Session C8: Development of Criteria for the Design and Dimensioning of Fish-Friendly Intakes for Small Hydropower Plant

Groningen, The Netherlands

Abstract:

To conciliate the hydroelectric production and the restoration and protection plans of migratory species, in particular salmon (Salmo salar), sea trout (Salmo trutta) and eel (Anguilla anguilla), and more generally the longitudinal continuity for fish species, it is necessary to avoid or at least reduce damages to fish passing through turbines. The best way to reduce fish mortality would be to install fish-friendly turbines, but it is not a cost-effective solution on existing installations and in the present state of the art their use is very limited in terms of head and discharge ranges. Transforming conventional intakes into socalled “fish-friendly” ones is therefore considered as one of the most acceptable solutions. We present here the development of criteria for the design and dimensioning of fishfriendly intakes for small hydropower plants in France (up to ≈ 100 m3/s until now). These criteria were established from the feedback following the evaluation of existing downstream bypasses in France and abroad, and from hydraulic studies on downscale models. Fish-friendly intakes comprise a trashrack designed to guide fish towards its downstream end and to the entrances of bypasses, through which fish safely reach the tailwater. Criteria concern (1) the clear space between bars to avoid the passage of fish through the trashrack and via turbines, (2) the inclination or angulation of the rack to guide fish towards the bypasses located at its downstream end, (3) the normal velocity through the rack to avoid fish impingement, and (4) the number, positions, dimensions, and discharge of bypasses to collect the fish. New formulae have also been proposed to evaluate head-losses for inclined or angled trashracks with low bar-spacing.

https://scholarworks.umass.edu/fishpassage_conference/2015/June24/16