Author(s): Clarisse Judes; Herve Capra; Agnes Barillier; Nicolas Lamouroux; Veronique Gouraud
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Keywords: No Keywords
Abstract: Hydropower plants managed by “hydropeaking” have a growing key role to play due to the expected future increase in energy demand, and the numerous advantages of these facilities (e. g. renewable energy, efficiency, rapid response to grid demand). However, mitigation measures have to be implemented to decrease their environmental impacts. These hydropower facilities use the available water reserves at the most opportune moment for the generation of electricity and release water stored in dam reservoirs by intermittence. Sudden changes in flow variations within the day or the week are induced in river reaches below plants. These variations are thus more frequent, intense and of shorter duration than natural flow variations related to floods for instance [1]. Hydropeaking cause significant variations in hydraulic parameters (water depth and current velocity) and increase near-bed shear stress. Those hydraulic parameters contributing to fish and macro -invertebrates habitat selection [2,3], physical habitat attractiveness may change rapidly and frequently in river reaches located downstream hydropower plants. This can cause drift of organisms with low swimming ability [4] or stranding of organisms preferentially living close to the shoreline [5,6]. Until today few studies have used flow metrics which describe flow alteration at the sub-daily time scale [7,8] to quantify fish response to hydropeaking. Long -time series of hourly discharge data are generally unavailable. The few existing studies were only interested in salmonidae species [9,10]. Moreover, the impact of hydropeaking on the structure and abundance of the whole fish community were described only qualitatively and were rarely related to hydropeaking characteristics [11,12]. Thus, the goal of our study was to characterize the response of fish assemblages of twenty or so species to variation in discharge by using metrics calculated on series of hourly flow downstream two different dams. We tested if the more intense sub-daily fluctuations they are (in terms of frequency, magnitude, time, duration, ramping rate), a more severe the change in fish community is observed.
Year: 2018