Research and analysis

INVEST: Investigating the vulnerability of estuarine water quality to climate change: summary

Published 27 February 2026

Applies to England

1. Chief Scientist’s Group report summary

This project used hydrological models and climate projections to investigate how the water quality of English estuaries may be impacted by climate change. As estuaries are important from both ecological and economic perspectives, this project will help inform adaptation strategies to ensure estuaries remain healthy and productive.

1.1 Background

Estuaries provide valuable ecological and economic services, but it is unclear how they will be impacted by climate change. There have been studies of individual estuaries, but little examining impacts on a national scale. Residence times (how long water remains in an estuary) are the primary driver of estuarine water quality, but again, little information exists for this crucial variable. As residence times are driven by hydrology, it is likely to be impacted by climate change. As such there has been a clear research gap hindering effective adaptation to climate change within estuaries.

1.2 Approach

The project used UK climate projections under a high emission scenario (UKCP18, RCP 8.5) as a basis for future conditions along with downscaled ocean and hydrological models. These were used to generate projections of changes in physical variables (temperature, salinity, residual surge) and provide inputs to 3D estuary models. These enabled an analysis of present-day conditions and how they will change into the near future (2020-2040) and far future (2060-2080) for all major (52) English estuaries. Additionally, hourly resolution projections of river flows were available for 10 estuaries. This enabled granular analysis of how changes in freshwater hydrology may impact estuarine environments. The 3D estuary models were used to calibrate simplified estuary box models. These box models are far more computationally efficient than the 3D models and can provide estimates of residence times under a much wider range of flow and tidal conditions.

1.3 Results

The project delivered projections of changes to sea surface temperatures, salinity, residual surge, and residence times for 52 English estuaries up to 2080. All estuaries are projected to warm substantially by the end of the century (annual maxima increase by 3.8-5.3oC), with estuaries in the North East experiencing the greatest warming (>0.6oC per decade). Such temperatures may persist for days or weeks. Residence times and salinities are projected to decrease in all estuaries, though the magnitude and pattern is highly variable between estuaries. Estuary morphology plays a major role in susceptibility to changes. Where available, river flow projections indicate that coincident events (for example, low flow/high surge) and extremes (flash floods and low flows) will become more frequent.

1.4 Conclusions

These results mark the first national-scale assessment of present-day English estuarine residence times, providing an extensive foundation for future work. The projections of future change fill a significant research gap for adaptation within estuaries. The findings are highly relevant for those working on estuarine ecology, water quality, and industrial clusters by providing projections of future conditions that can inform adaptation and regulatory strategies.  

1.5 Publication details

This summary relates to information from project SC230019 reported in detail in the following output:

• Report: SC230019
• Title: INVEST: Investigating the vulnerability of estuarine water quality to climate change
• Project managers: Alec Hutchings and Nick Hayes, Climate Change and Resource Efficiency, Chief Scientist’s Group
• Research contractor: Bangor University

This project was commissioned by the Environment Agency’s Chief Scientist’s Group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.

Enquiries: research@environment-agency.gov.uk.

© Environment Agency