An estimated 10,000,000 tonnes of sediment is carried up and down the Severn Estuary on a spring tide!

Amelia Chilcott
EIA Coordinator

Water quality refers to the physical, chemical and biological content of the water column. In the UK there are a number of European designations that are designed to protect water quality (e.g. the Water Framework Directive, the Bathing Water Directive and the Shellfish Water Directive) and Tidal Lagoon Power (TLP) has a responsibility to ensure that the likely impacts of any project are assessed against these.

The construction, operation and decommissioning of a tidal lagoon has the potential to affect water quality through a number of different pathways, including: changes in salinity and temperature, changes in sediment movement and concentration (resulting in alterations to oxygen uptake or distribution of contaminants) and changes to the flows and water levels (affecting concentration of pollutants).

In order to assess the likelihood of these potential changes, TLP are able to make use of a number of datasets already currently available. In order to support this information with more localised and detailed data, we are able to commission additional marine water quality surveys where required. Surveys allow the collection of water samples at set locations which can be analysed for salinity, temperature, dissolved chemicals, suspended solids and bacterial concentrations. If necessary, sediment plume modelling can also be undertaken to identify and predict the impacts of an increase in suspended sediment in the water column.

Tidal Lagoon Swansea Bay

As the operational Project will not itself be the source of any significant pollutants it is not expected to generate a direct impact on water quality. However, the Project will potentially have an indirect effect on water quality in Swansea Bay, because the lagoon presents a large obstruction in the Bay which will potentially modify the existing water movement, mixing and pollutant dispersion. In order to assess the effects of the Project on water quality, TLP commissioned a series of numerical models. These models were built around existing models, but were further enhanced and improved using newly available data and bespoke data collected specifically for the Tidal Lagoon Swansea Bay.

Case Study

Tidal Lagoon Plc


T: +44 (0)1452 303892

A: Pillar & Lucy House
Merchants Road
The Docks

Tidal Lagoon (Swansea Bay) Plc


T: +44 (0)1792 274006

A: 8th Floor
One Central Square
CF10 1FS

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