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Climate change affecting Scotland’s lochs and reservoirs

New research shows water is warming rapidly.

Climate change has already caused a rapid and extensive warming of Scotland’s lochs and reservoirs with impacts expected to intensify, research has revealed for the first time.

A report published today by Scotland’s Centre of Expertise for Waters (CREW), shows that between 2015 and 2019, 97% of monitored Scottish lochs and reservoirs have increased in temperature. While most warmed by up to 1.0°C per year over this period, 9% increased by more than that – some by up to 1.3°C per year.

Researchers warn that these changes increase the risk of harmful algal blooms developing, which could restrict their use for recreation and water supply, and as a safe habitat for wildlife.

It is expected that waters in the south and east of Scotland are expected to warm the most at first, but this climate-related impact will reach all parts of the country by 2040.

The report makes a number of recommendations to address these impacts in the immediate term, as well as further research to improve our understanding of climate impacts on the complex functioning of lochs and reservoirs.

Environment Minister Mairi McAllan said:

“This important research provides yet more worrying evidence of the risks of harm from climate change on Scotland’s water environment. It is vital that we do more to mitigate those impacts, to seek to reduce the pace of warming but also to adapt to it.  We have committed £243 million since 2015 through the Agri-Environment Climate Scheme to support land management practices which protect and enhance Scotland’s natural heritage, improve water quality, manage flood risk and mitigate and adapt to climate change.

“Scotland is renowned worldwide for the quality of our water. Research like this will be hugely valuable in informing the development of policy solutions and measures to mitigate and adapt to climate change, and also protect, restore and enhance these vital natural assets.”

Freshwater ecologist Dr Linda May of the UK Centre for Ecology & Hydrology (UKCEH), lead author of the report, said:

“This research has shown, for the first time, that climate change is already warming our lochs and reservoirs in Scotland, and that this trend is likely to continue.

“It provides early warning of the potential impacts of climate change on biodiversity, water supply and recreational use, and highlights the need for mitigation measures to be put in place as quickly as possible.”

Dr Pauline Lang, project manager for CREW, said:

“This pioneering research led by experts at the UK Centre for Ecology & Hydrology demonstrates that, without intervention, climate-driven risk is projected to further increase by 2040.  To prevent the modelled scenarios becoming reality, we trust the recommendations proposed will enable effective climate action for safeguarding freshwaters now and during the critical decades ahead.

“This project is a great example of how CREW can pivot towards Scotland’s water-related needs by bringing a community of researchers and stakeholders together to collaborate on addressing the most important environmental concerns of this time.”

NatureScot Freshwater and Wetlands Advice Manager Iain Sime said:

“Scotland, like the rest of the world, is facing an unprecedented climate emergency. The findings of this comprehensive review are stark, demonstrating the impact that climate change is already having on our freshwater lochs and reservoirs, and their biodiversity.

“The need for urgent action is clear, and at NatureScot we are using the £65m Nature Restoration Fund to prioritise efforts that support the conservation of our lochs and ponds.”

Scottish Environment Protection Agency (SEPA) Senior Ecologist Ian Milne said:

“CREW’s report, which used SEPA data from 142 lochs and reservoirs, is important in highlighting some of the climate change pressures Scotland’s environment is facing.

“The findings emphasise the significance of SEPA’s ongoing work to tackle the threats of climate change and biodiversity loss, which is being done in partnership with Scottish Government, local authorities, Scottish Water, environment and community groups, farmers, land managers and others through our River Basin Management Plans.”


Assessing climate change impacts on the water quality of Scottish standing waters has been developed by Scotland’s Centre of Expertise for Waters (CREW), in collaboration with NatureScot, SEPA, Scottish Water, Scottish Government and a team of researchers from the UK Centre for Ecology & Hydrology (UKCEH).

Monitoring between 2015 and 2019 showed that there was an increase in water temperature at 97% of Scottish lochs and reservoirs for which there were sufficient data.

While most (88%) warmed by 0.25°C to 1.0°C per year over this period, 9% increased by more than that – some by up to 1.3°C per year.

Warming and changes in rainfall patterns associated with climate change increase the risk of outbreaks of harmful algal blooms, which outcompete other freshwater plant species and produce toxins that can affect animals and people.

The report makes a number of recommendations; these include reducing the amount of phosphorus and nitrogen entering lochs and reservoirs from their catchments, because these are the main driver of algal blooms. Sources of these plant nutrients - present in synthetic fertilisers as well as human and animal waste - include farm runoff and waste water discharges. Actions, such as the creation of buffer strips and constructed wetlands, are already under way in many catchments across Scotland aimed at reducing nutrient inputs.

Funded by the Scottish Government, Scotland's Centre of Expertise for Waters (CREW) is a partnership between the James Hutton Institute and Scottish higher education and research institutes.


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