Is there a cure for St Albans’ diseased Verulamium Lake?

Ducks back at Verulamium lake

Ducks back at Verulamium lake - Credit: Archant

Verulamium lake, recently the upsetting scene of many ducks paralysed and dying of avian botulism, has been likened to a “toxic soup” by a district councillor.

Solutions are still being sought to clean up the tourist drawcard in Verulamium Park, which doubles as a sanctuary for wildfowl.

A significant number of birds died recently after an outbreak of type C avian botulism. Affected birds may be paralysed for three days before dying or recovering.

Methods of dealing with built-up silt at the beauty spot were discussed at a council scrutiny committee meeting last Thursday (5).

Jon Green, parks and green spaces manager, described the lake as a “shallow bowl with a large population of wildfowl, which has been increased with feeding, and that in itself has caused some water pollution.”

He said the lake works as a silt trap, and the council has been investigating ways of improving water quality including using aerators to boost oxygen levels.

Jon said dredging the base would be “extremely expensive” and not worth pursuing as silt would quickly build up again.

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A possible long term solution could be to remove silt from the lake, and put into gabian – wire – baskets filled with stone, that could be planted with aquatic plants to help remove nutrients.

A natural organism that feeds on silt, symbio, is currently being added to the water to help reduce nutrient levels, but the large numbers of waterfowl make this difficult to manage.

Cllr Robert Donald said a £4 million scheme had been in the pipeline years ago to improve the lake, by helping the River Ver flow better and turn it into a ‘proper chalk stream’.

But Verulamium Park ‘suffered’ as Heritage Lottery funding was instead channelled into London 2012.

Cllr Donald dismissed the use of aeration as ‘tinkering’ with the problem.

He said dredging would help if you “create a proper lake [but] it isn’t a proper lake. It is a pond at the moment.

“It heats up like a toxic soup which kills birds and fish.

“If you could get the Ver running through it, it would have a self-cleansing system. The lake needs to be sorted. It is resolvable, but it needs a lot of engineering and cash to do it.”

• Type C avian botulism has not been associated with human disease, but the council has advised visitors against bathing in or drinking the water, and recommends against allowing pets to access it.