In Canada, Water Survey of Canada, a division of the Water Resources Branch of Environment Canada, is responsible for the collection and processing of data from more than 3,300 active streamflow, water level and sediment data gauging stations. Because of the climatic conditions prevalent in Canada, an important part of the monitoring program is conducted under winter ice conditions. The determination of daily streamflow records during the winter period is important for several practical purposes, in particular for water power development. Essential to the computation of daily discharge records, are reliable streamflow measurements. However, discharge measurements under ice conditions are generally difficult to obtain because of severe weather conditions, hazardous field conditions, and ill-adapted field measurement techniques.

In this paper, the field methods and instruments, and computational methods used by Water Survey of Canada for streamflow measurement and computation under ice conditions are reviewed. Factors affecting the accuracy of discharge measurements performed under ice conditions are discussed. Newly developed instruments for use under ice conditions are described and their advantages discussed. A comparison between techniques used by Canada and other northern countries is also given. Areas of research and investigations for improvement in the overall quality of data are suggested.