The River Cam is being poisoned by sewage and nutrient overload – an article published in the Walden Local, 29th September 2021.

RICHARD PAVITT, district councillor and co-founder of Cam Upper Reaches Action Team, has been concerned with the river Cam since 2019. This is his latest report.

At the recent Eco Market on the Saffron Walden Common around 200 people picked up a leaflet titled “Our River is Dying.” It was part of an effort by action group CURAT to draw attention to the plight of the River Cam, which is not only critically low but is being poisoned by sewage and nutrient overload.

Several reports and even a parliamentary commission have drawn the same conclusion: England’s rivers are a touchstone  for environmental pollution and after years of neglect are in a dire state. Uttlesford’s rivers are no exception.

Two of these reports were released in September 2021. ’Troubled Waters’ published jointly by the RSPB, National Trust and Salmon & Trout Trust – says “a combination of untreated sewage, agricultural run-off, pesticides, mine pollution, plastics and pharmaceuticals threatens wildlife and has made rivers dangerous to bathe in.”


The problem is particularly bad in the south and east of England where over-abstraction of the chalk aquifer to supply household water is robbing rivers of their natural flow. A low flow means chemical pollution reaches higher concentrations with potentially deadly results for fish and wildlife.

The River Cam is part of a globally-rare network of chalk streams of which there are barely 200 in the world and more than 80% are in England. In 2019 the Cam was at its lowest level since records began 70 years ago.

Agriculture fertilisers have long been a problem but the single greatest contributor to the Cam’s woes has been housing development. Water is extracted from the aquifer via boreholes and piped to households before it reaches the chalk springs that would normally feed the Cam.

Once used, that water enters a sewage infrastructure that has not kept pace. Under investment has resulted in poorly treated water with high levels of phosphate being recycled into the river. Raw sewage also enters the river when rainfall overwhelms the system.  Last year water companies discharged sewage into English waterways 400,000 times over a period of 3.1million hours and that is only what was officially recorded.


Nutrient overload by phosphates and nitrates – from sewage and agriculture – can kill a river. A grey-brown slime coating everything below the water line is a tell-tale sign of excessive phosphate. Nutrients accelerate algae growth and can happen so rapidly that it robs water of oxygen killing fish and other aquatics, a process known as eutrophication. There was a major ‘kill’ on the Uttlesford stretch of the Cam in 2019.

Bacteria are a growing concern. Wild water swimming is popular on the Cam, especially as it nears Cambridge city, however the risks of bacteria from sewage has triggered a study of E.Coli in the water. A site on the river Thames in Oxford hoping to become an officially designated swimming spot has seen bacteria levels in the water at twice the recommended safety threshold, while another site downstream of a sewage works had E.Coli levels regularly at one hundred times the safe level.


Rivers are the lifeblood of biodiversity. Since 1970, freshwater species – not just fish but also birds and mammals reliant on river habitats – have seen an 83 percent decline globally. Destabilising our natural environment and especially our freshwater habitats is having serious consequences.

Rivers will also play an increasingly important role in or ability to cope with climate change as the frequency and severity of both flooding and droughts is likely to increase. Narrowing of the Cam due to sedimentation and phosphate-induced plant growth has increased the risk of  flooding. Ironically, tropical-style downpours do not rapidly refill the store of water in the chalk aquifer since most of the rain is washed out to sea. 

In a YouGov survey this summer, 83 percent of those surveyed said they are concerned about the impact of sewage pollution and 87 percent agree more needs to be done to help the UK’s freshwater habitats.

The ‘Troubled Waters’ report concludes that a properly funded monitoring and enforcement regime is needed to restore England’s “fragmented, polluted and degraded” rivers.

The Rivers Trust, in their report ‘The State of our Rivers’ says “the race to climate resilience will be won or lost on rivers – and right now we’re losing.”

Richard adds:

Numerous charities and action groups are campaigning to clean up England’s rivers. In our area CURAT (Cam Upper Reaches Action Team) was formed in 2020 and co-operates with Cambridge’s Cam Valley Forum and Friends of the Cam. The rivers & environmental campaigner, Feargal Sharkey, has also lent his support to protecting the Cam.

The Environment Agency (EA), a body sponsored by the Department for Environment, Food & Rural Affairs (DEFRA), is responsible for the health of our waterways. According to the EA only 14% of England’s rivers meet the “good” standard laid down by the EU.

Since 2010 Govt has slashed The Environment Agency budget by almost two thirds, leaving the agency incapable of policing the water companies, who have been left to regulate themselves with predictably poor results. Water supply and sewage treatment was privatised in 1989.

In 2012 the European Court of Justice ruled that sewage overflows should only ever be allowed in “exceptional circumstances” but the sheer scale of sewage entering the nation’s rivers suggests this has never been enforced. DEFRA is even suggesting that it should be relaxed to “infrequent” – a legal nicety that reduces still further the likelihood of water companies being held to account.

The Govt has trumpeted that it will “rip up the EU rule book” and put in place better standards – but it is hard to find anyone who believes they will be better. An Environment Bill is currently being batted between the commons and Lords with numerous amendments required by the Lords to make the bill fit for purpose.