The Archimedes hydro screw is an efficient and environmentally friendly method of generating hydroelectric power, utilising the natural flow of water to drive a rotating screw.

However, its implementation can create barriers for migratory fish species, disrupting their natural life cycle. Fish ladders provide an engineered solution to this challenge by allowing fish to bypass the obstruction while maintaining the ecological integrity of the waterway.

SWJ Consulting worked closely with the Environment Agency to design a fish ladder for migrating eels and salmon to reach their feeding grounds on the River Goyt in Stockport, Greater Manchester. An 18th Century Grade II Listed Cotton Spinning Mill, called Pear Mill, was to be powered by a 100kW Archimedes Hydroscrew, and a fish ladder was required. Read more here.

The fish ladders must be strategically positioned alongside or even within the hydropower infrastructure to optimise both energy efficiency and ecological function.

Considerations for Fish Ladder Design

There are several things to consider when designing a fish ladder, it is not just the structural requirements of the ladder and/or baffles that and allow the fish to pass, but the resting pools required for different species, as there are limits on the vertical heights and distance the fish could be expected to swim without rest. It’s important to balance the flow of the water with the overall height of the damn and provide rest pools for the fish. Other considerations include:

Hydraulic Design and Flow Control. The ladder design needs to ensure that water flow through it mimics the natural river conditions, providing a steady and manageable velocity to support fish movement. Flow rate calculations are critical to prevent excessive turbulence or stagnation, which could discourage fish passage.

Material Selection and Durability. Typically, Fish ladders are constructed using reinforced concrete, steel, or durable polymers to withstand constant water exposure and environmental wear. Anti-corrosion treatments, like galvanisation, and proper sealing techniques help ensure longevity in aquatic conditions.

Structural Stability and Load Considerations. The design must account for hydrostatic and dynamic loads, including changes in water levels and potential debris that could happen with the change of seasons. Winter can bring a rise in water levels and leaves and debris blown into the ladder in Autumn. Proper anchoring and reinforcement strategies must also be applied to prevent the ladder failing if there is bank erosion or the soil moves.

Compliance with Environmental Regulations

We work closely with the Environment Agency to ensure the fish ladder design complies with local and international environmental guidelines, including fish passage requirements and sustainability standards. They may require monitoring systems to be integrated to assess performance and make necessary adjustments over time.

Incorporating a fish ladder into an Archimedes hydro screw system is a crucial step in balancing hydroelectric efficiency with ecological preservation.

By applying structural engineering principles, and working closely with environmental experts, SWJ Consulting are able to help optimise hydraulic performance while creating an effective fish passage solution to support both energy production and aquatic biodiversity. The design and integration of these structures ensure that renewable energy projects can contribute positively to both human and environmental needs.

If you are working on a hydroelectric project give SWJ Consulting a call on 01993 225 085 Oxfordshire office, 02381 920 656 Southampton, or email mail@swjconsulting.co.uk