Overview

• Monitoring of 2024 data shows 464 combined sewer overflow sites inside English and Welsh national parks with an average 549 spill hours each and a total of 254,808 hours.
• Only 42% of water bodies in national parks met good ecological status, leaving about 57% failing the legal standard despite these landscapes’ protected status.
• Dartmoor recorded 49,076 spill hours and Eryri (Snowdonia) 47,187, with hotspots such as the Lymington River in the New Forest logging 2,800 hours.
• Campaigners attribute the scale to ageing, undersized infrastructure plus farm runoff and toxic contaminants, and they seek statutory targets including fixing all CSOs by 2035 and universal secondary treatment.
• The government cites a planned regulatory overhaul with new laws slated for 2026 and over £104bn of private investment, while water firms outline upgrades and timelines, including targeted overflows in the South Downs and New Forest and staged improvements in Dartmoor by 2035–2040.