New fish ladder on the Neckar weir: This is how we save the fish in Wendlingen!

New fish ladder on the Neckar weir: This is how we save the fish in Wendlingen!

An important environmental project is making progress in Wendlingen am Neckar: the construction of a modern fish ladder on the Neckar weir has officially started. The existing weir in Wendlingen, which is located at the level of the Otto Quarter, represents an almost insurmountable obstacle for fish. Before the redesign, the old fish ladder that was used to overcome the weir was already defective and ineffective, which is why it is now being replaced by an innovative slot pass.

The new slot pass will be designed to consist of tiered pools that will allow fish to overcome the weir and reach their spawning grounds upstream. The Stuttgart Regional Council initiated this measure to support fish migration and promote biodiversity in the Neckar. The project has a financial scope of 2.5 million euros, which will be borne entirely by the state and should be completed by mid-2026.

Construction work and challenges

Planning for the fish ladder turned out to be challenging. Limited space and underground pipes had to be taken into account, which brought additional complications during implementation. During the construction work there will be obstructions for pedestrians and cyclists, especially since the footbridge over the Neckar will be temporarily closed. Diversions will be set up via the Ulrichsbrücke.

In addition, parts of the existing bank reinforcements will be demolished to make room for the new slot pass. The work also includes the construction of a new flood protection wall and the use of precast concrete elements. At the same time, the operator of the adjacent hydropower plant is optimizing its inlet structure to ensure fish protection.

Technical details about the fish ladder

The new fish ladder is designed as a serpentine-like slot pass that guides the fish past the side of the weir. At the same time, a fish descent system with a lockable “slide” will be installed to enable the fish to overcome the approximately four meter high fall height without injury. These achievements are in line with the requirements of the EU Water Framework Directive, which requires optimal conditions for fish migration.

Fish ladders, or fish passes, are necessary in Germany for several reasons. They help to overcome migration barriers such as weirs and hydroelectric power plants. However, historically, fish ladders have not always been successful, particularly with salmonid species. Innovative solutions such as the new slot pass are intended to improve this in the future and increase the passage of fish in flowing waters.

With these advances, a significant step has been taken to ecologically improve the Neckar in Wendlingen, which not only benefits the fish, but also the entire ecosystem.