Thirlmere Resilience Project

Addressing water supply and climate risks in Cumbria

Sustaining reliable supplies of water, while improving climate resilience across a water catchment is a challenge for many water companies, including United Utilities, which operates in north-west England.

Thirlmere is a 5.6km long reservoir in Cumbria and its wider catchment area has recently experienced both drought and flooding. Storm Desmond in December 2015 caused significant catchment damage, including mobilisation of large volumes of sediment and a rapid increase in turbidity in the reservoir, putting the water supply for 700,000 customers at risk. The storm also damaged vital infrastructure across the country, and many homes and businesses were flooded.

Collaborative efforts for ecosystem restoration

The Thirlmere resilience project is part of United Utilities Catchment Systems Thinking (CaST) approach to managing catchments in a holistic, integrated manner. The project will utilise large-scale land management to restore ecosystems, peatlands and develop a catchment capable of supporting both environmental targets and guaranteeing water supplies for West Cumbria.

The project is a partnership with a range of organisations, including Cumbria Wildlife Trust, John Muir Trust, Natural England, West Cumbria Rivers Trust and the Centre for Ecology and Hydrology at Lancaster University. This collaborative approach provides a platform to understand the broader needs of the catchment and identify the right mechanisms for delivery. Data on weather, water quality, soils and erosion potential and vegetation and habitat quality are being gathered to support the project.

Nature-based solutions will be used to achieve the following:

• Secure a long-term, reliable supply of good quality raw water
• Retain water in the catchment and slow the flow of water to reduce the impacts of flooding and drought
• Stabilise soil and prevent landslips to minimise soil erosion and pollution
• Support a sustainable upland economy and resilient farming businesses
• Restore forest tracks, culverts and footpaths using natural materials
• Create self-sustaining mixed woodland, providing biodiversity and carbon sequestration
• Restore upland peat, and wet and dry heath lands
• Improve biodiversity, disease resilience and soil health
• Halt the decline in carbon carrying capacity and reverse the emission of CO2 from upland areas
• Improve the status of designated sites, such as the Lake District National Park
• Enhance recreation, improve footpaths and public rights of way

Building a sustainable and resilient catchment

In the first five years, peatland surveys will be undertaken to identify areas within the catchment in need of restoration, improve vegetation through management of grazing by sheep and deer and deliver a management plan setting out catchment management measures over a 10- to 40-year period.

Initial benefits of the work have started to emerge after just a few years, but it may take up to 40 years to create a truly sustainable and resilient catchment.