Water Quality Test Results

This page shows the results of our water quality tests, analysing for E. coli bacteria (which shows if there’s poo in the water), Phosphates and Nitrates

Zoom into the maps below to see the results of the E.coli tests. Click here to see the key to the maps and an explanation of what the numbers mean. Click here to see an overview of the water quality project.

Phosphate monitoring in the upper Bourn Brook and its tributaries, January to March 2022

This project showed that during this current period of sampling the vast majority of soluble, readily available phosphate measured in the Bourn Brook in the upper catchment originated from the discharged effluent from Bourn Sewage Treatment Works. Download report here.

Bacteria (E.coli) test results on effluent from Haslingfield Sewage Treatment Works 3 March 2022

CVF has successfully sampled a storm overflow event from Haslingfield Sewage Treatment Works.  The results demonstrate that such events are of real concern when it comes to the quality of our River’s water for safer bathing. Download report here

Bacteria (E.coli) test results 19 January 2022

A summary and discussion of the 2021 results is available here

Bacteria (E. coli) test results 24 August 2021

Water Quality Full Test Report No 2 August 2021

Bacteria (E. coli) test results 14 June 2021

Water Quality Full Test Report No1 June 2021


In each of the maps above, the E. coli readings are shown in 4 bands, ranging from the worst quarter for that day, which are shown with deep purple markers, to the best quarter, which are shown in yellow. Click on the marker (a star) to see the reading in units of E. coli/ 100ml of river water. The key Waste Water Treatment Works (which we suspect are the source of much of the problem) are shown by the little tap symbol

The official standards for bathing water are complicated, and based on multiple readings over a period of time. (This is because of the expected variability in readings). However levels of E.coli consistently over 1000 units / 100ml indicate a cause for concern.

For simplicity, we’re setting an aspirational target for the Cam of no more than 100 E. coli/100ml. This is based on the EU’s guidelines for high quality bathing water that are “to be achieved where possible” and the more stringent American standards. Note that drinking water should have no E. coli at all, and all of our readings show more than this.

Do join us. We plan to continue our investigations, and welcome help from those with relevant expertise. We also very much welcome contributions to the costs of the lab analysis, which costs us around £1000 per set of readings.