
Catchment Nutrient Balancing (CNB) Approach in the Petteril Catchment, Cumbria
Improving the Calthwaite Beck rural catchment water quality through Catchment Nutrient Balancing (CNB)
In the video below, James Airton, Natural Capital Strategy and Planning Manager at United Utilities presents a case study delivered in a tributary of the River Petteril, Calthwaite Beck, in Cumbria, UK, where the Catchment Nutrient Balancing (CNB) permitting approach was first piloted, bringing together local stakeholders to improve the health of the river through integrated catchment management.
This approach to CNB was piloted in the Calthwaite area of the Petteril catchment from 2019 to 2023. It was co-developed and tested by United Utilities (UU), the water company of the North-West of England, with the environmental regulator (the Environment Agency) and other key catchment stakeholders, as a new flexible permitting approach to achieving phosphorus reduction targets for a water company, based on the contribution from their wastewater discharges to phosphorus pollution in the river (their “fair share”), as required by the WFD.
This case study shows that the adoption of CNB, which enabled the delivery of integrated catchment approaches, led to a significant reduction in phosphorus loads, beyond regulatory requirements at Calthwaite WwTW, and an improvement in water quality in Calthwaite Beck from “poor” to “moderate” ecological status. The findings highlight the importance of collaborative engagement and taking a holistic approach to catchment management, to achieve visible results for regulatory performance and water quality compliance.
The content used for this introduction to the Calthwaite Beck CNB case study comes from a paper published in the Water Research Journal, In association with the International Water Association. The full paper, ‘Using an innovative Catchment Nutrient Balancing (CNB) approach to improve river water quality: A case study from rural sub catchment in Cumbria, United Kingdom’ can be downloaded here.
Calthwaite CNB Trial Results
Location
Calthwaite Beck rural catchment
Impact
60% reduction in catchment load vs 9% target
Longevity
Catchment reductions sustained for 3 years
Project Stakeholders

United Utilities

Eden Rivers Trust

Environment Agency

Natural England

Natural Course

Lancaster University
