Environmental monitoring

Dissolved oxygen, salinity levels, temperature, pH and a number of other parameters are continuously monitored from 9 locations throughout the Bay. Readings are taken every 15 minutes – you can view the data on the:

Hydrosphere website

The Cardiff Bay Barrage Act states that dissolved oxygen levels must be maintained above 5 milligrams per litre throughout the Bay. This standard was set to protect migratory fish, such as salmon and sea trout, which travel through the Bay on their way to and from their breeding grounds further up the rivers. Salinity levels are measured to ensure that the operation of the Barrage locks and sluice gates minimises the volume of seawater entering the Bay. This is important to ensure that a freshwater environment is maintained. Water samples are taken on a regular basis and analysed for additional water quality parameters, including metal salts and nutrients.

The Harbour Authority worked closely with public health advisors from Shared Regulatory Services and Public Health Wales to develop working practices to minimise the health risks to water users.

Bacterial water samples have been collected for 19 years, and the data derived from these have led to the development of a predictive water quality model. This model is run on a daily basis to predict the water quality in advance, and the output used to inform stakeholders on which activities are possible on that day.

Latest predicted water quality forecast