Environmental Flows
‘Releases from the Dee’s Reservoirs are done in an environmentally suitable way as possible’
The River Dee has one of the most highly regulated flow regimes in Europe. Water releases from man-made reservoirs and Wales’s largest natural lake are carefully managed to provide drinking water, reduce flood risk, and support recreation.
While this management is essential, the timing and pattern of flows can have unintended impacts on river wildlife, particularly on habitats and species that depend on natural flow variation.
Key challenges include:
- Hydropeaking – rapid fluctuations in water levels, particularly on the Tryweryn, which can disrupt habitats and create a hostile environment for wildlife
- Spate clipping – the dampening of natural high and low flows in the main Dee, reducing the frequency and duration of key cues that trigger fish migration
- Barriers – Bala sluice gates and Manley Hall Weir are essential for managing water flows, but they can delay the upstream and downstream migration of fish
Through this programme, the Dee Trust works to understand these impacts and identify practical changes that could improve conditions for wildlife while maintaining the benefits the river provides for people.
