Loch Leven, UK

For Demo sites: Buffer strips, shore-line wetland, habitat creation.

For Innovation Measures: Rainwater gardens.

Site description

Loch Leven is a large, shallow, lowland lake in Scotland, UK (13.3 km2 area; 3.9 m mean depth). Although original lake had a surface area of 17.8 km2 and a mean depth of 5.3 m, this changed when sluice gates were installed in 1839 to ensure a more stable water supply for downstream industry. The lake has every high conservation value as a Natura 2000 site, a Ramsar wetland and a National Nature Reserve. Its catchment covers an area of 145 km2 of which 80 per cent is used for intensive agriculture, 11 per cent for woodland and the remainder for habitation. When damaging algal blooms began to occur in the late 1970s/early 1980s, the size and severity of those blooms was found to be directly linked to the amount of phosphorus in the water. The main sources of this phosphorus were found to be runoff from farmland, effluent from wastewater treatment works and industry, and seasonal releases from the lake sediments. During the late 1980s, blooms of cyanobacteria caused fish kills and reduced amenity value, so a long-term programme of restoration was put in place. This aimed to enable restoration targets to be met by reducing the amount of nutrients (especially phosphorus) entering the lake by about 50 per cent.

Restoration measures applied

Between 1985 and 1995, wastewater treatment works were upgraded to tertiary treatment, industrial effluent was diverted, and buffer strips were installed along field margins, especially in erosion sensitive catchments. In addition, a new planning regulation was introduced to ensure that any new or upgraded rural properties did not increase the phosphorus input to the lake.

Current goals of restoration at the site

As a result of these interventions, the restoration targets set by the catchment management group had been met by 2007. Compliance continued until 2016, when algal blooms returned. As this appears to have been an effect of climate change, current goals for restoration and sustainable management include the combined mitigation of eutrophication and climate change impacts. A number of technical innovations and nature-based interventions are being considered to achieve this.

Sectors involved in lake basin management

Stakeholders include agricultural and wastewater sectors, and the tourism industry. The lake also provides recreational facilities such as angling, wildlife/bird watching, rambling and cycling. Regulatory and conservation bodies are responsible for ensuring good water quality and improving biodiversity at the site. The lake is privately owned and is also used by local schools for teaching.

Further reading

• May, L., Taylor, P., Thackeray, S., Spears, B., Gunn, I., Erica Zaja, Gouldsbrough, L., Hannah, M., Glendell, M., Gagkas, Z., Troldborg, M., Roberts M., Adams, K. 2024. Mitigating Climate Change Impacts on the Water Quality of Scottish Standing Waters. CRW2022_03. Centre of Expertise for Waters (CREW). Available online at: https://www.crew.ac.uk/publication/mitigating-climate-change-phase-2. ISBN: 978-1-911706-17-5. (Accessed 01/01/2025).
• May, L., Taylor, P., Gunn, I.D.M, Thackeray, S.J., Carvalho, L.R., Corr, M., Dobel, A.J., Grant, A., Nash, G., Robinson, E., Spears, B.M. 2022. Assessing climate change impacts on the water quality of Scottish standing waters. Main Report. CRW2020_01. Scotland’s Centre of Expertise for Waters (CREW). Available online here. ISBN 978-0-902701-03-8. (Accessed 01/01/2025).
• May, L., Olszewska, J., Dobel, A., Grant, A. and Spears, B. 2022. The potential role of nitrogen in the restoration of Loch Leven, a shallow loch in the Scottish Lowlands. Report to Scottish Environment, Food and Agriculture Research Institutes (SEFARI), 11 pp.
• D’Arcy, B.J., Kuhfuss, L., May, L., Audsley, R. 2022. Chapter 14: Socio-economic Impacts of Pollution & Restoration: Loch Leven Case Study, UK. In: Kajitvichyanukul & D’Arcy (eds.) Land Use and Water Quality – the impacts of diffuse pollution. IWA Publishing. https://doi.org/10.2166/9781789061123_213
• Spears, B.M., Ives, S.C., May, L. 2020. Loch Leven, UK: long-term (1985 to 2016) phosphorus dynamics in a shallow lake and its implications for water-quality management. In: Steinman, & Spears (eds.) Internal phosphorus loading in lakes: causes, case studies, and management. Plantation, Florida, J. Ross Publishing, 223-242.
• May, L., Spears, B. 2012. Loch Leven: 40 years of scientific research. Understanding the links between pollution, climate change and ecological response. Developments in Hydrobiology 218, 132pp. ISBN 978-94-007-4332-8.
• Spears, B.M., Defew, L.H., Heal, K., D’Arcy, B., May, L. 2011. The importance of aquatic plants in regulating stream bed sediment structure and phosphorus transport through the Loch Leven catchment. IWA Diffuse Pollution and Eutrophication Conference, New Zealand, September 2011.
• Loch Leven Catchment Management Plan. 1999. Loch Leven Catchment Management Plan. Report of the Loch Leven Area Management Advisory Group, 93 pp.