Abstract/Summary

Coastal power stations use sea water as a coolant. The cooling waters discharges released by nuclear power stations, referred to in this thesis as thermal plumes, result in locally raised temperatures of the surrounding environments in the coastal regions. Since raised temperatures can impact aquatic flora and fauna, there are environmental permits and policies describing the limits for the allowed maximum temperatures of the discharged thermal plumes. It is therefore of paramount importance that we can characterise the industrial thermal plumes to a sufficient extent. Achieving this using traditional methods has been challenging due to high cost of the field campaigns, high dependence on weather and no repetition of the measuring campaigns. Access to freely available high-resolution satellite imagery has opened up a potentially viable way of characterising surface thermal plumes through satellite remote sensing. Such observations present an opportunity to study sea surface temperature (SST) distributions in the vicinity of the power stations at spatial resolution of 30 m - 100 m and temporal resolution of up to 16 days. To evaluate the potential of high resolution remote sensing, a methodology for thermal plume detection is developed. Thermal plumes observed by the satellite imagery show high dependence on the tidal conditions for the majority of the investigated sites. The plumes have been found to be embedded within the tidal stream and their direction of dispersion followed the direction of the tidal currents. The observed surface thermal gains were highest in the summer months and lowest in the winter months. In order to gain understanding of plume dispersion subsurface, high resolution three dimensional (3-D) simulations coupled with satellite observations were used. Plume dispersion was modelled for an inter-tidal area during the ebb and the flood tide using FLOW-3D software. The simulated plume was found to raise to the surface and spread depending on the strength and direction of the tidal currents, with limited area of raised temperatures at the seabed concentrated close to the discharge pipes. Available satellite data was used to compare with the simulation outputs and gain validation of the high resolution 3-D model of the plume. Despite the potential of high resolution satellite data sets and 3-D simulations in understanding industrial thermal plumes, a thorough evaluation of their capabilities, limitations and a consideration of routine use of such techniques and scientific advances compared to traditional methods have not been fully explored in previous studies. This work provides a detailed comparison of thermal plume characterisation methods, their limitations and recommendations for future set-up.