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This article explores the trade-offs in the decarbonisation of the energy sector by analysing the legal arguments in favour of and against hydropower in EU law. It contends that the EU regimes in climate, energy and environmental law each value the advantages and disadvantages of energy production in different ways. In contrasting the approaches in these three areas of EU law, the article analyses how EU law governs the decarbonisation process in the context of hydropower. The analysis reveals a promising opportunity to reconcile the friction among climate, energy and environmental law while improving the ecological sustainability of hydropower production. [ABSTRACT FROM AUTHOR]

Climate change causes a problem for the energy system in Poland, which is based on the availability of water resources throughout the year. In situations of water scarcity resulting from increased demand or due to water deficits caused by the phenomenon of drought, it is necessary to develop efficient management methods that take into account the needs of all stakeholders and obtaining approval for new investments. The principles of Integrated Water Resources Management (IWRM) enable this efficiency to be achieved. The research used 51 questions in 3 surveys to assess the potential for IWRM implementation in 3 catchments located in an area of southern and south-western Poland with different topography, regional and socio-economic characteristics, i.e., the Białka (tourism domination), the Nysa Kłodzka (potential for hydropower) and the Widawa (lowland character). In order to interpret the results, the author's method of grouping survey questions from different sources was applied. The results of the study showed that there is considerable social potential and willingness to develop cooperation between different stakeholder groups but there are barriers related to the state of knowledge and its transfer between stakeholders. It is important not to ignore the stakeholders whose resistance can effectively delay investment processes. [ABSTRACT FROM AUTHOR]

The classification of a hydropower scheme as run-of-the-river (or run-of-river; ROR) evokes an image of a low-impact installation; however, examination of eight case studies worldwide shows that substantial negative societal and ecological impacts are tied to them, albeit in somewhat different ways. We conclude that ROR dams not only potentially displace communities, disrupt livelihoods, and degrade environments in surrounding areas, but they also divert water from areas of need, impact aquatic ecology through habitat destruction and disruption of fish migrations, emit non-trivial amounts of greenhouse gases over the lifespan of the project, and disrupt streamflow in downstream river sections. While these negative impacts vary on a case-by-case basis, medium and large ROR dams consistently have multiple and cumulative impacts, even when not having appreciable reservoirs. We contend that many impactful dams do not qualify as low-impact ROR projects, despite being defined as such. Such mislabeling is facilitated in part by the ambiguous definition of the term, which risks the ROR concept being used by proponents of impactful structures to downplay their negative effects and thus mislead the public or gain status, including within the Clean Development Mechanism in relation to mitigating climate change. [ABSTRACT FROM AUTHOR]

From less than three dozen in 1949, the number of small hydropower stations in the People's Republic of China grew to nearly ninety thousand by 1979. By the early 1980s, these stations were distributed across nearly 1,600 of China's 2,300 counties. In 770 counties, small hydropower was the primary source of rural electricity generation. This article offers a history and assessment of these developments, unsettling our traditional emphasis on large-scale hydroelectricity. The article begins by reconstructing the PRC's enormous investments in small hydropower from the 1950s to the early 1980s. This reconstruction, the first of its kind in the English language, not only helps reassess key periods and events in the history of the PRC but also establishes the position of small hydropower in the hydraulic history of the twentieth century. The article then turns to a discussion of the claimed impacts of small hydropower. As electricity became available for the first time in many parts of the Chinese countryside, it affected patterns of economic and social activity for hundreds of millions of people. Finally, the paper explores what the case of small hydropower can offer to conceptual and theoretical problems surrounding development, innovation, and the environment. Returning to the long-standing debate over scale and development, China's experience with small hydropower reminds us of the important role played by smaller-scale, appropriate, and self-reliant technologies in global energy history. [ABSTRACT FROM AUTHOR]

Fish biodiversity assessments are vital for understanding threats and aquatic ecosystem health. In the Poso River, Central Sulawesi, changes in biodiversity are influenced by habitat alteration, non-native species, and overfishing. This study evaluates fish and crustacean biodiversity in the Poso River system to address these challenges for improving fisheries management, conservation, and fish passage integration into hydropower development. The present biodiversity study utilized a comprehensive methodology that encompassed both traditional taxonomic approaches and DNA barcoding, specifically targeting the mitochondrial cytochrome c oxidase subunit-1 (COI) gene for accurate species identification and spatial boundary validation. The survey was conducted in the upstream, hydropower area and downstream areas of the river. We found 27 species of fish in the Poso River, including both native (e.g., Anguilla celebesensis, Oryzias nebulosus, Rhyacichthys aspro) and non-native species (e.g., Melanochromis auratus, Amphilophus trimaculatus, Oreochromis niloticus). Two International Union for Conservation of Nature (IUCN) red listed endangered species were also observed (e.g., Adrianichthys poptae and Mugilogobius sarasinorum). DNA barcoding was performed to examine species spatial boundaries. The fish population in the Poso River was dominated by non-native species, accounting for 85.70% of the total population. The upstream reaches had the highest fish abundance and diversity, while the downstream reaches had the lowest. There was, however, no significant difference in species richness and diversity across different locations and seasons. The dominance of non-native species in the Poso River necessitates the improvement of existing fishways within the hydropower dams potentially through the development of selective technology that can block the distribution of these non-native species. This research highlights the critical issue of non-native species proliferation and the potential threat they pose to native fish populations, providing valuable insights for conservation and management efforts in Indonesia and similar ecosystems worldwide. [ABSTRACT FROM AUTHOR]

Streamflow is significantly influenced by the increased temperature and rainfall inconsistency due to climate change. This study assesses the impacts of climate change on water availability and streamflow dynamics during the periods 2030–2069 and 2070–2099 for two greenhouse gas trajectories (SSP245 and SSP585) in the lower catchment of the Upper Sutlej River Basin (USRB). This study integrates data from the Coupled Model Inter-comparison Project Phase 6 (CMIP6) General Circulation Models (GCMs) with the SWAT hydrological model. This approach analyzes the complex interactions between climate variables and hydrological processes. NASA NEX-GDDP-CMIP6 Bias-corrected statistically downscaled data at 0.25° X 0.25° grid resolution are used. Under SSP245, projected streamflow for near future 2030 to 2069 shows increases up to 56.097% in December, while decreases reach -9.420% in August. For far future 2070 to 2099, increases are observed up to 41.846% in December, with decreases up to -25.670% in August. Under SSP585, for near future 2030 to 2069, decreases range from -7.616% in May to -13.614% in August. For far future 2070 to 2099, decreases range from -12.386% in October to -25.670% in August, while increases reach 46.211% in November. The insights derived are crucial information for assessing water resource vulnerability to climate change in mountainous regions. [ABSTRACT FROM AUTHOR]

Riverine habitat fragmentation by barriers, including impoundments, is common and their effects on obligate aquatic organisms are manifold. Organisms, such as Atlantic salmon (Salmo salar), that make extensive river migrations are particularly vulnerable to the effects of impoundments. In this study, we use acoustic telemetry to examine the migratory behaviour of Atlantic salmon, as they migrate to sea for the first time as juvenile 'smolts', in a river with a series of dams that form a complex hydropower scheme. We demonstrate that overall migration success in the River Dee catchment and particularly through standing waters was remarkably high. We speculate that high migration success in standing waters could be due to relative current speeds providing good quality directional cues to migrants. Migration success past the two dams in this study, was relatively high, although the number of unsuccessful passage attempts before a successful passage was also very high. The vast majority of smolts passed the dams when the turbines were operational. At one dam, smolts did not use an available fish pass but migrated through the generating turbines. These findings provide several routes through which generation could be managed to enhance the success of downstream smolt migration in rivers where there are similar patterns of hydrogeneration in place. [ABSTRACT FROM AUTHOR]

The current research aims to analyse the effect of the number and shape of the blades and the curvature of the flume bottom on the performance curves of undershot water wheels, based on experimental tests conducted in a fully instrumented laboratory facility. Six wheels are tested: four wheels with plane blades (16, 24, 36, 48) and two with 24 curved blades for two flume bottom configurations. Torque, mechanical power and mechanical efficiency performance curves are determined for several rotational speed and flow rate values. Results demonstrate that the maximum efficiency is achieved for the 36-plane blade wheel, the curved flume bottom reduces water losses under the wheel and increases efficiency, and the blades' shape strongly influences the wheel efficiency. Non-dimensional performance curves are provided to generalise the results. This research provides relevant contributions towards the development of a low-cost energy recovery solution to be applied in water infrastructures. [ABSTRACT FROM AUTHOR]

Renewable energy generation sector has grown rapidly over the past decade, driven by increasing investments, heightened political and public support, and advancements in technology. This review highlights recent technological developments in the sector and analyzes the state-of-the-art to uncover major overarching trends. The findings suggest that the main maturation directions for emerging renewable technologies are towards harnessing new untapped sources of renewables and combining energy generation with additional value creation for more versatile and effective land, infrastructure, or labor utilization. The overarching concept is clear: generating greater economic or environmental value with minimal investment. The key emerging technological trends were identified as the development of means for: distributed small-scale generation, large-scale land versatility, and accessing marine renewables. Notable examples of maturing technologies with significant deployment include agrivoltaics, floating photovoltaics, and floating wind, all of which are on track to becoming industrial standard practices. Looking ahead, the deployment of renewable energy technologies is expected to accelerate over the next decade, driven by rising demand, improved access to new energy resources, trends toward grid decentralization, expanding utility-scale energy storage solutions, and the economic benefits of co-located, multi-purpose installations.

Hydropower and photovoltaic (PV) power, the two dominant renewable energy sources in China, are crucial for decarbonization and climate change mitigation, leveraging their exceptional complementary value in the power system. However, the large-scale integration of PV power exacerbates several key issues concerning increased load variation, enhanced flexibility demand, and challenging congestion management. This study addresses these issues by developing a medium-short-term dispatch approach for a hydro-PV complementary system (HPCS), which leverages the flexibility of cascade hydropower and the potential value of hydro-PV complementarity. Firstly, a mathematical model is developed to optimize peak load shaving, while incorporating hydraulic-electrical coupling constraints and active regulation constraints of cascade hydropower in response to PV uncertainty. The model endeavors to optimize the hybrid operation of HPCS, exploiting hydro-PV complementarity to mitigate output variability and ensure a stable electricity supply. Subsequently, multidimensional decision variables in the model are subjected to an equivalent reformulation, leveraging the extremal principle and duality theory, and the nonlinear constraints are linearized by the special ordered sets of type 2 constraints. These methods enhance the model's solvability and computational efficiency. Finally, the proposed model is applied to the Beipan HPCS in China, determining the hydro-PV complementary dispatch strategies. The research findings can be summarized as follows: (1) the developed hydropower active regulation method ensures stable and adjustable hydro-PV output, reducing load variation by 137.96 MW and fully exploiting hydropower flexibility and hydro-PV complementarity; (2) the model demonstrates high reliability by significantly enhancing peak shaving during the flood season, even in the face of increased congestion management challenges; (3) the model balances congestion management difficulties across multiple channels, outperforming the conventional model by reducing the risk of renewable energy curtailment by up to 1885.95 MWh; (4) the model adapts to the dynamic combined growth of VRE and transmission capacity, making it a promising technology for alleviating transmission congestion caused by large-scale hydropower and VRE. • A hydro-PV complementary dispatch model is proposed. • The model is equivalently reformulated by extremal principle and duality theory. • The model ensures stable electricity supply under multi-transmission channels. [ABSTRACT FROM AUTHOR]

Increased utilization of hydraulic turbines as a regulatory tool for electrical grid stabilization forces some turbines to operate away from their design point, thus increasing wear and tear. In here, rotating vortex rope (RVR) mitigation by means of radial insertion of cylindrical rods in the draft tube is investigated experimentally on a 10 MW Kaplan turbine operating as a propeller. Pressure measurements in the draft tube, runner chamber and spiral casing, along with strain and acceleration measurements on the turbine shaft are performed to scrutinize the effectiveness of the mitigation system. Three part-load operating points are investigated, corresponding to 83%, 72%, and 68% of the guide vane servo stroke relative to the best-efficiency point opening. It is shown that the mitigation system dampens the harmful effects of the vortex rope at all operating points, especially at lower part-load conditions. Specifically, the pressure amplitude of the RVR fundamental mode inside the runner chamber reduces by 84%, 63%, and 73% at the three investigated operating points, relative to the amplitudes without mitigation. On the turbine shaft, the fundamental mode of the axial thrust oscillations at the RVR frequency reduces by 65%, 83%, and 95%. It is shown that the mitigation does not come with a high cost on the turbine time-averaged efficiency over the course of the measurements, the penalty being 2%, 2.5%, and 3.2% at the protrusion length where optimal mitigation is achieved at each operating point. For high-head machines, the penalty is expected to be lower since the relative importance of the draft tube diminishes for higher heads. • Vortex rope mitigation in a 10 MW prototype turbine by draft tube rod protrusion. • Pressure, acceleration, strain, and turbine efficiency measurements were performed. • Pressure oscillations, strain, and acceleration are reduced throughout the turbine. • The hydraulic efficiency penalty loss is less than three percentage points. [ABSTRACT FROM AUTHOR]

Marine renewable energy (MRE) harnesses ocean-based resources such as waves, tides, currents, and thermal or salinity gradients for sustainable power generation. It has the potential to complement existing renewable resources, support remote communities, and contribute to decarbonization efforts. However, understanding the hydrodynamic forces created by MRE devices and their impacts on marine life is critical for responsible deployment. To address these concerns, advanced sensor devices, including the Marine Sensor Fish (MSF), Sensor Fish Mini (SF Mini), and Flexible Sensor Fish (FSF), were developed to measure interactions between aquatic organisms and MRE systems. This paper details the design, manufacturing, calibration, and field deployment of these sensor suites, highlighting their ability to capture key physical stressors such as shear forces, pressure changes, and collision impacts. The MSF successfully evaluated turbine interactions at a tidal turbine in the Salish Sea, capturing data on turbulence, collision impact, and pressure gradients. The SF Mini validated hydrodynamic conditions in scaled hydraulic models, supporting computational fluid dynamics simulations. The FSF, with its flexible silicone body, measured species-specific impacts in turbulent environments. This research demonstrates the potential of Sensor Fish technology to advance sustainable marine energy systems by reducing biological impacts and informing environmentally sustainable designs., Competing Interests: Declaration of competing interest Zhiqun Daniel Deng reports financial support was provided by US Department of Energy Water Power Technologies Office and Office of Technology Transitions. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The SF Mini was patented (11533818 and 12144139)., (Copyright © 2025. Published by Elsevier B.V.)