As a validation study for the Global Soil Wetness Project, the output from the simple biosphere model produced by the Japan Meteorological Agency (JMA-SiB) is compared with observations. The Mackenzie River basin is selected as the study area to investigate the continental-scale hydrological cycle. Discharge data and four-dimensional assimilated data from 1987 to 1988 are used to evaluate the seasonal cycles of the runoff near the river mouth and the basin water storage. In this evaluation, a 1¿¿1¿ river routing scheme and a distributed runoff model are adopted for the water transport by rivers. For the case when the stream velocity u=0.3 m/s, the seasonal variation of the observed runoff near the river mouth is reproduced well by the local runoff derived from JMA-SiB. For this velocity the seasonal change of the observed water storage in the basin is expressed well by the soil moisture+snow water equivalent+channel storage simulated by JMA-SiB and the distributed runoff model. In the Mackenzie River basin, soil moisture is almost constant throughout the year, while snow water equivalent is responsible for the seasonal variation of the basin storage from winter to spring. The role of the channel storage is important after the melting season. Some systematic bias, however, is found between the observed and simulated basin storages after the summer of 1987. This feature can be attributed to the delay of the snowmelt and the surplus evapotranspiration in the melting season simulated by JMA-SiB. ¿ 1999 American Geophysical Union