The report describes the results of five transverse mixing and travel time tests carried out in March, 2003 on the Athabasca River between Fort McMurray and Embarras. The tests were carried out under ice-covered conditions in late winter. For the most part, measurements of the channel and ice characteristics, the discharge, and the concentrations within the dye cloud were carried out successfully under rather severe weather conditions. These measurements will provide a framework to better understand the mixing processes in the river during the winter. The dimensionless transverse mixing coefficients and travel times evaluated from the test data will be very helpful for selecting coefficients and calibrating two-dimensional water quality models of the study reaches and will therefore improve the assessment of wastewater management options in the study region.