Airborne remote sensing observations of topographic steering of cooling water discharges into coastal and estuarine waters

The interaction of cooling water discharges with tidal currents in coastal and estuarine sites having complex surrounding topography is very difficult to monitor by conventional boat surveys. Effective monitoring of this interaction is very important because of its consequences for the fate of effluent discharges at such sites. The synoptic capability of remote sensing, together with the high temporal and spatial resolutions offered by airborne remote sensing systems, make such techniques very useful for monitoring effluent discharges of this type. In this study, thermal infrared data from the Daedalus AADS 1268 Airborne Thematic Mapper have been used to study the dynamics of cooling water effluent fields affected by ambient water tides and complex surrounding topography at three nuclear power station sites in the UK, namely, Hunterston and Torness on the west and east coast of Scotland respectively, and Wylfa on the north coast of Wales. It is demonstrated that under certain tidal conditions for these sites, the surrounding topography plays a significant role in the dynamics of the cooling water discharge fields, by steering the resulting effluent field, and hence affecting the level of mixing of the effluent with the receiving ambient water. The study has also confirmed the usefulness of the so-called length scale approach (see, for example Fischer et al., 1979) for the analysis and interpretation of cooling water plume trajectories, by demonstrating the significance of these length scales on surface thermal infrared images of cooling water effluent fields in a cross flow at one these sites.