The dilution and dispersion of ballast water discharged into Goderich Harbor

► We describe the dispersion of ballast water discharged into Goderich Harbor. ► The ballast water was tagged with dye and magnetically-attractive tracer particles. ► After 2 days less than 20% of the ballast water remained in the harbor. ► Peak concentrations of dye after discharge were <5% of ballast tank concentrations. ► We compare our results with the International Maritime Organization's standards.