Citizen Crane volunteers at the three downstream sites in the river (Donkey Wood, Crane Park Island and Mill Road) have reported a pollution event - with low numbers of invertebrates in both January and February alongside extensive fungal blooms. The problem is particularly severe at Donkey Wood (see photo of the bloom from 5th March 2018) and appears to be linked to the outfall from Heathrow’s Eastern Balancing Reservoir.

The findings are being investigated by the Environment Agency as well as Heathrow. Historically, periods of cold weather have been followed by fungal blooms and linked to the use of glycol as a de-icer at the airport. Given the Citizen Crane data precede the recent severe cold weather last week then this problem may well intensify in the coming days and weeks. Our next survey will be on the weekend of 17th March.

FORCE understand the growth causes harm to invertebrates by smothering the river gravels and depriving them of oxygen. It should not be a risk to human health – although of course anyone going into the river should always carefully wash their hands before eating or drinking. FORCE are in regular contact with Heathrow and the EA and will report any further information we receive. It is suggested that anyone with dogs looks at the water first and keep them out if there is a lot of fungus. The amount will vary with time and location but could be present anywhere downstream of Donkey Wood to the Thames. It should not harm the dog but could be a major job to clean out of their fur. 

Judging from the experience of previous years the fungal growths will slowly dissipate over the next few months – and the river would benefit from heavy rainfall and high flushing flows.

Heathrow has responded to this long standing problem with interim improvements to the handling system at the Eastern Balancing Reservoir from this year and a new £17m treatment system is planned to be open by next winter. Hopefully this will be the last winter with glycol related pollution at this scale.



FORCE statement 9 March 2018