The return of water and salmon to the River Garry in Perthshire after 60 years is a real testament to the power of partnership working between SEPA, Scottish and Southern Energy (SSE) and the Tay District Salmon Fishery Board.
By working together the three organisations, along with other local stakeholders, have been able to balance delivering real environmental improvements, which will benefit the local community and economy, with sustained renewable energy production.
The river was one of the most abstracted in Scotland, due to water being diverted as part of the Tummel hydropower scheme, and had a ten mile stretch – much of it visible from the A9 – that had been dry since the mid-1950s. As a result its ecological status was bad.
Earlier this year SSE began removing physical barriers to migratory fish, such as Atlantic salmon, in order to enable this iconic species to access and re-colonise the River Garry. Water is now running through this previously dry stretch and will provide major benefits for adult salmon spawning and juvenile production. Salmon have already been seen in the river, showing that the project is a success – and there is even more work to come.
The ecological and economical balance
Hydro schemes play a vital role in generating renewable energy, but there is a fine balance between power generation and water bodies being substantially altered. Historical schemes such as the one at the River Garry were installed at a time when consideration for the natural environment was not as it is now. As a result what had been a major salmon river in the 19th and early 20th centuries had not seen a fish since a weir was built in the 1950s to stop them entering a river they could not migrate up and spawn in.
The challenge in returning water to the River Garry was ensuring there was enough water to allow salmon to return to the river and use it for spawning, the ecological benefit of reintroducing water to the river, while not impacting the important benefits which renewable energy generation provides to society and our economy.
Under the new arrangements 17 kilometres of habitat will once again be open for salmon to repopulate; 12 kilometres of the River Garry and five kilometres of the Allt Anndeir, which is a Garry tributary. Ecological benefits will also be gained from improved sediment continuity – and of course there will a much healthier general ecology of the river. The benefit to fish (in particular Atlantic salmon) is of course by far the biggest.
Downstream of the outlet, where the Garry meets the Errochty, the removal of the Struan weir means that sediment will flow more naturally into the downstream river (part of the Tay Special Area of Conservation) improving the river health there as well.
Re-watering the River Garry is possibly the biggest single improvement to Scotland’s water environment, and the project is not finished yet. Work has already started to return water to a further six kilometres upstream of the Garry weir.
Rivers such as the Garry which have been substantially changed due to physical alterations by human activity may not be able to meet their full ecological potential, but where we see significant ecological benefits could be achieved we will seek improvements.
Working together to find a solution
In addition to partnership working with external organisations, the work is a great example of cross-directorate working across SEPA.
Pauline Silverman, Water Specialist (hydropower) at SEPA said: “In terms of science, there is a limited set of data and understanding of the direct relationship between flows and ecology: how much water do fish need to re-colonise a river that has been without flow for decades? There is no definitive answer to actively manage flows to ‘mimic’ nature so we had to work together to find a solution that would work for the environment and the economy.
“What we have as a result is a relatively new and innovative approach to river management in Scotland, and there is no doubt that many people will be excited to see how the river develops over time.”
Watch Pauline’s video on Youtube to find out more about her role in the project.
SEPA worked with SSE and the TDSFB to establish how a beneficial flow could be reintroduced. For this we needed to negotiate a low flow that would be maintained as long as there is water in the local environment to practically do so, and higher flows to ensure salmon can migrate up into the river and successfully spawn. We
also needed to consider requirements for different stages in the lifecycles of the fish, sediment transport and movement for river habitats and other ecology, as well as flows to ensure the fish can negotiate tricky natural obstacles – of which there are a few on the lower sections of the river.
Ellen Willmott, Senior Specialist Scientist at SEPA, said: “All parties were involved in flow trials involving the active release of different flows from the weir. During these trials SEPA hydrologists have been out gauging different sections.” Watch Ellen’s video
All of this information has been used to create a monitoring plan which will ensure we can make sure the flows are doing what they need to. Detailed monitoring will ensure that the changes and improvements in flow will deliver the desired or expected outcomes. If they don’t we have the flexibility to try different or alternative solutions to tackle any of the aspects that may not be delivering an expected outcome.
Alistair Duguid, Senior Scientist at SEPA, said: “We have also measured potential available habitat through many transects throughout the whole section of river. There was a flyover with a plane taking 3D sonar pictures of the river to build a model to estimate the changes in habitat depending on flows.” Watch Alistair’s video
The plan is available to interested parties and will be overseen by a technical working group made up of SEPA, SSE and the TDSFB – which will also call on specific expertise if and when required.
The next part of the project will also include working on rewetting a section above the Garry intake weir. SSE’s licence has been varied to ensure a flow will be delivered in the Upper Garry no later than September 2018.
Reaching this point is a fantastic achievement, but it is only the beginning of a series of environmental improvements that the hydropower sector will make over the coming years on some of their historic assets, which were built and commissioned with no flow requirements downstream of dams.