Thesis Work – Overcoming hydraulic barriers: Design, construction, and hydraulic evaluation of a tube-fishway for juvenile eel trap-and-transport

About the Thesis Work

To comply with the European Water Framework Directive, which aims to achieve a “good” ecological status of all rivers, the national ongoing hydropower relicensing process (NAP) in Sweden works towards mitigating the environmental impacts of hydropower production. This, for example, includes the preservation and reinstatement of upstream and downstream river connectivity, necessary for many fish species to complete their life cycles, including the critical endangered European eel (Anguilla Anguilla).

After a long transoceanic journey from the Sargasso Sea, juvenile eels – known as elver - enter European rivers in search of feeding and nursing habitat where they can grow and mature. During their upstream migration, they often encounter multiple barriers, including hydraulic structures like dams and hydropower plants, which can severely hinder their passage. To support elver migration past these obstacles, trap-and-transport methods may be employed. This approach involves capturing and collecting elver at the base of such structures, and manually relocating them to upstream habitats.

While trap-and-transport can be an effective method to support upstream migration, it is often labour-intensive and can cause stress to fish due to frequent handling. This highlights the need to streamline the process by reducing manual intervention and minimizing fish handling. One proposed solution is to integrate a tube fishway system with an existing floating elver collector, creating a more automated and less intrusive means of transferring elvers. Tube fishways are closed conduit systems with dual pipes and valves designed to surge fish over barriers. While tube fishways have shown promising results in laboratory and field trials, their suitability for European species and their integration into trap-and-transport systems have yet to be explored.

The following tasks shall be completed as part of the thesis:

• Literature review on tube fishways, include operational concept, system components, hydraulic and hydrodynamic characterization of the surge phase, and fish behavioral response
• Design and construction of a laboratory prototype tube fishway, adapted specifically for elver trap and transport
• Experimental evaluation of the hydraulic and hydrodynamic conditions within the prototype under controlled conditions
• Adaptation and expansion of an existing numerical model to simulate flow conditions, transport time and capacity inside the tube fishway
• Development of recommendations for system improvement and potential installation of the prototype in a field setting

Your Profile

We are looking for a student or students who want to work towards fossil freedom and who are about to graduate from their academic studies. You are also someone who identifies with our principles: Active, Open, Positive, and Safety.

The applicant should have a background in environmental, hydraulic, or civil engineering (or similar), with a foundational understanding of hydraulics and fluid mechanics, and a keen interest in applying engineering solutions to ecological challenges such as fish migration. The applicant should enjoy hands-on experimental work and interdisciplinary approaches that bridge aquatic ecology and hydraulic design.

English language is a requirement.

The thesis is designed for one student and 30 credit points (approx. 6 months).

Please check with your course or module advisor for suitability before applying for this thesis.

• Start date: January/February 2026 or by agreement.
• Location: Älvkarleby, Sweden; a hybrid solution can be discussed
• Application – one file containing your CV and a copy of your transcripts.
• Application deadline: 2025-10-26.
• Contact person and supervisor at Vattenfall: Stephanie Mueller, +46 702135112, stephanie.mueller@vattenfall.com

Diversity and Inclusion – In Everything We Do

We are convinced that heterogeneous teams can outperform homogeneous ones. But we can only unlock the power of diversity when everyone feels included. Read more about our important work on diversity and inclusion at https://careers.vattenfall.com/se/sv/jobba-med-oss/mangfald-inkludering.

About Vattenfall

At Vattenfall, we are determined to enable fossil freedom. To succeed, we must first become fully fossil-free ourselves as one of Europe’s largest energy companies. But that is not enough. To contribute to a fossil-free society, we need to do more than just focus on sustainable energy production.

We believe that enabling fossil freedom requires us to address the challenge from a broader perspective than merely producing energy sustainably.

Join us on the journey towards fossil freedom.

As Vattenfall is part of Sweden’s critical infrastructure, many of our roles are security-classified. This means that, if this position is security-classified, final candidates may be subject to a special security clearance in accordance with the Security Protection Act.

To enable the fossil freedom that drives society forward – this is our purpose. We are looking for talented students who want to help us on our journey towards fossil freedom. By writing a thesis at Vattenfall, you will have a unique opportunity to contribute to our purpose.