ABSTRACT The present work is focused on the dispersion of a thermal effluent, produced by the Sines power plant, Portugal, along coastal waters. This facility intakes a yearly average around 40 m 3 /s of seawater, for the required cooling process, which is subsequently discharged back to the ocean at a 10 ºC increase in temperature. A three-dimensional hydrodynamic local model was nested into a regional model and set up to simulate the transport of the thermal effluent during two distinct periods, August and October 2013, respectively featuring dominant north and south wind. The simulations were performed for both situations, with and without the thermal discharge, where the later provides baseline scenarios. Obtained model results closely followed the existing field data. The temperature increase is shown to decay from 10 ºC near the outlet vicinity to 2 ºC at a distance of 2 km from the outlet for both scenarios. Even though the main driving force of this phenomenon is the wind, tidal conditions also have additional influence on thermal plume dispersion near the discharge area. In the north wind scenario the plume extends away from the coast while under south wind dominance the plume is contained near the coast, extending towards the inlet. As a consequence there is a positive feedback under south wind dominance, which is caused by the intake of already warm water from the thermal plume itself. Consequently, south wind dominance is the most unfavorable scenario for both coastal environment and the operational efficiency of the power plant. Keywords: Thermal discharge; Three-dimensional model; Coastal hydrodynamics; Water temperature Submission: 8 JAN 2015; Peer review: 1 MAR 2015; Revised: 20 MAY 2015; Accepted: 26 JUN 2015; Available on-line: 29 JUN 2015 This article contains supporting information online at http://www.aprh.pt/rgci/pdf/rgci-577_Salgueiro_Supporting-Information.pdf Salgueiro et al. (2015) 534 RESUMO Modelação de um efluente térmico numa zona costeira (central termoelétrica de Sines, Portugal) Este artigo tem como objetivo estudar a dispersão do efluente térmico da central termoelétrica de Sines (Portuga
