The Environment Agency and the University of Stirling have published a new report on the links between phosphorus concentrations and ecology in English rivers.

Phosphorus remains one of the most significant pollutants in England’s rivers. In recent decades, the overall concentration of phosphorous in English rivers has declined, most likely due to the introduction of phosphorus removal technologies at Sewage Treatment Works (STWs), changes to fertiliser use and adoption of best management practices in agriculture.

The new report, published on March 2, found that rivers where phosphorus concentrations dropped by larger amounts were more likely to show ecological improvement.

Reduced phosphorus levels and improved ecological indicators were both strongly associated with rivers in Eutrophic Sensitive Areas where significant investment in phosphorus removal at sewage treatment works has occurred - with 30 of 38 sites showing dual improvement (phosphate and River Macrophyte Nutrient Index).

Most catchments in England face multiple pressures with several significant water management issues needing to be tackled, before ecology can fully recover, underlining the importance of integrated catchment planning.

We continue to make progress towards the government's Environment Improvement Plan targets, set in the Environment Act 2021, for reducing nutrient pollution from wastewater.

For agriculture, this is being achieved through an expanded regulatory farm inspection programme, and our contributions to farm advice and incentive schemes, including Catchment Sensitive Farming and Environmental Land Management schemes.

Phosphorus reduction at sewage treatment works is one element of a comprehensive strategy that includes river basin management planning, coordinated drainage and wastewater management, and increasing investment in nature-based solutions.

Professor Nigel Willby, of the University of Stirling's Faculty of Natural Sciences, who specialises in freshwater sciences said: "Phosphorus is a significant pressure on freshwaters and sewage treatment is a major source of this phosphorus. Managing nutrient inputs should therefore benefit the ecological health of rivers.

"In this study, using data from hundreds of sites on English rivers with long runs of overlapping data on nutrients and biology, we found encouragingly that phosphorus levels have widely improved on a decadal scale.

"Biological improvements were commoner where phosphorus had also been reduced, often coinciding with the largest reductions in phosphorus, but were patchy and often took years to emerge. Nutrient loads to rivers evidently can be managed to give positive ecological outcomes but these are not quick or guaranteed wins."

Environment Agency's Chief Scientist Rob Bradburne said: “Our scientific evidence and data are crucial to understanding and tracking progress, enabling us to assess the impacts of decades of investment and regulation designed to reduce phosphorus pollution.

“This research confirms that phosphorus reduction in rivers is leading to ecological recovery with aquatic plant life beginning to shift towards a more diverse range of species.

“We need to maintain momentum and continue to bring nutrient levels down through wastewater management, river basin management planning and utilising nature-based solutions.”