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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]

Dams and weirs strongly affect or interrupt the longitudinal connectivity of rivers, by limiting the movements of several fish species while altering and fragmenting habitats. Fishways, especially pool-type fishways, are used to diminish this impact by enabling fish to negotiate barriers. The aim of this work is to study the behaviour of a small-sized resident cyprinid fish, the Iberian chub- Squalius pyrenaicus (Günther, 1868)-within a prototype of a pool-type fishway, equipped with both surface notches and bottom orifices, and experiencing two different flow regimes, plunging and streaming. Results show that the fish tended to be more successful in their upstream movements under streaming flow and that, for this regime, the surface notch was the preferred route for upstream movements. Flow velocity patterns corroborated the results, showing that the plunging flow regime may have driven fish downstream, while the streaming flow regime may have attracted fish upstream. The plunging flow also prevented access of this surface-oriented species to the surface notch, effectively reducing the area available for transport. Thus, the streaming flow regime can be a sound option for this and other small-sized species, as it enhances fish movements through the fishway. [ABSTRACT FROM AUTHOR]