Mapping the summer 2017 surface water circulation of Picton Bay, ON

On March 24, 2017, a fuel spill from a partially submerged barge in Picton Bay contaminated the source water for the drinking water supply of the local township. Immediately after the spill, management decisions regarding the water intake plant operations were made based on contaminant observations and projected wind conditions. From a management perspective, it is essential to understand all the dynamical forcing for a system to direct the best decision-making but, unfortunately, there are no historical observations of currents in Picton Bay or any in-depth numerical modelling studies that have established the circulation patterns or hydrodynamics of the bay. This paper presents observations of surface speeds and drifter pathways collected using Lagrangian drifters and compares the observations to the velocity field estimates from a wind forced three-dimensional hydrodynamic model. Surface drifters were deployed from July to September and moved southwest into the bay during each deployment with almost no tendency to turn and drift out of the bay. Model simulations indicated that currents in the bay are sensitive to small-scale local winds and that a boundary current exists that connects the spill site to the area of the water intake pipes in wind conditions that are to the southwest or southeast.