Measurements of coastal dispersion in Ontario lakes

Abstract

A series of dye injection experiments were carried out near the surface in the coastal waters of lakes Erie, Ontario, and Simcoe. The purpose of the experiments was to determine whether the relative dispersion in these regions was similar to that obtained in other oceanographical experiment. Rhodamine BA dye was injected at a constant rate (approximately 150 mg/s) at a depth 1 m below the surface from a raft anchored in 9 m of water (approximately 1.5 km offshore) for 6 to 8 h. Two-dimensional dye plume concentrations were measured at cross sections 60 to 830 m from the source. Relative dispersion coefficients were determined numerically from the measured concentration profiles. The horizontal dispersion coefficients (80 to 4100 cm2/s) were comparable to oceanographical values and exhibited a 1.33 power growth with distance from the source. Vertical dispersion coefficients were very small (less than 1 cm2/s) and relatively independent of distance from the source.