Council steps up efforts to tackle river weed

Date issued: 30 July 2020

Colchester Borough Council has increased patrols along a section of the River Colne, in a bid to control a seasonal build-up of surface weed.

Park Rangers have begun regular checks between East Bay and the site of the former lido near Colne Bank roundabout to monitor the growth and spread of the invasive green algae, which often flourishes on slow-moving watercourses during the warm summer months.

At least once a week, and more frequently when water levels allow, rangers open the weir gate at Middle Mill to help flush the weed downstream to East Bay and into the tidal stretch of the river from where – under normal conditions – it can flow onwards to the sea.

As a result, the build-up of weed between Colne Bank roundabout and Lower Castle Park is significantly less this year compared to last summer, when near-record-breaking temperatures and a lack of rainfall saw some sections of the river choked with weed.

However, despite ongoing measures to tackle the problem upstream, prevailing winds and possible water abstraction for a local reservoir have combined to slow movement downstream, at the East Bay end of the river, where over 200 metres of weed has amassed bank to bank. It means, unless substantially more rainfall boosts water levels and enables weir gates to open more frequently, specialist equipment may be required to shift it in the coming weeks.

Cllr Martin Goss, Portfolio Holder for Waste, Environment & Transportation, said: “Last year’s prolonged heatwave caused many rivers in the UK, including the Colne, to produce an over-abundance of algae. 
 
“With the weather being cooler this year – with less sunshine and more rainfall – the overall condition of the river has been a great deal better, with much less algae growth. There is, however, a short section where surface weed is more extensive than elsewhere and so we have asked the Environment Agency to undertake a health-check, including measuring oxygen levels, to ensure wildlife is safe.

“I would like to thank our Park Rangers for their efforts to tackle this recurring issue. As well as working closely with the Environment Agency to find an effective and lasting solution to the surface weed problem, we also continue to explore a range of measures, in consultation with users and stakeholders, to protect and enhance the fragile ecology of the River Colne, while boosting recreational and other amenity uses that it can sustain.

“This work will give rise, in due course, to a vision document for the river that will serve to protect and enhance its status as a natural and community asset.”
 
In early spring, Park Rangers worked to remove willow branches overhanging the river and causing an obstruction. To improve flow, several logjams and other debris were also removed from a section of the river in Castle Park, as well as a large blockage from beneath the Cricket Club bridge