Remote-sensing observations and analyses of cooling water discharges from a coastal power-station

Results are reported from a series of remote sensing investigations into the marine discharge of cooling water from a coastal power station complex. Qualitative observations and analyses of the spreading behaviour of the thermal discharge are presented for a range of tidal states, using ATM data from a series of aircraft overflights of the site. It is demonstrated that. under ebb flow conditions. the discharges from two adjacent outfalls are merged into an integrated surface plume in the far-field, and that the plume behaves subsequently as if generated by a single source. It is shown that the lateral spreading of the plume is inhibited significantly by coastal attachment and local thermal forcing and cross-flow effects. Calibrated overflight data from the thermal infrared bands have been used to quantify the unimpeded offshore spreading, and estimates are presented of the transverse turbulent diffusion coefficient epsilon(t) for the site in question. Values of epsilon(t) thus derived are shown to be in satisfactory agreement with estimates made directly at similar sites. Evidence is also presented to show how the presence of suspended sediment in the receiving waters, and the entrainment of bubbles and debris on the surface, can lead to the detection of the thermal discharge in visible and infrared spectral bands.