Water quality testing

Update July 2023

Eric Dougall of Bristol City Council Harbour staff has informed us that water quality testing will be resumed in Bathurst Basin, starting in July. The resumption of testing is most welcome news to all users of the Basin.

The latest readings for selected sites are available on the Bristol City Council webpage on water quality.

FOBB campaign

Water quality testing in Bathurst Basin was conducted monthly from April 1994 until October 2012, when it ceased. Following a Freedom of Information request by FOBB, the water was tested on three occasions – 13th, 20th and 27th September 2019. However, testing throughout the Floating Harbour was suspended at the start of the COVID-19 pandemic and when testing resumed on 7th July 2020,  Bathurst Basin was not included.

We have asked Bristol City Council to explain why water quality testing in the Basin has been discontinued again. We contacted Kathy Derrick, Sustainable City Team Manager, Bristol City Council and she offered two explanations:

  1. Sampling takes place ‘to provide knowledge to recreational users, boaters and working staff who may come into contact with the quality of the water – essentially the bacteria present, as an indicator of pollution’.  She continued: ‘Our understanding from the Harbour Master is that all water sport users originate from the Baltic Wharf end and that they only spend a fraction of their time in Bathurst Basin.’
  2. Weekly testing takes place at St Augustine’s Reach, Prince Street Bridge and Redcliffe Bridge. According to Kathy Derrick, ‘the data we collect from these sites is considered to be representative of the water quality in Bathurst Basin and therefore we do not consider it necessary to recommence sampling in Bathurst Basin’.

We have challenged both responses:

  1. The Avon Scout & Guide Canoe Club are based on Redcliffe Quay and they use Bathurst Basin to develop their skills, including recovery from capsizing. Bathurst Basin is also much used by other canoeists, kayakers, paddle-boarders as there is little or no boat traffic to disturb them.  And the Lower Guinea Street quay offers instructors and parents clear view of training activities.
  2. We have analysed water quality test data over the period April 1994 to March 2020 and compared readings at different locations taken on the same day. High readings at Baltic Wharf will trigger daily testing throughout the harbour and users would be advised to avoid using the harbour. Is the water quality reading at Baltic Wharf a good indicator of its quality in Bathurst Basin? For 293 tests conducted on the same day, Bathurst Basin e-coli readings were only weakly correlated with those taken at Baltic Wharf (correlation coefficients presented below). To illustrate: on 13th August 2019 the e-coli reading in Bathurst Basin was 4,000 CFUs compared with just 200 CFUs in Baltic Wharf. Total coliform and e-coli readings in Bathurst Basin are also only weakly correlated with those taken in St Augustine’s Reach, Redcliffe Bridge and Prince Street Bridge (details below). Water quality varies a great deal around the Floating Harbour.



We frequently observe enthusiasts, many of them children, entering the water in Bathurst Basin either by accident or as part of their training. If the cessation of Bathurst Basin testing was a cost-cutting exercise, it would make more sense to cease tests at one of the other test sites, like Prince Street Bridge where water sports activities do not take place. Parents and instructors of those developing their skills in the quiet water of Bathurst Basin need to be confident that their children are in a safe and clean environment.

Correlation coefficients

Measures how closely water quality readings in Bathurst Basin follow those at other sites taken on the same day. The closer the coefficient is to 1, the stronger the correlation.

Baltic Wharf: e-coli 0.516 (291 obs); total coliforms 0.666 (291 obs);
St Augustine’s Parade: e-coli 0.536 (286 obs); total coliforms 0.684 (285 obs);
Prince Street: e-coli 0.862 (287 obs); total coliforms 0.576 (285 obs);
Prince Street (removing one outlier): e-coli 0.609 (286 obs);
Redcliffe Bridge: e-coli 0.533 (106 obs); total coliforms 0.455 (105 obs).

Data obtained from the City Council Bristol Floating Harbour bacteriological water quality web page.

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