Ida Tavner

Tidal Lagoon Swansea

Location: Swansea, Wales

Ida Tavner is: technical Specialist Fisheries at Natural Resources Wales. One of the task that Ida has on her plate is environmental risk assessment . The day that I met her we went to the Swansea bay. She showed me the fish passage that allow fish to get into the basin above and future upstream.

Apart from that, she told me about the developments surrounding the tidal lagoon planned for Swansea bay. The government has decided to not invest further in the project and because of this the project may not have any future. The main claim made by the Wales government is that the tidal lagoon is simply to expensive in retrospect to offshore windmill parks. It is however a very interesting learning moment.

Planning a project of this magnitude has a lot of players involved. All these different parties have different wishes and together they aim to solve each other differences. 

One of the major challenges: is assessing the impacts of tidal barrages on fish. There is little to non existing knowledge how they will affect fish. Both migratory fish who might migrate to and from rivers in the vicinity, or indeed for some barrages need to cross the barrage to reach the river, but also for fish who live in the estuary or near the coast, close to the proposed development. 

Tidal lagoon or barrages rely of huge amounts of water going through the turbines to generate energy and this mean that there is potential for fish going through the turbines where they will be at risk from being struck by the turbines. Models have been developed for freshwater hydro power turbines which can be used to model the likelihood of fish being killed or damaged going through the turbines, but you also have to model how many fish will potentially encounter the turbines in the first place and this is a big challenge. There is little known about how migrating fish use these near coast and estuarien environments  so producing a model which is suitable to use in these very dynamic environments is incredibly hard.

Natural Resources Wales has been working with interested parties, such as Crown Estate, the marine renewable sector body Offshore Renewable Joint Industry Programme  (ORJIP) and others to identify and prioritise how these evidence gaps gets plugged. But in many cases plugging the gaps require large scale expensive fish tracking projects, hence we need a multi- body effort to address and finance the research. These days getting funding for some of these projects is not so easy.

Even Though tidal barrages is nothing new, this does not mean there is data regarding fish. For example in the 1960’s tidal barrage La Rance was build, St Malo France. However this one was built before there was environmental legislation. There is now an environmental legislation  which requires detailed environmental impact assessment to be done. Similarly, other tidal energy projects such as Annapolis in bay of Fundy, Canada were also build decades ago. So there are some important learning points from these, but none that are sufficiently similar to the proposals for tidal lagoons at Swansea or Cardiff to use as a ‘blue print’.  

For Natural Resources Wales this evidence gap, makes things difficult because as a regulator they need to balance the risk of this type of developments in light of the application gotten from the developer. Considering all the unknowns in the assessment from the developer and ensure that the risk have been correctly identified and can be mitigated against. But there are so many unknowns which makes difficult for us, the developer and for other stakeholders, such as fishing interests.

The only way to start making headway to address the evidence gaps for marine renewable energy: is working collaboratively across agencies, governments and industry.