Following a successful trial to improve fish migration combining an industrial dam and modern hydropower, work is now underway to make those changes a permanent reality.
A collaborative partnership with the Scottish Environment Protection Agency (SEPA) and the Galloway Fisheries Trust has enabled Drax, Galloway Hydro Scheme’s operator, to increase flows in the river and alter the frequency, duration and volume of ‘freshets’ (which mimic natural rainfall events) to help fish move up the river and migrate towards their spawning grounds.
Commissioned in 1935, the Galloway Hydro Scheme was the first large scale, integrated hydroelectric complex to be built in Britain. Dams, while an integral part of hydropower generation, can have a significant impact on the health of rivers and fish passage.
All salmon and sea trout ascending the River Dee in Kirkcudbright to spawn must first negotiate just over a kilometre of river before reaching the fish ladder at Tongland Dam. Previous research showed that some fish were taking days, or even weeks, to travel up this section. Salmon might be expected to travel a kilometre in an hour during active migration, so it’s hoped that the changes made to increase baseflows and freshet volumes will help fish have an easier and faster journey upstream, giving them the best chance possible of reaching the fish ladder and migrating further up the River Dee.
Fish biologists from the Galloway Fisheries Trust used their specialist knowledge of the river system and identified three main pinch points which migratory fish entering the river system must negotiate. It is important that flows over these pinch points help rather than hinder fish from travelling upstream and gaining access to the wider catchment.
After work which included flow trials to determine the optimal flows, Drax have voluntarily worked with SEPA to introduce a higher baseline compensation flow and supplementary freshet regime at key migration times between April and November. Early evidence from this activity suggests these increased flows could be assisting fish in their journey upstream.
This one-of-a-kind project sees the structure of the dam remaining unaltered while the utilisation of the water resources used by the hydro power plant is modified, to find the right balance between the generation of renewable power and river ecology.
SEPA continue to work closely with Drax through the River Basin Management Plan to identify opportunities to improve the ecological status of watercourses within the catchment.
The rivers Dee and Ken are home to the Galloway Hydro Scheme which spans approximately 900 km2 and incorporates numerous dams and power stations, producing a substantial amount of renewable energy each year.
Gillian Martin, Acting Cabinet Secretary for Net Zero and Energy, said:
“I welcome the collaborative approach taken by SEPA, Galloway Fisheries Trust and Drax to improve fish migration at the Galloway Hydro Scheme.
“This work will support the delivery of Scotland’s third River Basin Management Plan (RBMP) and our Wild Salmon Strategy to build resilience in our water environment and to protect and restore populations of wild Atlantic salmon in Scotland.”
David Harley, Head of Water at SEPA, said:
“At SEPA, we recognise the vital importance of renewable energy in our fight against climate change. However, it’s equally crucial that we safeguard the health and vitality of our rivers. The Galloway Hydro Scheme has been here since the 1930s, so these changes are the biggest improvements for migratory fish at this location in almost 100 years.
“We believe renewable energy can work in harmony with preserving our natural resources and, through our collaborative efforts with Drax and the Galloway Fisheries Trust, we aim to set a positive example for addressing similar challenges across Scotland.
“The trials have shown positive signs encouraging migratory fish to move up the river, a testament to the time and effort spent on this project by both Drax and the Galloway Fisheries Trust, alongside teams from across SEPA.”
Martin McGhie, Operations Manager for the Galloway Hydro Scheme, said:
“Protecting the natural environment in which our hydro power schemes operate is a key objective for Drax. Our Galloway Hydro Scheme has been operating within the Ken and Dee catchment for almost 90 years, however with the number of migratory fish entering this and other river systems under increasing pressure, we recognise the importance of ensuring the river conditions are optimised.
“Working in partnership with SEPA and the Galloway Fisheries Trust, we have been able to establish a baseline compensation flow and freshet release pattern that will support and encourage fish migration through a critical section of the catchment.”
Rowan McCleary, Biologist at Galloway Fisheries Trust, said:
“With returns of Atlantic salmon to the Kirkcudbrightshire Dee at an all-time low, it cannot be stressed enough how important the investment Drax and SEPA have pledged towards improving fish passage beneath Tongland is. Initial data suggests fish are positively reacting to this alteration in the compensation flow regime and with continual monitoring, we can help ensure that collaboratively, we deliver a brighter future for migratory fish returning to the Dee.
“This project supports our long-term goal to ensure the Dee can support a sustainable salmon population and we look forward to continuing our work with Drax and SEPA during this important phase of environmental improvements taking place at the bottom of the Dee.”
