Blenheim Palace: Water and Macroinvertebrate Sampling & Assessment


Blenheim Park, near Woodstock, Oxfordshire, is notified a Site of Special Scientific Interest (SSSI), and comprises an extensive area of ancient oak-dominated pasture woodland and a lake, which is one of the largest areas of open water in Oxfordshire and is of regional importance for breeding and wintering birds. The EC Water Framework Directive (WFD) (2006/60/EC) requires that all waterbodies meet ‘good ecological status’ by 2027. Over the past decade, however, there has been a perceived decline in the ecological quality of Blenheim Lake.

BSG Ecology’s role in the project

BSG Ecology was commissioned to investigate the current chemical and ecological status of Blenheim Lake and the River Glyme which feeds into it, and to make an assessment as to whether discharge from Woodstock Sewage Treatment Works was likely to be having a detrimental impact on water quality.

A sampling protocol was designed in consultation with Natural England and the Environment Agency, and comprised monthly water sampling and a Common Standards Monitoring condition assessment of the lake, as well as regular water and macroinvertebrate sampling of the River Glyme. A desk study analysis of historical Environment Agency chemical and biological data was also undertaken. Macroinvertebrate data were analysed using the River Invertebrate Classification Tool (RICT) and water quality assessments were made with reference to current WFD standards for lakes and rivers.


BSG Ecology produced a detailed report that provided an assessment of the overall quality of Blenheim Lake, recommendations for future monitoring and high-level advice on remediation measures for the lake. Our surveys provided evidence that Blenheim Lake is in unfavourable ecological condition due to its hyper-eutrophic state, and that this is likely to be having a variety of impacts on the lake’s biological diversity and ecosystem function.

BSG Ecology will work closely with Blenheim Estates, the Environment Agency, English Heritage and other key stakeholders over the coming months and years to produce and implement a management plan for the lake and upstream catchment, with the key aim of restoring the lake to favourable ecological status.


Blenheim Estates

Key Services

Heritage, South East