The final design of the fish pass at the Isola Serafini dam

The final design of the fish ladder [download all documents] has been completed. The fish ladder will allow to restore the River Po continuity, still interrupted by the presence of the dam of Isola Serafini, upstream of the confluence of the River Adda, about 300 km from the sea.

The migratory fish species, from the 50s of the last century, cannot exceed the dam in both directions due to the lack of a fish ladder. This situation causes a fragmentation of the populations, which can lead up to extinction. Such as the two other species of sturgeon native in Italy, common Sturgeon (Acipenser sturio) and the Beluga (Huso huso) as well as the sea lamprey (Petromyzon marinus) now disappeared. Euryhaline species such as Cheppia (Alosa fallax) and Thinlip Mullet (Liza ramada) still go back up the river. The river de-fragmentation will make available for the migratory species about 100 Km of the Po River and some of its feeder up to Casale Monferrato (AL). First of all Ticino River, key ground for Adriatic Sturgeon breeding, will be entirely accessible for 110 Km up to Lago Maggiore thanks to two fish ladder built next to the dams of Panperduto and Porto delle Torre. These two works were built also thanks to the two previous Life projects carried out by Parco del Ticino.

The Po de-fragmentation will interest not only big migratory species such as the Sturgeon, Cheppia and the European Eel but also many fish species of refresh water. In fact, these species must carry out migratory movements in order to execute their life-cycle. The reproductive strategy of the freshwater fish is to go back up the river and spawn upstream, in order to fight against the flow towards the sea, which would lead up to shift downstream. Spawn upstream allows species to re-populate also this part of a river but it stands to reason the huge damage provoked to these species if a fragmentation prevents them from spawning upstream. The huge biodiversity of Po River counts many species recognised by the Habitat Directive, and at least ten will take advantages from Po de-fragmentation. In addition to species included in Habitat Directive, there will be others, such as the European Eel, which will take advantages from the fish ladder. The European Eel, now in decline, is the object of a specific European regulation for its conservation implemented through a national plan that includes regional plans of Veneto, Emilia Romagna and Lombardy.

The implementation of this defragmentation project will include a wide area, including the Regions of Veneto, Emilia Romagna, Lombardy and Piedmont, up to and including the canton of Ticino, which would see again connected the Lake Lugano to the water grid of the valley, through the works of defragmentation carried out Tresa River and the River Ticino.

Locally the intervention insists on existing structures carried out for the construction of the dam of Isola Serafini, for hydroelectric use, which have provided the cut of a fluvial meander , creating two separate river courses for about 14 Km. This condition has a direct impact on the project. Therefore solutions have been found for both directions by providing for the realization of works that can reconnect the two branches of the valley with the river upstream.

The making of this fish ladder has the main objective of the reopening of the Po river corridor in this particularly strategic area. The final design represents the technical step essential in order to get the permissions to the concrete carrying out the work.

The final design was preceded by a careful and thorough study devoted to verify the conditions of placement of the work in the territorial, landscape and environmental context, and to ensure its best capabilities and effectiveness for the practicability of fish population.

After establishing the target of the project and identified the constraints for the design, has been defined and developed the final design solution also through a process of comparison and discussion with the representatives for the "Group fish passage" elected under the project Life supervision of this action planning. Particular attention was given to the constructive   confrontation with the managers of the dam of Enel Green Power. Thanks to them have been found useful and necessary solutions to contextualize the fish ladder with the imposing structures of the central and with underground utilities in the area of intervention.

Before reaching the final design were analyzed and compared, developed and then modified, several solutions. The final solution foresees the realization of a double passage Y-shaped, which will be able to connect the river upstream of the dam with the two branches (natural and artificial) of valley, by returning the possibility to go up the river to all native species, from migratory to sedentary, from large fish to those of smaller size.

The fish ladder will also be equipped with a experimental system for capturing, which will eliminate large predators exotic and withdraw temporarily for analysis or other - before their release back into the river - large specimens of endangered species preservation, as sturgeon; it will also house a sophisticated system of continuous monitoring that, in addition to verifying the efficiency of the transition, can be used to study multi-tasking on fish fauna, offering great opportunities for research in the field ichthyological and ecological.

The fish ladder is also designed to accommodate visitors who will be able to appreciate the structure and test the operation, through a viewing chamber, equipped with large windows on the two branches of the passage, which will open to view the underwater environment.

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