The experimental eel deterrence system, at the Enel Green Power dam in Creva on the Tresa river (Province of Varese, Italy), has been activated since January 2024!!

The intake structure of the Enel Green Power plant in Creva (Luino, Italy), adjacent to the dam, consists of two large spans, through which the water passes towards the hydroelectric plant. The spans are protected by two large grids in order to avoid the entry of floating bodies, they have a vertical development of about 16 m and are characterized by a spacing of 80 mm between the bars. The objective of the experimental deterrent system installed is to create a luminous “barrier” capable of discouraging adult migrating eels from entering the intake structure and thus diverting their transit towards the fish pass.

The installation of the system was a complex task because it required the intervention of divers specialized in operating in critical environments, moreover, the entire construction phase required constant coordination with Enel Green Power personnel to implement the stop of hydroelectric production and to program the water levels of the reservoir based on the activities of the construction site.

Let’s see in detail how this system is made. The deterrent system consists of 60 “lighting fixtures” mounted on custom-made stainless-steel brackets, which have been fixed to the IPE beams (positioned horizontally) present to support the two protective grids of the intake structure (one per span). The lighting covers are arranged in groups of 3 out of the 10 IPE beams present in each span over the entire height (about 16 m), for a total of 60 lamps (see project table). Each lamp is equipped with an independent power cable and an underwater connector located near the lamp, so that each individual light fixture can be easily replaced. The power cables are then progressively collected on a steel rope that rises on the edge until it reaches an electrical control panel, positioned inside the sluice gate room. The electrical panel, in addition to powering the 60 lamps with a low-voltage direct current, allows you to:

  1. program the days and hours of operation of the lamps;
  2. adjust the light intensity of the lighting fixtures and the “steady light” or “strobe light” mode;
  3. adjust the frequency of the strobe light (1 -> 30 Hz);
  4. have a diagnostic system that allows you to know the status of each illuminating body;
  5. check that only the lamps that are below the water level are switched on thanks to a water level sensor.

Some adult eels were equipped with tags (capable of providing information on their movements) and released at the same time of the deterrence system activation. This will help to evaluate the effectiveness of the system installed.

We will talk about this activity and the first results of the monitoring in a next article!

Stay tuned!

In the gallery there are some images of the construction phases and the video of the system.