Assessing climate change impacts on the water quality of Scottish standing waters

Scotland’s Centre of Expertise for Waters (CREW)
April 28, 2022

The recent UK Climate Change Committee (2022) Report to Scottish Parliament makes clear that ‘Scotland lacks effective monitoring and evaluation systems meaning that changes in aspects of many climate-related risks are largely unknown’. There is now an urgent need for evidence to evaluate climate change impacts to inform fit for purpose mitigation/adaptation strategies that can be created and implemented in Scotland without delay. These will safeguard the integrity, biodiversity and sustainable use of the water environment, for people and for nature.

The overall aim of this project was to compile and assess the key evidence available to improve our understanding of climate change impacts on the water quality of Scottish standing waters at national, regional and local scales. The project focused on the interactions between climate change, the drivers of eutrophication problems and their impacts. We synthesised information from the literature, expert opinion and monitoring data, and used statistical analyses and visualisation (mainly mapping) combined with climate change scenario modelling to address six strategic water research questions.

The key findings were that:

• Climate change is affecting the water quality of Scottish standing waters, specifically in relation to algal blooms, at multiple scales; mostly through increases in air temperatures and changes in rainfall patterns.
• Increases in Scottish loch and reservoir temperatures are closely related to changes in air temperatures; rapid and extensive climate change-driven warming of these standing waters has already occurred in recent years and is expected to continue increasing.
• Water temperature increases in many lochs and reservoirs have already been recorded; standing waters are projected to get warmer in the south and east of Scotland but this climate-related risk will spread further and reach all parts of Scotland by 2040.
• Climate change will increase the risk of algal blooms developing in Scottish lochs and reservoirs – especially potentially harmful cyanobacteria.
• Increases in algal blooms are often associated with a higher risk of potentially harmful toxins from cyanobacteria being released into the water; the likelihood of this occurring will increase with warmer temperatures and lower flushing rates.
• Currently, all types of Scottish standing waters in all areas and locations are at high risk of climate change impacts.
• Different types of lochs and reservoirs will respond differently to climate change impacts, with some more likely to develop water quality issues than others.
• Water temperatures across different types of lochs and reservoirs are already warming in most places; this climate-driven trend is projected to further increase from south to north, with an exacerbated water temperature situation expanding to all parts of Scotland by 2040.
• Climate change driven increases in water temperature and nutrient availability, and reductions in flushing rates, will increase the risk of water quality issues developing in Scottish lochs and reservoirs.
• Scottish loch and reservoir sensitivity factors will affect the risk of water quality issues developing due to climate change impacts.
• A whole system approach needs to be taken to mitigate future climate change impacts on standing waters.
• An integrated catchment-based approach needs to be taken for setting water quality targets and planning interventions.

This project made key recommendations on changes needed to adapt water policy and existing monitoring networks as part of Scotland’s strategic and coordinated response to the climate crisis, as well as informing the research direction and future phases of work.

View the report on 'Assessing climate change impacts on the water quality of Scottish standing waters', published by CREW – Scotland’s Centre of Expertise for Waters.

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