A model of the three-dimensional hydrodynamics, transport and flushing in the Bay of Quinte A. Oveisy a, ⁎, L. Boegman a , Yerubandi R. Rao b a Environmental Fluid Dynamics Laboratory, Department of Civil Engineering, Queen's University, Kingston, ON, Canada b Water Science and Technology Directorate, NWRI-Environment Canada, Burlington, ON, Canada abstract article info Article history: Received 31 October 2013 Accepted 15 January 2015 Available online 18 April 2015 Communicated by Jay Austin Keywords: Bay of Quinte Hydrodynamic model Nutrient transport Water quality model The Bay of Quinte, Ontario, receives excessive nutrient loads and suffers from poor water quality. The 70 km long z-shaped bay traps the nutrients due to limited flushing with Lake Ontario, leading to increased nutrient residence times. Therefore, it is important to understand the three-dimensional hydrodynamic conditions within the bay, as these drive horizontal transport, dilution of nutrient rich inflows and water exchange to the lake. In this study, the effects of meteorological forcing, river inflows and Lake Ontario exchange on the hydrodynam- ics and mixing were investigated using a numerical model. The model was validated against temperature time series and profile data, with a maximum root-mean-square deviation b 2.3 °C in comparison to observed temperature profiles. Six methods were applied to estimate flushing from the bay, with three methods (tracer release, drifter paths, bulk residence time) converging to predict the main channel of the bay flushes 5 times a year. Isolated embayments have higher water ages (4–5 months) and may trap nutrients with sufficient time and conditions for algae blooms to occur. Strong advection is modeled in the main channel, with low horizontal transport in the embayments and efficient flushing near the connection with Lake Ontario. This provides insight for watershed management, for example, to design ideal locations for nutrient discharges (e.g. wastewater plumes), to target specific rivers for nutrient load reductions, and to support future coupled hydrodynamic and biogeochemical modeling of the bay. © 2015 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved. Introduction The Bay of Quinte is a significant freshwater source for drinking, recreation and industry. The bay not only is narrow and sheltered, but also receives excessive pollutant and nutrient loads (Minns et al., 1986) leading to persistent toxic and bacteriological contamination, undesirable algae growth, fish toxicity, and taste and odor problems, which are exacerbated near Belleville, Hay Bay and Picton (Fig. 1). In 1986 the Bay of Quinte was classified as an Area of Concern in the Great Lakes basin by the International Joint Commission and a Remedial Action Plan (RAP) was initiated. The studies conducted under the RAP have been mostly observational and descriptive. The Great Lakes Laboratory for Fisheries and Aquatic Science has been monitoring water temperature and oxygen since 1972 (Minns, 2011), water quality both before and after phosphorus load re- ductions (Robinson, 1986), and phosphorus loads from municipal sewage treatment plants (STP) between 1965–2005 (Kinstler and Morley, 2005). Recent field monitoring was focused on management of taste, odor and toxins in the framework of the Bay of Quinte Harmful Algal Blooms (BQHABs) initiative (Watson et al., 2009), which is comprised of new fieldwork and analysis of the existing Bay of Quinte dataset. The study of exchange flows between the Bay of Quinte and Lake Ontario using current meter observations has also been undertaken (Freeman and Prinsenberg, 1986). Hydrodynamic and water quality box models have been applied to the bay. Moin and Thompson (2006) applied a one-dimensional (longitudinal) hydraulic model based on the solution of the St. Venant unsteady flow equations with reasonable success and utilized water temperature data to evaluate the health of fish species in the Bay of Quinte for a 100 year period under different water level scenarios. Minns and Johnson (1986) and Minns et al. (1986) included tributary inputs in a box-model and parameterized the exchange flow with Lake Ontario to study the budgets for phosphorous, nitrogen, and chlo- ride during 1965–81, 1992–2001 and 2002–2031 (Minns and Moore, 2004). Similarly, Razavi (2006) divided the bay into seven segments for mass balance modeling to determine the source and fate of contam- inants. They assessed the effects of four metals and thirteen hydropho- bic organic chemicals (HOCs) on the food web. Recently Zhang et al. (2013) and Kim et al. (2013) assessed and improved the capability of the Minns box model (Minns and Moore, 2004) to seasonally evaluate the regional nutrient loading to the Bay of Quinte and it's suitability for assessing relevant water quality parameters. They concluded that loading from the Trent River is the most important factor in the total Journal of Great Lakes Research 41 (2015) 536–548 ⁎ Corresponding author. E-mail address: a_oveisy@ce.queensu.ca (A. Oveisy). http://dx.doi.org/10.1016/j.jglr.2015.03.016 0380-1330/© 2015 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Great Lakes Research journal homepage: www.elsevier.com/locate/jglr