Mapping eutrophication risk from climate change: Future phosphorus concentrations in English rivers

Area of Science:

• Environmental Science
• Hydrology
• Water Quality Management

Background:

• Climate change is projected to exacerbate river eutrophication.
• Phosphorus is a key driver of eutrophication in English rivers.
• Reduced river flows, especially in summer, can increase phosphorus concentrations due to lower dilution.

Purpose of the Study:

• To assess the national-scale risk of eutrophication in English rivers under climate change scenarios.
• To evaluate the impact of future river flows and sewage treatment levels on phosphorus concentrations.
• To identify the timescale and spatial extent of potential eutrophication impacts.

Main Methods:

• Utilized a load apportionment model to analyze the relationship between river flow and total reactive phosphorus (TRP) at 115 sites across England.
• Estimated TRP concentrations for the 2050s using 11 climate change scenarios for river flows.
• Incorporated scenarios of current and enhanced sewage treatment levels.

Main Results:

• National maps indicate a slight, variable increase in annual average TRP concentrations, with more significant changes projected for summer.
• Reducing final sewage effluent TRP to 0.5mg/L P at all upstream treatment works was insufficient to meet EU Water Framework Directive standards.
• The study highlights that current and proposed mitigation measures may not be adequate to prevent eutrophication.

Conclusions:

• Climate change poses a significant risk to river water quality through increased eutrophication.
• Enhanced sewage treatment alone is insufficient to mitigate phosphorus pollution.
• Reducing diffuse pollution is crucial alongside improved wastewater management to protect river ecosystems.