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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Setting e-flows (instream, environmental or ecological flow regimes) for existing or new hydroelectric and other projects is a key worldwide consideration. A Canadian perspective and experience in arriving at e-flow regimes for ice-free or ice-covered rivers, with emphasis on small and large hydroelectric projects, is presented through general concepts and modeling approaches. Rather than a single standard approach, several methodologies are used throughout Canada, although in some regions preferred techniques may be favoured. Methods range from relatively simple desktop calculations based primarily on hydrological data to sophisticated hydrodynamic and habitat modeling followed by time series analyses. Method complexity usually depends on impact severity, particularly on fish and fish habitat. Multi-jurisdictional, legislative, climatic (e.g. ice regimes) and geographic landscapes present unique challenges for methods, data availability, and tools used to set e-flow regimes. Nature-mimicking approaches are also employed to enhance the ecological integrity of estimated flow regimes by imitating key elements of natural hydrographs and geomorphic features. More holistic approaches and scientific reviews may supplement studies, particularly when complex technical and societal issues are involved. Plans for new or modified hydroelectric projects strive to balance power generation with social and economic considerations, as well as river flow regimes for ecological needs, including fish and fish habitat. [ABSTRACT FROM AUTHOR]

Concern over effects of climate warming on shallow northern lakes elicits need for agency-led, long-term, biomonitoring programs to implement protocols applicable across large, remote landscapes. Here, we analyze composition of periphytic diatom communities accrued on artificial-substrate samplers in 33 and 48 lakes spanning broad hydrological gradients of the lake-rich Old Crow Flats (Yukon, Canada) during ice-free seasons of 2008 and 2009, respectively, to explore the ability of this approach to discern ecological responses to differences in basin hydrology and water chemistry. Multivariate analyses demonstrate water chemistry and periphytic diatom community composition differ among three isotope-defined hydrological lake categories (snowmelt-dominated, rainfall-dominated, intermediate). Some snowmelt-dominated lakes support moderate percent abundances of Rossithidium pusilla, Sellaphora laevissima, Tabellaria flocculosa str. III and T. fenestrata, associated with relatively high concentrations of major nutrients and DOC. Rainfall-dominated lakes have higher pH and ion content, yet diatom composition overlapped extensively with intermediate and snowmelt-dominated lakes. Water chemistry and diatom community composition did not differ between study years, despite almost four-fold greater snowfall in 2009. Thus, periphytic diatom communities on artificial-substrate samplers capture ecological differences across hydro-limnological gradients of Old Crow Flats, but longer time-series of data are required to assess their ability to track temporal responses to hydro-climatic variation. [ABSTRACT FROM AUTHOR]