Streamflow in the presence of stationary river ice cannot be derived directly from a continuous stage record and an open water rating curve. Ice covers and moving ice also present a serious challenge for new technologies (e.g. visual, acoustic, radar, electromagnetic) that measure flow velocities or water levels from above or below the water surface. Unfortunately, most cold region rivers experience some ice effect for at least part of the year, making many historical winter flow estimates uncertain. Knowledge of winter flows is important for several reasons: (1) winter flows are often unstable, especially during periods of changing ice conditions, and these fluctuations may be hidden in hydrometric records, (2) annual low flows often occur when ice is present, therefore impacting flow management and aquatic habitats, (3) the simulation of river ice breakup and associated ice jams requires accurate discharge estimates. The Water Survey of Canada and other agencies are increasingly including new knowledge and tools to create reliable winter discharge data sets derived from continuous stage measurements and (in some cases) under-ice velocity measurements. However, historical records will likely remain unchanged and will include an inherent uncertainty. Accurate historical records are important for river engineering and scientific activities such as flood mapping, the design of hydraulic structures, and the quantification of the impact of climate change on hydrological regimes. This presentation provides several examples of how historical flow data may be corrected using a simple backwater-based analytical method.