) addressing socioeconomic concerns.
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Turkey’s electricity mix is dominated by fossil fuels, but the country has ambitious future targets for renewable and nuclear energy. At present, environmental impacts of electricity generation in Turkey are unknown so this paper represents a first attempt to fill this knowledge gap. Taking a life cycle approach, the study considers eleven impacts from electricity generation over the period 1990–2014. All 516 power plants currently operational in Turkey are assessed: lignite, hard coal, natural gas, hydro, onshore wind and geothermal. The results show that the annual impacts from electricity have been going up steadily over the period, increasing by 2–9 times, with the global warming potential being higher by a factor of five. This is due to a four-fold increase in electricity demand and a growing share of fossil fuels. The impact trends per unit of electricity generated differ from those for the annual impacts, with only four impacts being higher today than in 1990, including the global warming potential. Most other impacts are lower from 35% to two times. These findings demonstrate the need for diversifying the electricity mix by increasing the share of domestically-abundant renewable resources, such as geothermal, wind, and solar energy.
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Abstract This paper applies a life cycle approach to evaluate for the first time the environmental impacts of renewable electricity in Turkey. There are 305 power plants utilising hydro, wind and geothermal resources, all of which are considered in the study. The results indicate that the impacts from large reservoir hydropower are lower than for the small reservoir (by 45%–72%) and run-of-river hydropower (by 74%–84%). The exceptions are the global warming potential (GWP) and summer smog which are two times and 45% higher for large than small reservoir, respectively. Onshore wind is the worst option overall, with nine out of 11 impacts higher than for hydropower and geothermal. However, its GWP is 9 times and 11% lower than for geothermal and large reservoir, respectively. Acidification from geothermal is 281 times higher than for wind power. Geothermal is the best option for six impacts. Large reservoir has the lowest depletion of elements and fossil resources as well as acidification. Small reservoir and run-of-river plants are the best and geothermal the worst options for the GWP. The majority of the annual impacts from the renewable electricity mix are from hydropower with the exception of acidification which is largely from geothermal electricity.
Book
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Environmental life cycle assessment is often thought of as cradle to grave and therefore as the most complete accounting of the environmental costs and benefits of a product or service. However, as anyone who has done an environmental life cycle assessment knows, existing tools have many problems: data is difficult to assemble and life cycle studies take months of effort. A truly comprehensive analysis is prohibitive, so analysts are often forced to simply ignore many facets of life cycle impacts. But the focus on one aspect of a product or service can result in misleading indications if that aspect is benign while other aspects pollute or are otherwise unsustainable. This book summarizes the EIO-LCA method, explains its use in relation to other life cycle assessment models, and provides sample applications and extensions of the model into novel areas. A final chapter explains the free, easy-to-use software tool available on a companion website. (www.eiolca.net) The software tool provides a wealth of data, summarizing the current U.S. economy in 500 sectors with information on energy and materials use, pollution and greenhouse gas discharges, and other attributes like associated occupational deaths and injuries. The joint project of twelve faculty members and over 20 students working together over the past ten years at the Green Design Institute of Carnegie Mellon University, the EIO-LCA has been applied to a wide range of products and services. It will prove useful for research, industry, and in economics, engineering, or interdisciplinary classes in green design. © 2006 by Resources for the Future. All rights reserved. All rights reserved.
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Brazil plans to meet the majority of its growing electricity demand with new hydropower plants located in the Amazon basin. However, large hydropower plants located in tropical forested regions may lead to significant carbon dioxide and methane emission. Currently, no predictive models exist to estimate the greenhouse gas emissions before the reservoir is built. This paper presents two different approaches to investigate the future carbon balance of eighteen new reservoirs in the Amazon. The first approach is based on a degradation model of flooded carbon stock, while the second approach is based on flux data measured in Amazonian rivers and reservoirs. The models rely on a Monte Carlo simulation framework to represent the balance of the greenhouse gases into the atmosphere that results when land and river are converted into a reservoir. Further, we investigate the role of the residence time/stratification in the carbon emissions estimate. Our results imply that two factors contribute to reducing overall emissions from these reservoirs: high energy densities reservoirs, i.e., the ratio between the installed capacity and flooded area, and vegetation clearing. While the models’ uncertainties are high, we show that a robust treatment of uncertainty can effectively indicate whether a reservoir in the Amazon will result in larger greenhouse gas emissions when compared to other electricity sources.
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Renewable energy systems reduce the greenhouse gas (GHG) emissions associated with energy generation. However, we live in a world with depleting reserves of natural resources, and significant quantities of raw materials are often embodied within renewable energy infrastructure. This paper examines the potential for ecodesign measures to improve the GHG and resource balance of five small-scale hydropower case studies (50-650 kW). A life cycle assessment (LCA) approach compares two specific environmental impact categories: global warming potential (GWP) and abiotic resource depletion potential (ARDP). A number of ecodesign measures were examined for each installation: powerhouse structure, concrete selection, roofing materials, excavation work and transportation. Ecodesign led to cumulative savings of between 2.1% and 10.4% for GWP, and ARDP savings of between 0.1% and 2.6%, for the hydropower installations. Small savings were made with each ecodesign measure applied in all case studies. Furthermore, applying a 1% materiality threshold as outlined by LCA standards was shown to under-estimate the total project burdens, and to neglect opportunities for burden savings through ecodesign. Ecodesign can promote the use of locally sourced materials and some measures can lead to time savings during the construction process. The findings demonstrate the potential for ecodesign to modestly improve the carbon and resource efficiency of hydropower projects.
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Purpose This paper explores the potential to simplify the life cycle assessment (LCA) process for a hydropower (HP) system, without significantly compromising the accurate representation of environmental burdens. Taking five HP case studies, two questions were addressed: (i) Does a 1 % materiality threshold capture at least 95 % of the key environmental burdens from cradle-to-operation? (ii) What is the effect of applying a materiality threshold based on the global warming potential (GWP) indicator for capturing other environmental impacts? Methods A comprehensively detailed inventory database was developed for five modern small- and micro-HP case studies (50–650 kW), representing run-of-river and water supply infrastructure installations from the UK and Ireland. Following ISO 14040 standards, the environmental burdens were quantified for these HP projects. Normalised results were compared against a natural gas combined cycle power plant (NG-CCP) reference system for marginal grid electricity generation. Results and discussion The adoption of a 1 % materiality threshold as advised by some guidelines led to cumulative omissions of up to 7.5 % of the total project burdens for some HP installations, contravening the 95 % inclusion target. The number of project components differed between the two types of HP projects and target exceedances were more likely for projects with more components. Using a lower materiality threshold of 0.2 or 0.5 % ensured that the 95 % target was achieved for all HP projects. Considering GWP as an indicator burden for assessing materiality thresholds led to significant omissions for other environmental burdens, e.g. abiotic resource depletion potential (ARDP). Omitting a number of small components with low-carbon contributions (e.g. copper wiring) led to a 19 % underestimation for contributors to the resource-based (GWP) impact categories. Conclusions A simplified methodology may not capture all environmental burdens for a hydropower system or fossil fuel-based power plant. Basing a 1 % materiality threshold on contribution to a single burden, such as GWP, can lead to omissions of significant contributory components for that burden, and larger omissions for other burdens. ARDP is a particularly important impact category for renewable energy systems and appears to be particularly sensitive to materiality thresholds. It is important that practitioners take care with materiality thresholds when evaluating the environmental performance of all types of renewable energy systems through LCA. Including a materiality threshold to draw practicable system boundaries is necessary; however, reducing the threshold contribution to 0.5 % would be more likely to ensure that at least 95 % of environmental burdens are accounted for.
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When carbon credit is granted for projects that would occur irrespective of any subsidy based on mitigation of global warming, the projects generate "hot air," or credit without a real climate benefit. This is the case for tropical hydroelectric dams, which are now a major destination for funds under the Kyoto Protocol's Clean Development Mechanism (CDM). The countries that purchase the credit generated by dams can emit more greenhouse gases without their being offset by genuine mitigation. The limited funds available for mitigation are also wasted on subsidizing dams that would be built anyway. Tropical dams also emit substantially more greenhouse gases than are recognized in CDM accounting procedures. Tropical hydroelectric emissions are also undercounted in national inventories of greenhouse gases under the United Nations Framework Convention on Climate Change, giving them a role in undermining the effectiveness of as-yet undecided emission limits. Brazil's Santo Antnio Dam, now under construction on the Madeira River, provides a concrete example indicating the need for reform of CDM regulations by eliminating credit for hydroelectric dams.
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Recognizing the issues of land shortage and growing concerns for protecting natural lands, installers and project developers, with the help of scientists and engineers, continuously try to locate alternative spots for photovoltaic (PV) system installations. In the present paper a novel approach is suggested and analysed: installing solar PV systems on the downstream face of existing dams. This approach provides advantages that could favour even large-scale systems with a capacity of several MWp. First, produced energy could cover water reservoirs' needs supporting energy-intensive processes as water pumping and treatment in a sustainable manner. Moreover, energy provision to inhabited areas near the dams and the subsequent creation of independent mini grids could mitigate energy poverty. In the case of hydroelectric dams, the so-created hybrid system (PV-hydro) could become notably efficient, because the intermittent solar energy would be counterbalanced by the flexibility of hydropower. Finally, we found a notable number of existing water reservoirs in Africa that are either under-utilized or non-powered. That unexploited energy potential can also be amplified by PV-system installation. The analysis included data collection from various sources. Datasets have been cross-checked and extended in the newly created GIS-based model, enabling the selection of the most suitable sites in South Africa, taken as case studies. Following their identification, the selected dams have been analysed using the PVGIS tool in order to estimate the annual energy production. The results have been very encouraging, indicating that PV systems on the face of dams are an advantageous option for renewable energy production.
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The two major pathways for energy utilization from biomass are conversion to a liquid fuel (i.e., biofuels) or conversion to electricity (i.e., biopower). In the United States (US), biomass policy has focused on biofuels. However, this paper will investigate three options for biopower: low co-firing (co-firing scenarios refer to combusting a given percentage of biomass with coal) (5%–10% biomass), medium co-firing (15%–20% biomass), and dedicated biomass firing (100% biomass). We analyze the economic and greenhouse gas (GHG) emissions impact of each of these options, with and without CO[subscript 2] capture and storage (CCS). Our analysis shows that in the absence of land use change emissions, all biomass co-combustion scenarios result in a decrease in GHG emissions over coal generation alone. The two biggest barriers to biopower are concerns about carbon neutrality of biomass fuels and the high cost compared to today’s electricity prices. This paper recommends two policy actions. First, the need to define sustainability criteria and initiate a certification process so that biomass providers have a fixed set of guidelines to determine whether their feedstocks qualify as renewable energy sources. Second, the need for a consistent, predictable policy that provides the economic incentives to make biopower economically attractive.
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Abstract In this paper, the environmental performance of electricity storage technologies for grid applications is assessed. Using a life cycle assessment methodology we analyze the impacts of the construction, disposal/end of life, and usage of each of the systems. Pumped hydro and compressed air storage are studied as mechanical storage, and advanced lead acid, sodium sulfur, lithium-ion and nickel–sodium-chloride batteries are addressed as electrochemical storage systems. Hydrogen production from electrolysis and subsequent usage in a proton exchange membrane fuel cell are also analyzed. The selected electricity storage systems mimic real world installations in terms of capacity, power rating, life time, technology and application. The functional unit is one kW h of energy delivered back to the grid, from the storage system. The environmental impacts assessed are climate change, human toxicity, particulate matter formation, and fossil resource depletion. Different electricity mixes are used in order to exemplify scenarios where the selected technologies meet specific applications. Results indicate that the performance of the storage systems is tied to the electricity feedstocks used during use stage. Renewable energy sources have lower impacts throughout the use stage of the storage technologies. Using the Belgium electricity mix of 2011 as benchmark, the sodium sulfur battery is shown to be the best performer for all the impacts analyzed. Pumped hydro storage follows in second place. Regarding infrastructure and end of life, results indicate that battery systems have higher impacts than mechanical ones because of lower number of cycles and life time energy.
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Purpose Small hydropower (SHP) in China has experienced soring development in the past two decades and has been assigned ambitious development goals recently, while its environmental performance remains unclear. This study is intended to provide a comprehensive assessment of the environmental impacts of SHP plants in China, to compare the results with its counterparts in other countries, and to identify the key factors in the mitigation of negative consequences. Methods A life cycle assessment of a SHP plant in Guizhou Province of China was conducted in a cradle-to-grave manner following the ISO 14040 guidelines. The functional unit is defined as 1 MWh of net electricity produced by the plant. The CML 2001 method was applied to characterize the environmental impacts. The environmental impact categories considered in this study included global warming (GWP), abiotic depletion (ADP), acidification (AP), freshwater aquatic ecotoxicity (FAETP), human toxicity (HTP), and photochemical ozone creation (POCP). Further contribution analyses and sensitivity analysis was performed to identify the key contributors to each impact category during the life cycle of the plant. Results and discussion For the case plant, the considered impacts are caused primarily by the construction stage. As for the materials and energy inputs, cement, steel, and electricity are the three dominating ones for the overall environmental impacts. Compared with SHP plants in other countries, the plant performs similar to the MW scale plants in Thailand and Japan but worse than the plant in Switzerland. Further comparison of life cycle inventories (LCIs) revealed that the quality of hydro-energy resources and acquisition of indigenous equipment technology is essential to their environmental performance. The results of the sensitivity analysis suggested that the amount of construction materials and energy consumption as well as the plant output influences its environmental performance significantly. Conclusions and recommendations The construction stage of the SHP plant is the most important source of environmental impacts. To minimize the impacts of this stage, optimization of the structural design and application of new construction materials and good construction practices is recommended. In addition, determining suitable installed capacity and advancing equipment technologies to ensure the optimal output is also crucial to improve the environmental performance of SHP plants in China, regarding the current serious problem of unstable operation.
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Forty years ago, the demolition of large dams was mostly fiction, notably plotted in Edward Abbey's novel The Monkey Wrench Gang. Its 1975 publication roughly coincided with the end of large-dam construction in the United States. Since then, dams have been taken down in increasing numbers as they have filled with sediment, become unsafe or inefficient, or otherwise outlived their usefulness ( 1 ) (see the figure, panel A). Last year's removals of the 64-m-high Glines Canyon Dam and the 32-m-high Elwha Dam in northwestern Washington State were among the largest yet, releasing over 10 million cubic meters of stored sediment. Published studies conducted in conjunction with about 100 U.S. dam removals and at least 26 removals outside the United States are now providing detailed insights into how rivers respond ( 2 , 3 ).
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Globally, the hydropower (HP) sector has significant potential to increase its capacity by 2050. This study quantifies the energy and resource demands of small-scale HP projects and presents methods to reduce associated environmental impacts based on potential growth in the sector. The environmental burdens of three (50-650 kW) run-of-river HP projects were calculated using life cycle assessment (LCA). The global warming potential (GWP) for the projects to generate electricity ranged from 5.5 to 8.9 g CO2 eq./kWh, compared with 403 g CO2 eq./kWh for UK marginal grid electricity. A sensitivity analysis accounted for alternative manufacturing processes, transportation, ecodesign considerations and extended project lifespan. These findings were extrapolated for technically viable HP sites in Europe, with the potential to generate 7.35 TWh and offset over 2.96 Mt of CO2 from grid electricity per annum. Incorporation of ecodesign could provide resource savings for these HP projects: avoiding 800,000 tonnes of concrete, 10,000 tonnes of steel and 65 million vehicle miles. Small additional material and energy contributions can double a HP system lifespan, providing 39 to 47% reductions for all environmental impact categories. In a world of finite resources, this paper highlights the importance of HP as a resource-efficient, renewable energy system.
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Tropical hydroelectric emissions are undercounted in national inventories of greenhouse gases under the United Nations Framework Convention on Climate Change (UNFCCC), giving them a role in undermining the effectiveness of as-yet undecided emission limits. These emissions are also largely left out of the Intergovernmental Panel on Climate Change (IPCC) Special Report on Renewable Energy Sources and Climate Change Mitigation, and have been excluded from a revision of the IPCC guidelines on wetlands. The role of hydroelectric dams in emissions inventories and in mitigation has been systematically ignored.
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Micro-hydropower (MHP) presents new opportunities to generate electricity from within existing water infrastructure. This paper quantifies the environmental impacts of electricity generation from three MHP case studies (15-140 kW) in the water industry, using a life cycle assessment approach. Environmental burdens were calculated per kWh electricity generated over nominal turbine operational lifespans. Compared with marginal UK grid electricity generation in combined cycle turbine natural gas power plants, normalised life cycle environmental burdens for MHP electricity were reduced by: >99% for global warming potential (GWP); >98% for fossil resource depletion potential; >93% for acidification potential; 50-62% for human toxicity potential. However, the burden for abiotic resource depletion potential was 251-353% higher for MHP than marginal grid-electricity. Different quantities of raw materials and installation practices led to a range in GWP burdens from 2.14 to 4.36 g CO2 eq./kWh. One case benefitted from very low site preparation requirements while others required substantial excavation works and material quantities. Carbon payback times ranged from 0.16 to 0.31 years, extending to 0.19-0.40 years for worst-case scenarios examined as part of a sensitivity analysis. The carbon payback period for future MHP installations was estimated to increase by 1% annually, as the carbon intensity of marginal grid electricity is predicted to decline. This study demonstrates that MHP installations in the water industry have a strongly positive environmental balance.
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Massive concrete dam projects will be constructed in the next 10years to respond to the increasing demand for clean energy and water resources in developing countries. Because of their ample use of cement, these projects have a significant environmental impact, including the production of carbon dioxide (CO2) emissions. Rock-filled concrete (RFC) is an innovative dam construction method that promises better environmental performance than conventional concrete (CC) in the material production stage by saving a large amount of cement. However, the environmental loads throughout the entire life cycle of a dam must be quantified. Thus, this paper aims to evaluate the environmental loads in the lifetime of a dam and reveal the environmental impact of RFC relative to CC over the entire life cycle of a concrete dam. Through reviewing the limitations of the existing life-cycle assessment (LCA) models, a hybrid LCA model is applied to achieve this goal. The results from a case study of a concrete dam project in China are presented to demonstrate the environmental benefit of RFC throughout the lifetime of a dam. The results indicate that RFC reduces greenhouse gas emissions by approximately 64% and energy consumption by approximately 55% compared with CC. With regard to each life cycle stage, RFC decreased the CO2 emissions by 72% in material production, 25% in transportation, 51% in construction, and 15.6% in operation and maintenance. The conclusion is that RFC is more environmentally responsible throughout the life cycle of a dam's, and that the environmental benefit of RFC may help to encourage decision makers to select the appropriate methods in the planning phase. (C) 2013 American Society of Civil Engineers.
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Human population growth, economic development, climate change, and the need to close the electricity access gap have stimulated the search for new sources of renewable energy. In response to this need, major new initiatives in hydropower development are now under way. At least 3,700 major dams, each with a capacity of more than 1 MW, are either planned or under construction, primarily in countries with emerging economies. These dams are predicted to increase the present global hydroelectricity capacity by 73 % to about 1,700 GW. Even such a dramatic expansion in hydropower capacity will be insufficient to compensate for the increasing electricity demand. Furthermore, it will only partially close the electricity gap, may not substantially reduce greenhouse gas emission (carbon dioxide and methane), and may not erase interdependencies and social conflicts. At the same time, it is certain to reduce the number of our planet’s remaining free-flowing large rivers by about 21 %. Clearly, there is an urgent need to evaluate and to mitigate the social, economic, and ecological ramifications of the current boom in global dam construction.
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Improved methods are needed to evaluate barriers and traps for control and assessment of invasive sea lamprey (Petromyzon marinus) in the Great Lakes. A Bayesian state-space model provided reach-specific probabilities of movement, including trap capture and dam passage, for 148 acoustic tagged invasive sea lamprey in the lower Cheboygan River, Michigan, a tributary to Lake Huron. Reach-specific movement probabilities were combined to obtain estimates of spatial distribution and abundance needed to evaluate a barrier and trap complex for sea lamprey control and assessment. Of an estimated 21 828 – 29 300 adult sea lampreys in the river, 0%–2%, or 0–514 untagged lampreys, could have passed upstream of the dam, and 46%–61% were caught in the trap. Although no tagged lampreys passed above the dam (0/148), our sample size was not sufficient to consider the lock and dam a complete barrier to sea lamprey. Results also showed that existing traps are in good locations because 83%–96% of the population was vulnerable to existing traps. However, only 52%–69% of lampreys vulnerable to traps were caught, suggesting that traps can be improved. The approach used in this study was a novel use of Bayesian state-space models that may have broader applications, including evaluation of barriers for other invasive species (e.g., Asian carp (Hypophthalmichthys spp.)) and fish passage structures for other diadromous fishes.
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The Xiaowan super-high arch dam has faced challenging construction problems. Here, we provide a scientifically-based reference for applying geomechanical model testing to support the nonlinear design of super-high arch dams. We applied experimental similarity theory and techniques. Based on four 3D geomechanical model tests, the dam stress characteristics, deformation distribution, and the safety factors of the dam foundation were identified and compared. We also analyzed cracking characteristics of the up- and downstream dam surfaces and induced joints in the dam heel, the rock mass failure process of the dam-foundation interface, and the abutments. We propose foundation reinforcement measures for weak rock masses, alteration zones, and other faults in the abutments based on the 3D and plane tests each at a different elevation. The results show that all dam deformations remained normal with no yielding or tensile cracking under a normal water load. The reinforced rock mass increased the crack initial safety in the dam heel and toe by ~20 %. The minimum crack initial safety factor (K 1) of the dam heel was 1.4. The induced joint in the dam heel contributed to a reduction in tensile stress at the upstream dam heel, improving K 1. Compared with similar projects following reinforcement measures, the abutment stiffness and overall stability of the Xiaowan arch dam satisfy operational requirements. Four years of monitoring operations show that key areas near the dam remained normal and the dam foundation is functioning well. Our results may also be applicable to the design and construction of similar projects worldwide.
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The Working Group III Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN) presents an assessment of the literature on the scientific, technological, environmental, economic and social aspects of the contribution of six renewable energy (RE) sources to the mitigation of climate change. It is intended to provide policy relevant information to governments, intergovernmental processes and other interested parties. This Summary for Policymakers provides an overview of the SRREN, summarizing the essential findings.
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Artificial reservoirs likely accumulate more carbon than natural lakes due to their unusually high sedimentation rates. Nevertheless, the actual magnitude of carbon accumulating in reservoirs is poorly known due to a lack of whole-system studies of carbon burial. We determined the organic carbon (OC) burial rate and the total OC stock in the sediments of a tropical hydroelectric reservoir by combining a seismic survey with sediment core sampling. Our data suggest that no sediment accumulation occurs along the margins of the reservoir and that irregular bottom morphology leads to irregular sediment deposition. Such heterogeneous sedimentation resulted in high spatial variation in OC burial—from 0 to 209 g C m−2 y−1. Based on a regression between sediment accumulation and OC burial rates (R 2 = 0.94), and on the mean reservoir sediment accumulation rate (0.51 cm y−1, from the seismic survey), the whole-reservoir OC burial rate was estimated at 42.2 g C m−2 y−1. This rate was equivalent to 70% of the reported carbon emissions from the reservoir surface to the atmosphere and corresponded to a total sediment OC accumulation of 0.62 Tg C since the reservoir was created. The approach we propose here allows an inexpensive and integrative assessment of OC burial in reservoirs by taking into account the high degree of spatial variability and based on a single assessment. Because burial can be assessed shortly after the survey, the approach combining a seismic survey and coring could, if applied on a larger scale, contribute to a more complete estimate of carbon stocks in freshwater systems in a relatively short period of time.
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This study proposes a successive improved dynamic programming (SIDP) algorithm for hydropower reservoir operation based on an analysis of concavity, complementarity, and monotonicity of hydropower problems. For single-period hydropower generation, storage and release have diminishing marginal contributions to hydropower generation (i.e., concavity), and there is also a complementary effect between storage and release (i.e., release becomes more productive with increased storage). For multiple-period hydropower generation, the complementarity is shown to influence the concavity of objective function and the monotonicity of operation decisions, and is the major cause of complexity in hydropower operation. With the mathematical derivations, this study proposes a concave approximation to the hydropower generation function and a SIDP algorithm for hydropower reservoir operation. The efficiency of SIDP is demonstrated with two hypothetical case studies of long-term hydropower scheduling, which shows that the computation time of SIDP increases linearly with the number of storage intervals (i.e., O(n)), whereas DP shows a quadratic increase (i.e., O(n2)).
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Appropriate layer quantity has been considered to model the sequential construction of a high embankment dam over 300 m and its effect on the predicted settlement of the 314 m high Shuangjiangkou dam has been discussed. The simulation results have demonstrated that at least 25 layers are required to accurately model the stage construction of a high embankment dam over 300 m. The stress and deformation within the dam and the foundation during the dam construction and reservoir filling have been simulated using finite element analysis. Saturated-unsaturated seepage theory is used to analyse the transient seepage field in the dam and in the foundation. Two different cases about the construction and the operation are modelled. One involves gradual reservoir filling after the completion of sequential construction, whereas the other involves sequential construction and reservoir impounding by several interleaved stages. The simulation results for both cases have been compared and discussed.
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Tropical hydroelectric dams are now one of the main destinations for funds under the Kyoto Protocol’s Clean Development Mechanism (CDM), with 1482 dams approved for credit and 840 dams in the CDM ‘pipeline’ awaiting approval. Thousands of dams are being built by countries such as China, India and Brazil, irrespective of any additional subsidy based on mitigation of climate change. Carbon credit granted to projects that would occur anyway allows the countries purchasing the credit to emit greenhouse gases that are not offset. Damage to global climate is further increased by CDM accounting procedures that undercount the greenhouse gases emitted by tropical dams. Still more damage stems from the limited mitigation funds being squandered on ‘nonadditional’ projects such as dams. An example indicating the need to eliminate credit for hydroelectric dams is provided by the Jirau Dam, now nearing completion on the Madeira River near Brazil’s border with Bolivia. The dam has severe impacts in addition to climate change. The project was approved (registered) by the CDM Executive Board on 17 May 2013.
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Hydropower is very important for electricity supply security in the European inter-connexion as well as for the economy of regions (primarily peripheral) that possess water resources. Its future may however be jeopardized by several factors: climate change, the development of new renewable energy, the creation of super and micro-grids, and progress in power storage technology. Energy and climate policy, as well as electricity market design and dynamics play a pivotal role. This article carries out a comprehensive analysis of all these factors and discusses the future of hydropower. This discussion follows an overview of the present situation and of future drivers. The technical, environmental, economic and political aspects of the problem are analyzed with an interdisciplinary approach. The stakes as well as the uncertainties are highlighted. The conclusion is that hydropower has a promising future, particularly in light of emerging sustainable energy policy, but that the risks should not be overlooked. Academics will find a comprehensive interdisciplinary analysis of hydropower in this article, whereas public bodies, communities and hydropower companies can identify the strategic variables that should be taken into consideration in the decision making process. The end of water concessions or authorizations is also evoked.
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For 7-8% growth rate that India is aspiringfor, its energy needs will increase correspondingly. The challenge is to provide desired quality power in a sustainable manner and at reasonable cost. Small hydropower has the potential of about 15000 MW in India and considered to be a reliable source of electricity generation. Three run-of river small hydro-power projects in India has been identified and their Life Cycle Analysis has been carried out by using the economic input output (EIO) technique. The energy use, greenhouse gas (GHG) emissions and energy pay-back period (EPBT) were quantified for these small hydro power plants.
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Book
This book explains the history and politics of dam building worldwide. It describes the many technical, safety and economic problems that afflict the technology, and explores the role played by international banks and aid agencies in promoting it. The author also examines the rapid growth of the international anti-dam movements, and stresses how replacing large dams with less destructive alternatives will depend upon opening up the dam industry's practices to public scrutiny.
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Safety protocols for dams worldwide are currently based mainly on: understanding possible failures; quantitative risk assessment; justification of risks taken (with reference to accepted standards and good practices); historical records of dam performance; new criteria and state-of-the art designs; the need to prioritize research; solutions to known problems; better communication of risks to the public, civil organizations and decision- makers; and the improvement of risk management through dearly defining and assigning responsibilities (Bowles, 2013). In addition, these protocols are equally applied to dam owners, regulatory organizations, insurance companies and consulting companies. This article discusses the current framework used to evaluate dam safety at the international level and proposes a specific methodology to evaluate existing dams in Mexico. It also discusses the urgent need to study the possibility of removing dams that present unacceptable risks and for which rehabilitation is not cost-effective.
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Dams are a major contributor to the historic decline and current low abundance of diadromous fish. We developed a population viability analysis to assess demographic effects of dams on diadromous fish within a river system and demonstrated an application of the model with Atlantic salmon in the Penobscot River, Maine. We used abundance and distribution of wild- and hatchery-origin adult salmon throughout the watershed as performance metrics. Salmon abundance, distribution to upper reaches of the Penobscot watershed, and the number and proportion of wild-origin fish in the upper reaches of the Penobscot watershed increased when dams, particularly mainstem dams, were removed or passage efficiency was increased. Salmon abundance decreased as indirect latent mortality per dam was increased. Salmon abundance increased as marine or freshwater survival rates were increased, but the increase in abundance was larger when marine survival was increased than when freshwater survival was increased. Without hatchery supplementation, salmon abundance equalled zero with low marine and freshwater survival but increased when marine and freshwater survival rates were increased. Models, such as this one, that incorporate biological, environmental, and functional parameters can be used to predict ecological responses of fish populations and can help evaluate and prioritize management and restoration actions for diadromous fish.
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Electricity generation is a key contributor to global emissions of greenhouse gases (GHG), NOx and SO2 and their related environmental impact. A critical review of 167 case studies involving the life cycle assessment (LCA) of electricity generation based on hard coal, lignite, natural gas, oil, nuclear, biomass, hydroelectric, solar photovoltaic (PV) and wind was carried out to identify ranges of emission data for GHG, NOx and SO2 related to individual technologies. It was shown that GHG emissions could not be used as a single indicator to represent the environmental performance of a system or technology. Emission data were evaluated with respect to three life cycle phases (fuel provision, plant operation, and infrastructure). Direct emissions from plant operation represented the majority of the life cycle emissions for fossil fuel technologies, whereas fuel provision represented the largest contribution for biomass technologies (71% for GHG, 54% for NOx and 61% for SO2) and nuclear power (60% for GHG, 82% for NOx and 92% for SO2); infrastructures provided the highest impact for renewables. These data indicated that all three phases should be included for completeness and to avoid problem shifting. The most critical methodological aspects in relation to LCA studies were identified as follows: definition of the functional unit, the LCA method employed (e.g., IOA, PCA and hybrid), the emission allocation principle and/or system boundary expansion. The most important technological aspects were identified as follows: the energy recovery efficiency and the flue gas cleaning system for fossil fuel technologies; the electricity mix used during both the manufacturing and the construction phases for nuclear and renewable technologies; and the type, quality and origin of feedstock, as well as the amount and type of co-products, for biomass-based systems. This review demonstrates that the variability of existing LCA results for electricity generation can give rise to conflicting decisions regarding the environmental consequences of implementing new technologies.
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This paper gives a review of small hydropower technology. A Small hydropower (SHP) plant uses impulse or reaction turbines and is mainly 'run-off-river'. SHP technologies currently used in generating electricity for rural electrification in both developed and underdeveloped countries are helping to slow down climatic change, creating employment opportunities, and are having low maintenance costs (but high capital costs).
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Different types of hydropower schemes utilize different construction methods and have different carbon footprints. However, differences in carbon footprints between different schemes have been largely ignored when comparing environmental impacts for decision making. Thus, this paper aims to study and compare the carbon footprints of two types of Nuozhadu hydropower schemes with the same scale: an earth-core rockfill dam (ECRD) and a concrete gravity dam (CGD). The hybrid life cycle assessment (LCA) method combines the completeness of economic input-output LCA (EIO-LCA) and the specificity of process-based LCA (PA-LCA). It was applied to quantify the carbon footprint over the whole life cycle of the hydropower system. The evaluation of the carbon footprint considered the emissions from material production, transportation, construction, and the operation and maintenance phases for a period of 44 years. All relevant materials and energy consumption were included. It was found that the ECRD reduced CO2 emissions by approximately 24.7% compared to the CGD. With respect to each stage of the life cycle, the ECRD decreased CO2 emissions by 46.1% for material production, 16.5% for transportation and 9.0% for operation and maintenance but increased emissions by 6.6% for construction due to the heavy workload. Operational maintenance was the greatest contributor to CO2 emissions, followed by the production, construction and transportation stages. These results indicate that ECRDs are more environmentally responsible throughout its life cycle. This knowledge could help decision makers in the design phase looking to choose the appropriate type of hydropower system.
Article
Controversy surrounds the green credentials of hydroelectricity because of the potentially large emission of greenhouse gases (GHG) from associated reservoirs. However, limited and patchy data particularly for China is constraining the current global assessment of GHG releases from hydroelectric reservoirs. This study provides the first evaluation of the CO2 and CH4 emissions from China's hydroelectric reservoirs by considering the reservoir water surface and drawdown areas, and downstream sources (including spillways and turbines, as well as river downstream). The total emission of 29.6 Tg CO2/year and 0.47 Tg CH4/year from hydroelectric reservoirs in China, expressed as CO2 equivalents (eq), corresponds to 45.6 Tg CO2eq/year, which is 2-fold higher than the current GHG emission (ca. 23 Tg CO2eq/year) from global temperate hydropower reservoirs. China's average emission of 70 g CO2eq/kWh from hydropower amounts to 7 % of the emissions from coal-fired plant alternatives. China's hydroelectric reservoirs thus currently mitigate GHG emission when compared to the main alternative source of electricity with potentially far great reductions in GHG emissions and benefits possible through relatively minor changes to reservoir management and design. On average, the sum of drawdown and downstream emission including river reaches below dams and turbines, which is overlooked by most studies, represents the equivalent of 42 % of the CO2 and 92 % of CH4 that emit from hydroelectric reservoirs in China. Main drivers on GHG emission rates are summarized and highlight that water depth and stratification control CH4 flux, and CO2 flux shows significant negative relationships with pH, DO, and Chl-a. Based on our finding, a substantial revision of the global carbon emissions from hydroelectric reservoirs is warranted.