Abstract
River freezing is a common phenomenon at high latitudes. The Lena River, one of the four largest rivers flowing into the Arctic Ocean, freezes over completely from early December to late April. The process of riverโice formation affects not only the river flow and local energy regime, but also influences hydrological and thermal conditions in the Arctic Ocean. In this study, a combined hydrological model used for a coldโregion basin (Ma et al., 2000. Hydrological processes 14: 639โ651) was further developed to model hydrological processes in the Lena River. A simple method of accumulated degreeโdays was used in describing riverโice growth and decay. River flow routing was used to compute the hydrograph according to the depth of runoff stored in the river and the season. The combined model system was applied to the Lena River basin, using data for the period October 1986 to September 1987, and produced modelled hydrographs at six river sections that were an improvement on those resulting from the earlier study. Although the simulation duration in this study was limited to 1 year, it is expected that the model system will be an effective tool in making hydrological simulations in cold regions in the future. Copyright ยฉ 2002 John Wiley & Sons, Ltd.