The hydrodynamics and contaminant transport in the nearshore region of Lake Ontario, from Port Hope to Cobourg, were simulated. The model results were comprehensively validated against observations of water level, temperature, and currents collected during April-September, 2010. The model generally agrees well with the observations. A RMS error of similar to 2 degrees C was simulated and normalized Fourier norm (between 0.45 and 1.17), indicating that both the thermal stratification and currents are well-simulated, respectively, and are comparable to other model applications. Internal Kelvin waves were not observed and the internal Poincare wave oscillation was observed offshore, but not modeled. Rather, up-welling and down-welling events caused by southwesterly and northeasterly winds, respectively, were both modeled and observed to be the dominant large-scale hydrodynamic processes. The episodic events lasted for 4-5 days with the upwelling front extending similar to 10 km offshore. The up-welling and down-welling events generated geostrophic alongshore currents or coastal jets of similar to 20 cm . s(-1). The influence of these dynamics on the transport of river and wastewater-treatment plant plumes, toward drinking water intakes, was investigated using tracer release simulations. Tracer concentrations in the range of 10-0% (i.e., 70-90% dilution) were found at the Port Hope and Cobourg drinking water intakes. The tracer concentrations were primarily influenced by the proximity of the intakes to the plume origins and the wind direction, which governs the direction of the alongshore currents resulting from the up-welling and downwelling events. These results will help municipalities better understand the transport of contaminants in the nearshore zone relative to drinking water intakes. (C) 2014 American Society of Civil Engineers.