Author(s): Margaret Kadiri; Reza Ahmadian; Bettina Bockelmann-Evans; David Kay; Roger Falconer
Keywords: Eutrophication; Tidal barrage; Severn Estuary; Nutrients; Renewable energy
Abstract: The potential impacts of two different modes of operation of a tidal barrage (i. e. ebb-only and flood-ebb operating modes) on the eutrophication potential of the Severn Estuary were assessed in this study using a simple modelling approach adopted by the UK’s Comprehensive Studies Task Team (CSTT). The model predictions were compared against CSTT thresholds for assessing eutrophication in estuaries and coastal waters. The estuary was found to be potentially eutrophic under no barrage conditions as well as under the ebb-only and the flood-ebb operating modes. Potential maximum primary production was found to be significantly higher under the ebb-only and the flood-ebb operating modes compared to the no barrage condition. This is believed to be a direct consequence of increased water residence time and greater light availability behind the barrage. However, the conditions for phytoplankton growth are likely to be more favorable under ebb-only operating mode as the potential maximum primary production was found to be significantly greater under ebb-only operating mode with largely decreased turbidity compared to flood-ebb operating mode with only a small reduction in turbidity.