Water Quality

This page introduces our water quality testing work. We want to understand the sources of the poor water quality in our local rivers so we can get the pollution stopped. 

You can see our test results here, and our advice to swimmers here.

CVF’s two main concerns are the health risk from bacteria and viruses from human and animal faecal sources, and secondly the detrimental effects of eutrophication. Eutrophication is the process by which rivers become excessively enriched with minerals and nutrients such as nitrate and phosphate. This has a significant detrimental effect on the ecological balance of the river and increases the growth of algae and invasive plants such as Floating Pennywort. Excessive plant growth reduces biodiversity, sensitive plants suited to low nutrients decline, and plant decomposition by bacteria results in reduced oxygen levels which harms invertebrates, fish and other wildlife.

We all want Chalk streams – and the Cam is one – to be crystal clear and unpolluted.  We all want the Cam to become cleaner and less eutrophic. This needs both less pollution, and clean water to dilute and wash away contamination. However, in summer the water levels in our aquifier are now so low that the “natural” flow rate reduces significantly, which increases the concentrations of organisms arising from sewage effluent, of soluble nutrients and of other pollutants. In an attempt to maintain river flows and reduce the concentrations to permitted levels, water is pumped out of the aquifier into the rivers.

This circular process of abstracting scarce water from the aquifer and then augmenting the Chalk streams is ecological madness: we need to reduce  the pollution at source.

To try to find out where the pollution is coming from locally, we are monitoring water quality.  To explore faecal contamination, we are taking water samples at strategic points and having them analysed for E. coli and intestinal enterococci bacteria, which is well recognised as a reliable indicator of human faeces (poo) contaminating the water. We are also sampling for phosphate and nitrate.

You can see our test results here

Advice to swimmers and river users

The official current standards for Designated Bathing Waters in England are based on multiple bacterial counts by the Environment Agency over a summer season which are used to give the waters a classification status for the following season.  Unfortunately, even though lots of people swim in the Cam, the Environment Agency is not testing the Cam as there are no ‘designated stretches’. 

Although we expect that swimmers and other river users will find the results of great interest, however please note that our results should NOT be used as guidance as to where or when it is safe to swim.  We are amateur volunteers, and although our test samples are analysed by a UKAS accredited professional lab, we are NOT testing according to statutory standards set by Defra. 

There may be nasty human pathogenic organisms in the river that our indicator bacteria counts don’t reveal, and we know that changes in the weather and rainfall will influence the results. For examples, some of the sewage treatment works above Cambridge occasionally discharge untreated sewage mixed with storm water (combined sewage overflows – CSOs). 

As our database builds and if results are consistent, we hope we can give a broad view on stretches which appear to be more or less safe.

Our general advice is to

  • Use your own judgement about when and where its safe for you to swim.
  • Never drink water from the Cam (always keep your mouth shut when swimming)
  • Dry off by vigorous rubbing with a towel.
  • Shower as soon as possible after leaving the water, particularly if you’ve got muddy.
  • Don’t swim just downstream of sewage treatment works. 
  • The Rivers Trust advise not to swim in the days after a period of heavy rainfall. 

Don’t forget that some faecal presence in the river is natural.

Do join us.

To continue this work and help clean up the Cam, we very much welcome volunteers to help collect samples, and contributions towards the costs of the lab analysis. This costs around £1000 per set of tests. 

We are grateful to our sponsors and supporters for funding this work

2022 sponsors and supporters

Newnham Riverbank Club.

Other anonymous donors

2021 sponsors and supporters