Water withdrawals from the Lower Athabasca River will increase with the expansion of the oil sands mining operations, and may affect the ice regime of this reach. A three-year program was established to develop an appropriate modeling tool to address this issue. The main purpose of this first year of study was to establish the main conditions describing the winter ice regime of an 80 km reach of the Athabasca River, spanning from Fort McMurray to Bitumount. Hydrometeorological and ice cover characterization data was collected for the 2006/07-winter season through the implementation of an extensive field monitoring program. Preliminary numerical modeling of thermal and hydraulic processes was conducted in River1D and River2D. The ice regime of the reach was observed to be highly two-dimensional, due to the presence of numerous islands, sand bars and industrial warm water outfalls. To account for these factors, several limitations of the models must be addressed.