What are the ongoing issues affecting the River Cam?

Summer in Cambridge is a time when usually the River Cam is full of visitors punting past King's College, yet just a few hundred metres downstream safety concern have been raised that could threaten the future of the waterway.

Jesus Green Lock in the city centre has been closed since May 2024 because of structural issues, and on Thursday parts of the nearby embankment were closed off due to severe deterioration.

Now a report commissioned by Cambridge City Council has revealed the extent of underwater erosion of the lock's structure.

Jesus Green Lock is maintained by The Conservators of the River Cam, an organisation originally set up to look after the River Cam in the 1700s.

The organisation's income comes from fees it charges users of the river. It currently does not receive any taxpayer money, but city councillors have previously called for this to change.

Cambridge City Council is responsible for the section of the embankment that has been closed off.

Cheney Payne, the Liberal Democrat councillor for Castle ward, visited the area and described a "collapse" of the bank which had "given way" next to the lock.

Since the lock was closed, two surveys have been carried out by Hestur Limited on behalf of Cambridge City Council.

The reports, obtained by the BBC as part of an Environment Information Regulations request, said erosion has "revealed timber piles" and was probably in part due to "inadequate repairs in the past".

It said previous repairs to a wall did "not reflect the brick used in the original construction".

"This coupled with the standard of workmanship has been a significant contributory factor in the current conditions found," the report stated.

The report did not indicate how long ago those repairs were carried out and highlighted the lock was first built in circa 1832.

The lock is Grade II listed, therefore any works may require listed building consent, and the report questions "whether the repairs carried out to date were undertaken with such consent in place".

Cambridge city councillor have previously raised concerns around water quality of the River Cam.

Eleanor Toye-Scott, a Green Party councillor, raised the most recent motion earlier this month, which called for the recognition of water depletion on future development and voiced concerns about sewage discharge in the river.

The motion claimed there were 1,700 sewage incidents in 2025.

Payne has also raised concerns about the long-term effects of the Jesus Green Lock closure, citing fears that the water level in the Cam could reduce and become a "muddy trickle".

Cambridge City Council said it was "working at pace to appoint a contractor" to repair the embankment near Jesus Lock.

"The condition of the riverbank continues to be monitored and appropriate safety measures will stay in place or be adjusted as necessary.

"The issue relates to the condition of the riverbank structure itself and is not the result of a wider collapse," it added.

David Goode, the chair of the Cam Conservators, said the group and the city council were hoping to carry out works to the bank at the same time.

"We've had a price back, it's commercially confidential at this time.... the council are going out to tender in the very near future.

"We hope that by getting that job done by a single contractor... both the city council and the conservancy will get a better price and will be able to work together and get the Cam back into a condition that everyone wants it to be."

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