Welsh Harp Reservoir draining reveals litter and 'secret river'

However, the removal of around 400 Olympic sized swimming pools worth  of water from Welsh Harp Reservoir in Brent has also exposed something else. Litter, and lots of it.

The Brent Reservoir was built in 1835 to supply water to the Grand Union Canal. It is a Site of Special Scientific Interest (SSSI) due to the birds breeding in the surrounding wetlands, as well as being home to 16 protected plant species.

The work is being carried out after crowdfunding from the Canal and River Trust charity. (Image: Martin Francis / LDRS)

In October last year, the Canal and River Trust – a national charity that looks after the site – began a five month, £2 million maintenance project to repair the sluice gates that control the water levels in the reservoir. 

As well as revealing the ‘secret river’ – called the Silk Stream – that was originally dammed to form the reservoir, the drainage of around one million cubic metres of water, which took around four weeks to complete, also provides a “unique opportunity” to remove rubbish that has been dumped over the years.

The trust set-up a crowdfunding campaign which aims to raise £15,000 to fund the removal of “tonnes of litter” that has been washed or dumped into the water. The site is frequently a victim of fly-tipping and rubbish also enters the reservoir via the River Brent and the Silk Stream.

The Silk Stream (Image: Martin Francis / LDRS)

The Canal and River Trust’s director for London and the South East, Ros Daniels, said: “The Welsh Harp, with Brent Reservoir at its heart, is one of London’s most significant urban wild spaces. […] Sadly, local wildlife is fighting a constant battle against plastic pollution and fly-tipping from external sources.”

He added: “Over the years our reservoir has filled with rubbish, threatening the health of water birds and all the wildlife that makes its home here.

"But now we have a unique opportunity, while the reservoir is drained for maintenance work, to clear up the reservoir for both nature and people.”

During the draining process, it was also necessary to remove the many thousand fish that call the reservoir their home. It’s estimated that more than 100,000 fish have been rescued since the process started – including a massive mirror carp much to the shock of two contractors brought in to carry out the operation.

It’s achieved with the use of electro-fishing, which involves passing an electric current through the water to temporarily stop the fish from swimming whereby they can be more easily netted. The rescued fish will then be rehomed in “nearby canal locations”.

The reservoir’s water supply comes from the River Brent and the Silk Stream. When the work is complete, the sluice gates will be closed to allow the reservoir to refill, which is expected to take between two and four weeks. The refill is expected to be complete by the end of February, with the project to be finished by March.

The Canal and River Trust national fisheries and angling manager, John Ellis, said: “When the reservoir has refilled with water, we plan to restock it with native fish species, including roach and perch, beginning in the spring and completed next autumn and winter.”