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The wide-ranging adverse changes caused by hydropower in freshwater ecosystems call for implementing environmental responsibility on the part of the hydropower sector. This article analyses the interplay between the two key EU legal instruments in this respect: the revision of out-dated hydropower permits required under the EU Water Framework Directive and operator liability for water damage under the Environmental Liability Directive. To complement this analysis, the article provides a concrete example of the two directives' combined framework, or at least its multiple implementation challenges, using the specific case of one Member State; Finland. The article concludes that, although the two instruments have the potential to offer a rather powerful framework for environmental responsibility, realising this policy aspiration may be seriously undermined by problems in implementation. The insights presented call attention to the applicable means on both national as well as EU levels to rectify the situation. [ABSTRACT FROM AUTHOR]

This paper offers a historical overview of the first century of hydropower in the US from today's perspective of the water/energy nexus. Hydropower emerged as a technology in the 1880s and its development expanded until large dam building ended in the US in the 1970s-1980s. I summarize the century from the two different angles of the water sector and the electric power sector, as the roles and strategic importance of hydropower changed dramatically in the two sectors, in the parallel histories of water development and electric power development. The paper emphasizes the electricity side of the hydropower story because the water and environmental aspects are more widely known. During the first 50 years, hydropower dams were far more important to the electric power sector than they were to the water sector. Dams were juicy economic prizes that were fought over by private and public power utilities, politicians and government officials, and other interest groups, and that were built into the core of regional power grids during their foundational decades. Control of hydropower symbolized the deeper political and economic conflicts between public and private interests in the power sector, with hydropower becoming strongly identified with public power. In both sectors, there was a major turning point in the 1930s because of the growth and intervention of the Federal government in the New Deal. The earlier trends reversed and over the next 50 years hydropower became essential in the water sector -- scaling up rapidly as the critical factor in paying for Federal multi-purpose water projects -- and secondary in the power sector (with regional exceptions). In the power sector, hydropower's trajectory after the 1930s was paradoxical. It boomed in absolute terms, quadrupling in generating capacity as Federal agencies built hundreds of large dams, but hydropower's relative importance in the power sector declined steadily as the rest of the sector grew even faster. The half-century of hydropower's greatest expansion ended by its taking a smaller role in the overall power grid. Over the long run, the dynamics of the energy sector have dominated the water sector, a lesson that may apply to other examples of the water/energy nexus in the US and abroad. [ABSTRACT FROM AUTHOR]

The article provides information on the practice in hydropower plants in Germany including water law permit, financial compensation and residual water increase. Topics include authorization in the event of structural changes, considerable public interest and water management office and nature conservation authority.

Hydroelectricity is playing a significant role in lowering CO2 emissions as it contributes a desirable platform to fulfill the growing energy demand while releasing fewer GHGs in comparison to other fossil fuels. Utilizing the trans-log production model, this study is an endeavor to investigate the potential inter-fuel substitution by estimating the substitution elasticity between pairs of coal, natural gas, petroleum, and hydroelectricity to suggest policy for Pakistan to achieve higher economic growth, environmental sustainability, and increased energy access by its citizens. Over the period 1980–2013, the ridge regression was approved to estimate the model's parameters. The findings show that the output elasticity of hydroelectricity is the highest and all the factor inputs are substitutes; whereas, the elasticity of substitution between coal vs. natural gas is the highest, thus suggesting an increased focus on the coal extraction to switch from the alternative usage of gas. Moreover, encouragement of energy subsidy programs, coupled with taxes and infrastructural developments, can be adapted to redirect technology towards hydroelectricity. Hence, the result that hydroelectricity is substituted for all fuels submit that Pakistan has the potential to switch from petroleum to cleaner energy; therefore, reducing the adverse environmental implications and to retain the ability to fuel its energy sector. [ABSTRACT FROM AUTHOR]

Ecosystems and biodiversity produce benefits to society, but many of them are hard to quantify. For example, it is unclear whether European societies gain benefits from experiencing rivers that host high native biodiversity. Without such knowledge, monetary investments into ecologically oriented river management plans are difficult to justify. The objective of this study was to reveal how the public in four European countries values ecological characteristics of domestic rivers and the outcomes of hypothetical river basin management plans designed to improve river ecosystems, particularly fish biodiversity. We conducted a choice experiment among the populations in Norway, Sweden, Germany, and France. We found similar preference structures in all countries with high marginal willingness-to-pay for improvements of abiotic river attributes (increased accessiblity of the river banks, improved bathing water quality, decreased river fragmentation). Citizens also benefited from certain fish species occurring in a river with native salmonid species being more valued than nonnatives, particularly in Norway, and from the degree of a river's native biodiversity. Welfare measures calculated for selected river basin management plans (policy scenarios) revealed societal benefits that were primarily derived from ecological river management whereas a scenario focusing on hydroelectricity production generated the lowest utility. We conclude that ecological river management may produce high nonmarket economic benefits in all study countries, particularly through the management of abiotic river attributes and the restoration of declining or extinct fish species. Our results help to inform decisions on restoration efforts by showcasing the benefits that these measures have for the public. [ABSTRACT FROM AUTHOR]

Highlights • Consider the ecological base flow, fish habitat flow and navigable flow. • Combine the three methods to calculate the comprehensive ecological water demand. • Establish three operation models considering comprehensive ecological water demand. • Quantitatively analyze the relationship between power generation and ecologic flow. • NSGA-II is employed to solve multi-objective problem. Abstract Hydropower plants operation may change river flow, thereby degrading the stability of river ecosystems. The primary purpose of this paper is to compute the comprehensive ecological water demand and establish ecological operation models to quantitatively analyze the interactions between power generation and degree of ecological flow satisfaction under different operation modes. The comprehensive ecological water demand takes the river base flow, ecological flow process and ecological water demands of fish habitat during the spawning period into account. The driest monthly streamflow under a 90% frequency method, range of variability approach and two-dimensional depth-averaged finite element model were adopted to obtain the ecological flow. In addition, to study the impacts of the ecological operation of hydropower plants on power generation, three optimal operation models including a maximum power generation model (Model-I), a minimum ecological change model (Model-II) and a multi-objective optimization operation model (Model-III), are established. In model-II, the average annual power generation of the cascade hydropower plants decreased by 10.61% compared with Model-I, and meanwhile the degree of ecological change reduced by 75.41%, which means, the reduction of power generation by 35.66 × 108 kWh could lead to a reduction of 11.4% on the degree of ecological degradation. Afterwards, the multi-objective problem of economic and ecological benefits in model-III was solved by the application of NSGA-II. Among them, scheme 3 is recommended for Model III, and its power generation and degree of ecological change are 311.69 × 108 kWh and 6.64%, respectively. In general, mutual restrictions and conflicts between power generation and ecological demand are inevitable, but they can be optimized through multi-objective ecological operation models to fetch the coordinated development of economy and ecology. [ABSTRACT FROM AUTHOR]

This study experimentally manipulated olfactory cues in a river by adjusting hydropower operation and monitored behavioural responses of 193 adult sockeye salmon, Oncorhynchus nerka (Walbaum), using radio telemetry. Experimental dilution of olfactory cues in a tributary to 72% natal water relative to non‐natal water was associated with 80% reduced odds of fish entering the tributary from a river mainstem and increased migration times by an average of 12.2 hr, with females taking 4.6 hr longer than males to enter the tributary. Additionally, males delayed 2.7 hr longer than females at a diversion outlet in the river mainstem that discharged a natal water source during experimentally diluted olfactory conditions. Increased migration time associated with dilute olfactory cues would decrease energy available for reproduction and potentially reduce fitness. Hydropower managers should continue to regulate natal water conditions in the Seton River during sockeye salmon migrations to avoid negative impacts on migration timing and success. [ABSTRACT FROM AUTHOR]

Repeat spawners of anadromous salmonids may contribute significantly to population resilience by providing multiple cohorts to both seawater and freshwater life stages. In this study, winter survival of sea trout (Salmo trutta Linnaeus, 1758) post spawners (kelts) was 89%. Sea survival increased linearly with female length with a return probability between 30% and 50%, whereas males attained a maximum return probability of 60% at 520 mm. Of the returning sea trout, 40% skipped spawning and they had significantly lower condition factor as kelts compared with those who returned after one summer. These results suggest that sex-specific differences in individual post-spawning growth–survival trade-off exist and that energetic status of descending kelts may influence the probability to skip spawning. We discuss to what extent hydropower may reduce post-spawning survival due to blocking of river descent opportunities, potentially altering the fitness landscape and favouring new life-history adaptations. From a management perspective, it is concluded that it is crucial to maintain connectivity in regulated rivers, allowing fish to complete repetitive spawning and feeding migrations, thus contributing to population productivity. [ABSTRACT FROM AUTHOR]

Abstract: Small hydropower projects (SHPs) are promoted as environmentally benign alternatives to larger dams; however, the impacts of SHPs have been poorly studied, especially in tropical developing countries, where their growth is being encouraged. This study assessed the impacts of two SHPs on freshwater fish communities in the Western Ghats biodiversity hotspot of India. Two dammed and one undammed tributary of the Netravathi River, having similar stream order, elevation, and surrounding land‐use types, were identified as test and control sites respectively. Stream geometry, water chemistry, and fish assemblages were compared across upstream, dewatered, and downstream location categories within and across the three streams. Flow alterations induced by SHPs affected the dewatered river stretches most severely. Stream wetted width and depths diminished drastically in dammed dewatered segments, and consequently this region was characterized by elevated water temperature and reduced dissolved oxygen. Fish species composition varied significantly between dammed and undammed sites, across the upstream, dewatered, and downstream location categories. Dammed segments had lower fish species richness, diversity, and endemicity, and were dominated by eurytopic species (adapted to lentic conditions), unlike the control site, which was dominated by rheophilic species (adapted to flowing waters). Regression analyses indicated that fish species richness in dammed streams increased with distance from the dam in the upstream direction. The SHPs were found to have severe impacts on stream geometry, water chemistry, and aquatic biota, especially in the dry season. Given the ambitious targets of planned SHP growth, most of which are within ecologically fragile regions, changes in SHP operations and policies are proposed to enable the conservation of river fish diversity. These include mandatory environmental impact assessments, conserving undammed headwater streams in regulated basins, maintaining adequate environmental flows, and implementing other mitigation measures. [ABSTRACT FROM AUTHOR]

A steel gate is one of the major components of a hydraulic power station for storing water and monitoring the water level. In cold regions, the temperature decreases to well below the freezing point, and the water turns to ice, which can apply high loads on the steel gate, leading to large deformations and failure of the gate. This study aims to monitor and analyse the ice load distribution on a steel gate using an inverse method. As a case study, a steel gate at the hydraulic station on the Songhua River in Harbin is selected. The steel gate is equipped with several vibrating wire strain gauges, and deformation data for various locations on the structure was collected for 100 days. As experimental identification of the system transfer matrix requires information concerning the actual loads, which is not directly attainable, the transfer matrix was constructed using a finite element method. Five inverse methods were verified with a certain number of load patterns to determine the optimal method. The ice load distribution obtained using the optimal method is verified with the deformation data, indicating accurate load identification. Consequently, variation in the ice load distribution during the freezing period is monitored, and the relationship between the total ice force and temperature is obtained. During the winter of 2015–2016, the average ice line load gradually increased until reaching a maximum of approximately 25 kN/m on 11 Dec. 2015. Subsequently, the ice line load fluctuated between 17 and 25 kN/m. Finally, the ice released all of the force within 3 days beginning on 15 Mar. 2016. [ABSTRACT FROM AUTHOR]

The Yangtze River is one of the largest and most important rivers in the world. Over the past several decades, the flow regime of the Yangtze River has been altered by human activities, particularly dam construction. Hydrological regimes will be further influenced due to more dams that have been planned and are being built in the upper reach of the Yangtze River (URYR). In this context, to assess the impacts of cascade dam development on the natural flows, four different scenarios of the reservoirs' combination are simulated with a hydrological model (the Soil and Water Assessment Tool) in the URYR. Flow regime changes were investigated using the eco-flow metrics and minimum/optimal ecological flow with the simulated daily river flows. The results indicate that eco-surplus in low flows and eco-deficit in high flows greatly increases due to reservoir operations when more reservoirs are put into service. The minimum ecological flow and the optimal ecological flow cannot be guaranteed from September to November, which is a crucial time for fish spawning. To maintain the natural regime while meeting the requirements for the river ecosystem, we propose that the lower and satisfactory operation limits are 11,680 m 3 /s and 7235 m 3 /s and 16,300 m 3 /s and 9130 m 3 /s, respectively. Optimizing cascade reservoir operational rules is needed to achieve a better balance between ecological and socio-economic demands in the Yangtze River Basin. [ABSTRACT FROM AUTHOR]

The electricity sector in Malaysia is dominated by fossil fuels. This has immensely increased the amount of CO 2 emissions and other pollutants. The objective of this paper is to investigate the potential for inter-fuel substitution between the four major fuels of coal, gas, oil, and hydropower that are currently being used in the generation of electricity in Malaysia. Using a translog production function, the study adopted a ridge regression procedure to estimate the parameters. The results suggest a potential for substitution among the fuels. Hydropower is observed to be a substitute for other fossils fuels which is an indication that the country can gradually move towards adopting a cleaner fuel in the generation of electricity. We also extended the analysis to Thailand and China to show the consistency of the method when applied to different countries. [ABSTRACT FROM AUTHOR]

This paper analyses the economic viability of twelve pumped-storage hydropower plants equipped with different fixed-speed and variable-speed units and with and without considering hydraulic short-circuit operation. The analysed plants are assumed to participate in the day-ahead energy market and in the secondary regulation service of the Iberian power system. A deterministic day-ahead energy and reserve scheduling model is used to estimate the maximum theoretical income of the plants assuming perfect information of the next day prices, the residual demand curves of the secondary regulation reserve market and the percentages of the real-time use of the committed reserves. An estimate of the minimum theoretical pay-back period is obtained from the maximum theoretical income as a result of the scheduling model. Results indicate that the economic viability with and without variable speed units and operating or not in hydraulic short-circuit mode is not discarded if the plants also participate in the secondary regulation service, and that the minimum theoretical pay-back periods can be reduced significantly when the plant is equipped with variable speed units and/or operates in hydraulic short-circuit mode. In addition, the maximum theoretical income obtained with the used optimization model and the proposed pumped-storage hydropower plants are significantly higher than the real income obtained by plants that are currently operating in the Iberian system. [ABSTRACT FROM AUTHOR]

Global transition towards renewable energy production has increased the demand for new and more flexible hydropower operations. Before management and stakeholders can make informed choices on potential mitigations, it is essential to understand how the hydropower reservoir ecosystems respond to water level regulation (WLR) impacts that are likely modified by the reservoirs' abiotic and biotic characteristics. Yet, most reservoir studies have been case-specific, which hampers large-scale planning, evaluation and mitigation actions across various reservoir ecosystems. Here, we investigated how the effect of the magnitude, frequency and duration of WLR on fish populations varies along environmental gradients. We used biomass, density, size, condition and maturation of brown trout ( Salmo trutta L.) in Norwegian hydropower reservoirs as a measure of ecosystem response, and tested for interacting effects of WLR and lake morphometry, climatic conditions and fish community structure. Our results showed that environmental drivers modified the responses of brown trout populations to different WLR patterns. Specifically, brown trout biomass and density increased with WLR magnitude particularly in large and complex-shaped reservoirs, but the positive relationships were only evident in reservoirs with no other fish species. Moreover, increasing WLR frequency was associated with increased brown trout density but decreased condition of individuals within the populations. WLR duration had no significant impacts on brown trout, and the mean weight and maturation length of brown trout showed no significant response to any WLR metrics. Our study demonstrates that local environmental characteristics and the biotic community strongly modify the hydropower-induced WLR impacts on reservoir fishes and ecosystems, and that there are no one-size-fits-all solutions to mitigate environmental impacts. This knowledge is vital for sustainable planning, management and mitigation of hydropower operations that need to meet the increasing worldwide demand for both renewable energy and ecosystem services delivered by freshwaters. [ABSTRACT FROM AUTHOR]

Increasing hydropower electricity production constitutes a unique opportunity to mitigate climate change impacts. However, hydropower electricity production also impacts aquatic and terrestrial biodiversity through freshwater habitat alteration, water quality degradation, and land use and land use change (LULUC). Today, no operational model exists that covers any of these cause-effect pathways within life cycle assessment (LCA). This paper contributes to the assessment of LULUC impacts of hydropower electricity production in Norway in LCA. We quantified the inundated land area associated with 107 hydropower reservoirs with remote sensing data and related it to yearly electricity production. Therewith, we calculated an average net land occupation of 0.027 m²⋅yr/kWh of Norwegian storage hydropower plants for the life cycle inventory. Further, we calculated an adjusted average land occupation of 0.007 m²⋅yr/kWh, accounting for an underestimation of water area in the performed maximum likelihood classification. The calculated land occupation values are the basis to support the development of methods for assessing the land occupation impacts of hydropower on biodiversity in LCA at a damage level. [ABSTRACT FROM AUTHOR]

Experiences of migratory species in one habitat may affect their survival in the next habitat, in what is known as carryover effects. These effects are especially relevant for understanding how freshwater experience affects survival in anadromous fishes. Here, we study the carryover effects of juvenile salmon passage through a hydropower system (Snake and Columbia rivers, northwestern United States). To reduce the direct effect of hydrosystem passage on juveniles, some fishes are transported through the hydrosystem in barges, while the others are allowed to migrate in-river. Although hydrosystem survival of transported fishes is greater than that of their run-of-river counterparts, their relative juvenile-to-adult survival (hereafter survival) can be less. We tested for carryover effects using generalized linear mixed effects models of survival with over 1 million tagged Chinook salmon, Oncorhynchus tshawytscha (Walbaum) (Salmonidae), migrating in 1999-2013. Carryover effects were identified with rear-type (wild vs. hatchery), passage-type (run-of-river vs. transported), and freshwater and marine covariates. Importantly, the Pacific Decadal Oscillation (PDO) index characterizing cool/warm (i.e., productive/nonproductive) ocean phases had a strong influence on the relative survival of rear- and passage-types. Specifically, transportation benefited wild Chinook salmon more in cool PDO years, while hatchery counterparts benefited more in warm PDO years. Transportation was detrimental for wild Chinook salmon migrating early in the season, but beneficial for later season migrants. Hatchery counterparts benefited from transportation throughout the season. Altogether, wild fish could benefit from transportation approximately 2 weeks earlier during cool PDO years, with still a benefit to hatchery counterparts. Furthermore, we found some support for hypotheses related to higher survival with increased river flow, high predation in the estuary and plume areas, and faster migration and development-related increased survival with temperature. Thus, pre- and within-season information on local- and broad-scale conditions across habitats can be useful for planning and implementing real-time conservation programs. [ABSTRACT FROM AUTHOR]

Dams located upstream only release water during the period of hydropower generation. This induces short-term fluctuations of water discharge in the downstream reach, which is called hydropeaking. As occurs quite often, if the temperature of the water released form the upstream dam is different from the water that is flowing in the downstream reach, the water temperature also tends to show short-term fluctuations, which is called thermopeaking. This study investigates the impacts of both hydropeaking and thermopeaking on the downstream habitat. The study area is a 2.3 km long reach located downstream from the Goesan Dam in the Dal River, Korea. To assess such impacts, this study conducted physical habitat simulations. The CMS-Flow model was used for the computation of the flow and water temperature, and the GEP model for the habitat simulation. Three physical habitat variables, flow depth, velocity, and water temperature, were used. The Zacco platypus was selected as the target fish in the study area. Simulation results indicated that the hydropeaking flows significantly reduced both the CSI and the WUA when compared with the natural flow regime. In addition, the use of the water temperature in the physical habitat simulations further decreased both CSI and WUA, indicating that thermopeaking is as important as hydropeaking in this type of assessment. [ABSTRACT FROM AUTHOR]

The energy need increases in parallel with the increase in the world population and the technological advancements. The pollution arising from the energy production by the fossil fuels have exceeded the acceptable dimensions in recent years. Since many countries, including Turkey, cannot produce fossil fuel from own resources so as to satisfy the needs, they spend a significant part of the domestic income for the energy import. As from the early of the 2000s in Turkey, it has been enabled to generate electricity from the water and wind power by the private sector by constituting the legal basis. Much as this approach has provided a sum of increment for the national-sourced energy production, the legislative regulations remain incapable about the issues such as not to interfere to the national sources beyond the sufferable border and also not to be endangered the sustainability of the ecosystem. Moreover, there are technical and administrative difficulties to make the precautions of laws and regulations actual. Eastern Black Sea region is almost selected as the pilot area for building the run-of-the-river hydroelectric stations (RORHS), and it is planned to make 316 RORHS in 5 provinces as of 2010. The carrying capacity of this geography, the load and such effects of the facilities to be built for carrying the energy produced. These plants which have been put into practice without making any remark and comprehensive research to analyze the region-wide and on basin-basis cause serious apprehensions. The need for the local community to the water source, desires and expectations aren't considered enough. Moreover, there is not provided training for both of the individual entrepreneurs and the local community to gain environmental consciousness at sufficient level. It should be kept in mind that the training to increase the knowledge and consciousness levels of especially the investors about the nature conservation may be more effective than the penal measures. [ABSTRACT FROM AUTHOR]

This paper briefly discusses the assessment of hydropower resources (mainly, Small Hydropower, SHP) in the light of general methodologies of renewable energy potential, highlighting the particularities of hydropower. A short review of the EU Water Framework Directive (WFD) from the hydropower development perspective is provided, especially focusing on the impact of power plant pre-planning mechanisms whereby rivers or their reaches are listed as exempt from damming (so-called ‘no go areas’). The hydropower regulation (for prospective hydropower schemes) in the country is critically reviewed, and the current state of the drafting of river basin management plans is presented. Practically speaking, the national water law does not guarantee a declared statement of sustainable use of water resources because of the introduced list of protected rivers exempt from dam construction. In a number of multipurpose water resource development projects that override public interests, e.g., inland navigation and historic water mills, power generation is a secondary service unable to be implemented, due to on the list of protected rivers. In this paper, based on the geospatial datasets of water streams and their environmental attributes, three pre-planning levels for hydropower development are proposed, and the environmentally compliant potential of the SHP is identified. The remaining SHP potential (117 GWh/year or close to 6% of the gross theoretical potential) is among the lowest ones in the EU. The disproportionate environmental constraints in Lithuania are a key factor preventing the development of hydropower and the multipurpose use of water resources. [ABSTRACT FROM AUTHOR]

Small hydropower stations in remote areas promote regional economic development and social progress. Social sustainability assessment which immensely decides the success of small hydropower development has been paid little attention currently. Meanwhile, present methods tend to fail the social sustainability assessment due to following three problems. Firstly, the uncertainty of information cannot be fully described. Secondly, the correlation among indicators lacks rationality. Thirdly, the ranking methods adopted in previous studies are not appropriate for social sustainability assessment of small hydropower. To deal with the above problems, a Preference Ranking Organization. Method for Enrichment Evaluations (PROMETHEE) outranking method using hesitant fuzzy linguistic term set (HFLTS) is proposed. Firstly, the HFLTS is introduced to describe the uncertainty of information. Then, the Analytical Network Process (ANP) method is adopted to measure the correlation between indicators. Moreover, the PROMETHEE method is employed to rank the social sustainability of each alternative. Then an empirical study is carried out to prove that the proposed methodology is effective and practical. Finally, public recognition is discovered as the key indicator by comparative analysis and discussion. This study provides an innovative perspective for the social sustainability assessment of small hydropower and contributes to making more rational and scientific decisions. [ABSTRACT FROM AUTHOR]

The United States is home to 2198 dams actively used for hydropower production. With the December 2015 consensus adoption of the United Nations Framework Convention on Climate Change Paris Agreement, it is important to accurately quantify anthropogenic greenhouse gas emissions. Methane ebullition, or methane bubbles originating from river or lake sediments, has been shown to account for nearly all methane emissions from tropical hydropower reservoirs to the atmosphere. However, distinct ebullitive methane fluxes have been studied in comparatively few temperate hydropower reservoirs globally. This study measures ebullitive and diffusive methane fluxes from two eastern Washington reservoirs, and synthesizes existing studies of methane ebullition in temperate, boreal, and tropical hydropower reservoirs. Ebullition comprises nearly all methane emissions (>97%) from this study's two eastern Washington hydropower reservoirs to the atmosphere. Summer methane ebullition from these reservoirs was higher than ebullition in six southeastern U.S. hydropower reservoirs, however it was similar to temperate reservoirs in other parts of the world. Our literature synthesis suggests that methane ebullition from temperate hydropower reservoirs can be seasonally elevated compared to tropical climates, however annual emissions are likely to be higher within tropical climates, emphasizing the possible range of methane ebullition fluxes and the need for the further study of temperate reservoirs. Possible future changes to the Intergovernmental Panel on Climate Change and UNFCCC guidelines for national greenhouse gas inventories highlights the need for accurate assessment of reservoir emissions. [ABSTRACT FROM AUTHOR]

An indicator of quantifying eco-environmental vulnerability was established by synthesizing 12 variables, mainly retrieved from satellite data with incorporation of analytical hierarchy process (AHP). Six vulnerability levels of potential, slight, light, medium, heavy , and very heavy were graded to depict changes of vulnerability over temporal and spatial scales. The proposed approach was employed to study spatiotemporal eco-environmental vulnerability with Landsat data acquired in 1989, 2003, and 2014 for the Thua Thien – Hue Province, Vietnam. Over the time periods of 1989–2003 and 2003–2014, both heavy and very heavy vulnerability levels exhibit an increasing trend in both magnitude and spatial size: The former raised from 5.9% in 1989, to 7.9% in 2003, and 15% in 2014; and the later increased from 1.2% in 1989, to 3.2% in 2003, and 7.3% in 2014. Both levels mainly appeared on urbanized area, bare land, semi-bare land, agricultural land, and sparse forests. In contrast, there was a significant decline in potential vulnerability level with 36.4% in 1989, 30.9% in 2003, and 19.2% in 2014, while the remaining vulnerability levels slight, light, and medium fluctuated slightly, increased in 2003 and decreased in 2014. Supporting reasons for such changes include: (1) deforestation, agriculture intensification, construction of three hydro-electric projects during the period 2003–2014; and (2) significant expansion of urbanized area leading to differences in thermal signatures in urban areas as compared with rural areas. The findings demonstrate that eco-environmental vulnerability is primarily exaggerated by anthropogenic activities through land use/land cover (LULC) changes and further enhanced by natural processes including disasters in the Thua Thien – Hue Province of Vietnam. The correlation between land surface temperature (LST) and Normalized Difference Built-up Index (NDBI) is found to be positively correlated with 0.87, 0.89, and 0.84 for 1989, 2003, and 2014, respectively. In contrast, LST-Normalized Difference Vegetation Index (NDVI) is found negatively correlated with respect to the spatiotemporal trend of environmental vulnerability with −0.81, −0.81, and −0.76 in 1989, 2003, and 2014, respectively. In addition, areas having potential, slight, and medium thermal environmental levels are decreased from 1989 to 2003 to 2003–2014. At the regional scale, increased anthropogenic activities through land’s modification have intensified the eco-environmental vulnerability in the study area. The currently proposed methodology is feasible for evaluating long-term eco-environmental changes processes by using remote sensing data, and valid for the other regions. [ABSTRACT FROM AUTHOR]

Economic expansion and related resource and infrastructure needs provoke an increase of socio-environmental conflicts worldwide, and methodologies for their comprehensive analysis and understanding are necessary. The present paper suggests a methodology for the analysis of socio-environmental conflicts on hydropower, developed from a case study on the São Luiz do Tapajós project in Brazil. On the basis of qualitative semi-structured interviews, a stakeholder definition and conflict analysis were carried out. The analysis shows that at least five different sub-conflicts, each one with its own characteristics, can be distinguished, and that negotiation on many of these conflicts is difficult. Confrontation processes are therefore likely to occur. The current strategy of conflict treatment falls short of the situation; instead solutions must be sought looking at the underlying conflict causes. A restructuring of the energy policy and the approach to traditional populations is a necessary precondition if robust and comprehensive solutions on the current socio-environmental conflicts on hydropower in the Amazon were to be found. [ABSTRACT FROM AUTHOR]

This paper describes and validates the HydroCalculator Tool developed by Conservation Strategy Fund. The HydroCalculator Tool allows researchers, policy-makers and citizens to easily assess hydropower feasibility, by calculating traditional financial indicators, such as the levelized cost of energy, as well as greenhouse gas emissions and the economic net present value including emissions costs. Currently, people other than project developers have limited or no access to such information, which stifles informed public debate on electric energy options. Within this context, the use of the HydroCalculator Tool may contribute to the debate, by facilitating access to information. To validate the tool’s greenhouse gas calculations, we replicate two peer-reviewed articles that estimate greenhouse gas emissions from different hydropower plants in the Amazon basin. The estimates calculated by the HydroCalculator Tool are similar to the ones found in both peer-reviewed articles. The results show that hydropower plants can lead to greenhouse gas emissions and that, in some cases, these emissions can be larger than those of alternative energy sources producing the same amount of electricity. [ABSTRACT FROM AUTHOR]

One important environmental issue of hydropower in the Columbia and Snake River Basins (Pacific Northwest region of United States) is elevated total dissolved gas (TDG) downstream of a dam, which has the potential to cause gas bubble disease in affected fish. Gas supersaturation in the Columbia River Basin primarily occurs due to dissolution of bubbles entrained during spill events. This paper presents a physically based TDG model that can be used to optimize spill operations in multireservoir hydropower systems. Independent variables of the model are forebay TDG, tailwater elevation, spillway and powerhouse discharges, project head, and environmental parameters such as temperature and atmospheric pressure. The model contains seven physically meaningful experimental parameters, which were calibrated and validated against TDG data collected downstream of Rock Island Dam (Washington) from 2008 to 2012. A sensitivity analysis was performed to increase the understanding of the relationships between TDG downstream of the dam and processes such as air entrainment, lateral powerhouse flow, and dissolution. [ABSTRACT FROM AUTHOR]

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Although Small Hydropower Projects (SHPs) are encouraged as sources of clean and green energy, there is a paucity of research examining their socio-ecological impacts. We assessed the perceived socio-ecological impacts of 4 SHPs within the Western Ghats in India by conducting semi-structured interviews with local respondents. Primary interview data were sequentially validated with secondary data, and respondent perceptions were subsequently compared against the expected baseline of assured impacts. We evaluated the level of awareness about SHPs, their perceived socio-economic impacts, influence on resource access and impacts on human-elephant interactions. The general level of awareness about SHPs was low, and assurances of local electricity and employment generation remained largely unfulfilled. Additionally most respondents faced numerous unanticipated adverse impacts. We found a strong relationship between SHP construction and increasing levels of human-elephant conflict. Based on the disparity between assured and actual social impacts, we suggest that policies regarding SHPs be suitably revised. [ABSTRACT FROM AUTHOR]

The people's perception on environmental and socio-economic impacts due to three hydro-electric projects (HEPs; commissioned and under construction) were studied in the north-west Indian Himalaya. Surveys among 140 project-affected people (PAPs) using a checklist of impacts indicate that among the negative impacts, decrease in flora/fauna, agriculture, flow of river, aesthetic beauty; and increase in water pollution, river bed quarrying for sand/stone, human settlement on river banks and social evils; and among the positive impacts, increase in standard of living, road connectivity, means of transport, public amenities, tourism and environmental awareness were related with HEPs. The PAPs tend to forget the negative impacts with the age of the HEPs after it becomes functional, and the positive impacts seem to outweigh the negative impacts. Study concludes that it is difficult to separate the compounding impacts due to HEP construction and other anthropogenic and natural factors, and in the absence of cause-and-effect analyses, it is hard to dispel the prevailing notion that HEPs are undesirable in the study area that led to agitations by the environmentalists and stopped construction of one of these HEPs. To overcome the situation, multi-disciplinary scientific studies involving the PAPs need to be carried out in planning and decision-making to make HEPs environment friendly and sustainable in this region. There is also a need to adopt low carbon electric power technologies and promote a decentralized energy strategy through joint ventures between public and private companies utilizing locally available renewable energy resources. [ABSTRACT FROM AUTHOR]

Background: This study aims to describe the role of mobility in malaria transmission by discussing recent changes in population movements in the Brazilian Amazon and developing a flow map of disease transmission in this region. Methodology/Principal findings: This study presents a descriptive analysis using an ecological approach on regional and local scales. The study location was the municipality of Porto Velho, which is the capital of Rondônia state, Brazil. Our dataset was obtained from the official health database, the population census and an environmental database. During 2000–2007 and 2007–2010, the Porto Velho municipality had an annual population growth of 1.42% and 5.07%, respectively. This population growth can be attributed to migration, which was driven by the construction of the Madeira River hydroelectric complex. From 2010 to 2012, 63,899 malaria-positive slides were reported for residents of Porto Velho municipality; 92% of the identified samples were autochthonous, and 8% were allochthonous. The flow map of patients' movements between residential areas and areas of suspected infection showed two patterns of malaria transmission: 1) commuting between residential areas and the Jirau hydropower dam reservoir, and 2) movements between urban areas and farms and resorts in rural areas. It was also observed that areas with greater occurrences of malaria were characterized by a low rate of deforestation. Conclusions: The Porto Velho municipality exhibits high malaria endemicity and plays an important role in disseminating the parasite to other municipalities in the Amazon and even to non-endemic areas of the country. Migration remains an important factor for the occurrence of malaria. However, due to recent changes in human occupation of the Brazilian Amazon, characterized by intense expansion of transportation networks, commuting has also become an important factor in malaria transmission. The magnitude of this change necessitates a new model to explain malaria transmission in the Brazilian Amazon. [ABSTRACT FROM AUTHOR]

Kenya'swater abstractionmustmeet the projected growth inmunicipal and irrigation demand by the end of 2030 in order to achieve the country's industrial and economic development plan. The Masinga dam, on the Tana River, is the key to meeting this goal to satisfy the growing demands whilst also continuing to provide hydroelectric power generation. This study quantitatively assesses the reliability and robustness of the Masinga dam system under uncertain future supply and demand using probabilistic climate and population projections, and examines how long-term planning may improve the longevity of the dam. River flow and demand projections are used alongside each other as inputs to the dam system simulation model linked to an optimisation engine to maximise water availability. Water availability after demand satisfaction is assessed for future years, and the projected reliability of the system is calculated for selected years. The analysis shows that maximising power generation on a short-term year-by-year basis achieves 80%, 50% and 1% reliability by 2020, 2025 and 2030 onwards, respectively. Longer term optimal planning, however, has increased system reliability to up to 95% in 2020, 80% in 2025, and more than 40% in 2030 onwards. In addition, increasing the capacity of the reservoir by around 25% can significantly improve the robustness of the system for all future time periods. This study provides a platform for analysing the implication of different planning and management of Masinga dam and suggests that careful consideration should be given to account for growing municipal needs and irrigation schemes in both the immediate and the associated Tana River basin. [ABSTRACT FROM AUTHOR]

The article discusses the environmental conditions in Chile's Biobío River Basin and America's Columbia River Basin in relation to climate change, hydropower, and the relationship between culture and the environment. A comparison of the water resources, dams, and water infrastructure development in Chile and the U.S. is provided, along with Chilean water law and a prior appropriation legal doctrine. The legal aspects of dam buildings are assessed.

The article discusses small hydropower's potential role in global sustainable development and energy production as of 2017, and it mentions issues involving the electrification of rural areas, climate change mitigation-related incentives, and flexible licensing and monitoring for small hydropower developments. It states that small hydropower is a renewable energy technology that is able to provide clean and safe electricity to rural and urban regions. Scottish small hydropower is assessed.

Hydroelectric reservoirs are novel ecosystems that provide a variety of important services. To manage these ecosystems and their fish populations effectively, we need to develop conceptual frameworks for predicting their short- and long-term responses. To advance this goal, we revisited and tested the 'trophic surge hypothesis, TSH.' The TSH has been widely cited in the literature, but has not been empirically tested across numerous reservoirs. The TSH suggests that fish populations should show a hump-shaped pattern (i.e., the non-equilibrium phase) after river impoundment. As such, we assembled 40 recruitment and 109 adult fish abundance time series from 19 species distributed across seven reservoirs from temperate and boreal regions, and applied curve fitting analyses and model selection. We found that the hump-shaped pattern was the predominant pattern across individual time series, providing moderate support for the TSH. Fish recruitment increased substantially during reservoir filling and was followed by an increase in adult fish lagging 3-4 years behind. The non-equilibrium phase was transient and lasted roughly eight years for recruits, whereas it could be much longer for adults. When time series were combined across regions and sites, the support for the TSH was weaker. However, we observed significant variability in the duration, timing, and magnitude of the surge across individual time series and found that the total flooded area was the most influential predictor to explain this variability. In conclusion, the TSH and related metrics can be a useful and general predictive framework to understand how fish populations may respond to impoundment. In particular, long-term management recommendations could be short-sighted if formulated before convincing evidence has emerged to show that the reservoir reached its new trophic equilibrium. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis on the ecological benefit and loss of Xiaolangdi reservoir from its completion in 2000 to 2012. We firstly propose a three-step framework of the ecological benefit–loss evaluation for hydropower projects, in accordance with which an index system of riverine wetland ecosystem services valuation was established originally. Then we make a quantitative valuation on the change of riverine wetland ecosystem services caused by this project. Finally, the ecological benefit and loss of the project in the riverine wetland were evaluated in two aspects of positive impacts and negative impacts. The results showed that (1) the positive impacts of Xiaolangdi reservoir mainly included 9 categories of ecosystem services: flood control, ice prevention, sedimentation reduction, energy substitution, emission reduction benefit, water supply, afforestation, shipping and entertainment; the total ecological benefit of the project in the riverine wetland was 26.2058 billion yuan. (2) The negative impacts of Xiaolangdi reservoir mainly included 5 categories: loss due to land submergence, heritage submergence, water and soil erosion, reservoir sedimentation and immigration; the total ecological loss of the project in the riverine wetland was 24.2167 billion yuan. (3) From 2000 to 2012, the net value of ecological benefit–loss for the project was 1.9891 billion yuan. [ABSTRACT FROM AUTHOR]

The ecological compensation for hydropower development should internalize the exterior costs of losses to both humans and the environment from hydropower projects and their associated resettlement projects in a reservoir wetland. However, the externalities from the resettlement are rarely considered in current compensation policies or regulations, and thus many new environmental issues arise in the reservoir wetland region. In this context, an ecological compensation accounting method for hydropower resettlement was established in this study based on human welfare change. Within it, the preferences of respondents for environmental, social, and cultural attributes can be identified and evaluated through an integration of a choice experiment with a random utility model. Thus, the ecological compensation standard for hydropower resettlement could be determined, while various compensation schemes can be considered for the wetland region in accordance with the preferences of re-settlers. With a case study of the Pondo hydropower resettlement project in Tibet, China, the results showed the utility of the respondents for a single attribute ranged from 43.08 to 127.69 CNY, with the sequence of importance being natural environment, religious practice, and social relationships. Accordingly, the ecological compensation standard for the Pondo hydropower resettlement would be set in the range of 90–127.69 CNY per year, per family. Comprehensive environmental, social, and cultural compensation should be considered to improve human welfare and ecological service function in the Pondo reservoir wetland region. [ABSTRACT FROM AUTHOR]

Schizothorax prenanti ( S. prenanti ) is a second-class provincial protected endemic fish within the upper reaches of the Min River. The spawning season of S. prenanti extends from March to April. Habitat alteration and the construction of multistage dams have resulted in a rapid decline of the S. prenanti population. To assess the potential effects of a reduced flow volume on the S. prenanti spawning habitat area in downstream of dams, we combined River 2D and a habitat similarity evaluation model through the following steps. First, we conducted surveys of S. prenanti and the substrate composition in a natural habitat reach and a hydropower-affected reach. Second, hydraulic simulations were performed over a range of flows using River 2D. Third, vague sets of habitat variables were individually defined based on multi-expert opinions. Fourth, we estimated the weighted similarity of the S. prenanti spawning habitat using input variables (water depth, velocity) from River 2D. Fifth, we verified the model with S. prenanti survey data. Hydraulic simulations for velocity and depth yielded accuracies of approximately 84–97% and 81–98%, respectively. The weighted similarity simulations showed that weighted similarity increased with the flow up to a threshold range of approximately 130–150 m 3 /s; beyond this range, the weighted similarity decreased. The weighted similarity in the natural habitat reach was higher than in the restored reach at the same flow volume due to geography. The habitat similarity model provides restoration targets and thresholds for decision makers to develop a proactive conservation strategy for wetland management. [ABSTRACT FROM AUTHOR]

To alleviate the negative impacts on ecosystem caused by cascaded development of Yuan River, this study quantified the ecological requirements and incorporated them into the cascaded reservoir operating schemes to provide the streamflow that balances fish habitat protection and hydropower generation. Physical habitat simulation model is proposed to simulate the relationship between streamflow and physical habitat for various life stages of Cyprinus rubrofuscus Lacépède and Bagarius rutilus Ng & Kottelat , and to determine the ecological requirement as a discharge range associated with the upper area of a certain proportion of maximum Weighted Usable Areas ( WUA ). Then the optimal operation model of cascaded reservoirs is established. Maintaining over 70% of maximum WUA as an example, the optimization technique could increase the hydropower generation of cascaded reservoirs by 3.60%, 1.93% and 4.19%, and also improve the ecological conditions by increasing the WUA s by 11.3%, 17.9% and 16.2% for Section A and 7.4%, 12.4% and 14.4% for Section B under wet, normal and dry conditions, respectively. Furthermore, the trade-offs between hydropower production and fish habitat conservation are discussed. The optimal compromises were identified at the knick points in the established relations where 50%–70% of maximum WUA are conserved at a cost of 11.72–52.11 billion kW h (1.8%–8.4%) power generation loss. [ABSTRACT FROM AUTHOR]

Large numbers of households and communities will not be connected to the national electricity grid for the foreseeable future due to high cost of transmission and distribution systems to remote communities and the relatively low electricity demand within rural communities. Small-scale hydropower used to play a very important role in the provision of energy to urban and rural areas of South Africa. The national electricity grid, however, expanded and offered cheap, coalgenerated electricity and a large number of hydropower systems were decommissioned. In this study, a feasibility and implementation model was developed to assist in designing and financially evaluating small-scale hydropower (SSHP) plants. The implementation model describes steps to be followed in identifying a technically possible and economically feasible opportunity to develop a SSHP site for rural electrification. The development model was used in designing the Kwa Madiba SSHP plant. The Kwa Madiba SSHP plant was economically evaluated on net present value, internal rate of return, levelised cost of energy, financial payback period and cost/benefit ratio. The outcome of this study proved that it is technically possible to provide SSHP installations for rural electrification in South Africa that are more feasible than local or national electricity grid extensions or even alternative energy sources such as diesel generators. It was concluded that the levelised cost of SSHP projects indicates that the cost of SSHP for low energy generation is high compared to levelised cost of coal-fired power generation. However, the remoteness of SSHP for rural electrification increases the cost of infrastructure to connect remote rural communities to the national electricity grid. This provides a low cost/benefit ratio and renders technically implementable SSHP projects for rural electrification feasible on this basis. [ABSTRACT FROM AUTHOR]

The State of São Paulo in Brazil experienced in 2014 and early 2015 an expressive precipitation deficit, leading to drought conditions with impacts in water availability for public consumption, hydropower generation, and agriculture, particularly during austral summer. This study performs a detailed diagnostics of the observed precipitation during 2014 and early 2015 over a particular region of São Paulo State, which includes the massively populated metropolitan region of São Paulo. The diagnostic was designed to provide answers to a number of relevant questions for the activities, decisions, and strategic planning of several sectors (e.g., general public, media, and high-level governments). Examples of questions such diagnostics can help answer are: How much precipitation has the region received? Has the region experienced drought conditions in the past? When have similar drought conditions been observed in the past? What has been the observed precipitation pattern in the last years? How severe/rare were the 2014 and 2015 droughts? When does the rainy season typically start/end in the region? What happened during the 2013/2014 and 2014/2015 rainy seasons? The performed diagnostics based on historical 1961/1962-2014/2015 records revealed that the 2013/2014 austral summer was a very rare event classified as exceptionally dry. Similar drought events were previously recorded but with smaller magnitude in terms of precipitation deficits, making the 2013/2014 drought event the driest on the examined record. In fact, the region has been experiencing a precipitation deficit pattern since 1999/2000. One of the contributing factors for the expressive precipitation deficit in 2014 was the abnormally early end of the 2013/2014 rainy season in the region. [ABSTRACT FROM AUTHOR]

Run of the river (RoR) hydropower projects are generally considered more environmentally sustainable as compared to their reservoir based counterparts. Further, impacts of these projects are supposed to be in proportion to their installed capacity. Large numbers of this category of hydropower projects in different size ranges are coming up in Himalayan regions. Un-sustainable construction/operation practices adopted during development and/or running of these projects are posing an environmental threat to this fragile and youngest mountain range of the world. This research paper presents a public perception cum data collection study on the environmental impacts of small and large RoR hydropower projects located in western Himalayan region of India. A structured questionnaire was designed to collect the primary data pertaining to intangible impacts while secondary data was collected to analyse tangible environmental parameters. The study concludes that every environmental impact of SHPs is not 'small' as compared to LHPs. Ignoring the environmental impacts of SHPs may not be a good practice. [ABSTRACT FROM AUTHOR]

Non-parametric Mann-Kendall, double mass curve analysis and annual variation analysis were used to analyze the spatial and temporal changes in runoff and sediment loads at the Jiuzhou, Jiajiu and Yunjinghong hydropower stations in the Lancang River from 1964 to 2010. The results indicate that the inter-annual and annual distributions of sediment have significantly changed since the 1990s, and that sediment discharge has increased at the Jiuzhou station, while sediment discharge has declined at the Jiajiu and Yunjinghong stations. Overall, annual runoff distribution patterns have been consistent since the 1990s. Spatial and temporal changes in runoff and sediment loads in the Lancang River have been attributed to the construction of hydropower stations, changes in land use and precipitation patterns. The results can provide guidance for the environmental protection and ecological restoration of rivers in the Southwest of China. [ABSTRACT FROM AUTHOR]

Climate change is impacting water users in many sectors: water supply, farming, industry, hydropower, fishing, housing, navigation and health. Existing situations, like population growth, movement of populations from rural to urban areas, poverty and pollution can aggravate the impacts of climate change. The aim of the study is to evaluate the vulnerability of different water user groups to climate change and define communities' adaptation strategies in the Comoe River Basin. Information was collected on communities' concerns and perception on changes in climate and potential adaptation measures and strategies. Results show that 95 % of the sample in the study communities had heard of it and are aware that climate change is occurring. They have been experiencing changes in economic activity and cropping pattern, reduced water level in rivers, crop failure, delay in cropping season, new pests and diseases, food insecurity, drop in income and decline in crop yield. Results also show that communities employ various adaptation strategies including crops diversification, substitution and calendar redefinition, agroforestry, borrowing from friends and money lenders and increasing fertilizer application. [ABSTRACT FROM AUTHOR]

Hydropower development in Xizang (Tibet) Autonomous Region plays a vital role in co-control of local air pollutants and greenhouse gas (GHG) in China. According to emission factors of local air pollutants and GHG of coal-fired power industry in different hydropower service regions, we estimate the effect and synergy of local air pollutants and GHG reduction achieved by hydropower development in Tibet, examine the main factors constraining the effect and synergy, using correlation analysis and multiple regression analysis. The results show that: 1) During the period from 2006 to 2012, the effect of local air pollutants and GHG reduction achieved by hydropower development in Tibet decreased as a whole, while the synergy increased first and decreased afterwards. 2) The effect and synergy of local air pollutants and GHG reduction achieved by hydropower development in Tibet vary significantly across different hydropower service regions. The effect based on emission levels of Central China power grid (CCPG) and Northwest China power grid (NCPG) was more significant than that based on emission level of national power grid (NPG) from 2006 to 2012, and the synergy based on emission levels of CCPG and NCPG was also more significant than that based on emission level of NPG from 2010 to 2012. 3) The main factors constraining the effect and synergy based on emission levels of NCPG and CCPG included SO removal rate and NO removal rate, the effect and synergy based on emission level of NPG was mainly influenced by net coal consumption rate. 4) Transferring hydropower from Tibet to NCPG and CCPG, and substituting local coal-fired power with hydropower can greatly help to co-control local air pollutants and GHG, transform the emission reduction pattern of the power industry and optimize energy structure. [ABSTRACT FROM AUTHOR]

The Zambezi River Basin in southern Africa is relatively undeveloped from both a hydropower and irrigated agriculture perspective, despite the existence of the large Kariba and Cahora Bassa dams. Accelerating economic growth increases the potential for competition for water between hydropower and irrigated agriculture, and climate change will add additional stresses to this system. The objective of this study was to assess the vulnerability of major existing and planned new hydropower plants to changes in climate and upstream irrigation demand. Our results show that Kariba is highly vulnerable to a drying climate, potentially reducing average electricity generation by 12 %. Furthermore, the expansion of Kariba generating capacity is unlikely to deliver the expected increases in production even under a favourable climate. The planned Batoka Gorge plant may also not be able to reach the anticipated production levels from the original feasibility study. Cahora Bassa's expansion is viable under a wetting climate, but its potential is less likely to be realised under a drying climate. The planned Mphanda Nkuwa plant can reach expected production levels under both climates if hydropower is given water allocation priority, but not if irrigation is prioritised, which is likely. For both Cahora Bassa and Mphanda Nkuwa, prioritising irrigation demand over hydropower could severely compromise these plants' output. Therefore, while climate change is the most important overall driver of variation in hydropower potential, increased irrigation demand will also have a major negative impact on downstream plants in Mozambique. This implies that climate change and upstream development must be explicitly incorporated into both project and system expansion planning. [ABSTRACT FROM AUTHOR]

During August-September 2012, we sampled six hydropower reservoirs in southeastern United States for CO2 and CH4 emissions via three pathways: diffusive emissions from water surface; ebullition in the water column; and losses from dam tailwaters during power generation. Estimates of average areal emission rates of CO2 attributable to the six reservoirs (i.e., reservoir plus tailwater emissions) ranged from 994 to 2760 mg⋅m-2⋅day-1, which is low to moderate compared to CO2 emissions rates reported for tropical hydropower reservoirs and boreal ponds and lakes, and similar to rates reported for other temperate reservoirs. Similar average rates for CH4 were also relatively low, ranging from 6 to 187 mg⋅m-2⋅day-1. On a whole-reservoir basis, estimates of total emissions of CO2 ranged 10-fold, from 42,740 kg per day for Fontana to 501,151 kg per day for Guntersville, and total emissions of CH4 ranged over 30-fold, from 251 kg per day for Fontana to 9153 kg per day for Allatoona. Emissions through the tailwater pathway varied among reservoirs, comprising from 19% to 65% of total CO2 emissions and 0% to 84% of CH4 emissions, depending on the reservoir. Emission rates were significantly correlated with several reservoir morphological and water quality characteristics, including metrics related to vertical stratification (e.g., minimum water column temperature and maximum dissolved oxygen) and reservoir productivity (e.g., water transparency and chlorophyll a concentration). [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the cause of several unexpected high amplitude oscillations that occurred in the surge tank water level of a real hydropower plant during secondary load-frequency control (LFC) maneuvers, after the replacement of the turbine runner, and to propose solutions that allow the power plant to continue providing secondary LFC in a safe and reliable manner. For this purpose, a simulation model has been developed and calibrated from data gathered during several on-site tests. Two different solutions are proposed in order to cope with the observed problem: using a state-dependent load change rate limiter or modifying the hydro turbine governor gains; the turbine governor remains the same as before the runner replacement. The proposed solutions are tested against a set of realistic secondary LFC signals by means of simulations and compared to each other as a function of the probability that the surge tank water level descends below a minimum safe level and the quality of the secondary LFC response. The results presented in the paper demonstrate the validity of the methodology proposed to determine the state-dependent ramp limit, as well as its effectiveness to prevent the surge tank drawdown and to provide clear insight into the trade-off between response quality and power plant safety. [ABSTRACT FROM AUTHOR]