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Sustainable global energy production is back-stopped by hydropower which is responsible for a significant share of the green energy produced worldwide. Hydropower, however, does not come without some environmental impacts but has worked to reduce those impacts. Here, we discuss the historical, legislative, and design configurations of hydropower facilities located in three of the world’s most important producers: Brazil, Canada, and Norway. The background is intended to inform the collection of scientific papers from each country aimed at assessing and improving the sustainability of hydropower production that form the core of this special issue on sustainable hydropower. We review the development and key legislative history for hydropower in each country and point out the common backgrounds and interests each nation has in the continued sustainable development of its hydropower resources.

Hydropeaking refers to the mode of hydropower dam operation where sub-daily changes in flow are used to vary the generation of electricity in accordance with demand. A typical pattern produces maximum power during the day (i.e., the peak), and minimal power at night. Hydropeaking is considered necessary to stabilize the energy grid since it is the only reliably flexible method of producing electricity besides fossil fuels. With the planned phase-out of traditional coal-fired electricity production across Canada by 2030, and the increased reliance on intermittent wind and solar generation, the flexibility of hydropeaking will assume an increased importance. However, hydropower generation comes with costs; hydropeaking in particular is considered one of the most ecologically harmful modes of operation since downstream biota are subjected to flows that deviate greatly from typical natural flow regime patterns. The ecological effects of hydropeaking have been examined in a growing body of literature, but mitigation options do exist that include dam operational and/or structural modifications. This paper will explore the importance of hydropeaking in the Canadian electricity system, the ecological consequences of flexible hydropower, and mitigation options that could potentially strike a balance between meeting Canadian energy needs and minimizing ecosystem impacts.

Total dissolved gas (TDG) supersaturation downstream of hydropower plants may cause gas bubble disease (GBD) and harmful effects in fish. Little is known about tolerance levels of TDG supersaturation on Atlantic salmon (Salmo salar Linnaeus, 1758) in natural rivers. The present study investigated the effects of TDG supersaturation on the survival of Atlantic salmon smolts at two field sites in Norway. Here, we kept smolts in cages at increasing distances from hydropower plants known to cause TDG supersaturation and at control sites. We recorded fish mortality and examined for GBD using a stereo microscope. Mortality and symptoms of GBD commenced in fish exposed to an average of 108.3% TDG (maximum 111.0%, water depth 0.55 m) for 2 days. Significant differences in time before mortality at the control sites and test sites commenced at 110.2% TDG (maximum 111.8%) for 3 days. The study indicates that Atlantic salmon may be more vulnerable to TDG supersaturation than Pacific salmonids, which are considered at risk when the TDG is above 110%. In addition, the study provides important data to link effects caused by TDG in the laboratory and in the field.

The Archimedes/Archimedean screw generator (ASG) is a fish-friendly hydropower technology that could operate under a wide range of flow heads and flow rates and generate power from almost any flow, even wastewater. The simplicity and low maintenance requirements and costs make ASGs suitable even for remote or developing areas. However, there are no general and easy-to-use guidelines for designing Archimedes screw power plants. Therefore, this study addresses this important concern by offering a simple method for quick rough estimations of the number and geometry of Archimedes screws in considering the installation site properties, river flow characteristics, and technical considerations. Moreover, it updates the newest analytical method of designing ASGs by introducing an easier graphical approach that not only covers standard designs but also simplifies custom designs. Besides, a list of currently installed and operating industrial multi-Archimedes screw hydropower plants are provided to review and explore the common design properties between different manufacturers. On top of that, this study helps to improve one of the biggest burdens of small projects, the unscalable initial investigation costs, by enabling everyone to evaluate the possibilities of a green and renewable Archimedes screw hydropower generation where a flow is available.

Most of the hydropower generated in Canada’s western province of British Columbia is generated by a small number of large storage or diversion projects that impound large rivers. All but one were built between 1950 and 1985; a period when environmental considerations for large projects were evolving to present-day social, political and regulatory standards. Large projects result in ecosystem transformations; river valleys are converted to reservoirs, and the release of water for power generation results in highly altered flow regimes downstream of dams. I describe the effects of three projects on aquatic ecosystems and measures that have been taken over the past 60 years to monitor and mitigate those effects, with an emphasis on downstream effects to fish populations. I briefly review methods that were used to predict effects, particularly on key fish species, and consider the role of adaptive management and its alternatives on resolving uncertainties about ecological effects of large hydroelectric projects.

The electric sector simultaneously faces two challenges: decarbonization to mitigate, and adaptation to manage, the impacts of climate change. In many regions, these challenges are compounded by an interdependence of electricity and water systems, with water needed for hydropower generation and electricity for water provision. Here, we couple detailed water and electricity system models to evaluate how the Western Interconnection grid can both adapt to climate change and develop carbon-free generation by 2050, while accounting for interactions and climate vulnerabilities of the water sector. We find that by 2050, due to climate change, annual regional electricity use could grow by up to 2% from cooling and water-related electricity demand, while total annual hydropower generation could decrease by up to 23%. To adapt, we show that the region may need to build up to 139 GW of additional generating capacity between 2030 and 2050, equivalent to nearly thrice California’s peak demand, and could incur up to $150 billion (+7%) in extra costs. The authors link water and electricity system models to evaluate how the electric grid can both adapt to climate change impacts and decarbonize, while also accounting for dependencies and climate vulnerabilities of the closely coupled water sector.

By hindering migration and inducing direct turbine mortality during downstream migration, hydropower is regarded as one of the most serious threats to anadromous salmonids. Yet, little attention has been paid to long-term turbine-induced selection mechanisms effecting fish populations. This work evaluates turbine and post-turbine survival of PIT-tagged wild brown trout smolts. By estimating individual river and sea survival rates, we were able to compare survival rates of smolts that had migrated through the turbine with smolts that had bypassed the turbine, as well as investigate both natural and anthropogenic size-selective mechanisms operative on the population. Total river-descent survival probability was 0.20 for turbine migrants and 0.44 for bypass migrants. The surviving turbine migrants were significantly smaller than their bypass counterparts and more exposed to predation from Northern pike. The estimated mean-adjusted selection gradient was − 0.76 for turbine migrants and + 1.85 for the bypass migrants. The resulting disruptive selection may ultimately lead to increased phenotypic smolt size variation provided sufficient additive genetic variance associated with smolt size. Mitigation measures at hydropower plants are thus essential for preserving sustainable populations of anadromous fish and maintaining population genetic variation.

The recent large-scale hydropower development in the Amazon basin has raised concerns about the impacts on the movements of migratory fishes such as goliath catfish (Brachyplatystoma spp.). In the Madeira River, the efficiency of a 1400-m long fishway in the Santo Antônio hydropower plant (SAE HPP) was evaluated between 2012 and 2016 using telemetry techniques. Tagged fish (N = 388) were released 2000 m downstream of the dam and near the entrance or inside the fishway (N = 149). Fixed radio stations monitored fish movements and residence near 14 different structures of the SAE HPP; four acoustic receivers in the reservoir and one downstream the dam monitored whether fish moved away or past the dam. The findings revealed that 15% of the fish released downstream were detected near the dam but none were detected in the reservoir upstream. For the group of fish released in the fishway, no B. rousseauxii (N = 64) was detected moving upstream and into the reservoir and 5 individuals of B. vaillantii (N = 41) exited the fishway to the reservoir. This was the first long-term telemetry monitoring of fish movements near a dam in the Amazon and the results provided evidence of inefficiency of the fishway for the target species, which led the hydropower company to reconstruct the fishway.

Planned decommissioning of coal-fired plants in Europe requires innovative technical and economic strategies to support coal regions on their path towards a climate-resilient future. The repurposing of open pit mines into hybrid pumped hydro power storage (HPHS) of excess energy from the electric grid, and renewable sources will contribute to the EU Green Deal, increase the economic value, stabilize the regional job market and contribute to the EU energy supply security. This study aims to present a preliminary phase of a geospatial workflow used to evaluate land suitability by implementing a multi-criteria decision making (MCDM) technique with an advanced geographic information system (GIS) in the context of an interdisciplinary feasibility study on HPHS in the Kardia lignite open pit mine (Western Macedonia, Greece). The introduced geospatial analysis is based on the utilization of the constraints and ranking criteria within the boundaries of the abandoned mine regarding specific topographic and proximity criteria. The applied criteria were selected from the literature, while for their weights, the experts’ judgement was introduced by implementing the analytic hierarchy process (AHP), in the framework of the ATLANTIS research program. According to the results, seven regions were recognized as suitable, with a potential energy storage capacity from 1.09 to 5.16 GWh. Particularly, the present study’s results reveal that 9.27% (212,884 m2) of the area had a very low suitability, 15.83% (363,599 m2) had a low suitability, 23.99% (550,998 m2) had a moderate suitability, 24.99% (573,813 m2) had a high suitability, and 25.92% (595,125 m2) had a very high suitability for the construction of the upper reservoir. The proposed semi-automatic geospatial workflow introduces an innovative tool that can be applied to open pit mines globally to identify the optimum design for an HPHS system depending on the existing lower reservoir.

Because of growing interest in deploying newer very low head (VLH) turbine technology to generate electricity in rivers, there is a need to assess how fish fare in interactions with VLH turbines. We assessed injury and mortality rates from experimental VLH turbine entrainment of fish species local to the study site at Wasdell Falls on the Severn River, Ontario, which is one of the first such VLH installations in North America. Using balloon tags to recapture fish and before/after entrainment assessments, we found minimal injury and mortality differences between control (no entrainment) and treatment (entrainment) groups. One adult northern pike (Esox lucius Linnaeus, 1758; 1.16% of total entrained fish) was killed by turbine strike. Abrasion-related injuries (i.e., scale loss, torn fins) were the most common form of injury in both control and treatment fish, which was likely attributed to handling and not turbine passage per se. Telemetry monitoring of a subset of fish revealed that post-passage mortality was low. These results suggest that VLH turbine entrainment has negligible effects on the fish species studied here, and thus, VLH turbines may be suitable for increasing generating capacity at low head dam sites with minimal risk to fish.