With a fish-eye view of dams, Verena Fernandes makes the case for engineers to adapt designs based on animal behaviour science to improve the impact on wildlife and nature.
For centuries, dams allowed humans to store water for dry season, create navigable water channels, and generate energy through hydroelectric power plants.
However, if we look from a fish’s perspective, it may not be so beneficial. For them, dams and other hydraulic structures can be insurmountable obstacles.
The problem from the salmon’s point of view
Many fish species, like the Atlantic salmon (Salmo salar), need unobstructed waterways because they depend on different conditions throughout their lifecycle. Atlantic salmon are born in the upper course of rivers and migrate to the seas or oceans, where they find better food supplies to grow and mature. Once they reach adulthood and it's time for reproduction, open waters are no longer the most favourable environment; salmon must swim upstream to lay their eggs.
The restriction of migration can lead to short-term consequences as well as devastating long-term problems.
The immediate effect is the reduction in the fish count, which can have an impact on local communities that rely on the fishery. In the long run, the effect can be the unbalance of the local environment, with many other species being affected.
The approach to help salmon
Engineers are very inventive in creating solutions to remedy the salmon’s problems.
What started in the 19th century with side channels for fish, developed in the present to fish ladders, fish elevators, pre-cast concrete or plastic bypass devices. In emergency situations, even pressurised tubes, known as the Whooshh system, are employed to transport fish from one side of a dam to the other.
Nevertheless, most of the time, the approach is reactive.
It's rare for wildlife to take precedence among priorities when it comes to surveys and preliminary studies in the development of an infrastructure project. Frequently, wildlife is seen as a constraint which narrows down the possibilities for innovative and sustainable solutions.
Implemented solutions don't always work as expected. There have been examples recorded in which fish tried to take shortcuts through hydroelectric turbines, resulting in tragic endings, and/or fish just not being able to find the entrance to the bypass, and as result, not using the devices in an effective way.
Regulations and guidance
The European Water Framework (2000) sets the standards for what it means for a river or water channel to be in a good ecological state, including not only parameters for water quality and quantity, but also standards in terms of biodiversity and natural-like balance. The aim is to bring water bodies to good or very good ecological states.
Since the EU Water Framework, a lot of effort has been made to develop methods to proactively tackle the problem by changing perspective: turning attention away from hydraulic engineering towards other fields of knowledge, for instance, ethohydraulic.
The science behind it
Ethohydraulic is the combination of ethology and hydraulic. Ethology is a field of science that objectively studies the behaviour of organisms when exposed to stimuli from their surroundings.
The ethohydraulic research usually follows a few steps:
- Study of the design or existing structure looking at geometric parameters and hydraulic conditions. This will allow the construction of a physical model in a laboratory to mimic the real situation. It's usually not viable to replicate the real structure on a 1:1 scale, so the models are, in most cases, built with reduced scales, preserving similarity with the real structure.
- Living fish are entered into the model and their behaviour is observed. Scientists may vary conditions, such as geometry features, flow velocities and directions, flow impulses, turbulence, to test how they will react to variations.
- The results are interpreted, and recommendations are made to orient design changes and propose alterations to existing structures.
With this interdisciplinary approach, engineers, biologists, and ecologists learn which stimuli can make salmon identify a favourable route for migration, to ensure we're not blindly building bypasses and hoping they will work.
Change of paradigm
I was a student when I first heard about fish bypasses.
At the time, it was something that had never crossed my mind: I was impressed that there were people working on these. Later, when I started working, I realised how difficult it is to balance all potential impacts of a project, putting all pieces together to ensure we're doing everything we can to reduce the impact.
As mentioned, the EU Water Framework provided the general guideline, however, there are still no standard solutions. The cost to achieve fit-for-purpose devices through ethohydraulic research can be high, nevertheless, the cost of not approaching the risks, and not considering the impacts of infrastructure on fish, can be even higher. We can no longer ignore the impact infrastructure delivery and operation causes on the planet.
Our duty, as engineers, is to promote innovative solutions and contribute to sustainable development. Eliminate, reduce, and mitigate the impacts of infrastructure shall be our end goal, not only a design checklist exercise.
The change of perspective to see beyond the superficial consequences can help us learn from others' experiences. This is something that we can do by being curious, asking questions and allowing ourselves to look beyond strictly engineering matters.
I definitely believe engineers must promote innovative sustainable solutions. A change of mindset is required, so why don’t we start now, asking the salmon?
